Publications

The New Zealand Building Code (like many others) is a performance-based standard; however, the application of performance-based design is rare in practice. Typical design practice considers the capacity of individual elements in the building and does not allow for the full load-displacement response of the building system. This paper presents a case study where a performance-based design approach was used for the design of a new building on an existing foundation system and how it was able to illustrate compliance with the New Zealand Building code. Show more…The case study found that a capacity-based design approach was likely an impractical way to illustrate compliance with the Building Code. Given the significant negative project impacts including programme delays, environmental impacts and cost increases associated with adopting a new foundation system, a performance-based assessment was completed. With strong interaction between the geotechnical and structural engineers, a non-linear vertical pile spring analysis was undertaken, allowing the design team to demonstrate that the existing foundation system complied with the building code, avoiding the significant negative project impacts. Show less…

14th Australia New Zealand Conference on Geomechanics, Cairns, 2023

Geopier Rammed Aggregate Piers® (RAPs) are a ground improvement technology that creates a densified column of aggregate surrounded by a stiffened matrix soil. This paper describes the design and construction of RAPs at Te Kaha, a $683- million Multi-Use Arena under construction in Christchurch, New Zealand. Show more…CLL Projects are constructing 8331 RAPs including 1092 tension RAPs to depths between 5.5 to 12m to provide a ground improvement system supporting the arena. Design considerations include estimation of soil densification in a wide range of soil conditions (sand, silty sand, silt and gravel), analysis of liquefaction triggering before and after ground improvement, numerical analysis to predict the bearing capacity and settlement of the foundations, and prediction of uplift capacity for tension RAPs. The design predictions and the actual results from verification testing are compared, including pre- and post- improvement CPTs and tension load tests. At Te Kaha the RAP installation resulted in a significant increase in sandy soils between the RAP elements. The CPT results consistently underestimated the fines content of the soil. The tension load test results showed that the uplift capacity is dependent on the soil conditions at the tip of the tension RAP. If adequate confinement cannot be achieved at the base the tension RAP ‘unravels’ and the capacity is much lower than typical design methods would predict. Show less…

14th Australia New Zealand Conference on Geomechanics, Cairns, 2023

Auckland Council owns and operates approximately 600 stormwater ponds and wetlands, most of which involve dams. This valuable infrastructure supports the financial, social, cultural, and environmental wellbeing of communities, present and future, by providing flood mitigation, water quality treatment, amenity, ecological value, and cultural heritage value, as well as mitigating the impacts of land development and climate change. Show more… In the first few months of 2023, the Auckland region was subject to two catastrophic storm events in quick succession, including Auckland’s largest ever rainfall event. This paper shares the experience from the emergency response for a large portfolio of stormwater dams in a regionwide, multi-month series of record floods, to share learnings with others that may face similar situations. Several factors were identified as beneficial for emergency response. These included having a mature dam safety management system, a practiced response team, and pre-established relationships with dam safety advisors and contractors. In a series of large-scale storm events, other hazards will likely need to be considered alongside the dam safety threat, the health, safety, and wellbeing of the response team requires extra consideration, and there is especial value in simple systems and concise communication. Show less…

ANCOLD 2023 Conference on Dams

Over the past 40 years, the advantages of utilising geosynthetic barriers versus traditional earthen barrier materials have been well documented: greater project economy, extended service lives, enhanced environmental protection, greater site safety, etc. Show more…Achievements such as conserving water resources and enabling beneficial site reuse have even given geosynthetic engineering a level of social importance. As such, the use of geosynthetic barriers has increasingly been required by government regulators around the world. This is true in modern waste management landfill design. However, there are still regions and applications in which the use of these barrier technologies should be more widely adopted. This paper highlights an overview of applications where geosynthetic barriers are used, and where regulation or recommendations are available, and it describes other emerging applications where geosynthetic barriers are starting to be used. Show less…

12th International Conference on Geosynthetics, 2023, Roma, Italy (12ICG)

Wave overtopping occurs as waves pass over the coastal edge and flow onto the land behind. This can result in a hazard to vehicles and pedestrians and flooding or damage to the built environment. To date, predictive formulae for overtopping have been primarily developed in a laboratory setting. Comparatively few studies involve the field measurement of overtopping because environmental conditions such as wind and water levels have a large influence on the overtopping rate (amongst many other factors), and the measurement of overtopping discharge is practically difficult due to enormous spatial and temporal variation in overtopping volumes. Show more…This paper discusses key challenges for local government coastal managers in New Zealand relating to overtopping hazard, highlighting a need for pragmatic guidance on monitoring, application within an adaptive management, and assessment of Relative Sea Level Rise (RSLR) effects on future hazard.
Two methods to measure wave overtopping in the field were investigated in this study; using either catch devices that measure volume, or camera monitoring. This paper shows, by considering a site along Tamaki Drive in Auckland, how monitoring and measurements of overtopping is important as part of the Ministry for the Environment (MfE) recommended Dynamic Adaptive Policy Pathway (DAPP) approach to managing associated hazards.
Finally, this study shows how future overtopping hazards associated with RSLR can be assessed by remodelling incremental rises applied to historic water level records. It is found that even small amounts of RSLR can dramatically increase the exposure of coastal communities to overtopping hazards. Show less…

Australasian Coasts and Ports Conference, 2013, Sydney

The use of single layer, concrete armour units for coastal edge protection in place of rock is becoming increasingly common. Revetments constructed from these units can provide benefits of a reduced footprint, reduced material usage and transport costs as suitable rock becomes increasingly difficult to source, and reduced construction timeframes. Show more…XblocPlus® units have been adopted as the primary armouring for a major shared-path infrastructure project within Te Whanganui-a-Tara, Wellington Harbour. The Ngā Ūranga ki Pito-One Project comprises a 4.5 km shared (pedestrian/cycling) pathway between Ngā Ūranga and Pito-One. The XblocPlus® units are patternplaced interlocking armour concrete units that remain stable at steep slope angles while providing high coastal performance. However, these units have had limited application in seismically active regions. Therefore, the behaviour of the individual armour units and overall revetment during, and following seismic activity was assessed in detail to assess performance and enable development of a post-seismic inspection and repair strategy.
The response of a revetment to seismic shaking, particularly the interlocking of the individual XblocPlus® units and interaction with the ground profile below is complex and could not be determined using a single method or model. Therefore, a suite of complementary models was used to assess the behaviour of individual components and combined performance of the revetment asset under the design earthquake events. This paper describes the various physical and numerical models used to determine performance and to inform the design and repair strategy of XblocPlus® revetment.
The physics-based model Unreal Engine was calibrated against uni-directional testing on a physical shake table and run for 3D design earthquake timeseries to assess how the individual XblocPlus® units reacted to shaking. Limit equilibrium and time history finite element modelling were carried out to understand how the ground profile supporting the revetment might perform. These results were then used in the 3D physics-based model in Blender to determine the unit response to slope deformation. The XblocPlus® response to shaking and slope deformation was combined to create a post-seismic revetment condition, which in turn was tested by physical modelling in a wave flume against to assess hydraulic stability performance under moderate storm events (i.e., before a repair could be enacted). Following this, an inspection and repair strategy was developed. Show less…

Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland

The Ōpōtiki Harbour Development (“OHD”) is the first river port to be constructed in over 100 years in New Zealand. Te Whakatōhea have developed an offshore mussel farm and onshore processing factory and need a navigable harbour entrance to connect these resources. Show more…The OHD scheme comprises twin 400 m long training walls to fix a dynamic river mouth, around 700,000 m3 of dredging in intertidal and subtidal areas and approximately 20 hectares of constructed fore and mid dune to close the existing river mouth. The OHD is located in a sensitive estuary environment fed by two major rivers. The estuary contains numerous threatened fauna, is subject to constant morphological change and provides an important recreational resource for the Community.
To ensure opportunities for innovation in design and construction were optimised, the resource consents granted for the OHD deferred most environmental impact avoidance, remediation, or mitigation to a suite of Environmental Management Plans (“EMP”) to be prepared in parallel with the Detailed Design of the project. These EMP manage a range of impacts, such as sediment contamination, saline wedge connection to inanga spawning habitat, disturbance to dotterel breeding areas, water quality (TSS and clarity), native fish migration, training wall related downdrift erosion, and sediment deposition within riverine riparian vegetation and seagrass assemblages.
Timeframes to design and construct the OHD were very tight with many inter-dependencies in the project plan. The Technical Liaison Group (“TLG”) comprising representatives of tangata whenua and a range of regulatory agencies were required to contribute to the development of the EMP.
To ensure the OHD project was delivered within a compressed programme, meticulous planning and execution of the environmental management regime was required. To this end, partnership was key. The OHD design and construction project team worked with the ocean, rivers, nature, tangata whenua, regulators, the Community, and other professionals. Show less…

Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland

The Ōpōtiki Harbour Development involves stabilising the entrance of the Waioeka River to allow reliable and safe access for maritime activity. Te Ara Moana a Toi (“A path to the sea”) is the first major river training works to be constructed in Aotearoa, New Zealand in over 100 years. The project involves constructing twin 400m long training wall breakwaters, dredging a 120m wide navigable channel into the Harbour, closing the natural river mouth, and forming a new dune habitat. Show more…Construction of the Ōpōtiki Harbour Development Project commenced in late 2020 by HEB Construction. The opening of the new harbour entrance is expected to be completed in late 2023/early 2024.
Construction at the end of a dynamic sand spit within the coastal zone is inherently uncertain with dynamic morphological processes and testing environmental conditions. As expected with a project of this scale, the coastal environment has provided many challenges and opportunities for designers and constructors alike during the construction stage. This paper covers significant construction milestones, environmental monitoring data, challenges, and innovations undertaken during construction. These include construction observation techniques, environmental monitoring data, and innovations developed to successfully undertake construction of the new harbour opening while being 300m offshore within the surf zone. These challenges and innovations include the ground improvement methods undertaken, withstanding and adapting to extreme wave conditions during construction, dredging techniques, and the philosophy behind the new channel opening and subsequent existing river mouth closure expected to occur in mid-2023. Show less…

Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland

The 10 km stretch of foreshore between two of New Zealand’s largest cities Wellington and Hutt City is a crucial infrastructure corridor combining cycleway, road and rail, as well as sub-surface utilities. Recent storm events have caused significant damage to, and overtopping of, the current rock revetment structure resulting in the rail line being undermined and closed for extended periods. Future proofing the foreshore is integral for the longevity and function of this corridor and the Te Ara Tupua Alliance have been tasked with redeveloping it. Show more…UNSW Water Research Laboratory (WRL) undertook a large physical modelling program (over a 100 individual tests) to assist optioneering for a range of coastal protection designs. 2D flume testing was conducted to assess both the stability and overtopping performance of rock and concrete armoured (modified XblocPlus) revetments and vertical walls equipped with sloped crown walls.
All tests were conducted using irregular wave time series derived from several spectral conditions. Analysis of wave buoy records showed that both wind waves and swell entering the harbour could be expected to impact the project area. As such, sensitivity testing for overtopping was conducted using custom-generated bimodal conditions with different wind/swell ratios. Physical model testing results showed that overtopping volumes were highly sensitive to the long period wave component within the bimodal spectrum.
The findings of this extensive physical modelling program highlight the limitations of standard empirical methods for assessing overtopping under bimodal wave climates, the importance of extending beyond conventional unimodal wave climates when designing coastal structures, and the importance of using on-site wave data to best model potential overtopping volumes and safely optimize designs. Show less…

Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland

This paper presents a review of the Golden Cross Landslide near Waihi 17 years after its successful stabilisation by use of major drainage and earthworks. The landslide is interesting because of its size,
2100 m long, 500 m to 1000 m wide and up to 145 m deep, and supports a large tailings dam retaining approximately 1.7 million cubic metres of tailings from the previous gold mining operation. Show more…The paper includes a review of historic and current landslide movement rates (from inclinometer and GPS data), piezometric data and presents an assessment of the ongoing effect of the stabilisation measures. Comment is also made on the long term relative effectiveness of the various stabilisation
measures from the nearly 20 years of data available. Show less…

12th Australia – New Zealand Geomechanics Conference, Wellington, 2015

Urban beaches in semi-sheltered harbor environments are highly valued public spaces that require detailed understanding of coastal dynamics for appropriate management. Understanding the dynamics these environments is challenging due historic management interventions such as renourishment and hard infrastructure. As a result, commonly applied modelling and hazard assessment methods are not necessarily appropriate for semi-sheltered often fetch-limited urban beaches, without site-specific calibration. Show more…This paper focuses on the calibration and potential applications of three different numerical models to better understand coastal processes on the Sandringham Beach in Port Phillip Bay, Victoria. First, the shoreline position model ShorelineS was applied to understand beach rotation, seasonal trends in shoreline movement and long-term rates of shoreline change. Model calibration was informed by monthly monitoring data, including drone-based topographic surveys and wave buoy data. Next, the storm response model XBeach was calibrated using observed wave events and measured changes in the coastal profile. The models were collectively used to give new insight on the beach dynamics at short, medium, and long timescales.
Outputs of the XBeach and ShorelineS modelling were then used to inform variables for projecting shoreface translation to sea level rise using the ShoreTrans model, where the sensitivity to different trajectories of barrier rollover and translation were assessed. Isolating the cross-shore adjustment in ShoreTrans allowed the idealised beach topography to be reconstructed for a sea level rise scenario representing the year 2100. Balance of alongshore sediment flux was achieved by passing volume from profile to profile according to the net sediment balance in the system, informed by long-term rates.
The paper introduces a conceptual a multi-model workflow that is proposed for exploring present day and future scenarios, with application for hazard management and adaptation design. Show less…

Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland

The Te Ara Tupua Ngā Ūranga ki Pito-One Project comprises a 4.5 km shared (pedestrian/cycling) pathway between Ngā Ūranga and Pito-One in Te Whanganui-a-Tara, Wellington with dual outcomes of rail/road corridor resilience improvement and mode shift. The project presented the challenging design requirements of managing the safety of shared path users through a coastal edge design that is controlled by tight geometric (elevation and toe position) constraints, a range of unique edge protection structures, and a bimodal wave climate. This challenge was addressed through site and design specific physical and numerical modelling, data driven overtopping analysis and a forecast model development for safety management during operation. Show more…The range of edge protection structures proposed include XblocPlus armour unit revetments, rock armour revetments with mid-tide berms of varying width, and vertical concrete seawalls with return crest walls. The present empirical guidance on overtopping performance of these structure configurations is not widely developed in literature, at least with sufficient reliability to inform design on this project. An additional complicating factor was a bimodal wave climate, the swell component of which was discovered to have a significant effect on anticipated overtopping flows.
As such, structure- and site-specific physical modelling was undertaken to inform the overtopping analysis at the UNSW Water Research Laboratory. The results of the physical model tests were used to develop site-specific, data-driven formula based on relationships between relative overtopping and relative freeboard, as presented in the EurOtop manual. These relationships were used to understand overtopping potential along the project site both now and in the future through development of a 30-year overtopping timeseries. In parallel, a two-layer phase resolving, non-hydrostatic XBeach solver was calibrated to match the wave transformation of the bi-modal wave climate and physical model overtopping results allowing wave conditions and resultant overtopping flows to be extracted anywhere along the project site.
This was used to inform design crest levels future adaptation timeframes and options, and to develop an overtopping forecast model to inform path warnings and closure during operation. The results of this analysis highlighted the importance of understanding site-specific influences on overtopping flows, not all of which are able to be fully understood through adoption of standard empirical overtopping formula. Show less…

Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland

Modern-day coastal engineering faces two key challenges: firstly, providing adequate protection under anthropogenic increases in sea level, and secondly, reducing environmentally detrimental engineering practices that are further driving changes to the climate. With this, nature-based solutions that minimise detrimental environmental effects whilst providing sufficient protection are increasing in their uptake. At present, the application of these nature-based engineering strategies is restricted to low-energy wave environments with minimal spatial constraints. Hybridisation (combined use of nature-based and traditional hard engineering strategies) enables the use of these nature-based principles in higher-energy and urban environments. This paper explores the use of hybridisation with coastal vegetation, by exploring the ability of vegetation to attenuate wave overtopping flow on the crest of coastal defence structures. Show more…Physical modelling experiments were conducted in the University of Auckland’s wave flume with a small-scale sloped seawall retrofitted with model vegetation on the crest of the seawall. This preliminary testing found that the model vegetation reduced mean overtopping discharges by 60-80% when evaluated against their nonvegetated counterpart. Numerical model testing was conducted by calibrating to and expanding on the physical model analysis. This was achieved by implementing a one-dimensional non-hydrostatic XBeach model. Numerical model testing used a multiple linear regression analysis to test the sensitivity of the wave overtopping response to various vegetation parameters. From this, the reduction in mean overtopping flow due to the incorporation of vegetation was found to be most strongly correlated to vegetation width, stem density and stem diameter, with increases in any of these parameters leading to substantial decreases in mean overtopping flow.
Both the physical and numerical model testing were limited by their use of idealised structure and vegetation parameters. However, despite these limitations, this study provides a framework for future testing that should seek to further solidify the wave overtopping performance of this hybrid strategy. Show less…

Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland

The Te Ara Tupua Ngā Ūranga ki Pito-One (Ngauranga to Petone) Project comprises a 4.5 km shared (pedestrian/cycling) pathway between Ngā Ūranga (Ngauranga) and Pito-One (Petone) in Te Whanganui-a-Tara, Wellington. The Project will be located on the seaward side of the State Highway 2 and the rail corridor and will provide safe walking and cycling infrastructure as well as enhancing the resilience of the transport corridor. The Project involves temporary and permanent works in and adjacent to the coastal marine area, including multiple rock and concrete armour revetments, ūranga (landings), seawalls, offshore habitats and culvert extensions, and will result in over 5 Ha of permanent marine habitat loss. Show more…To avoid, minimise and compensate for the impact on the marine environment, a number of innovative ecological enhancements have been incorporated into the Project design. Two rock armour offshore habitats will provide undisturbed roosting habitat for coastal avifauna. 235 little blue penguin nesting boxes will be incorporated within the revetment and Ūranga. Gravel beaches will be nourished to provide 10-25 years of resilience to future sea level rise. Over 240 ECOncrete® tide pools will be integrated in clusters within the intertidal bench of the rock revetments and offshore habitats, providing habitat and water retaining features for marine life as well as foraging habitat for coastal birds. Finally, some 1850 XblocPlus® units, that form part of the revetment, will be ecologically enhanced using increased surface complexity. The integration of these ecological enhancements within the design was developed in collaboration between ecologists, landscape architects, engineers and mana whenua and drew inspiration from the existing ecology, coupled with cultural narrative.
This project will be the first application of many of these ecological enhancement features in New Zealand. The features will improve the ecological value of the coastal pathway and provide a more resilient marine ecosystem within Te Whanganui-a-Tara (Wellington Harbour). The project provides a case study for how ecological features can be successfully implemented into coastal infrastructure and an opportunity to measure the ecological performance of these features in a New Zealand context, so that future installations can more accurately predict the ecological gains likely to be achieved when balancing against unavoidable biodiversity losses. Show less…

Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland

Delivery of major transport infrastructure projects at the coast requires a careful balance between numerous project drivers, including cost, program, environmental, regulatory and stakeholder considerations. These often-conflicting drivers have the potential to disrupt a project, if not managed carefully, leading to delays, cost over-run, conflict and sub-optimal outcomes. Show more…The Ngā Ūranga ki Pito-One Project comprises a 4.5 km shared pathway between Ngā Ūranga and Pito-One in Te Whanganui-a-Tara, Wellington. The Project will be located on the seaward side of the state highway and the rail corridor and will provide safe walking and cycling infrastructure and enhance the transport corridor’s resilience. The Project includes all of the above-mentioned drivers including partner and stakeholder expectations, very tight environmental and ecological constraints, budget expectations, a difficult design environment adjacent to a major fault-line and exposed to southerly wind and wave climates, limited local rock supply and construction workspace.
Delivery of the Project from concept design through to construction is being delivered by the Te Ara Tupua Alliance, comprised of owners Waka Kotahi NZ Transport Agency, working in partnership with mana whenua (Indigenous partners), contractors HEB and Downer and designers Tonkin + Taylor. To address the many project challenges, an innovative approach to design was implemented during initial concept phases. This included an agile design philosophy with sprint design and review cycles enabling fast paced integration of design, construction, environmental and cultural objectives. This approach included several innovations in the final design, most notably the adoption of modified XblocPlus® concrete armour units for primary armouring. These single-layer, pattern-placed units are to be used for the first time in Australasia and have resulted in significant cost and programme savings to the Project, but have also included bespoke modifications to achieve improved aesthetic, ecological and cultural outcomes. Show less…

Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland

The Peka Peka to Ōtaki Expressway (PP2Ō) is a 13 km long, 4-lane expressway located on the Kāpiti Coast north of Wellington, New Zealand, serving as a replacement for the existing State Highway 1 (SH1). To the south, it connects with the MacKays to Peka Peka Expressway, and its northern extension reaches beyond the Taylors Road intersection on the current SH1. Show more…At both the southern and northern sections of the alignment, soft and highly compressible peat and organic silt up to about 7 m depth were encountered. The presence of soft soils is a consequence of topographical and geological factors which has resulted in poorly drained conditions.
This paper provides an overview of the ground improvement techniques implemented to address geotechnical challenges associated with these soft soils, and the observational approach adopted during the construction phase. Show less…

New Zealand Geomechanics News Issue 106 December 2023 p. 50-60

Design or assessment of structures founded on ground with a potential for seismic induced ground displacements requires careful consideration of the associated soil structure interaction (SSI). These seismic ground displacements could be due to liquefaction and cyclic displacement or lateral spread, or due to slope instability. Potential ground movement and SSI includes considerable uncertainty. Show more…Three case studies describe application of these principles. These principles include developing possible scenarios of ground movement, ground and structure shaking and SSI, and testing the design relative to these scenarios. Relative stiffness of ground and structural elements needs to be considered in developing these scenarios. Is the structure pushing the ground or is the ground pushing the structure? The impact of SSI on the magnitude of ground displacement needs to be considered. Will the SSI arrest the ground movement or will the ground movement potentially pull the structure apart? The presented principles and case studies focus on qualitative and simplified numerical assessments. Where considered appropriate and necessary, higher level analyses including dynamic finite element modelling could be undertaken. These higher level analyses should be to supplement rather than replace the simplified methods described in this paper. Higher level analyses could be particularly useful in understanding possible mechanisms of SSI. Assessment would require engineering judgement considering all available information. Show less…

NZSEE Conference 2024 Wellington

Stormwater management is a critical aspect of creating sustainable and resilient cities in the face of pressures such as ongoing urbanisation, ageing infrastructure, climate change, loss of productive soils and infrastructure affordability. However, the continued degradation of our waterways is evidence that the prevailing notion of ‘sustainable’ stormwater management isn’t working and a paradigm shift is required. This paper explores the application of systems thinking to the domain of stormwater management, emphasising the importance of adopting a holistic perspective and using non-structural solutions to enhance system resilience and regenerative outcomes (i.e. outcomes that achieve restoration across multiple domains rather than simply the reduction of harm. Show more…Systems thinking is a holistic approach to understanding and solving problems by examining the interconnected relationships and dynamics within systems. Unlike linear thinking (which focuses on isolated cause-and-effect relationships) or reductionist approaches, systems thinking recognises the interdependence of various elements to better understand system behaviour. In this sense, systems thinking is a perspective that can be applied to any technical field and is needed more than ever to develop robust and enduring responses to society’s many complex challenges.
Stormwater management in New Zealand in recent decades has typically focused on managing three primary objectives: (1) flooding, (2) stream erosion and (3) water quality. These have typically been managed with the adoption of structural solutions such as pipes and devices such as ponds, while the implementation of approaches such as Water-Sensitive Urban Design (WSUD) has been limited. This approach of focusing on managing the symptoms of changes to the water cycle (runoff quality and quantity) rather than root causes (e.g. increases in impervious area) has contributed to an urban environment characterised by high imperviousness that results in poor stormwater outcomes as well as a host of non-stormwater related city planning issues.
However, as urbanisation continues at a historic pace and local government faces increasing financial pressure, can we really continue to rely on (attempting to) engineering our way out of the problem? The conventional approach to stormwater management, with a heavy reliance on engineered devices and infrastructure, has led to residual environmental effects (as demonstrated by the continued degradation of our waterways), low levels of resilience, and high embodied carbon emissions. Is this approach really sustainable?
Approaches such as WSUD and sponge cities are discussed as examples of a systems thinking approach that can provide more robust and resilient solutions than conventional stormwater management (when applied well). However, incorrect implementation and limited uptake of these approaches shows that these frameworks are not enough on their own without further system interventions.
This paper seeks to use a systems thinking lens to examine the current approach to stormwater management in New Zealand, why it is falling short, and examples of systemic solutions that could lead to better outcomes. The aim of this paper is to equip stormwater practitioners with some of the language, tools and principles of systems thinking in the context of stormwater management to aid with a shift toward regenerative solutions. Show less…

Water NZ Stormwater Conference, 2024, Wellington

Hutt City Council (HCC) was granted $99 M of funding through the Infrastructure Acceleration Fund (IAF) to deliver stormwater and wastewater infrastructure improvements to enable growth, a project now known as Water Infrastructure for Growth (WIG). The stormwater infrastructure improvements are aimed at removing impediments to housing for predicted population growth in Lower Hutt in the late 2020s and 2030s. This intensification will be entirely brownfield redevelopment. The WIG project is critical to enabling the local stormwater network to keep pace. Its growth-and future-oriented objectives (rather than seeking to solve a present-day flooding problem), and immediate infrastructural focus, are challenging the project team to ensure the project benefits can be realised over time. Show more…Stopbanks provide the wider area with fluvial flood protection from Te Awa Kairangi – the Hutt River, but the low-lying area behind the stopbanks is prone to stormwater flooding. Moreover, the existing stormwater infrastructure in the Opahu Stream catchment, behind the stopbanks, is already at capacity. Even accounting for the on-site storage required under HCC’s District Plan, the frequency and intensity of stormwater flooding is projected to worsen with future growth, and particularly as the effects of climate change and sea level rise continue to be realised. HCC has identified various preferred intensification areas and types of development within the catchment. The scale of predicted future flooding is too great a problem to overcome through reliance on hydraulic neutrality and minor network upgrades alone.
This project is currently at feasibility and optioneering stage, with potential solutions being assessed against: (i) the additional capacity they provide in the primary network; (ii) the level of reduction to flood hazard in the preferred growth areas; and (iii) affordability. Given the significant existing constraints, the upgrades will require pumped solutions to convey stormwater from the Opahu Stream to Te Awa Kairangi. However, early in the optioneering stage the project team explored options that sought to maximise the use of Water Sensitive Urban Design concepts such as: (i) utilising and enhancing existing overland flow paths, (ii) improving stream conveyance/daylighting, and (iii) detention storage on areas of existing green space.
In addition to the infrastructure improvements which are the focus of the WIG project, the work has brought into sharp focus a need for a broader approach to maximise project benefits in the face of uncertainty. Some lessons learnt and recommendations for wider implementation include identifying and preserving overland flow paths in the course of development; masterplanning and steering development into areas better able to be serviced by stormwater infrastructure, while implementing stricter hydraulic neutrality requirements outside of these areas; and identifying large publicly owned sites for on-site stormwater management.
This paper will provide a summary of the infrastructural solutions being considered for this brownfield urban intensification, and the wider actions that are likely to be required in order for predicted growth to be enabled without increasing flood risk to current and future residents. Show less…

Water NZ Stormwater Conference, 2024, Wellington

Whanganui Prison occupies a highly constrained site from which stormwater is discharged directly to the sensitive receiving environments of Lake Pauri, Lake Wiritoa, and surrounding wetlands. An application by Ara Poutama Aotearoa / Department of Corrections to renew the existing discharge consent was lodged in 2013. This provided an opportunity for Corrections to think differently about the way it manages stormwater, and about its own role as an environmental steward. The consent was granted in 2020 following extensive information gathering, concept development, consultation, and collaboration, in which cultural aspirations and the unique operational requirements of a prison came to shape the design process. Show more…SThis paper describes the evolution of stormwater treatment design at Whanganui Prison over the last ten years. It illustrates how the way in which the problem is defined, and the perspectives behind this, drives the design response and, ultimately, the nature of the outcomes.
Central to this journey was Corrections’ partnership with the Whanganui Prison Tangata Whenua Engagement Group (WPTWEG). This vital collaboration shifted the focus of stormwater treatment from simply meeting minimum regulatory requirements to ensuring that the health of the lakes was at the centre of all decisions. This saw the early treatment concept mature into a comprehensive water management philosophy that accounts for cultural values as well as regulatory targets and practical engineering considerations.
The initial treatment concept focussed on proprietary devices retrofitted into a severely hydraulically-constrained stormwater network that discharges to a sensitive but degraded coastal lake environment. The concept was developed without a thorough understanding of the environmental setting, the nature of the discharge quality, or an explicit statement of what the devices were expected to achieve. However, when elements of importance to local iwi were captured alongside the operational and security requirements of the prison, and site investigations improved understanding of contaminant sources, the design criteria widened to include cultural and environmental objectives.
Under the guidance of the WPTWEG, a hybrid design – currently under construction – was developed in which nature-based elements were adopted to reinstate some aspects of the natural water cycle that had been lost. Rainwater harvesting and a naturalised outfall are proposed to further contribute to this outcome.
Corrections’ journey has demonstrated that contemporary stormwater management is not a purely technical or engineering endeavour. When the principles of Te Mana o te Wai are allowed to inform stormwater management decisions, a range of positive outcomes beyond just regulatory compliance can accrue.
The Whanganui experience has led Ara Poutama Aotearoa / The Department of Corrections to change the way in which it implements water quality improvement at its facilities. Cultural input to design is now sought as a matter of course, including at facilities that do not face the same pressures on freshwater protection as Whanganui. Show less…

Water NZ Stormwater Conference, 2024, Wellington

In the realm of flood management, the pursuit of resilience remains elusive, hindered by a fundamental challenge: the absence of a shared understanding of what resilience entails and the benchmarks we aspire to achieve. Past flooding incidents in New Zealand and overseas serve as stark reminders of the repercussions of navigating preparedness, response, and recovery without a clear definition of resilience. Our cautionary tale is beginning to write itself. Show more…This paper will explore differing definitions to seek alignment, including Treasury’s discussion that “the concept of resilience is wider than natural disasters and covers the capacity of public, private and civic sectors to withstand disruption, absorb disturbance, act effectively in a crisis, adapt to changing conditions, including climate change, and grow over time”.
Judith Rodin’s influential work focuses on the triple nature of resilience—asset management with its associated risk frameworks, psychological resilience, and systems thinking—each integral to comprehending the multifaceted landscape of resilience within the flood context.
At its core, resilience transcends mere asset protection; it embodies a symbiotic relationship between infrastructure resilience and human adaptability. Rodin’s framework underscores the imperative of integrating asset management principles, risk management frameworks such as ISO 31000, with a profound understanding of human resilience—the ability to cope and recover from stressors inherent in natural hazard events. Lessons from the Christchurch earthquakes showed the importance of building social capital from grassroots, a fundamental factor for resilience.
Moreover, in a world governed by complex systems and associated interdependencies, the significance of systems thinking cannot be overstated. Flood management operates within a dynamic ecosystem of interconnected variables, necessitating a paradigm shift towards holistic, systems-based approaches to resilience-building. This paper explores how our definition of resilience must be flexible enough to stay relevant in an increasingly complex world, whilst staying pragmatic to be effectively applied in everyday use.
Indicators and metrics are paramount for understanding the efficacy of our strategies. However can resilience be measured, and how do we differentiate risk from resilience? Following defining resilience, these will be the focal questions for this paper.
Simply put, high resilience communities can be described as those where impacts are not felt as deeply, and recover rapidly to be stronger post-event, providing metrics such as depth of impact (absorption) and speed of recovery (adaptability). Beyond these, infrastructure metrics include robustness and redundancy. Exploring how these can be measured is critical to helping monitor and tailor resilience interventions accordingly.
As we navigate the complexities of defining resilience within the stormwater and flood sector, it becomes evident that resilience is not a static endpoint but a perpetual journey—a moving goalpost that adapts to evolving challenges and aspirations.
Ultimately, this paper advocates for a collective re-evaluation of our approach to resilience within flood management, emphasizing the need for a shared vocabulary and framework. By embracing a nuanced understanding of resilience—one rooted in systems thinking and human adaptability—we can embark on a transformative journey towards a more resilient future, where storms will continue to disrupt, yet communities recover stronger. Show less…

Water NZ Stormwater Conference, 2024, Wellington.

Source water risk management plans (SWRMPs) are comprehensive plans designed to help manage and protect the quality and quantity of drinking water at its source. The Water Services Act 2021 mandates the development and implementation of SWRMPs for all registered water suppliers in New Zealand. Show more…While limited guidance exists for SWRMP development, Tonkin & Taylor Ltd has worked with clients to provide a robust and scalable methodology across varied water supplies and multiple regions, including Auckland, Canterbury, Wellington, and the Hawkes Bay. This paper outlines our process and methodology, which includes identification of potential contaminant sources (hazards), catchment risk assessments (CRA) and the development of source-specific SWRMPs. An overview of several case studies is also presented to illustrate the process and outcomes. Show less…

Water New Zealand Annual Conference, 2023, Wellington

Finding the right funding to fix our massive infrastructure gap will be key to ensuring a sustainable water future. Show more…In the first of this two-part series, Brad explores alternative funding sources that could be used to help bridge the water infrastructure gap. Examples inlude our sovereign wealth funds such as our NZ Super Fund, ACC and KiwiSaver, which collectively represent $200 billion. Show less…

Water : official journal of Water New Zealand Issue 234 May/June 2024 p. 26-32

Cycline Gabrielle severly damaged a large portion of the Palmerston North to Gisborne line (PNGL). The damage included large embankment washout failures, blocked/damaged culverts, underslips/overslips, scour damage to tracks, loss/reduction of drainage, silt inundation and structural damage to bridges/tunnels. Show more…Tonkin & Taylor Ltd were engaged by KiwiRail to provide specific geotechnical field support during the initial ‘Make Safe’ works on the Napier to Wairoa section of the PNGL.
The premise of the ‘Make Safe’ works is to undertake works that reduce the likelihood of further damage and deterioration of the line under normal annual rainfall conditions and across the next two winters. This was considered to be a suitable timeframe to allow the ‘Make Safe’ requirements to still be satisfied based on the level of engineering being undertaken across the line. Importantly, the focus was not necessarily to reinstate the track for train movements but rather to allow , where possible, rail enabled plant to access sections of the line safely. Show less…

NZ Geomechanics News Issue 107 June 2024 p. 82-91

In this second article of a two-part series, Brad discusses market-based mechanisms such as incentives and disincentives, innovative impact finance and delivery models that could improve our infrastructure efficiency based on success abroad.

Water New Zealand Journal Issue 235 July/August 2024 p. 38-42

The Resource Management Act 1991 (RMA) protects wetland and river features through section 13. How these features are defined depends on which piece of legislation is relied upon, with slightly different definitions included in the RMA, the National Policy Statement for Freshwater Management 2020 (NPS FM) and Regional Plans. While many of these definitions are similar, small nuances can wreak havoc – both in what to call something and subsequently what the consenting implications are. Show more…Since the introduction of the NPS FM, defining these features has become a hot topic, mostly, in our opinion, because of the prohibited activity status applied to many activities affecting natural inland wetlands in the original version of the National Environmental Standards for Freshwater (NES F) (September 2020).
Consequently (and despite having been subject to protection in some form since 1991), delineation of wetlands and whether something was a stock-pugged river or a degraded wetland became a point of contention. ‘Is it a wetland’ has become as triggering to some as the concept of nuclear power (of note as it is one of the widely recognised prohibited activities in Aotearoa New Zealand).
One theme all these definitions have in common is an implied state of mutual exclusivity and stationarity – that if something is a river, it can’t be a wetland (and vice-versa) and that they will remain static through time. What these definitions, policies and rules fail to appreciate is that, in reality, rivers and wetlands are aquatic ecosystems that exist on a continuum of form and function.
From a scientific point of view, aquatic systems have significantly more nuanced characters, behaviours and values (e.g. types such as intermittent, perennial, wandering, braided, valley fill, marsh, swamp…). How these systems behave is driven not by a definition in a piece of legislation, but rather by the prevailing landscape and ecological controls. River and wetland systems may fluctuate between different forms and states depending on numerous climatic, hydraulic and landscape factors.
Policy aside, it is the science, form, and function of these aquatic systems that tells us what we need to do to maintain their ecological and morphological integrity, not the definition introduced by the government of the day. Understanding the character and behavior of these systems in their landscape context is essential to inform decision making, ensuring that water sensitive urban design and nature-based solutions are implemented in a way that respects the processes and functions of these systems, and ensures a measure of success.
Within this paper we describe the science behind the characterisation of these aquatic systems, reflecting on their ecological and morphological function, and what this means for designing nature-based stormwater and flood management solutions that work with the landscape and ecological processes and controls. We explore the implications of the statutory framework and what this means in practice in respect of stormwater management. Lastly, we highlight how wetlands and streams provide an opportunity to integrate ecological, amenity, stormwater and flood management outcomes, while enabling future development. Show less…

NZ Stormwater Conference 2024

Following the September 4th 2010 Mw7.1 and February 22nd 2011 Mw6.2 Earthquakes in Canterbury, New Zealand, liquefaction-induced lateral spreading was observed along the Avon and Heathcote rivers. Detailed field measurements following the events provide a benchmark to evaluate the efficacy of lateral spreading prediction models under real world conditions. Show more…This paper presents the development of 2D effective stress finite difference models in FLAC2D of two transects along the rivers, and compares numerical results to observed displacements for the two major seismic events. The liquefiable soil was modelled with the PM4Sand model, and an automated calibration procedure was developed to determine the model inputs based on CPT results. The displacements during the earthquake excitation and post-shaking during pore pressure dissipation were quantified. Overall the simulations show reasonably consistent ground displacements at the channel free-face for both events and both transects, though recognising significant uncertainties in the simulations and field measurements. The results of the numerical simulations highlight the importance of both geometric (notably the channel width) and soil properties as key factors that influence lateral spreading displacements. The simulation results provide some confidence that detailed finite difference models can reasonably capture the expected level of ground movement during a lateral spreading event. Show less…

8th International Conference on Earthquake Geotechnical Engineering (ICEGE), 2024, Osaka

Variable or unknown ground conditions are a major contributor to uncertainty in a geotechnical project and arise as a result of the geomorphological processes that shaped the land. The planning of a ground investigation programme can be thought of as a sampling optimisation problem, seeking to balance precision, accuracy, and costs through selection of an investigation density that achieves a degree of residual uncertainty that is sufficient for the intended purpose. Show more…This study draws on detailed observations of the patterns of liquefaction-induced land damage mapped across Christchurch City during the 2010 – 2011 Canterbury Earthquakes, and uses the variability in the observed damage as a proxy for variability in the underlying shallow ground conditions. The correlation between investigation density and residual uncertainty in ground conditions is examined using a Monte Carlo approach, varying size of the study area and the investigation spacing. The hypothesis is that as the total area investigated increases, the spacing between investigations can be increased while still achieving the same degree of residual uncertainty in the ground conditions. The results of this study were used to set the minimum investigation density recommendations for land use planning and subdivision in the New Zealand guidance on geotechnical investigations for earthquake engineering. Show less…

8th International Conference on Earthquake Geotechnical Engineering (ICEGE), 2024, Osaka

Geopier Rammed Aggregate Piers® (RAPs) are a ground improvement technology that creates a densified column of aggregate surrounded by a stiffened matrix soil. This paper describes the design and construction of RAPs at Te Kaha, a $683-million Multi-Use Arena under construction in Christchurch, New Zealand. CLL Projects are constructing 8331 RAPs including 1092 tension RAPs to depths between 5.5 to 12m to provide a ground improvement system supporting the arena. Show more…Design considerations include estimation of soil densification in a wide range of soil conditions (sand, silty sand, silt and gravel), analysis of liquefaction triggering before and after ground improvement, numerical analysis to predict the bearing capacity and settlement of the foundations, and prediction of uplift capacity for tension RAPs. The design predictions and the actual results from verification testing are compared, including pre- and post- improvement CPTs and tension load tests. At Te Kaha the RAP installation resulted in a significant increase in penetration resistance of sandy soils between the RAP elements. The CPT results consistently underestimated the fines content of the soil. The tension load test results showed that the uplift capacity is dependent on the soil conditions at the tip of the tension RAP. If adequate confinement cannot be achieved at the base the tension RAP ‘unravels’ and the capacity is much lower than typical design methods would predict. Show less…

8th International Conference on Earthquake Geotechnical Engineering (ICEGE), 2024, Osaka

Many state-of-practice methods for predicting liquefaction manifestation, such as the Liquefaction Severity Number (LSN), are known to suffer from significant overprediction in regions characterised by complex soil profiles comprising interbedded sands, silts, and clays. These methods typically analyse discrete soil layers, and sum results layer-by-layer, which does not properly account for system effectsa. Show more…We demonstrate that machine learning techniques can be used to identify cases where simplified layer-bylayer liquefaction vulnerability indices give overestimated surficial liquefaction manifestation. Specifically, we have developed a convolutional neural network model. With the aim of better accounting for system effects, the model considers the full length of a CPT profile simultaneously to capture system effects of soil profiles such as interbedding, rather than processing and then aggregating information in discrete layers.
A database of over 47,000 case histories was used for training and model evaluation, spanning ten New Zealand earthquakes. Special techniques were used to address sampling bias and class imbalance. Finally, an adjustment procedure is proposed, which uses the machine learning model to improve the accuracy of LSN for specific site categories, resulting in significant accuracy improvements.
This research has been funded by Toka Tū Ake EQC to advance liquefaction science, and support a range of applications in New Zealand, including local government planning, public engagement and education, and loss modelling. Show less…

NZSEE Conference 2024 Wellington

The Seismic Assessment of Existing Buildings Guideline, Section C4: Geotechnical Considerations, was first published in July 2017. That first issue included several aspects of assessment which had not been previously applied, including allowance for the non-linear behaviour of soils (geotechnical step change). Show more…The subsequent 6 years have provided the opportunity to apply the geotechnical step change methodology to various building assessments and to obtain feedback. This has highlighted the need to clarify and further develop the geotechnical step change methodology. A project is now in progress to update C4. This paper reports on the likely conclusions of the update project. Those conclusions are yet to be recorded in an update of C4. The update to C4 is to clarify the purpose of the step change factor of 2. The purpose of that factor is to provide an assessed %NBS which represents a buffer from loss of gravity support of the structure. A method has been developed to vary the step change factor between 1 and 2 depending on the ability of the structure to maintain gravity support and the life safety consequences of loss thereof. The step change methodology has been extended to cover earthquake induced ground displacements which are not covered by the current C4. Guidance is to be provided on the level of conservatism to be applied in evaluating geotechnical parameters and allowance for uncertainty. It is also proposed to enhance the guidance on desk top studies and other aspects of geotechnical assessment. Show less…

NZSEE Conference 2024 Wellington

Liquefaction is a major concern regarding earthquake damage to infrastructure. Recent earthquakes in New Zealand and resulting liquefaction caused significant damage to buried pipeline systems. Following the 4 September 2010 Mw=7.1 Darfield earthquake, five earthquakes (22 February 2011, Mw=6.2, 13 June 2011, Mw=5.3 at 1 p.m. and Mw=6.0 at 2:20 p.m. and 23 December 2011, Mw=5.8 at 1:58 p.m. and Mw=5.9 at 3:18 p.m.) and thousands of aftershocks have been recorded in the area of Christchurch, NZ. Show more…These earthquakes termed the Canterbury Earthquake Sequence (CES) are unprecedented in terms of repeated earthquake shocks with substantial levels of ground motion affecting a major city with modern infrastructure. This study focuses on the effects of 22 February 2011 Christchurch earthquake induced liquefaction on buried pipelines. Correlations were developed between pipe damage, expressed as repairs/km, and a recently developed parameter called liquefaction severity number (LSN). Cone Penetration Test (CPT) based liquefaction triggering procedures were used to calculate LSN values. Studies by Tonkin and Taylor [1,2] and van Ballegooy et al. [3, 4, 5, 6] have shown that LSN provides a good correlation with land and esidential house foundation damage observations recorded in Canterbury. According to results obtained in this study for buried pipelines, LSN has reasonably good correlation with asbestos cement (AC), cast iron (CI) and polyvinyl chloride (PVC) pipeline damage. Show less…

16th World Conference on Earthquake Engineering, Santiago, 2017

The Manukau Harbour is located on the West Coast of New Zealand’s North Island in the Auckland Region. It has been identified as a potential greenfield port location to replace the cargo operation of the Ports of Auckland, which is located on the East Coast within the Waitematā Harbour. Exposure to large and persistent swell from the Southern Ocean and Tasman Sea, high tidal range, fast tidal currents, and a very large and shallow ebb tide delta at the Manukau Harbour entrance present several challenges to opening and maintaining a navigation channel in this location. Show more…To test the feasibility of the proposal, an in-depth understanding of the ebb tide delta dynamics and sediment transport mechanisms was needed. Using data collected from the field, satellite imagery, and a combined analytical and numerical modelling approach we have estimated capital dredge volumes and importantly rates of sediment infill to the channel at differing temporal scales from individual storms to annual rates and decadal evolution. It has been shown that the ebb tide delta has a rotational morphology over an approximate 20 to 25-year cycle which can affect the capital dredge volumes by up to 10M m3 depending on the position of the channel and banks within the cycle. A net movement of sediment from the south to the north through longshore processes have been shown to contribute 1.5M m3 / year to the system, however, it is the sediment recycled around the ebb tide delta through wave and tidal flows that look to govern the maintenance dredge requirement and therefore the viability of the harbour serving as a port location. Work is still progressing to finalise the technical feasibility of this. Show less…

35th Pianc World Congress, Cape Town, 2024

Many state-of-practice methods for predicting liquefaction manifestation, such as the Liquefaction Severity Number (LSN), are known to suffer from significant overprediction in regions characterised by complex soil profiles comprising interbedded sands, silts, and clays. These methods typically analyse discrete soil layers, and sum results layer-by-layer, which does not properly account for system effectsa. Show more…We demonstrate that machine learning techniques can be used to identify cases where simplified layer-bylayer liquefaction vulnerability indices give overestimated surficial liquefaction manifestation. Specifically, we have developed a convolutional neural network model. With the aim of better accounting for system effects, the model considers the full length of a CPT profile simultaneously to capture system effects of soil profiles such as interbedding, rather than processing and then aggregating information in discrete layers.
A database of over 47,000 case histories was used for training and model evaluation, spanning ten New Zealand earthquakes. Special techniques were used to address sampling bias and class imbalance. Finally, an adjustment procedure is proposed, which uses the machine learning model to improve the accuracy of LSN for specific site categories, resulting in significant accuracy improvements.
This research has been funded by Toka Tū Ake EQC to advance liquefaction science, and support a range of applications in New Zealand, including local government planning, public engagement and education, and loss modelling. Show less…

NZSEE 2025 Annual Conference

Over the past 40 years, the advantages of utilising geosynthetic barriers versus traditional earthen barrier materials have been well documented: greater project economy, extended service lives, enhanced environmental protection, greater site safety, etc. Show more…Achievements such as conserving water resources and enabling beneficial site reuse have even given geosynthetic engineering a level of social importance. As such, the use of geosynthetic barriers has increasingly been required by government regulators around the world. This is true in modern waste management landfill design. However, there are still regions and applications in which the use of these barrier technologies should be more widely adopted. This paper highlights an overview of applications where geosynthetic barriers are used, and where regulation or recommendations are available, and it describes other emerging applications where geosynthetic barriers are starting to be used. Show less…

12th International Conference on Geosynthetics, 2023, Roma, Italy (12ICG)

As our understanding of natural hazards and climate risk improves, how do we enable individual decision makers to be best informed? Our paper will focus on the communication of risk information, and how the psychology of individuals controls the success. Through looking at existing research to understand the differing ways we perceive and communicate risk, our paper highlights the requirement to ensure more effective public risk information and enable effective decision making within our communities. We focus on two key aspects that inform an individual’s response to risk, the cognitive and emotional dimensions, which refer to how much people know and understand about risk, and how someone feels about risk. Our paper will capture the psychological responses when informed about risk and look to establish principles for risk communication for differing individuals and communities. Concepts such as ‘probability neglect’ further impact risk information and decision making of the public, demonstrating the need for our industry to better communicate risk to enable effective decision making.

NZSEE 2025 Annual Conference

Peat/organic soils are characterised by low undrained shear strength, high compressibility and are susceptible to significant ground settlements, creating challenges for engineers and developers. Since construction in 2015, a housing subdivision in Auckland, has been impacted by ground settlement and distortions to foundations and superstructures. The pattern of distortions are indicative of differential settlements resulting from mixed foundation types, being part-piled and part-ground bearing over soft compressible peat.

Show more… Mixed foundations are sometimes used where dwellings are built adjacent to or over services, with piles being used to transfer loads to below the level of the services. A number of dwellings within the subdivision, which were constructed with mixed foundation types, have required regular intervention works to maintain dwelling serviceability. Foundation distortion correction works were trialled on one damaged property with the purpose of proving the adopted remedial methodology and substantiating future foundation performance. The remedial works involved disconnecting piles and implementing staged and cycled surcharge loading with water tanks on the foundation slab. This method was used to verify the performance of the slab and to measure the dwelling response to the change of support. Water tanks were positioned near the locations of the most significant distortions and subjected to loading cycles over several weeks while monitoring changes in floor distortion. The trial results successfully demonstrated compliance of the corrective works with the performance expectations of the New Zealand Building Code. This paper presents the challenges and solutions implemented on the trial property during the foundation distortion correction works.Show less…

15YGPC 15th ANZ Young Geotechnical Professionals Conference Adelaide 2024

The highway embankments and railway tracks constructed on soft soils are particularly vulnerable to increased cyclic stress, which can cause uncontrolled deformation, undrained failure, migration of fines and associated mud pumping. This paper presents a significant contribution to the field by reporting the effectiveness of geosynthetics in mitigating fluidization potential of soft soil. Laboratory experiments were undertaken using a dynamic filtration apparatus (DFA) and a cyclic triaxial apparatus (CTA) to analyse the cyclic response of soft subgrade under impeded drainage conditions.

Show more…  This study critically evaluates the role of geosynthetics in controlling the occurrence of soil fluidization by assessing the build-up of excess pore water pressure (EPWP), the variation in particle size distribution (PSD) and the moisture content (MC). The outcomes of this study reveal that prefabricated vertical drains (PVDs) are effective in alleviating the EPWP developed in middle or deeper soil layers, whereas geocomposites can facilitate surficial drainage. This paper emphasizes the practical implications and the significance of improved drainage and swift dissipation of EPWP on low-lying saturated soils for enhanced track design. Show less…

15YGPC 15th ANZ Young Geotechnical Professionals Conference Adelaide 2024

Following the damaging climate related rainfall events in Aotearoa in early 2023, regulatory controls that come into play during and after state of emergencies resulted in legally enforced, restricted access to more than 2000 private houses (Television New Zealand 1 News, 2023). Many of these restrictions were placed on private houses in the form of Red Placards or Dangerous Building Notices as a result of landslides that either damaged or had a perceived risk of damaging the residential houses which could result in deaths or serious injuries to the occupants.

Show more…  The purpose of these restrictions, which are applied under the Civil Defence and Emergency Management (CDEM) Act 2002 and 2016 Amendments or the Building Act 2004, is to ensure the safety of people living in the affected houses and/or the public and/or adjacent buildings. The impact on the occupants of the forced evacuation is, however, traumatic, which raises a number of important issues around both the process and the outcome. This paper sets out the issues around restricting access to houses when property damaging landslides occur or are considered likely to occur and presents some suggestions as to how these situations could be better managed in future events. This paper draws from the authors’ experiences and observations in responding to landslide events across New Zealand, assessing resultant damage, and managing the removal of red placards from residential dwellings. Show less…

15YGPC 15th ANZ Young Geotechnical Professionals Conference Adelaide 2024

The Te Ara Tupua Ngā Ūranga ki Pito-One Project comprises a 4.5 km shared (pedestrian/cycling) pathway between Ngā Ūranga and Pito-One in Te Whanganui-a-Tara, Wellington with dual outcomes of rail/road corridor resilience improvement and mode shift. The project presented the challenging design requirements of managing the safety of shared path users through a coastal edge design that is controlled by tight geometric (elevation and toe position) constraints, a range of unique edge protection structures, and a bimodal wave climate. This challenge was addressed through site and design specific physical and numerical modelling, data driven overtopping analysis and a forecast model development for safety management during operation. Show more…The range of edge protection structures proposed include XblocPlus armour unit revetments, rock armour revetments with mid-tide berms of varying width, and vertical concrete seawalls with return crest walls. The present empirical guidance on overtopping performance of these structure configurations is not widely developed in literature, at least with sufficient reliability to inform design on this project. An additional complicating factor was a bimodal wave climate, the swell component of which was discovered to have a significant effect on anticipated overtopping flows.
As such, structure- and site-specific physical modelling was undertaken to inform the overtopping analysis at the UNSW Water Research Laboratory. The results of the physical model tests were used to develop site-specific, data-driven formula based on relationships between relative overtopping and relative freeboard, as presented in the EurOtop manual. These relationships were used to understand overtopping potential along the project site both now and in the future through development of a 30-year overtopping timeseries. In parallel, a two-layer phase resolving, non-hydrostatic XBeach solver was calibrated to match the wave transformation of the bi-modal wave climate and physical model overtopping results allowing wave conditions and resultant overtopping flows to be extracted anywhere along the project site.
This was used to inform design crest levels future adaptation timeframes and options, and to develop an overtopping forecast model to inform path warnings and closure during operation. The results of this analysis highlighted the importance of understanding site-specific influences on overtopping flows, not all of which are able to be fully understood through adoption of standard empirical overtopping formula.Show less…

The Te Ara Tupua Ngā Ūranga ki Pito-One Project comprises a 4.5 km shared (pedestrian/cycling) pathway between Ngā Ūranga and Pito-One in Te Whanganui-a-Tara, Wellington with dual outcomes of rail/road …

Modern-day coastal engineering faces two key challenges: firstly, providing adequate protection under anthropogenic increases in sea level, and secondly, reducing environmentally detrimental engineering practices that are further driving changes to the climate. With this, nature-based solutions that minimise detrimental environmental effects whilst providing sufficient protection are increasing in their uptake. At present, the application of these nature-based engineering strategies is restricted to low-energy wave environments with minimal spatial constraints. Hybridisation (combined use of nature-based and traditional hard engineering strategies) enables the use of these nature-based principles in higher-energy and urban environments. This paper explores the use of hybridisation with coastal vegetation, by exploring the ability of vegetation to attenuate wave overtopping flow on the crest of coastal defence structures. Show more…Physical modelling experiments were conducted in the University of Auckland’s wave flume with a small-scale sloped seawall retrofitted with model vegetation on the crest of the seawall. This preliminary testing found that the model vegetation reduced mean overtopping discharges by 60-80% when evaluated against their nonvegetated counterpart. Numerical model testing was conducted by calibrating to and expanding on the physical model analysis. This was achieved by implementing a one-dimensional non-hydrostatic XBeach model. Numerical model testing used a multiple linear regression analysis to test the sensitivity of the wave overtopping response to various vegetation parameters. From this, the reduction in mean overtopping flow due to the incorporation of vegetation was found to be most strongly correlated to vegetation width, stem density and stem diameter, with increases in any of these parameters leading to substantial decreases in mean overtopping flow.
Both the physical and numerical model testing were limited by their use of idealised structure and vegetation parameters. However, despite these limitations, this study provides a framework for future testing that should seek to further solidify the wave overtopping performance of this hybrid strategy.Show less…

Modern-day coastal engineering faces two key challenges: firstly, providing adequate protection under anthropogenic increases in sea level, and secondly, reducing environmentally detrimental engineering practices that are further driving changes to …

The Te Ara Tupua Ngā Ūranga ki Pito-One (Ngauranga to Petone) Project comprises a 4.5 km shared (pedestrian/cycling) pathway between Ngā Ūranga (Ngauranga) and Pito-One (Petone) in Te Whanganui-a-Tara, Wellington. The Project will be located on the seaward side of the State Highway 2 and the rail corridor and will provide safe walking and cycling infrastructure as well as enhancing the resilience of the transport corridor. The Project involves temporary and permanent works in and adjacent to the coastal marine area, including multiple rock and concrete armour revetments, ūranga (landings), seawalls, offshore habitats and culvert extensions, and will result in over 5 Ha of permanent marine habitat loss. Show more…To avoid, minimise and compensate for the impact on the marine environment, a number of innovative ecological enhancements have been incorporated into the Project design. Two rock armour offshore habitats will provide undisturbed roosting habitat for coastal avifauna. 235 little blue penguin nesting boxes will be incorporated within the revetment and Ūranga. Gravel beaches will be nourished to provide 10-25 years of resilience to future sea level rise. Over 240 ECOncrete® tide pools will be integrated in clusters within the intertidal bench of the rock revetments and offshore habitats, providing habitat and water retaining features for marine life as well as foraging habitat for coastal birds. Finally, some 1850 XblocPlus® units, that form part of the revetment, will be ecologically enhanced using increased surface complexity. The integration of these ecological enhancements within the design was developed in collaboration between ecologists, landscape architects, engineers and mana whenua and drew inspiration from the existing ecology, coupled with cultural narrative.
This project will be the first application of many of these ecological enhancement features in New Zealand. The features will improve the ecological value of the coastal pathway and provide a more resilient marine ecosystem within Te Whanganui-a-Tara (Wellington Harbour). The project provides a case study for how ecological features can be successfully implemented into coastal infrastructure and an opportunity to measure the ecological performance of these features in a New Zealand context, so that future installations can more accurately predict the ecological gains likely to be achieved when balancing against unavoidable biodiversity losse.Show less…

The Te Ara Tupua Ngā Ūranga ki Pito-One (Ngauranga to Petone) Project comprises a 4.5 km shared (pedestrian/cycling) pathway between Ngā Ūranga (Ngauranga) and Pito-One (Petone) in Te Whanganui-a-Tara, Wellington. …

Delivery of major transport infrastructure projects at the coast requires a careful balance between numerous project drivers, including cost, program, environmental, regulatory and stakeholder considerations. These often-conflicting drivers have the potential to disrupt a project, if not managed carefully, leading to delays, cost over-run, conflict and sub-optimal outcomes. Show more…The Ngā Ūranga ki Pito-One Project comprises a 4.5 km shared pathway between Ngā Ūranga and Pito-One in Te Whanganui-a-Tara, Wellington. The Project will be located on the seaward side of the state highway and the rail corridor and will provide safe walking and cycling infrastructure and enhance the transport corridor’s resilience. The Project includes all of the above-mentioned drivers including partner and stakeholder expectations, very tight environmental and ecological constraints, budget expectations, a difficult design environment adjacent to a major fault-line and exposed to southerly wind and wave climates, limited local rock supply and construction workspace.
Delivery of the Project from concept design through to construction is being delivered by the Te Ara Tupua Alliance, comprised of owners Waka Kotahi NZ Transport Agency, working in partnership with mana whenua (Indigenous partners), contractors HEB and Downer and designers Tonkin + Taylor. To address the many project challenges, an innovative approach to design was implemented during initial concept phases. This included an agile design philosophy with sprint design and review cycles enabling fast paced integration of design, construction, environmental and cultural objectives. This approach included several innovations in the final design, most notably the adoption of modified XblocPlus® concrete armour units for primary armouring. These single-layer, pattern-placed units are to be used for the first time in Australasia and have resulted in significant cost and programme savings to the Project, but have also included bespoke modifications to achieve improved aesthetic, ecological and cultural outcomes.Show less…

Delivery of major transport infrastructure projects at the coast requires a careful balance between numerous project drivers, including cost, program, environmental, regulatory and stakeholder considerations. These often-conflicting drivers have the …

The 10 km stretch of foreshore between two of New Zealand’s largest cities Wellington and Hutt City is a crucial infrastructure corridor combining cycleway, road and rail, as well as sub-surface utilities. Recent storm events have caused significant damage to, and overtopping of, the current rock revetment structure resulting in the rail line being undermined and closed for extended periods. Future proofing the foreshore is integral for the longevity and function of this corridor and the Te Ara Tupua Alliance have been tasked with redeveloping it. Show more…UNSW Water Research Laboratory (WRL) undertook a large physical modelling program (over a 100 individual tests) to assist optioneering for a range of coastal protection designs. 2D flume testing was conducted to assess both the stability and overtopping performance of rock and concrete armoured (modified XblocPlus) revetments and vertical walls equipped with sloped crown walls.
All tests were conducted using irregular wave time series derived from several spectral conditions. Analysis of wave buoy records showed that both wind waves and swell entering the harbour could be expected to impact the project area. As such, sensitivity testing for overtopping was conducted using custom-generated bimodal conditions with different wind/swell ratios. Physical model testing results showed that overtopping volumes were highly sensitive to the long period wave component within the bimodal spectrum.
The findings of this extensive physical modelling program highlight the limitations of standard empirical methods for assessing overtopping under bimodal wave climates, the importance of extending beyond conventional unimodal wave climates when designing coastal structures, and the importance of using on-site wave data to best model potential overtopping volumes and safely optimize designs.Show less…

The 10 km stretch of foreshore between two of New Zealand’s largest cities Wellington and Hutt City is a crucial infrastructure corridor combining cycleway, road and rail, as well as …

Urban beaches in semi-sheltered harbor environments are highly valued public spaces that require detailed understanding of coastal dynamics for appropriate management. Understanding the dynamics these environments is challenging due historic management interventions such as renourishment and hard infrastructure. As a result, commonly applied modelling and hazard assessment methods are not necessarily appropriate for semi-sheltered often fetch-limited urban beaches, without site-specific calibration. Show more…This paper focuses on the calibration and potential applications of three different numerical models to better understand coastal processes on the Sandringham Beach in Port Phillip Bay, Victoria. First, the shoreline position model ShorelineS was applied to understand beach rotation, seasonal trends in shoreline movement and long-term rates of shoreline change. Model calibration was informed by monthly monitoring data, including drone-based topographic surveys and wave buoy data. Next, the storm response model XBeach was calibrated using observed wave events and measured changes in the coastal profile. The models were collectively used to give new insight on the beach dynamics at short, medium, and long timescales.
Outputs of the XBeach and ShorelineS modelling were then used to inform variables for projecting shoreface translation to sea level rise using the ShoreTrans model, where the sensitivity to different trajectories of barrier rollover and translation were assessed. Isolating the cross-shore adjustment in ShoreTrans allowed the idealised beach topography to be reconstructed for a sea level rise scenario representing the year 2100. Balance of alongshore sediment flux was achieved by passing volume from profile to profile according to the net sediment balance in the system, informed by long-term rates.
The paper introduces a conceptual a multi-model workflow that is proposed for exploring present day and future scenarios, with application for hazard management and adaptation design.Show less…

Urban beaches in semi-sheltered harbor environments are highly valued public spaces that require detailed understanding of coastal dynamics for appropriate management. Understanding the dynamics these environments is challenging due historic …

The Ōpōtiki Harbour Development (“OHD”) is the first river port to be constructed in over 100 years in New Zealand. Te Whakatōhea have developed an offshore mussel farm and onshore processing factory and need a navigable harbour entrance to connect these resources. Show more…The OHD scheme comprises twin 400 m long training walls to fix a dynamic river mouth, around 700,000 m3 of dredging in intertidal and subtidal areas and approximately 20 hectares of constructed fore and mid dune to close the existing river mouth. The OHD is located in a sensitive estuary environment fed by two major rivers. The estuary contains numerous threatened fauna, is subject to constant morphological change and provides an important recreational resource for the Community.
To ensure opportunities for innovation in design and construction were optimised, the resource consents granted for the OHD deferred most environmental impact avoidance, remediation, or mitigation to a suite of Environmental Management Plans (“EMP”) to be prepared in parallel with the Detailed Design of the project. These EMP manage a range of impacts, such as sediment contamination, saline wedge connection to inanga spawning habitat, disturbance to dotterel breeding areas, water quality (TSS and clarity), native fish migration, training wall related downdrift erosion, and sediment deposition within riverine riparian vegetation and seagrass assemblages.
Timeframes to design and construct the OHD were very tight with many inter-dependencies in the project plan. The Technical Liaison Group (“TLG”) comprising representatives of tangata whenua and a range of regulatory agencies were required to contribute to the development of the EMP.
To ensure the OHD project was delivered within a compressed programme, meticulous planning and execution of the environmental management regime was required. To this end, partnership was key. The OHD design and construction project team worked with the ocean, rivers, nature, tangata whenua, regulators, the Community, and other professionals.Show less…

The Ōpōtiki Harbour Development (“OHD”) is the first river port to be constructed in over 100 years in New Zealand. Te Whakatōhea have developed an offshore mussel farm and onshore …

The use of single layer, concrete armour units for coastal edge protection in place of rock is becoming increasingly common. Revetments constructed from these units can provide benefits of a reduced footprint, reduced material usage and transport costs as suitable rock becomes increasingly difficult to source, and reduced construction timeframese. Show more…XblocPlus® units have been adopted as the primary armouring for a major shared-path infrastructure project within Te Whanganui-a-Tara, Wellington Harbour. The Ngā Ūranga ki Pito-One Project comprises a 4.5 km shared (pedestrian/cycling) pathway between Ngā Ūranga and Pito-One. The XblocPlus® units are patternplaced interlocking armour concrete units that remain stable at steep slope angles while providing high coastal performance. However, these units have had limited application in seismically active regions. Therefore, the behaviour of the individual armour units and overall revetment during, and following seismic activity was assessed in detail to assess performance and enable development of a post-seismic inspection and repair strategy.
The response of a revetment to seismic shaking, particularly the interlocking of the individual XblocPlus® units and interaction with the ground profile below is complex and could not be determined using a single method or model. Therefore, a suite of complementary models was used to assess the behaviour of individual components and combined performance of the revetment asset under the design earthquake events. This paper describes the various physical and numerical models used to determine performance and to inform the design and repair strategy of XblocPlus® revetment.
The physics-based model Unreal Engine was calibrated against uni-directional testing on a physical shake table and run for 3D design earthquake timeseries to assess how the individual XblocPlus® units reacted to shaking. Limit equilibrium and time history finite element modelling were carried out to understand how the ground profile supporting the revetment might perform. These results were then used in the 3D physics-based model in Blender to determine the unit response to slope deformation. The XblocPlus® response to shaking and slope deformation was combined to create a post-seismic revetment condition, which in turn was tested by physical modelling in a wave flume against to assess hydraulic stability performance under moderate storm events (i.e., before a repair could be enacted). Following this, an inspection and repair strategy was developed.Show less…

The use of single layer, concrete armour units for coastal edge protection in place of rock is becoming increasingly common. Revetments constructed from these units can provide benefits of a …

Wave overtopping occurs as waves pass over the coastal edge and flow onto the land behind. This can result in a hazard to vehicles and pedestrians and flooding or damage to the built environment. To date, predictive formulae for overtopping have been primarily developed in a laboratory setting. Comparatively few studies involve the field measurement of overtopping because environmental conditions such as wind and water levels have a large influence on the overtopping rate (amongst many other factors), and the measurement of overtopping discharge is practically difficult due to enormous spatial and temporal variation in overtopping volumes. Show more…This paper discusses key challenges for local government coastal managers in New Zealand relating to overtopping hazard, highlighting a need for pragmatic guidance on monitoring, application within an adaptive management, and assessment of Relative Sea Level Rise (RSLR) effects on future hazard.
Two methods to measure wave overtopping in the field were investigated in this study; using either catch devices that measure volume, or camera monitoring. This paper shows, by considering a site along Tamaki Drive in Auckland, how monitoring and measurements of overtopping is important as part of the Ministry for the Environment (MfE) recommended Dynamic Adaptive Policy Pathway (DAPP) approach to managing associated hazards.
Finally, this study shows how future overtopping hazards associated with RSLR can be assessed by remodelling incremental rises applied to historic water level records. It is found that even small amounts of RSLR can dramatically increase the exposure of coastal communities to overtopping hazards.Show less…

Wave overtopping occurs as waves pass over the coastal edge and flow onto the land behind. This can result in a hazard to vehicles and pedestrians and flooding or damage …

The Ōpōtiki Harbour Development involves stabilising the entrance of the Waioeka River to allow reliable and safe access for maritime activity. Te Ara Moana a Toi (“A path to the sea”) is the first major river training works to be constructed in Aotearoa, New Zealand in over 100 years. The project involves constructing twin 400m long training wall breakwaters, dredging a 120m wide navigable channel into the Harbour, closing the natural river mouth, and forming a new dune habitat. Show more…Construction of the Ōpōtiki Harbour Development Project commenced in late 2020 by HEB Construction. The opening of the new harbour entrance is expected to be completed in late 2023/early 2024.
Construction at the end of a dynamic sand spit within the coastal zone is inherently uncertain with dynamic morphological processes and testing environmental conditions. As expected with a project of this scale, the coastal environment has provided many challenges and opportunities for designers and constructors alike during the construction stage. This paper covers significant construction milestones, environmental monitoring data, challenges, and innovations undertaken during construction. These include construction observation techniques, environmental monitoring data, and innovations developed to successfully undertake construction of the new harbour opening while being 300m offshore within the surf zone. These challenges and innovations include the ground improvement methods undertaken, withstanding and adapting to extreme wave conditions during construction, dredging techniques, and the philosophy behind the new channel opening and subsequent existing river mouth closure expected to occur in mid-2023.Show less…

The Ōpōtiki Harbour Development involves stabilising the entrance of the Waioeka River to allow reliable and safe access for maritime activity. Te Ara Moana a Toi (“A path to the …

Karangahape Road Station will be a new underground station on the Contract C3 of City Rail Link project in Auckland. The C3 comprises of 3.5 km twin-tunnel underground rail underneath Auckland’s city centre, two new underground stations at Aotea and Karangahape and expanded station at Mount Eden. The Karangahape Road Station is a 30 M-deep mined binocular underground station, with two shafts, platforms, lifts, escalators, rooms housing station and tunnel services equipmewnt, and an entrance at Merciry Lane and Beresford Square. Show more…This paper presents the story of the future proofing through project development of the station design, starting as a six-car station with a single entrance in reference design. The station will be built to accommodate nine-car trains. One of the key decisive facors being unprecendented increase in rail patronage in Auckland. Longer platform tunnels extended the tunnel mining to zones of shallow overburden and demands for tunnel ventilation brought challenges for ground support of large span platform tunnels at junctions with ventilation adits.Show less…

Karangahape Road Station will be a new underground station on the Contract C3 of City Rail Link project in Auckland. The C3 comprises of 3.5 km twin-tunnel underground rail underneath …

Claystone deposits are commonly intercepted in road slope cuttings, for example in Southern Queensland and thus the understanding of the shear behaviour of these deposits is important for geotechnical engineers for design, construction, and maintenance works. These sedimentary deposits are often weakly bonded, and the engineering behaviour is akin to heavilyoverconsolidated plastic clays. Show more…Apart from difficulties in sampling these deposits, interpretation of shear behaviour in triaxial tests is often challenging. The paper presents the results of a triaxial investigation and discusses some of the challenges involved in the conduct and interpretation of the results. Further, the pitfalls of directly using the laboratory shear results at the field scale are highlighted, drawing attention to the potential for progressive and delayed failures that are observed in the field. Some requirements for constitutive modelling for numerical analysis are also emphasized.Show less…

Claystone deposits are commonly intercepted in road slope cuttings, for example in Southern Queensland and thus the understanding of the shear behaviour of these deposits is important for geotechnical engineers …

The New Zealand Building Code (like many others) is a performance-based standard; however, the application of performance-based design is rare in practice. Typical design practice considers the capacity of individual elements in the building and does not allow for the full load-displacement response of the building system. Show more…This paper presents a case study where a performance-based design approach was used for the design of a new building on an existing foundation system and how it was able to illustrate compliance with the New Zealand Building code. The case study found that a capacity-based design approach was likely an impractical way to illustrate compliance with the Building Code. Given the significant negative project impacts including programme delays, environmental impacts and cost increases associated with adopting a new foundation system, a performance-based assessment was completed. With strong interaction between the geotechnical and structural engineers, a non-linear vertical pile spring analysis was undertaken, allowing the design team to demonstrate that the existing foundation system complied with the building code, avoiding the significant negative project impacts.Show less…

The New Zealand Building Code (like many others) is a performance-based standard; however, the application of performance-based design is rare in practice. Typical design practice considers the capacity of individual …

Geopier Rammed Aggregate Piers® (RAPs) are a ground improvement technology that creates a densified column of aggregate surrounded by a stiffened matrix soil. This paper describes the design and construction of RAPs at Te Kaha, a $683- million Multi-Use Arena under construction in Christchurch, New Zealand. Show more…CLL Projects are constructing 8331 RAPs including 1092 tension RAPs to depths between 5.5 to 12m to provide a ground improvement system supporting the arena. Design considerations include estimation of soil densification in a wide range of soil conditions (sand, silty sand, silt and gravel), analysis of liquefaction triggering before and after ground improvement, numerical analysis to predict the bearing capacity and settlement of the foundations, and prediction of uplift capacity for tension RAPs. The design predictions and the actual results from verification testing are compared, including pre- and post- improvement CPTs and tension load tests. At Te Kaha the RAP installation resulted in a significant increase in sandy soils between the RAP elements. The CPT results consistently underestimated the fines content of the soil. The tension load test results showed that the uplift capacity is dependent on the soil conditions at the tip of the tension RAP. If adequate confinement cannot be achieved at the base the tension RAP ‘unravels’ and the capacity is much lower than typical design methods would predict.Show less…

Geopier Rammed Aggregate Piers® (RAPs) are a ground improvement technology that creates a densified column of aggregate surrounded by a stiffened matrix soil. This paper describes the design and construction …

Communication and interaction between the project structural and geotechnical engineers are critical to obtain an efficient building solution for the site, building owner and occupants. This is particularly important at concept development phase when building form and type is being assessed. This paper provides a case study of soil-structure interaction and the holistic concept development of a four-storey apartment type building and concrete raft foundation overlying potentially liquefiable soil. Show more…It examines how a lightweight structure can have benefits from a sustainability, seismic performance, and overall cost perspective. The site comprised liquefiable soils approximately 3 m below foundation level. The Structural Engineer and Geotechnical Engineer worked together to examine the seismic and sustainability performance of a robust reinforced concrete raft foundation for three potential superstructure types: timber, reinforced concrete and steel. For simplicity, this paper presents the two maximum and minimum structural types for seismic performance and sustainability, being reinforced concrete and timber. It was established that the seismic performance of a lightweight timber structure was significantly improved compared to a conventional concrete structure. As a result, the timber structure option only required a 400 mm thick concrete raft. Whereas the conventional concrete structure option required a 900 mm thick concrete raft with poor seismic performance, and potential for additional ground improvements. It was also assessed that the timber structure option had significantly less embodied carbon compared to a conventional concrete structure. A major contribution to this was the differences in the concrete raft thickness. The improvement in foundation design, improvement in seismic performance, and reduction in embodied carbon contributed to the building owner’s selection of the timber structure concept and avoided the need for expensive ground improvement.Show less…

Communication and interaction between the project structural and geotechnical engineers are critical to obtain an efficient building solution for the site, building owner and occupants. This is particularly important at …

River mouths are often highly dynamic environments, fluctuating in location and depth with riverine and coastal processes. Where river training structures restrict the river to a fixed location, these structures must be protected against the effects of scour occurring within the main channel. Show more…One possible toe protection method is to construct a “falling toe” (or “falling apron”) to launch material onto the developing slope formed by the scour. Data from physical model studies and field installations are limited, making it difficult to assess the general behaviour of the falling toe during the scour process and therefore the optimal placement volume and geometry.
This paper describes a physical model study undertaken at the University of Auckland Fluid Mechanics Laboratory to investigate the performance of the toe armour during scour, and to document the scour development (and the response of the falling toe) during several experiments. The physical model study was undertaken at a geometric scale of 1:30 within a recirculating hydraulic flume. Time-dependent scour depth measurements obtained using an array of acoustic sensors and time-lapse photograph observations are combined with photogrammetry and post-test excavations to gain a complete understanding of the behaviour of the falling toe in response to scour of the channel test section.
As the scour developed within the channel, the falling toe was launched to create a 1:2 slope protected by a single layer of armour material, irrespective of the presence of an underlayer. The toe of the armoured slope was periodically buried and uncovered by bedforms under live-bed conditions. The amount of crest retreat was governed by the scour depth and the number of armour layers providing material to the protected slope. Scale and model effects are discussed along with general principles for design.Show less…

River mouths are often highly dynamic environments, fluctuating in location and depth with riverine and coastal processes. Where river training structures restrict the river to a fixed location, these structures …

A public open space on the Tāmaki Makaurau waterfront known as ‘Te Wānanga’ has been constructed as part of a wider transformation of the Tāmaki Makaurau downtown area. The project constitutes a tidal shelf of interconnected spaces, a coastal forest, and apertures to the sea below. Green-lipped mussel (kūtai) restoration is incorporated into the design, with the aim of re-establishing ‘living’ systems in the Tāmaki Makaurau urban marine environment. Show more…Māori knowledge and philosophy have strongly influenced the co-design process. Green-lipped mussels were once abundant in the Hauraki Gulf, before overfishing and pollution caused stocks to collapse in the mid-1900s. Successful translocations of mussels have been undertaken as part of the ‘Revive our Gulf’ project, but have not previously been attempted in the Tāmaki Makaurau city centre. Trials of pile wraps and a novel floating buoy system seeded with mussels were deployed in June 2020, to inform the final deployment in May 2021. Success criteria include survival and growth rates of mussels, and establishment of other native and non- native species, with the aim of providing targeted substrate and systems to enhance native biodiversity. So far, the mussels are holding their own, and attracting other native species even in this heavily impacted environment. However, as seen in other urban marine environments, there is competition from invasive species such as Undaria and the Mediterranean fanworm. Given its location in the heart of the city the project provides an excellent opportunity to educate the general public about pollution and invasive species, and to showcase the cultural and ecological benefits of shellfish restoration through a co-design process.Show less…

A public open space on the Tāmaki Makaurau waterfront known as ‘Te Wānanga’ has been constructed as part of a wider transformation of the Tāmaki Makaurau downtown area. The project …

Ground improvement by means of Controlled Modulus Columns (CMCs) usually involves the construction of a Load Transfer Platform (LTP) over the CMCs, especially for construction of low embankments over soft soil, to carry the overburden load and transfer to the CMCs, thereby not loading the surrounding soft soils, and avoiding excessive total and differential settlement. Show more…This paper provides a case study of a design undertaken for CMCs without an LTP, taking advantage of a relatively high embankment (4.5 m). Compacted fill and gravel working platform layers have been considered to be sufficient to dissipate any differential settlement at the surface of the embankment, without a need for an LTP. Available settlement monitoring data has confirmed the settlement to be within tolerable limits. Advantages of this method include time and cost savings, as well as environmental benefits.Show less…

Ground improvement by means of Controlled Modulus Columns (CMCs) usually involves the construction of a Load Transfer Platform (LTP) over the CMCs, especially for construction of low embankments over soft …

In June 2017 Emirates Team New Zealand defeated Oracle Team USA, seizing the opportunity to host the 36th America’s Cup on the Waitematā Harbour in Tāmaki Makaurau Auckland. Auckland last hosted this international sporting event in 2003. Continued urban regeneration along Auckland’s waterfront meant that the previous event infrastructure had since been redeveloped for other uses.Show more…
The lack of space to host the event was a serious test for the City. Together with central Government, Auckland Council recognized the significant potential economic, social and reputational benefits of the Cup to Auckland and New Zealand – the opportunity to adapt a waterfront brownfield site at pace, helping a flagship event and the City to thrive. Delivery of the complex, highly visible project with an immovable deadline, called for a proactive and collaborative approach. The Wynyard Edge Alliance was formed by Auckland Council and central Government in July 2018 to design and construct the infrastructure.
This case study examines how, by coming together around a collective goal of “creating a stage for the America’s Cup and a waterfront destination that Kiwis and visitors love”, the Wynyard Edge Alliance, and its participants, overcame challenges relating to land availability, water space and funding constraints to deliver the infrastructure required to host the event in time for the syndicates arrival. It particularly focuses on:
• how the split between temporary and permanent infrastructure was used to maximise legacy value within funding constraints.
• the design issues faced in terms of design life, durability and contamination.
• accommodating the wide-ranging needs of superyachts, international race syndicates and vibrant public
spaces.
• the solutions found to accommodate sea level rise for new infrastructure and address resilience challenges
for 100-year-old wharves and reclamation
• repairs to repurpose and extend the useful life of the 100-year-old Wynyard Wharf
Keywords: America’s Cup, temporary infrastructure, marine structures, repurposing and reuse, brownfield.Show less…

In June 2017 Emirates Team New Zealand defeated Oracle Team USA, seizing the opportunity to host the 36th America’s Cup on the Waitematā Harbour in Tāmaki Makaurau Auckland. Auckland last …

A magnitude 7.8 earthquake struck the Kaikōura coastline in November 2016 causing widespread uplift and landslides closing State Highway 1 and Main North Rail Line. Ōhau Point was the location one of the largest and most challenging landslides, with more than 160,000 cubic meters of rock falling from the surrounding cliffs and inundating the road and rail corridors. Show more…Recovery works by the North Canterbury Transport Infrastructure Recovery (NCTIR) Alliance reinstated the roadway further seaward and at a lower level than previous due to residual landslide and rockfall risk. A unique combination of steep offshore bathymetry and rock outcrops resulted in focusing of wave energy and overtopping to occur at a higher frequency and magnitude than was initially expected. This overtopping presented a potential hazard to road users and to the road infrastructure itself during extreme events. This paper presents the results of extensive physical modelling undertaken at the Water Research Laboratory at UNSW Sydney to investigate the overtopping processes and to assist NCTIR in evaluating options for mitigating hazard at the site. The section of road and seawall at the site is fronted by a nearshore zone with highly complex bathymetric features, and as such, a quasi-threedimensional model was required to simulate the complex 3D effects of the nearshore wave field and overtopping process.Show less…

A magnitude 7.8 earthquake struck the Kaikōura coastline in November 2016 causing widespread uplift and landslides closing State Highway 1 and Main North Rail Line. Ōhau Point was the location …

Tsunami pose a significant risk to many urban centres in New Zealand. Having methods to assess the extent and flow regimes of tsunami allow the development of appropriate mitigation measures. Simulation of tsunami inundation using numerical methods has typically been undertaken assuming a bare-surface terrain with roughness coefficients applied based on land cover, rather than incorporating buildings and vegetation into the elevation model. Show more…This is often a consequence of computational limitations restricting the spatial resolution able to be modelled during large-scale tsunami inundation assessments. These coarse resolutions mean that buildings and infrastructure are unable to be realistically modelled. This is of particular concern in dense, urban environments where tsunami flow characteristics are likely to be strongly influenced by built infrastructure.
This research investigated the effect that spatial resolution, roughness coefficient parameterisation and buildings/topographic representation had on the expected flow characteristics during a hypothetical modelled tsunami inundation event. A high-resolution study area at Mount Maunganui, New Zealand was selected due to its characteristics as a densely built-up, low-lying area, with a known existing tsunami hazard. Non-linear shallow water wave equation (NLSW) based models were employed during this study.
The study showed that results were most substantially influenced by different building representations in the simulations. Results showed that buildings had the ability to block and channelize flow, resulting in differences in maximum flow depths, peak flow velocities and hazard classification between the bare-surface terrain and higher-resolution building-resolving models. The addition of buildings led to higher peak depths and velocities in certain locations thereby increasing or decreasing the expected hazard potential during the modelled event. The high-resolution model outputs are also able to be more effectively used to promote community engagement with respect to tsunami hazard and encourage improved public understanding of the threat. Building-resolving simulations can be presented visually in a high-resolution, three-dimensional (3D) animation, thereby allowing the public to appreciate the potential devastation of a tsunami event in a real-time video format.Show less…

Tsunami pose a significant risk to many urban centres in New Zealand. Having methods to assess the extent and flow regimes of tsunami allow the development of appropriate mitigation measures. …

Areas susceptible to coastal erosion have traditionally been mapped as lines on a map. This was based on single values that were derived using a ‘building block’ approach. More recently, coastal erosion extents have been assessed probabilistically to account for environmental and data uncertainty. Nonetheless, single lines are still typically mapped for selected probabilities of exceedance. Show more…Often, many lines are mapped because of specific sea level rise scenarios, timeframes and selected probabilities of exceedance that are typically considered and this can be confusing for stakeholders. Furthermore, coastal erosion extents can also be useful when undertaking risk assessments for coastal adaptation planning, but single lines are of limited value.
Instead of mapping multiple lines for selected probabilities of exceedance, a raster-based mapping approach can be used for both hazard and susceptibility assessments. This allows the full range of probabilities of exceedance being mapped in a combined manner. Raster maps can be shown in the form of a graduated shading, which can be used to find a probability of exceedance for a selected scenario for a location of interest (e.g. road or house). Separate shadings can be created for each timeframe and sea level rise scenario, which could be integrated in a web-based tool using a slider to select the scenario of interest. This would enable probabilistic risk assessments to be undertaken, as well as providing useful information for landowners and infrastructure managers.
This paper outlines how probabilistic methods and improved mapping can enhance the overall effectiveness and engagement from a coastal erosion susceptibility assessment. This includes full probabilistic assessments and raster-based mapping for beach shorelines. For cliff shorelines, a quasi-probabilistic approach is typically adopted, with the cliff toe retreat assessed probabilistically with single stable angles projected landward from a selected probability of exceedance up to where it intersects with ground levels. Raster based mapping for cliff shorelines using a fully probabilistic approach is introduced to allow raster maps being created for cliff shorelines.
The motivation for these improvements is to assist with effective and strategic management at the coast and to assist with communicating uncertainty to communities and stakeholders.Show less…

Areas susceptible to coastal erosion have traditionally been mapped as lines on a map. This was based on single values that were derived using a ‘building block’ approach. More recently, …

Cobham Drive, Wellington, is the site of a newly constructed footpath and cycleway with 430 m of associated erosion protection in the form of rock revetment. Habitat enhancement over and above rock placement was required to provide habitat complexity and enhanced ecological function post-construction.Show more…
Marine flora and fauna that reside in coastal areas are impacted by anthropogenic changes to coastlines, leading to loss of coastal habitat and their associated ecosystem services. Ecological enhancements or interventions are becoming increasingly common to address human induced changes to coastlines. Drawing on local and international examples, we identified ecological enhancement features to re-instate ecological values in a hard-engineered environment.
The first feature was pre-cast enhancement tiles that were designed to incorporate ecological specifications in tandem with cultural aspects. The tiles were designed at 400 mm x 400 mm (width and height) and 100 mm deep, using concrete with an ‘acid finish’ that provided additional texture and roughness.
Secondly, we recommended retrospective amendments to the rock revetment material in the form of drill-cored rock pools of varying diameter and depth to mimic natural rock pools in the intertidal zone.
The proposed enhancements were designed within site constraints, such as the small tidal range, local site conditions, rock type and size that was used for erosion protection and known fauna (little penguins / kororā) in the immediate vicinity.
Further, to protect kororā using the site for nesting and moulting, T+T ecologists developed a fauna management plan to protect kororā during construction, and to identify appropriate mitigation in the form of Department of Conservation standard nesting boxes that were installed by contractors above high tide and landward of the revetment.Show less…

Cobham Drive, Wellington, is the site of a newly constructed footpath and cycleway with 430 m of associated erosion protection in the form of rock revetment. Habitat enhancement over and …

Te Wānanga, Auckland’s new waterfront public space, is part of the Downtown Infrastructure Development Programme, which aimed to revitalise the waterfront of downtown Auckland through a series of interconnected projects. The public space comprises an approximately 1,600 m2 suspended reinforced concrete wharf, featuring both an irregular seaward edge and numerous irregularly shaped apertures for architectural features. Show more…These include deck-mounted suspended steel planters which hold large Pōhutukawa trees, woven suspended nets, open apertures with sculpted steel balustrades and suspended mussel floats and ropes, as well as a series of safety piles along the seaward edge. Te Wānanga aims to blend the boundary between the city and the harbour with its architectural design inspired by New Zealand’s coast and culture. The unique architectural form, the low-lying deck level, proximity to Quay Street seawall, interface with simultaneous projects, and time pressure all added technical complexity. Overcoming this required in-depth analysis of wave-structure-soil interaction and close collaboration with the project partners. Development of a comprehensive structural model allowed for geometrical complexity to be accurately considered for rapid assessment of alternative construction staging options and for sensitivity analyses to varying ground conditions to be carried out. This allowed risks associated with unforeseen ground conditions during the construction phase to be managed. An adaptive design approach allowed for the architectural form of the low-lying deck to be retained whilst managing the future risk of wave overtopping through the later raising of the deck level. Wave uplift proved to be a significant load, especially for future sea level scenarios over the design life. However, seismic loading and durability considerations provided the critical design case scenarios..Show less…

Te Wānanga, Auckland’s new waterfront public space, is part of the Downtown Infrastructure Development Programme, which aimed to revitalise the waterfront of downtown Auckland through a series of interconnected projects. …

Wave overtopping of coastal infrastructure such as rail, road and shared pathways can be hazardous to users and potentially threaten structural integrity and reliability. A Trigger Action Response Plan (TARP) provides a robust framework for mitigating risk by defining response actions based on escalating trigger levels. Show more…These actions, and their expected frequency of occurrence can be implemented into construction or operational programs and adjusted as new data becomes available or engineering modifications are made.
This paper presents an overview of this framework applied to a case study at Ōhau Point, north of Kaikoūra, New Zealand. This site was significantly impacted during the November 2016 magnitude 7.8 earthquake with a large landslip inundating both the State Highway 1 road and Main North Line rail corridors. Recovery works undertaken by the North Canterbury Transport Infrastructure Recovery (NCTIR) Alliance reinstated the roadway further seaward and at a lower level than previous due to residual landslide and rockfall risk. A unique combination of steep offshore bathymetry and rock outcrops resulted in focusing of wave energy and overtopping to occur at a higher frequency and magnitude than expected. This overtopping posed risks to the recovery team and the public and potentially to the structure itself during extreme events.
A work programme was initiated to investigate and mitigate this risk. This comprised field data collection including detailed bathymetric and topographic surveys, an offshore wave buoy and camera system, numerical wave hindcast, development of image processing techniques to automatically detect overtopping events and physical modelling of the 3D environment to quantify overtopping flows during typical and extreme events. The programme resulted in the development of a Trigger Action Response Plan (TARP) defining threshold wave and water level conditions for a range of actions including traffic management, road closure and post-event structural inspection. This TARP was successfully used to manage risk while longer term mitigation measures were tested and implemented. The TARP was then modified to incorporate the reduced overtopping magnitude and frequency resulting from the engineering worksShow less…

Wave overtopping of coastal infrastructure such as rail, road and shared pathways can be hazardous to users and potentially threaten structural integrity and reliability. A Trigger Action Response Plan (TARP) …

The Rawene Reserve landslips occurred in 2017 and resulted in the partial loss of a sealed carpark behind the Mokoia Road shops in Birkenhead, Auckland. The landslips are inferred to have occurred within uncontrolled fill materials placed in a gully during the 1960s and 1970s, and along softened and pre-sheared zones within residually weathered soils of the East Coast Bays Formation. Show more…The main landslip formed a debris flow of material which travelled up to 300 m downslope damaging local infrastructure, and inundating properties and local streams. Emergency action and stabilisation measures were undertaken by Auckland Council to prevent further movement, to make the surrounding area safe and allow for longer term repair works. Stabilisation measures included temporary sheet piles, cantilevered timber pole walls, an anchored concrete piled palisade wall, earthworks, and subsoil drainage. Engineered fill was placed to buttress the slope and form a new carpark. Construction was completed and the carpark reopened in October 2019, two years after the initial landslip event. Monitoring of strain in the piles using rebar strainmeters confirmed pile performance. The project was challenging given its urban location, multiple affected stakeholders and the emergency response required.Show less…

The Rawene Reserve landslips occurred in 2017 and resulted in the partial loss of a sealed carpark behind the Mokoia Road shops in Birkenhead, Auckland. The landslips are inferred to …

Assessment of offensive odour risk in accordance with Environment Protection Authority of Victoria (EPA) Publication 1883 Guidance for assessing odour, June 2022 (EPA Publication 1883) is based on the downwind odour frequency (as measured in a field odour survey) multiplied by the annual wind frequency of that particular downwind direction (which can be sourced from wind measurements or from meteorological modelling). Show more…When odour presence is observed during calm conditions, the frequency of calm conditions replaces the wind frequency in assessing odour risk. By convention, a ‘calm’ is said to occur when wind speeds are less than 0.5 m/s, as this is a typical stall speed for older ‘cup and vane’ type wind instrumentation used in weather stations. However, if newer and more sensitive technologies such as ultrasonic wind sensors are used in the field, wind measurement can be more refined. Accuracy of measurement can be achieved to the level of 0.1 m/s and measurement starting threshold as low as 0.01 m/s. Hence, for assessing odour risk, the definition of ‘calm’ may need to change from convention as field experience corroborates that wind movement can still be physically detected below 0.5 m/s. This case study seeks to explore whether changing the definition of calm winds would affect the categorisation of offensive odour risk under EPA Publication 1883, and how this s may affect the type of wind data to be used for an odour risk assessment.Show less…

Assessment of offensive odour risk in accordance with Environment Protection Authority of Victoria (EPA) Publication 1883 Guidance for assessing odour, June 2022 (EPA Publication 1883) is based on the downwind …

When installing anchors in weak argillaceous rocks selecting appropriate ultimate grout to ground bond strength parameters can be challenging, yet critical to ensure safe and rational anchor design. Literature notes groundwater and/or drill flush type can influence the ultimate bond strength due to water softening effects. Show more…One tool which can be deployed to increase the capacity of an anchor in weak rock is underreaming, locally increasing the diameter of the anchor fixed length. This paper summarises anchor investigation tests undertaken in the Mount Messenger Formation in North Taranaki. It compares the ultimate capacities of straight shafted anchors drilled with air and water flush, in addition to an underream anchor. The data presented may support anchor practitioners working in similar ‘papa’ lithologies, or equivalent Late-Miocene soft rocks in New Zealand and internationally.Show less…

When installing anchors in weak argillaceous rocks selecting appropriate ultimate grout to ground bond strength parameters can be challenging, yet critical to ensure safe and rational anchor design. Literature notes …

On 1 January 2020, the allowable sulfur content of marine fuels, as capped under Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL), fell from 3.5 percent by weight to 0.5 percent by weight. Although, at the time of writing, New Zealand had not yet acceded to Annex VI, all ocean-going ships entering New Zealand ports are flagged to states that are party to Annex VI. Show more…Therefore, the effects of the Annex VI ‘Sulfur 2020’ Regulations are expected to largely have been realised. Monitoring for sulfur dioxide and PM10 is undertaken by the Bay of Plenty Regional Council at a number of sites in the Mt Maunganui area close to the Port of Tauranga, which is the largest port in New Zealand in terms of total cargo volume. The monitoring data has been investigated to evaluate the impacts of the Sulfur 2020 Regulations on sulfur dioxide and particulate matter air quality in the Mt Maunganui area. The paper also considers what further air quality improvements might be observed once New Zealand accedes to Annex VI.Show less…

On 1 January 2020, the allowable sulfur content of marine fuels, as capped under Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL), fell from …

The Ōpōtiki Harbour Development Project involves stabilising the entrance of the Waioeka River to allow reliable and safe access for maritime activity. This project is the first major river training works to be designed in New Zealand in over 100 years and involves construction of twin 400 m long training wall breakwaters, dredging a navigable channel into the Harbour, and closing the natural river mouth. Show more…The design solution chosen involves conventional rubble mound breakwaters armoured with Hanbar concrete armour units and includes a wide rock armoured toe apron. Design of the Harbour entrance breakwaters has involved a complex process of defining both coastal and river design parameters that input into the detailed design of the structures. Key aspects of both coastal and river processes were modelled numerically and physically with the results of the modelling feeding into the detailed design of the structures. Data obtained from site investigations was used to inform and calibrate the modelling and design decisions alongside predicted climatic changes to the coastal and river hydrology over the design life of the structures. Compared to the engineers of 100 years ago we have a greater understanding of the construction environment and more design tools, however this creates additional challenges. This paper discusses how the respective models were used to calibrate and evaluate the design parameters from both coastal and river processes. It also discusses some of the design philosophy and decisions made during detailed design particularly in relation to design wave height and the effects of waves against currents, the choice of KD value for stability design of the armour units, calibration of the calculated and modelled wave overtopping flows, requirements and feasibility for ground improvements, and the design philosophy behind the choice of toe apron design..Show less…

The Ōpōtiki Harbour Development Project involves stabilising the entrance of the Waioeka River to allow reliable and safe access for maritime activity. This project is the first major river training …

The Ōpōtiki Harbour Development Project involves stabilising the entrance of the Waioeka River to allow reliable and safe access for maritime activity. This project is the first major river training works to be designed in New Zealand in over 100 years and includes twin 400 m long training wall breakwaters, dredging of a navigable channel into the harbour, and closing the natural river mouth. Show more…Accurate definition of wave height reaching the structure is a key design parameter for armour sizing, setting crest elevation and determining wave penetration into the harbour. To model wave processes for the design, a high-resolution numerical wave model was required to resolve nearshore transformation, refraction, diffraction, and reflection off the structure. The fully non-linear Boussinesq model Funwave-TVD was used to for this work, in conjunction with physical modelling in the wave basin with WRL. This paper discusses how numerical and physical modelling methods were used in a complementary and iterative manner to inform and test the design. Reflection was a key consideration during the modelling work. Reflection and any resulting convergence needed to be accounted for within the breakwater channel, however, amplification from reflection radiating out to the open sea needed removing to optimise the unit sizing. Wave reflection in the numerical model was assessed using a range of linear and directional spectral methods, with limited success. Improved handling of reflection for the design objective was achieved by repeating simulations with and without the breakwater structures. Reflection off the structures was controlled in the numerical model using a local friction on the breakwater face that achieved a reflection coefficient of 0.3-0.4 to match physical modelling observations. Physical modelling results were also used to validate and calibrate the numerical model. A scaled version of the final design was tested in a 3D physical model for confirmation of stability.Show less…

The Ōpōtiki Harbour Development Project involves stabilising the entrance of the Waioeka River to allow reliable and safe access for maritime activity. This project is the first major river training …

Provision of accurate meteorology both at the surface and upper air levels is a key input for atmospheric dispersion models. At locations which are distant from observation stations in Australia and New Zealand, meteorological datasets have historically been produced using the prognostic model section of The Air Pollution Model (TAPM). Show more…More recently, and since TAPM has ceased to be updated by CSIRO, dispersion modelling has been based on prognostic data that has been downscaled using the Weather Research Forecasting (WRF) model. Due to the computational power required to run the WRF model many practitioners opt to purchase the data from third party suppliers. Modelling from the currently available third party suppliers is based on land use information which is nearly 20 years out of date. This paper presents an approach to incorporate the most accurate available data for terrain (ALOS Global Digital Surface Model (AW3D30)) alongside land use information derived from a blend of the National Vegetation Information System (NVIS) and Catchment scale land use (CLUM) for Australia and the Land Use and Carbon Analysis System (LUCAS) data for New Zealand. This paper uses this information to compare the model predictions for TAPM, WRF using default data and WRF using modified terrain and land use in comparison to observed data in Canterbury, New Zealand to a resolution of 1 km.Show less…

Provision of accurate meteorology both at the surface and upper air levels is a key input for atmospheric dispersion models. At locations which are distant from observation stations in Australia …