Publications

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 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…

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 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

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 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

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

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 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…

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

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…

17th Australasian Tunnelling Conference, 2021, Melbourne

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

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…

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

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…

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

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…

Proceedings of the 7th International Young Geotechnical Engineers Conference, 2022, Sydney

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

14th Australia & New Zealand Young Geotechnical Professionals Conference, Rotorua, 2022

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

14th Australia & New Zealand Young Geotechnical Professionals Conference, Rotorua, 2022

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

Australasian Coasts & Ports 2021 Conference, Christchurch

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…

26th CASANZ (Clean Air Society of Australia & NZ) Conference 2022, Adelaide

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…

14th Australia & New Zealand Young Geotechnical Professionals Conference, Rotorua, 2022

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…

26th CASANZ (Clean Air Society of Australia & NZ) Conference 2022, Adelaide

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…

26th CASANZ (Clean Air Society of Australia & NZ) Conference 2022, Adelaide