This paper discusses how hydraulic modelling has been developed and utilised to inform floodplain planning including flood damage assessments, engineering upgrades, prioritising response, planning controls, community consultation, effects assessment and planning for climate change impacts. KCDC have applied a detailed understanding of flooding risk developed through hydraulic modelling as a powerful tool to shape the future of the Kapiti Coast.
This paper reviews the various water quality and ecological issues present at Chelsea Ponds, including eutrophication and avian botulism. The potentially complex aetiology of these issues is addressed, considering past and present land use, including the role of accumulated sediment, air discharges and, potentially landfill leachate in these processes. The ongoing environmental management of the ponds is discussed, with reference to the amenity value that the ponds potentially provide. In this respect, this paper touches upon the wider issue of providing increased public amenity from ponds that perform a stormwater treatment function.
This paper looks at subsequent recovery stage for stormwater, including the detailed condition assessment, development of a stormwater strategy for these areas and subsequent revision of the strategy based of the classification of large portions as red zones. The focus of this paper is on the Council’s approach and the key lessons learnt.
Bioretention devices are a Low Impact Design device used to treat pollutants found in stormwater runoff. Research assessed combinations of manufactured materials readily available in Auckland which create physical and chemical properties of filter media to satisfy objectives for stormwater management. The investigation included: establishing physical characteristics and performance criteria; investigating available materials; particle size distribution testing (PSD); compaction assessment; hydraulic conductivity testing; media chemistry analysis; and water quality testing.
This paper describes the model’s conceptualisation and development. It explains the methodology used to deliver the project on time and budget while achieving the required outputs. It also discusses the limitations of certain aspects of the results and the potential advancements that could be made for marginal additional cost. Finally, it examines the lessons learnt and how they can be applied to future projects.
This paper outlines the methodology for the detailed stormwater modelling of the Auckland CBD. This complex modelling approach posed a few interesting technical challenges that are also discussed including the relevant solutions found and the lessons learnt.
The Auckland Council 2011 Stormwater Flood Modelling Specifications recommends modelling software based on the St Venant equations, but warns “Performance of hydraulic structures should always be cross-checked with manual calculations or other software”. The New Zealand Standard NZS 4404:2010 goes further and states “Stormwater systems shall be designed by calculating or computer modelling backwater profiles” using the Bernoulli solution.
Stormwater ManageThis paper will describe some of the innovative solutions that were developed for the Wynyard Quarter and discuss how they might benefit other urban renewal projects.ment, Stormwater, Low Impact Design, Urban Renewal, Contamination
The key innovation reported in this paper is the development of a catchment scale method for assessing the stormwater management costs associated with urban development. This research extends current international practice which typically operates at the scale of individual stormwater management devices.
Stormwater Management, Integrated Catchment Management Planning, Water Quality, Cycleway, Integration, BioengineeringThis paper documents the planning and design processes that have underpinned this project. In particular it will address the following key elements:
The Central Auckland Stormwater Initiative (CASI) is a regionally-significant programme initiated by Auckland Council to deliver improved stormwater services in the problematic and strategically-important central area of Auckland. Sub-catchments include the western part of the Auckland Isthmus, including the Central Business District (CBD) and covers an area from St Heliers in the east to the Whau Estuary in the west. CASI subcatchments generally discharge stormwater into the southern part of Waitemata Harbour.
Auckland Council established the Central Auckland Stormwater Initiative (CASI) to investigate options to alleviate flood hazards and address other stormwater management issues in central Auckland, which includes the Meola, Oakley and Epsom catchments among others. A series of CASI technical workshops resulted in the identification of probable high-level solutions to address flooding. This paper provides background on flood issues in Meola and details stormwater management and flood mitigation options.
Auckland Council is responsible for the management of the estimated $2.5 billon dollars worth of stormwater infrastructure which services over 510,000 rateable properties within 235 catchment management areas. In order to meet strategic stormwater management objectives, define funding level gaps and reach stated levels of service, it is necessary to look forward into the future and estimate the amount of capital expenditure required to improve system function and performance.
This paper reviews the NPSFM and the way in which it may be implemented by local and central government. It goes on to review the potential implications for stormwater management best practice in order to achieve the overall objectives that will be required to be met. The paper also highlights what could usefully come from the LAWF process, how we could expect the Government to react to it and the consequential implications for stormwater management.
Infiltration practices have the potential to ‘return’ excess stormwater runoff from developments back into the ground. Infiltration offers a multitude of benefits resulting in extensive implementation nationally and internationally and offers an opportunity to implement Low Impact Design (LID).
This paper also summarises additional initiatives and approaches to be taken in overcoming the challenges relating to the integration of stormwater operations for the region.
The Auckland Council is required to obtain resource consents for stormwater discharges from the region’s stormwater networks. These are referred to in the Proposed Auckland Regional Plan: Air, Land and Water (ALW Plan) as network discharge consents (NDCs). In the past NDCs were applied for by the legacy territorial authorities primarily based on drainage catchments although some councils, including Auckland and North Shore Cities, sought to obtain discharge consents on a city-wide, whole-of-network basis. With the establishment of the Auckland Council as a Unitary Authority over the Auckland region, the Council’s Stormwater Unit is developing a framework that provides an overarching approach for progressing NDCs under the new Council.
This paper describes conceptual stream enhancement options considered for Meola Creek as part of the Central Auckland Stormwater Initiative (CASI) in Auckland.
This paper considers the wide ranging physical dynamics that come into play during actual flood events. This paper provides a reality check on what actually happens during extreme flood events and advocates for more consideration of potential blockage, obstructions, changes to waterways during flood events and impacts on water level associated with velocity and momentum.
This paper firstly presents a number of issues and approaches to design that should be considered when undertaking detailed stormwater design. Secondly, the paper presents a number of examples of construction difficulties and their solutions. The paper is based on information obtained both through research and the experience of the authors.
This paper describes the design challenges with stormwater disposal to soakage for the CSM, and how these were resolved. Due to high groundwater levels, there is a risk of groundwater levels rising close to the base of the soakage disposal areas in extreme conditions. In these circumstances, conventional assumptions about unconstrained vertical discharge to ground no longer apply, and an understanding of horizontal groundwater movement and groundwater mounding was required. The combined probability of an extreme high groundwater level and a large design storm also needed to be understood, as well as the consequences of such events for design. This led to risk management decisions around the implications of low probability but high consequence events, and design of contingency measures to address these. This paper will examine the issues, the design approach, and the solutions adopted.
The paper will highlight some of the pitfalls that arise from trying to adapt the policy from a pipe design and discharge approach to that of soakage system and retention design.
It also outlines some of the pitfalls we have encountered in the design, installation and maintenance of such systems.
A stormwater pond was constructed by a private development company in 2004 at Carol Lee Place, Albany Heights, Auckland in order to meet stormwater quality, extended detention and peak flow attenuation objectives for a 2.97 hectare residential catchment. The pond has since failed to perform to the required standards and is undersized to achieve the required stormwater management objectives and meet consent conditions. In 2010 the former North Shore City Council undertook a detailed evaluation of the existing pond and identified a number of options for its redevelopment.
Navigation through the entrance of the Whakatane River in Bay of Plenty, New Zealand has deteriorated due to shallow draft conditions to the point where safe access is not possible for significant periods of the time. This is affecting the viability of commercial and tourist operations based in Whakatane as well as posing a danger to recreational users.
This paper presents the earthquake physical effects and the assessment of change in flood hazard. It also discusses and the range of outputs required to make engineering decisions on the future of Brooklands, within the context of a changing regulatory environment where decision makers have required detailed analyses of this complex system to be undertaken rapidly.