It can be a challenge to manage the complex flooding risks in urban areas. With New Zealand’s topography and climate, many densely developed and vulnerable communities are often located in small, steep flood prone catchments.
Development of effective plans for stormwater quality management to mitigate the degradation of freshwater quality in urban catchments demands an explicit understanding of the catchment both spatially and temporally.
This paper discusses the design process, the implementation and lessons learned as well as customer feedback from key stakeholders including the developer and Auckland Council, who will ultimately be the asset owners of these WSUD features within the development.
At a time of increasing national focus on urban water quality, Stu Farrant from Morphum Environmental was awarded a 2018 Winston Churchill fellowship to undertake international travel and research to better understand the enabling factors which have supported globally leading cities in addressing the complex issues of urban water management.
Streams in Auckland Region have been found to exhibit loss of natural functioning of freshwater systems and the degradation of their values as a consequence of intensive urban development. Conventional development, unless mitigated, significantly increases runoff volumes and the duration and frequency of elevated peak flows which consequently degrade the morphological and ecological functions of freshwater systems.
The effects of inlet and outlet configurations in sediment retention ponds (SRPs) have been widely investigated by a number of researchers; however, the challenges associated with the proper inlet and outlet design still exist when considering temperature differentials in the ponds.
This paper builds on that earlier work (McConchie & Belleville 2010) which noted “The temporal pattern of the design rainfall needs to be accommodated within any rainfall-runoff model if it is to produce realistic hydrological outputs…the actual temporal distribution of storm rainfall at any specific location may be distinctly different to the generalized distribution. This will result in unique storm runoff which must be related to that of the design event.
In June 2017, a one in 50-year storm event caused 1000m3 of material to fall into a water canal which is used to irrigate up 60,000ha of the Canterbury Plains. This material had to be removed and a grassed spillway installed to prevent any more erosion and stabilizing the slope during storm events.
The paper will present ways to access (consolidated) information using (for example) ESRI StoryMaps, interactive web-based tools and GIS information resources to support City scale master planning and catchment scale studies.
Stormwater is known to be a major source of contaminants to aquatic environments within urban areas. Research and monitoring over the past two decades has provided a good understanding of the types of contaminants and the concentrations of these from different land uses and land covers, such as roading, roofing and residential areas.
This paper outlines how to spatially identify coastal areas that are sensitive to extreme tides and rainfall, how to understand what catchments might be susceptible to rising sea levels in the future and what ground elevations will sea levels now and in the future effect pluvial flooding. It can be used to understand the effect of rising sea levels will have on flooding in low-lying coastal areas, better assess development in coastal areas and to minimise numerous joint probability modelling runs.
This paper outlines the methods that have been used in Christchurch to estimate and plan for combined tidal and stormwater flooding risk using analyses of historical data and hydraulic modelling approaches. The results of these analyses have been used to develop planning rules and infrastructure programmes.