Designing groundwater sensitive urban development, 3rd Water Sensitive Cities Conference
The 3rd Water Sensitive Cities Conference was held in Perth last month. Hosted by CRC for Water Sensitive Cities, the conference brought together university, industry and government partners, aiming to shape our cities and towns into more liveable, resilient and sustainable places in the future. The conference provided an opportunity to learn how Water Sensitive Cities are being implemented in Australia and overseas.
On the last day of the conference, Urbaqua Director Helen Brookes presented a session on groundwater sensitive design in partnership with Professor Carolyn Oldham from the University of Western Australia.
Carolyn started the session with an interesting introduction on the formation of Perth coastal soils including the sandy soils and alluvial clays. She described local groundwater conditions and linked this with an understanding of Perth native vegetation and their water needs. Carolyn discussed the interaction between stormwater and the superficial aquifer, noting that these interactions can lead to an increase in the concentration of nutrients (TN and TP) in shallow groundwater. Carolyn described the importance of variable redox conditions in stormwater systems and their relationship with the site’s nutrient balance.
Helen then provided a range of Water sensitive urban design (WSUD) options to optimise redox and nutrient conditions. This included incorporating a number of different treatment elements into various aspects of urban form, such as biofilters, tree pits, swales and subsurface wetlands. Helen’s simple tips included limiting subsoil drainage to where it’s really needed, and providing treatment at free outlets.
The second half of the session focused on measures to monitor treatment system performance. This includes improved understanding of monitoring variables such as time of year and catchment location. Other consideration include meteorological data, existence of controlled/uncontrolled inflows and outflows and stormwater and groundwater exchange and their interactions through different seasons. Following discussion of these factors, Helen and Carolyn recommended that water sampling was undertaken at least 3 times a year and for 3 years and to refer to the CRC for Water Sensitive Cities new publication, “A guide for monitoring the performance of WSUD elements in areas with high groundwater” for further guidance.
Other great information is contained in CRCWSC reports on the performances of the Anvil Way Compensation Basin Living Stream and Wharf Street Constructed Wetland. These reports can be used to assist with the design of future systems and monitoring programs.
Helen closed the workshop Helen summarising our experience in monitoring and providing some practical advice for design adaptations to facilitate easier monitoring. These included suggestions for locating flow monitoring equipment at bubble-up pits, upstream junction pits or using standpipe arrangements in raingardens or biofilters.