Managing Urban Hydrology to Protect Environmental Values

Stormwater management in urban catchments has increasingly focused on filtering and biological treatment of runoff to improve water quality. Whilst stormwater quality is a key concern, changes to runoff flow rates and volumes can often have detrimental impacts on natural environments. Indeed hydrology changes due to urban development can be a significant threat to coastal wetland vegetation and the associated wildlife.

As demonstrated in a recent project on Porters Creek Wetland for Wyong Shire Council, increased runoff from stormwater can lead to drowning of trees and weakening of tree root support in wetlands.

Dead and fallen trees then open up the wetland canopy enabling invasive plant species to establish, reducing habitat for native fauna. Stormwater flows have also increased erosion of creek bed and banks, resulting in increased sediment and nutrients loads being directed to the wetlands.

Water management strategies are an essential component of environmental controls governing future development within sensitive coastal catchments. We believe that these strategies require clear objectives and targets for managing both hydrology and water quality.

As we did for Porters Creek, the strategies should also contain details of specific measures for mitigating detrimental impacts, and for rehabilitating/retrofitting existing underperforming stormwater infrastructure. Hydrological modelling and detailed flow analysis are usually necessary to assess conditions and demonstrate feasibility of proposed measures.

BMT WBM is at the leading edge of urban water modelling and management, providing innovative and practical solutions to the impacts of existing and future development, from lot scale to catchment scale.

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