Directing urban development to the right places: Assessing the impact of urban development in an estuarine environment

The New South Wales Government regularly imposes dwelling increases on local councils across the State. These increases are predicated on the supposition that the population of the Greater Sydney Metropolitan Area will continue to expand exponentially, and that accommodation for this burgeoning population needs to be found. Given this continued pressure from State Government, Councilsin the affected regions need to understand the carrying capacity for land within their local government areas. The methods by which the State Government and Councils currently decide where people are to be housed are based on limited information with little scientific understanding of the consequences of these actions on the local environment. The challenge for Councils is to ensure an adequate supply of houses to meet State Government requirements, while ensuring that development is socially, environmentally and economically sustainable. The work presented in this paper describes the development of a method to determine the impact of development on a receiving waterway based on water quality criteria. It is based on mathematical programming linked with multi-criteria analysis and kinematic waveequation representing travel time of pollutants to the estuary. A GIS component is applied to underpin multiple spatial constraints on where housing development can take place, and to provide an effective means of visually analysing land developmentscenario impacts produced by the model. A test case study that demonstrates the developed method is presented. As impacts on waterway health are a concern with regards to virtually any urban development we see a wide application of the proposed methodology well beyond the study area.