In the Sydney region, approximately 50% of the area of pre-European freshwater wetlands and 80% of the saltmarsh area has been lost in the past 200 years. Although direct and intentional destruction by drainage and filling has been the major cause, general degradation from the "unintentional" effects of urbanisation has caused the loss of any freshwater and saline wetlands. Wetlands in the urban areas exhibit symptoms of failing processes, limited functions and visual degradation.
There is considerable value in examining the decaying bodies of wetlands lying littered around our urban landscapes. A comparative survey of urban wetlands and their catchments, both the surface watershed and the catchment of stormwater drains, can provide empirical insight into wetland functions and processes, and the impacts of urbanisation on them. This paper identifies the common symptoms and causes of wetland degradation that must be addressed in any wetland rehabilitation strategy. The pathways by which the wetland is linked, and interacts with, it's catchment(s) are modelled in conceptual diagrams to allow analysis of impact control and mitigation opportunities.