Defining urban diffuse pollution loading and receiving water hazards.

The use of unit area loading approaches to address the requirements of the US Clean Water Act (CWA) and the EU Water Framework Directive (WFD) to identify and manage diffuse urban pollution sources is outlined. Issues relating to traditional volume-concentration probabilistic modelling are highlighted and the robustness of total maximum daily load (TMDL) approaches is discussed. A hazard assessment methodology for catchment scale identification of source area pollutant loadings and receiving water ecological impacts is developed based on urban land use activities.