Application of an urban runoff model using surface specific parameters

Abstract

Catchment urbanisation has led to a dramatic decline waterway health. The high percentage of impervious surfaces prevalent in urban areas can affect the ecological, economic and social function of our creeks, rivers and bays. Current engineering practice aims to limit this decline using the principles of water sensitive urban design (WSUD). An essential component of this design process is the estimation of stormwater pollutant loads based on catchment characteristics. Current practice involves the estimation of pollutant loads based on land use type. As WSUD seeks to emphasise ‘at source’ controls there is a need to estimate for finer scale catchments. It is anticipated that the use of surface type rather than land use type to determine catchment pollutant loads will prove more accurate at a finer scale. A mass balance model developed by Brodie (2006) utilises surface type to determine pollutant loads. This dissertation applies Brodie’s mass balance model to a small catchment in Brisbane, QLD to determine the ability of the mass balance model to predict suspended solid loads. This dissertation compares the measured and predicted event mean concentrations of suspended solids over a number of storm events. The result was a poor correlation between predicted and measured data sets due to large inaccuracies in the measured rainfall and use of previously calibrated particle accumulation and washoff parameters not specific to the catchment. A major outcome involves providing comments on the further application of the mass balance model and conducting an error analysis to determine highly sensitive model parameters. The outcome is applicable to stormwater engineers and future users of the mass balance model.