Assessment of build-up and wash-off process uncertainty and its influence on stormwater quality modelling

Abstract

Current practice in stormwater quality modelling constraints the generation of reliable information about catchment scale stormwater quality due to the lack of robust methods to assess the inherent uncertainty in pollutant build-up and wash-off processes. This chapter presents an approach to quantify process uncertainty as an integral part of stormwater quality predictions. The approach primarily aims to mathematically incorporate the characteristics of process variability into stormwater quality models, and thus quantifying the resulting uncertainty. The application of the new approach revealed that compared to wash-off process uncertainty, the build-up process uncertainty has a greater influence on the prediction of event mean concentrations (EMCs) of particulate solids in urban catchments. Further, it was found that process uncertainty differently influences stormwater quality predictions corresponding to storm events with different intensities, durations and resulting runoff volumes. Planning and management decision making needs to specifically address the changes in the load and composition of particulate solids and associated pollutants during dry weather periods and the storm events that can potentially influence high variations in stormwater quality.