Understanding uncertainty associated with stormwater quality modelling

Abstract

Stormwater quality modelling is the common practice for generating information necessary for decision making in the design of stormwater pollution mitigation measures. However, the reliability of modelling outcomes largely depends on two types of uncertainty, namely, uncertainty inherent to stormwater pollutant processes and process modelling uncertainty. The inherent process uncertainty arises due to the intrinsic variability in stormwater pollutant processes. The modelling uncertainty arises from model structure and parameters, and input data and calibration data. The chapter establishes the context for defining and quantifying the uncertainty inherent to pollutant build-up and wash-off processes by bringing together current scientific knowledge from research literature. The temporal changes in particle size results in different particle behaviour during build-up and wash-off, leading to variations in particle-bound pollutant load and composition. Accordingly, the variation in particle size over time can be used as a basis for accounting for process variability in stormwater quality modelling, and thereby assessing process uncertainty.