Inherent errors in pollutant build-up estimation in considering urban land use as a lumped parameter.

Stormwater quality modeling results are subject to uncertainty. The variability of input parameters is an important source of overall model error. An in-depth understanding of the variability associated with input parameters can provide knowledge on the uncertainty associated with these parameters and can assist in uncertainty analysis of stormwater quality models and decision making based on modeling outcomes. This paper discusses the outcomes of a research study undertaken to analyze the variability related to pollutant build-up parameters in stormwater quality modeling. The study was based on the analysis of pollutant build-up samples collected from 12 road surfaces in residential, commercial, and industrial land uses. It was found that build-up characteristics vary appreciably even within the same land use. Therefore, using land use as a lumped parameter would contribute significant uncertainties in stormwater quality modeling. Additionally, it was found that the variability in pollutant build-up can be significant depending on the pollutant type. This underlines the importance of taking into account specific land use characteristics and targeted pollutant species when undertaking uncertainty analysis of stormwater quality models or in interpreting the modeling outcomes.