Objective

The primary objective of this application tutorial is to expand surface drainage hydraulic analysis to include water quality modeling. It involves simulating pollutant buildup, washoff, and routing to estimate the quality of stormwater discharged at the catchment outlet under post-development conditions—without the implementation of any runoff controls such as BMPs or detention systems. To assess how storm volume influences pollutant loading, the tutorial evaluates runoff loads from two small 2-hour storm events with rainfall depths of 0.1 inch and 0.19 inch. These results will then be compared to the pollutant loads produced by a 2-year design storm event with a volume of 1.0 inch, as used in previous tutorials.