A Simplified Approach to Automatically Build and Evaluate Urban Hydrology and Green Infrastructure at the Municipal Scale Using SWMM

Using available urban stormwater management models can be a complicated task for untrained users or in municipalities without a robust GIS/modelling program. However, many municipalities are still faced with the task of evaluating how urbanization and current green infrastructure programs will impact urban drainage systems as well as the hydrologic water balance. As a result, there is a need to be able to build and evaluate a simple urban hydrology model at the municipal scale particularly for the evaluation of green infrastructure. In this study, to reduce the barriers of developing a complete stormwater management model (SWMM) model, a procedure for creating a simplified SWMM model was developed. The simplified model was corroborated with a complete SWMM model and National stormwater calculator for an urban area located in south-east of Fort Collins, Colorado. The modelling approach considered three scenarios with different amounts and types of green infrastructure consistent across all three models. The first scenario involved a baseline scenario of the current catchment condition and two additional scenarios simulated the implementation of combinations of green infrastructure. Continuous simulations were ran using local climate data for a 35-year period. The models also were tested against design storms. A probabilistic approach was used to determine the sensitivity and uncertainty of the simplified model in comparison to the complete SWMM model and National stormwater calculator results. Overall, results showed a strong agreement between the developed simplified version and the complete SWMM model. The approach was adopted into an online urban hydrology tool to automate the generation and evaluation of SWMM models for any area within the United States to improve decision making.