A Methodology for Calibrating SWMM Models.
Computer simulation models of stormwater systems have become established tools for predicting the hydrologic response of a watershed and evaluating the capacities of associated hydraulic conveyance systems. Their usefulness extends from the capacity to model complicated drainage systems to the ability to quickly analyze the impact of various storms and land use conditions. Obtaining maximum value from a computer analysis depends to a large degree on the quality of available data and the calibration techniques employed to relate the response of the computer model with the watershed and drainage system. Invariably, predicted flood flows are extrapolated beyond available measured watershed response data. However, a well-planned model calibration effort can result in a simulation model that is verifiable and truly representative of the physical system.
Calibration techniques, presented herein, have been developed and applied to a large number of urban and urbanizing watersheds in the United States over the last 25 years, utilizing several mathematical models. This paper summarizes the most recent application to several watersheds within the City of Grand Rapids, Michigan. The methodology emphasizes the following:
1. sequential calibration
2. utilization of specific parameters in each sequence
3. utilization of appropriate storm events for each sequence
4. careful selection of monitoring sites, and
5. taking the necessary steps to collect ‘good’ data.
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