Siting Surface Infiltration-Based Stormwater Control Measures Using a Geographic Information Systems Approach

Infiltration-based stormwater control measures (SCMs) are commonly the preferred practice implemented to mitigate the hydrologic impacts of urbanization, such as increased surface runoff volumes from small to moderate rain events and degraded surface water quality. Infiltration-based SCMs, however, can fail for a number of reasons including improper siting or inadequate maintenance resulting in large capital expense and also a time period where the hydrologic and water quality benefits are not being realized. Identifying a suitable site is one critical factor in the long-term success of an infiltration-based SCM. This paper develops a preliminary infiltration rating (PIR) that is a composite rating calculated in a geographic information system that assesses the likelihood of success of a future surface infiltration-based SCM at a given location. The input variables to the PIR include the surface saturated hydraulic conductivity (Ksat), depth to water table, topographic slope, and relative elevation, all of which are readily available from online sources. The PIR was calibrated and validated using maintenance inspections from 104 rain gardens completed by the Anoka Conservation District in Minnesota. The validation set resulted in the PIR predicting an accurate or conservative estimate of the rain garden performance in 85% of rain gardens. The PIR can serve as an effective planning tool for siting future surface infiltration-based SCMs in the land development process and can guide the site-specific investigation.