CASFM Stormwater Quality Committee


CASFM Home Field Trips LID Photo Database LID in the news Helpful links


Current stormwater management professionals recognize that stormwater quality and quantity are integrated. The historic management method has been to construct connected impervious area and conveyance infrastructure to “get rid” of surface runoff. This management method conveys all storm events, both large and small, to drainage ways, and the resulting flows contribute to channel scouring, widening, down-cutting and general modifications to the natural receiving waterways. This has degraded the natural environment along receiving waterways and increases the need for expensive restorative maintenance and repairs by local jurisdictions. 

We encourage management practices and land development technologies that promote the absorption of smaller, more frequent precipitation events (i.e., source controls) to minimize impacts on receiving waters. The Urban Drainage and Flood Control District provides planning and design guidance through their Urban Storm Drainage Criteria Manual – Volume 3. Much of it is based on the fact that the Denver Metropolitan area and much of the eastern high plains of Colorado along the foothills have a mean storm depth of 0.4 inches and that 80% of runoff events can be treated by capturing the Water Quality Capture Volume (WQCV). The WQCV is based on approximately 0.6 inches of precipitation during a storm event.

LID techniques and runoff volume reduction principles provide many benefits:


The Stormwater Quality Committee seeks to promote stormwater management techniques for the built environment to improve surface runoff water quality, protect receiving water quality, and protect aquatic and riparian habitat by facilitating discussion, information exchange, and education regarding:

These techniques will be promoted through field trips, photo database, identified training opportunities, and the annual CASFM conference.

CASFM Stormwater Quality Committee Chair

Holly Piza came to the Urban Drainage and Flood Control District with 12 years of experience as a consulting engineer. This experience includes design of drainage and flood control facilities, channel improvements, drainage remediation, hydrologic and hydraulic modeling, and floodplain mapping and revisions. 

She joined the Master Planning Program at the Urban Drainage and Flood Control District and co-authored a rewrite of Volume 3 of the Urban Storm Drainage Criteria Manual which includes Best Management Practices for storm water quality. 

Ms. Piza also assists with research at six Best Management Practice test sites where the district samples inflow and outflow and collects data on rainfall and runoff.