Stormwater best management practices ineffective?

Urban stormwater research conducted by Penn State University revealed little difference between managed and unmanaged flows, using traditional stormwater infrastructure, or best management practices (BMPs). Urban hydrographs aren’t altered as much as assumed to be.

“We were not able to detect any difference in flows created by stormwater management,” summarized Jonathan Duncan, Assistant Professor of Hydrology, College of Agricultural Sciences.

He elaborated on the meticulous study design, “No one wants to hear this, but we have a high level of confidence in our data and experimental design that reduced variability across sub-watersheds we studied… (our study was) conducted with detailed watershed-scale hydrology data.”

The findings are somewhat surprising since data are from the Dead Run watershed in Maryland, in particular Baltimore County, which Duncan describes as “the most intensely gauged urban watershed in the world.”

Researchers analyzed two decades of ecological and gaging data related to stormwater flows and specifically, hydrologic response in three small, highly impervious urban sub-watersheds to “pulse” rainfall events. Watershed-average rainfall data generated by local radars was used to pinpoint local storm hyetographs for each event, compensating for the extreme variability of rainfall intensity of short-duration storm events.

The hydrograph response for the three watersheds was remarkably uniform despite contrasts in stormwater management, impervious cover and spatial patterns of land use describes the Hydrological Processes-published paper.

New insights by Duncan et al recommend green infrastructure is likely to be more effective for stormwater management.

Kisters has been working with Polypipe Civils & Green Urbanisation to lead the development and adoption of more blue-green infrastructure. In the center of Manchester, England, atop a commercial office building, the rooftop features a permeable surface that captures rainwater like green infrastructure. The blue aspect of this project is the ability to later reuse the water for garden irrigation or release runoff avoiding utility overflows during heavy rainfall — based on integrated weather forecasts. Partners also include EPG, Bruntwood Works, and United Utilities.