Effects of green infrastructure on urban streams
Green infrastructure is a novel, decentralized type of stormwater management, and may also be called distributed stormwater management or Low Impact Development (LID). Green infrastructure is intended to preserve or restore pre-development hydrologic conditions in urbanized watersheds by retaining and infiltrating stormwater close to its source. Our study watershed in Clarksburg, Maryland, is a 1.11 square km watershed which was built out using green infrastructure with 73 infiltration-based stormwater facilities including dry wells, dry swales, and underground recharge facilities. We used nearby instrumented watersheds for comparison in which land cover changed little over the study time period (2004-2014). We examined the changes in base flow before, during, and after urban development over 10 years of streamflow record and compared the alterations to nearby forested and urban control watersheds.
We found that base flow significantly increased in the developing watershed, over the time period when the watershed was built out, relative to nearby forested and urban control watersheds. We also used linear regression of base flow between watersheds as a way to separate out climatic effects, and preliminary results indicate that the relationship between the study watershed and nearby control watersheds changed significantly over time. Lastly, we examined base flow recessions and the study watershed appeared to have a slower recession rate after development. Previous studies have investigated the effects of individual green infrastructure facilities, but watershed-scale understanding has been lacking. This is one of just a few known studies which examine distributed stormwater management in new development on a watershed-scale. Results indicate that relative to nearby control watersheds, base flow quantity increased and base flow recession slowed with urban development using green infrastructure on a watershed scale.
This information is preliminary and is subject to revision. It is being provided to meet the need for timely ‘best science’ information. The assessment is provided on the condition that neither the U.S. Geological Survey nor the United States Government may be held liable for any damages resulting from the authorized or unauthorized use of the assessment.