Sustainable stormwater management using rain gardens in urban areas

Abstract

Stormwater runoff and combined sewer overflows in urban areas are the leading causes of flood and water quality degradation. Green infrastructures (GI) were introduced to treat stormwater runoff onsite to reduce these effects. A project was conducted in St. Louis, Missouri, US to assess the impact of installing one type of GIs (rain gardens) on the volume reduction of stormwater runoff from urban streets served by a combined sewer system. The rain gardens were installed in a six-block area between late 2013 to early 2014. After separating stormwater runoff flow from base flow in the sewer system, rain gardens efficiency was evaluated based on comparing the pre-installation condition in 2011/2012 and the post-installation condition in 2014. A reduction in the volume of stormwater runoff by installing the rain gardens was significant only at two sites. However, analysis was hampered by the high variability of the flow data and the difficulty in measuring flows in the sewers. For this type of field experiment, it is important to develop advanced flow measurement devices to overcome the problems of high variation in data and pay high attention to selecting the proper statistical tests to evaluate the stormwater runoff reduction.