Comparing the Effectiveness of Rain Barrels and Detention Ponds on Peak Flow Reduction in a Semi-Urban Watershed

Rain barrels are useful for stormwater management where conditions of on-site space are limited for retrofitting techniques. This paper aims at determining the scope of the effectiveness of rain barrels on reduction of direct runoff peak flow and volume. The Sugar Creek Watershed in the northwest of Illinois is simulated with a historical storm and design storms of 2-, 10-, 25-, 50-, and 100-year return periods for three different scenarios: only rain barrels, only detention ponds, and the combination of these two. For a storm with the return period less than 3 years, harvesting all rainfall volume received by rooftops, rain barrels are sufficient for flood control. In individual design to achieve the same flood control goal, compared with detention ponds, desired number of rain barrels need to harvest 10% to 15% more of the runoff volume of 2- to 100-year storms, and occupy up to 0.22% larger surface area of the watershed in case of a 100-year storm and as low as 0.13% less for a 5-year storm, which are 0.18 km2 and 0.11 km2, respectively. In combined design of capacity number of rain barrels with detention ponds, the overall combined area is slightly larger than the area of detention ponds in individual design, but the area of detention ponds in combined design is greatly reduced by more than 67% compared with the area of detention ponds in individual design