Thomas G. Franti, Associate Professor, University of Nebraska-Lincoln

Steven N. Rodie

David P. Shelton

Track: Research

Abstract:

There is little information on the effectiveness of homeowner-maintained rain gardens that rely on deep percolation as the method for water exfiltration. The objective of this project was to evaluate the hydrologic properties of twelve established residential rain gardens using a stormwater runoff simulator, and to visually evaluate their plant performance. A volume-based design storm of 1.2 inches (90% Water Quality Volume) was applied in each garden based on their respective catchment characteristics. Hydrologic data collected including ponding zone storage capacity, infiltration rate, drain time, soil characterization, and observations of berm, outflow, and grading performance. Plant data collected included species type, placement, survivability, and maintenance. Results indicate that rain gardens constructed on loamy to silty clay loam soils in a residential watershed in Lincoln, NE can infiltrate at the rates recommended by state and national guidelines. Every rain garden tested drained in 30 h or less, with six gardens draining in less than one hour. Rain garden storage capacity was poor with only two gardens able to hold the water quality design runoff volume. On average, rain gardens studied were able to hold only 40% of the design storm volume. Plants were found to survive well if placed properly, but were often overcrowded, or improperly placed in too much shade, or over mulched.