Long-Term Vegetation Dynamics in Residential Rain Gardens
Image credit: AGUAbstract
Rain gardens are among the most widely implemented forms of nature-based stormwater infrastructure, yet relatively little is known about how their plant communities change over time following installation. Because vegetation drives many ecological processes within rain gardens, including evapotranspiration, pollutant uptake, soil stabilization, and habitat provision, understanding long-term vegetation dynamics is critical for evaluating the sustainability of residential green stormwater infrastructure. This study evaluates vegetation communities in more than 150 residential rain gardens installed through the Washington, D.C. Department of Energy and Environment’s RiverSmart Homes program between 2010 and 2023, with an emphasis on systems older than five years. Ecological field assessments include vegetation cover, species richness, native and non-native species composition, invasive species cover, and site conditions such as shade exposure and maintenance observations. Preliminary results show that many aging rain gardens continue to support dense vegetation cover, indicating that complete ecological failure is uncommon even after a decade or more. However, vegetation composition changes through time - native species richness tends to decline in older rain gardens, often accompanied by increases in non-native ornamental species. Invasive species were commonly observed, particularly in heavily shaded gardens, but generally comprised a small proportion of overall richness. These findings suggest that long-term ecological change in residential rain gardens occurs gradually and may be associated with certain maintenance behaviors and changing site conditions, resulting more often in shifts in community composition than vegetation loss. Understanding these patterns can help inform long-term maintenance strategies, planting recommendations, and performance assessment frameworks for aging green stormwater infrastructure in residential settings.
Emma Ruggiero
PhD Student
