Predicting rain garden performance under back-to-back rainfall conditions using stochastic life-cycle analysis

Rain garden performance is highly variable, with antecedent soil moisture playing a role in short- and long-term performance. We use a stochastic life-cycle analysis framework to evaluate how interstorm duration and back-to-back rainfall events affect the performance of a test rain garden in a clayey native soil. Our analysis uses the concept of ‘fragility’ to depict the conditional probability of failure of the rain garden under different storm magnitudes and interstorm durations. We also evaluate the probability of rain garden failure at 1–24 month intervals using a Monte Carlo-based approach. Our results show that the test rain garden is likely to fail in the case of two large (>6.5 cm) back-to-back rain events with short interstorm duration (<24 hr) in a climate representative of the U.S. Midwest. We conclude that rain gardens can function effectively in clayey native soils under a variety of storms, when designed appropriately.