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The effectiveness of stormwater management strategies is a key issue affecting decision making on urban water resources management, and so proper monitoring and analysis of pilot studies must be addressed before drawing conclusions. We performed a pilot study in the suburban Shepherd Creek watershed located in Cincinnati, Ohio to evaluate the practicality of voluntary incentives for stormwater quantity reduction on privately owned suburban properties. Stream discharge and precipitation were monitored 3years before and after implementation of the stormwater management treatments. To implement stormwater control measures, we elicited the participation of citizen landowners with two successive reverse-auctions. Auctions were held in spring 2007, and 2008, resulting in the installation of 85 rain gardens and 174 rain barrels. We demonstrated an analytic process of increasing model flexibility to determine hydrologic effectiveness of stormwater management at the sub-catchment level. A significant albeit small proportion of total variance was explained by both the effects of study period (∼69%) and treatment-vs.-control (∼7%). Precipitation–discharge relationships were synthesized in estimated unit hydrographs, which were decomposed and components tested for influence of treatments. Analysis of unit hydrograph parameters showed a weakened correlation between precipitation and discharge, and support the output from the initial model that parcel-level green infrastructure added detention capacity to treatment basins. We conclude that retrofit management of stormwater runoff quantity with green infrastructure in a small suburban catchment can be successfully initiated with novel economic incentive programs, and that these measures can impart a small, but statistically significant decrease in otherwise uncontrolled runoff volume. Given consistent monitoring data and analysis, water resource managers can use our approach as a way to estimate actual effectiveness of stormwater runoff volume management, with potential benefits for management of both separated and combined sewer systems. We also discuss lessons-learned with regard to monitoring design for catchment-scale hydrologic studies.
