Intro to Storm Water Issues - Quantity and Quality.

The Low Impact Development philosophy attempts to mimic pre-development hydrology through the implementation of permanent stormwater control measures (SCMs) that evapotranspire or infiltrate stormwater runoff. Implementation of these practices, such as bioretention and permeable pavement, has been shown to reduce runoff volume and peak flow rate, which impact surface water bodies negatively and cause erosion. However, these practices rely heavily on the underlying soils for transmission of water through infiltration; therefore, they function more effectively in sandy soils. Limited field research has been undertaken into the performance of these systems in clay soils. A study was recently completed along the Lake Erie shoreline of Northern Ohio which monitored the performance of bioretention and permeable pavement SCMs over HSG C and D soil types. Hydrologic and climatic monitoring was undertaken for seven SCMs to quantify the water balance over a minimum of 1 year of monitoring. Results showed that while these systems do not function as well as they would in sandy soils, they still function to reduce runoff volume, even in heavy clay soils. The field data were used to calibrate a hydrologic model (DRAINMOD) adapted to predict long-term bioretention and permeable pavement functionality. These calibrated models were used to conduct a sensitivity analysis for bioretention and permeable pavement performance as a function of underlying soil type and design characteristics. The focus of this presentation will be on the performance of stormwater controls as a function of in situ soil type and methods to improve infiltration during the construction of these systems.