518 - The Role of Estimated Soil Parameters on Bioretention Modeling

A new model for bioretention design, DRAINMOD-Urban, has shown good performance at small timesteps (1-5 minute) of matching both drainage and overflow volumes and event hydrographs. DRAINMOD-Urban uses the soil-water characteristic curve to consider the effect of soil moisture in the bioretention cell profile between storm events. Due to the dynamic changes in water table depth and soil moisture within bioretention cell media, soil properties play an important role model performance. Yet, these soil characteristics are not easily measured in the field or laboratory, so many models use estimations and simplifications often based on soil texture. Pedotransfer functions have also been used in modeling efforts to gain required soil inputs from easily measured soil properties. In this study, pedotransfer functions were used to derive the required soil parameters for DRAINMOD-Urban. Simulations with measured soil parameters were compared to those calculated by pedotransfer functions to understand the level of detail required for adequate simulation of flow through a bioretention system. This study will provide valuable information on the importance soil parameters play in modeling of bioretention cells and if pedotransfer functions can be used to reduce soil input complexity without hindering model performance.