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Comparison of Measured and Simulated Urban Soil Hydrologic Properties
Schifman, L. AND W. Shuster. Comparison of Measured and Simulated Urban Soil Hydrologic Properties. Journal of Hydrologic Engineering . American Society of Civil Engineers (ASCE), Reston, VA, 24(1):04018056, (2019).
As part of contemporary stormwater management, urban communities are increasingly integrating different types of green infrastructure (GI, i.e., infiltration, storage) into their portfolio of stormwater control measures (Fletcher et al., 2014). In this context, green infrastructure serves as a break in pervious surface, and can be used to increase sewershed detention capacity, keep stormwater volume from entering the centralized collection system, and temper the inlet storm hydrograph peak. While the hydrology of impervious surfaces is relatively straightforward, pervious surfaces move from unsaturated to saturated states and regulate runoff losses via the infiltration process (e.g., infiltration-excess), and thus the runoff hydrograph (Woolhiser et al., 1996). This characteristic ranks hydraulic conductivity of soils among one of the most sensitive parameters that can shape the runoff dynamic in mixed impervious-pervious urban environments. We define infiltration as the rate at which water moves from the surface into the shallow subsurface that is usually unsaturated at the onset of rainfall, whereas drainage is the rate of flow in a saturated subsoil horizon. Therefore, accurate hydraulic conductivity values that represent the near-surface hydrology of a small catchment area (e.g., a vacant lot) may contribute to the planning and design process for infiltrative green infrastructure technologies. Properly designed, these technologies can play a key role in reducing the amount of inflow into wastewater collection systems, minimize return flow, and lower the risk of system malfunctions such as a combined or septic sewer overflow events.
Urban communities use hydrologic models to plan for and assess the effectiveness of stormwater control measures. Although emphasis is placed on soils as permeable surfaces that regulate the rainfall-runoff process, representative soil hydrologic parameters for urban areas are rare. The extent to which measured and commonly simulated hydrologic data may differ is also largely uncharacterized. As part of the US EPA urban soil assessment, infiltration and drainage rates were measured in 12 cities, and the authors compared these measured data to estimates generated from the EPA National Stormwater Calculator (NSWC), United States Department of Agriculture (USDA) Soil Survey Geographic Database (SSURGO), and USDA Rosetta. The analysis highlights the overall lack of soil hydrologic data for many cities in the NSWC and SSURGO and show that common prediction algorithms for infiltration and drainage poorly represent urban soil hydraulics. Paired comparison of field-measured values and model-estimated values resulted in root-mean-square errors ranging from 23 to 173 mm/h. These findings are presented in the context of planning for effective stormwater and wastewater management practices, and the need for confirming simulation results with site-specific field data.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
SUSTAINABLE TECHNOLOGY DIVISION