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Real-Time Hydrology of LID Systems, Rainfall-Runoff Hydrographs, and Modeling
Citation:
Ballestero, T., J. Houle, T. Puls, L. Mather, I. Barbu, R. Brown, AND Mike Borst. Real-Time Hydrology of LID Systems, Rainfall-Runoff Hydrographs, and Modeling. Presented at International Low Impact Development Conference 2015, Houston, TX, January 19 - 21, 2015.
Impact/Purpose:
Continuous monitoring of moisture content within bioretention and permeable pavement systems demonstrate that these systems rarely achieve saturation. Bioretention systems typically have a focused hydrograph at one or two locations where water enters the surface of the system and then is expected to spread over the surface of the entire filter. The inflow hydrograph vertically infiltrates into the bioretention media very proximal to where the water enters the system, with only large storms delivering sufficient water to cover the surface of the entire system. The bioretention media can serve to throttle the flow, with this physically occurring by unsaturated hydraulics. Comparison of the moisture content profiles and outflow hydrographs from underdrains underscore the importance of the unsaturated flow throttling mechanism.
Description:
Continuous monitoring of moisture content within bioretention and permeable pavement systems (porous asphalt and permeable pavers) demonstrate that these systems rarely achieve saturation. This is understandable for the permeable pavement because the watershed area to filter area ratio is usually one to one, however bioretention systems can exhibit ratios of twenty to one or higher. The permeable pavement shows fairly uniform loading since direct precipitation is the inflow hydrograph. Bioretention systems, on the other hand, typically have a focused hydrograph at one or two locations where water enters the surface of the system and then is expected to spread over the surface of the entire filter. More commonly however, the inflow hydrograph vertically infiltrates into the bioretention media very proximal to where the water enters the system, with only large storms delivering sufficient water to cover the surface of the entire system. The bioretention media can serve to throttle the flow, with this physically occurring by unsaturated hydraulics. Comparison of the moisture content profiles and outflow hydrographs from underdrains underscore the importance of the unsaturated flow throttling mechanism. Soil moisture at different levels in a bioterention system was measured via calibrated time domain reflectometry (TDR). The TDR probes were also used to compare vertical in situ moisture fluxes to downward infiltration and upwards evapotranspirative (ET) fluxes as well as overall water balance. ET and infiltrative losses were high and promoted upwards of 70% runoff reductions. As expected, these losses are seasonal in nature.
URLs/Downloads:
http://submissions.mirasmart.com/ASCE/LID2015/Itinerary/ConferenceMatrixEventDetail.asp?id=26
http://content.asce.org/conferences/lid15/program.html