Evaluation of costs and efficiencies of urban Low Impact Development (LID) practices on stormwater runoff and soil erosion in an urban watershed using the Water Erosion Prediction Project (WEPP) model

Authors: GUO, TIAN - Purdue University; SRIVASTAVA, ANURAG - University Of Idaho; Flanagan, Dennis; LIU, YAOZE - State University Of New York (SUNY); ENGEL, BERNARD - Purdue University; McIntosh, Madeline

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2021
Publication Date: 7/30/2021
Citation: Guo, T., Srivastava, A., Flanagan, D.C., Liu, Y., Engel, B.A., McIntosh, M.M. 2021. Evaluation of costs and efficiencies of urban Low Impact Development (LID) practices on stormwater runoff and soil erosion in an urban watershed using the Water Erosion Prediction Project (WEPP) model. Water. 13. Article 2076. https://doi.org/10.3390/w13152076.
DOI: https://doi.org/10.3390/w13152076

Interpretive Summary: Runoff and soil erosion are critical problems that affect many land uses, including urban areas where soils may often be left bare and vulnerable due to construction activities. Additionally, urban areas often have many surfaces where water cannot infiltrate into the soil, such as roads and parking lots. These modifications to the soil surface can greatly alter the surface hydrology and risk of increased runoff and sediment losses. Practices to reduce or minimize runoff and erosion in urban areas include native vegetation plantings, permeable pavement, rain gardens, and detention ponds. In this study, we examined the effectiveness of the different practices for a 141-ha watershed in Austin, Texas by applying a process-based water erosion computer simulation model with inputs specific for the climate, soils, topography, and land management scenarios. We also computed the costs of implementing the different practices, so that we could determine the most cost-effective. Results indicated that scenarios with native vegetation plantings were the most cost-effective with the greatest reductions in runoff and sediment losses. Permeable pavement was more effective in reducing daily runoff rates, runoff depths, and sediment delivery from extreme storm events for hillslopes than the rain gardens or native vegetation plantings. These results impact scientists, urban planners, and conservation agency personnel trying to determine best and most economical practices to reduce runoff and sediment losses from urban areas.

Technical Abstract: Storm events and soil erosion can adversely impact flood control, soil conservation, water quality, recreation economy, and ecosystem biodiversity in urban systems. Urban Low Impact Development practices (LIDs) can manage stormwater runoff, control soil losses, and improve water quality. The Water Erosion Prediction Project (WEPP) model has been widely applied to assess the responses of hydrology and soil losses to conservation practices in agricultural and forested areas. This research study is one of the first to calibrate the WEPP model to simulate acceptable streamflow discharge in the Brentwood watershed in Austin, Texas, and apply the calibrated WEPP model to assess the impacts of LIDs. The costs and impacts of various LID scenarios on annual water balance, and monthly average, and daily runoff volumes, and sediment losses at hillslopes and at the watershed outlet were quantified and compared. The LID scenarios identified (native planting in Critically Eroding Areas (CEAs), native planting in all suitable areas, native planting in CEAs with detention ponds, and native planting in all suitable areas with detention ponds) could reduce the predicted average annual stormwater runoff by 20% - 24% and sediment losses by 86% - 94% at the watershed outlet, and reduce the average annual soil loss rates on hillslope profiles in sub-watersheds by 86% - 87% with the lowest costs ($2,991/yr - $5,257/yr). Watershed/field characteristics, locations, areas, costs, and the effectiveness of the LIDs were essential in choosing the LID scenarios. These research results can help guide decision-making on the selection and implementation of the most economical and suitable LIDs to strengthen climate resilience and environmental sustainability of urban systems.