COMPREHENSIVE RESEARCH AND IMPACTS OF MANAGEMENT OF IMPERVIOUSNESS ON WATERSHED HYDROLOGY

Authors: SHUSTER, W - USEPA; ZHANG, Y - OAKRIDGE INST. SCI & EDU; Bonta, James - Jim; THURSTON, H - USEPA; Pappas, Elizabeth

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/15/2004
Publication Date: 10/11/2004
Citation: Shuster, W.D., Zhang, Y., Bonta, J.V., Thurston, H., Warnemuende, E.A. 2004. Comprehensive research and impacts of management of imperviousness on watershed hydrology. Proceedings of 2004 CIGR International Conference, Oct. 11-14, 2004, Beijing, P.R. China.

Interpretive Summary: Increasing area of impervious surface is the most notable change in hydrology in urbanizing watersheds, and its impacts on the hydrologic cycle and terrestrial ecology are many. The mechanisms through which these impacts are manifested are not well understood, hampering their effective management. We have identified two areas of research focus, the first is a watershed assessment of the alteration of hydrologic cycle in response to urbanization due to spatial location of imperviousness; and the second is a low-cost approach to managing storm water runoff at the watershed scale. There are few or no studies that we are aware of which determine the underlying mechanisms and extent of these impacts over the course of landscape alteration through the incremental addition of impervious surfaces over time. The United States Environmental Protection Agency (USEPA)-Office of Research and Development (ORD)-National Risk Management Research Laboratory (NRMRL) and the United States Department of Agriculture (USDA)-Agricultural Research Service (ARS) initiated a pilot program to study the impacts of different extents and geometries of simulated impervious surface on experimental watersheds located at the North Appalachian Experimental Watershed, Coshocton, Ohio (USA). As a complement to the experimental investigation of fundamental processes in urban hydrology, we are exploring distributed stormwater management practices that may mitigate the deleterious impacts of stormwater flows in a previously developed 150 hectare residential neighborhood where impervious surface impacts are typically left unmitigated. Here, we use an urban watershed as a pilot study to determine whether altering imperviousness of houses and house lots through Best Management Practices (BMPs; e.g., rain gardens) can be implemented throughout the residential areas. Also, we are exploring whether an economic incentive program can be developed, which centers on trading detention responsibility among lot holders to achieve a preset watershed-level cap on runoff. We implemented a before-after/control-impact experimental design and initiated hydrologic and ecological monitoring at five stations distributed across the various land uses and impacted areas to determine whether the placement of BMPs at the lot in the residential area have effected an improvement in hydrologic and ecological status for tributaries draining urbanized areas of the watershed. We present a basic description of the background and experimental approach for these projects. These urbanization projects are beginning and will provide science-based environmental and economic information on BMPs and runoff producing processes. They will be of interest to those persons interested in evaluations of BMPs such as environmental regulating agencies (e.g., USEPA, state EPAs), universities, watershed groups, and university and government researchers.

Technical Abstract: Impervious surface is one of the primary agents of hydrologic change in urbanizing watersheds, and its impacts on hydrologic cycles and terrestrial ecological regimes are multifold. The mechanisms through which these impacts are manifested are not well understood, hampering effective management of these impacts. We have identified two areas of research focus, the first is in-situ assessment of the alteration of hydrologic cycle in response to urbanization; and the second is a systemic, low-cost participatory approach to managing storm water runoff at the watershed scale. There are few or no studies that we are aware of which determine the underlying mechanisms and extent of these impacts over the course of landscape alteration through the incremental addition of impervious surfaces over time. The United States Environmental Protection Agency (USEPA)-Office of Research and Development (ORD)-National Risk Management Research Laboratory (NRMRL) and the United States Department of Agriculture (USDA)-Agricultural Research Service (ARS) have initiated a pilot program to study the impacts of different extents and geometries of simulated impervious surface on experimental watersheds located at the North Appalachian Experimental Watershed, Coshocton, Ohio (USA). As a complement to the experimental investigation of fundamental processes in urban hydrology, we explore distributed stormwater management practices that may mitigate the deleterious impacts of stormwater flows in a previously developed 150 hectare residential neighborhood where impervious surface impacts are typically left unmitigated. Here, we use an urban watershed as a pilot study to determine whether parcel-level Best Management Practices (BMPs; e.g., rain gardens) can be implemented throughout the residential areas, and on the basis of an economic incentive program, which itself centers on trading detention responsibility among parcel holders to achieve a preset watershed-level cap on runoff. We have implemented a before-after/control-impact experimental design and initiated hydrologic and ecological monitoring at five stations distributed across the various land uses and impacted areas to determine whether the placement of BMPs at the parcel level in the residential area have effected an improvement in hydrologic and ecological status for tributaries draining urbanized areas of the watershed. We present a basic description of the background and experimental approach for these projects.