|BOOMER, KATHLEEN - Nature Conservancy|
|GELDER, BRIAN - Iowa State University|
|MCLELLAN, EILEEN - Environmental Defense|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2015
Publication Date: 4/27/2015
Publication URL: http://handle.nal.usda.gov/10113/60766
Citation: Tomer, M.D., Boomer, K.M., Porter, S.A., Gelder, B.K., James, D.E., McLellan, E. 2015. Agricultural conservation planning framework: 2. Classification of riparian buffer design-types with application to assess and map stream corridors. Journal of Environmental Quality. 44:768-779.
Interpretive Summary: Riparian zones can be managed in different ways to improve water quality, by intercepting surface runoff, influencing shallow groundwater, and by stabilizing streambanks. A method to identify and map these riparian management opportunities for watershed planning has been developed. The locations of major surface runoff contributions and widths of shallow water table zones along a stream are classified to provide recommendations for buffer vegetation and width. Buffer designs include multi-species buffers of varying widths, buffers that trap runoff and sediment, buffers that can mitigate contaminants in shallow groundwater, and places where narrow buffers can improve or maintain streambank stability. This system was evaluated for six headwater watersheds in Iowa and Illinois. The number of riparian zones with wide zones of shallow water table varied among Major Land Resource Areas, but were the most common setting in all six watersheds, being found along 23-53% of streambanks. Riparian zones with wide areas of shallow water table are difficult to farm, but could be managed to emphasize mitigation of flood impacts or nutrient loads. Riparian settings where buffers should be designed to intercept runoff and/or stabilize streambanks consistently occupied about 2.5% (+/- 0.2%) of the watersheds and would intercept overland flows from 81-94% of the watershed land areas. This riparian-type classification scheme could provide a basis for developing riparian corridor plans and identifying management priorities in headwater watersheds in glaciated landscapes of the agricultural Midwest. Application is meant to provide an information resource for local planning and watershed improvement efforts. Software tools that apply the classification system to watershed data and provide maps to help in planning are being made available. This software will be of interest to watershed planners, and agricultural and conservation interest groups interested in planning methods that can improve water quality and ecosystem services while maintaining agricultural productivity.
Technical Abstract: A watershed’s riparian corridor presents opportunities to stabilize streambanks, intercept runoff, and influence shallow groundwater with riparian buffers. This paper presents a system to classify these riparian opportunities and apply it towards riparian management planning in HUC12 watersheds. High resolution (3-m grid) digital elevation models derived from LiDAR (Light Detection And Ranging) data are analyzed to identify spatial distributions of surface runoff contributions and shallow water tables in a watershed’s riparian zones. Results are tabulated and a cross classification is applied to convey recommendations for buffer vegetation and width. Classes of buffers include those primarily placed to: 1) trap runoff and sediment; 2) influence shallow groundwater; 3) address both runoff and shallow groundwater, and; 4) maintain/improve stream bank stability. This system was applied to two headwater watersheds from each of three landform regions found in Iowa and Illinois. Riparian buffers that could intercept runoff and/or stabilize streambanks would occupy about 2.5% of the total areas of these watersheds, but intercept runoff contributions from 81-94% of the watersheds. However, the distributions of riparian zones where shallow water tables (SWT) were >25 m wide varied according to landform region. Nevertheless, these riparian zones with a wide SWT area were the most common riparian setting in all six watersheds, and found to occupy 23-53% of stream bank lengths among the six watersheds. The wide SWT setting provides opportunities to reduce nutrient loads carried via groundwater, and could be managed for a variety of ecosystem services. This riparian classification and mapping system should provide a consistent basis for developing riparian corridor plans and identifying management priorities in Midwestern headwater catchments where high resolution elevation data are available.