Agricultural Conservation Planning Framework: 2. Classification of Riparian Buffer Design Types with Application to Assess and Map Stream Corridors

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.