HYDROLOGIC AND TERRAIN VARIABLES TO AID STRATEGIC LOCATION OF RIPARIAN BUFFERS

Authors: Burkart, Michael; James, David; Tomer, Mark

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2003
Publication Date: 9/1/2004
Citation: Burkart, M.R., James, D.E., Tomer, M.D. 2004. Hydrologic and terrain variables to aid strategic location of riparian buffers. Journal of Soil And Water Conservation. 59(5):105-115.

Interpretive Summary: Methods for defining the placement of vegetated buffers along streams (riparian areas) to meet specific water quality goals are needed to obtain the maximum benefit from the investment in the minimum amount of land planted to buffers. The results of this study show that areas along small, permanently flowing streams may provide better opportunities to locate buffers than areas along larger streams. Riparian areas along small streams have features that will allow the buffers to intercept water-borne contaminants in sufficient quantities to show measurable differences in the stream. The four indicators examined in this study may provide information to locate buffers in specific positions along streams to meet specific water quality goals. The methods for calculating these indicators use elevation data readily available for most of the United States. These results may be important to producers and agency staff who are planning the location of buffers for one of several water-quality objectives. Methods for defining the placement of vegetated buffers along streams (riparian areas) to meet specific water quality goals are needed to obtain the maximum benefit from the investment in the minimum amount of land planted to buffers. The results of this study show that areas along small, permanently flowing streams may provide better opportunities to locate buffers than areas along larger streams. Riparian areas along small streams have features that will allow the buffers to intercept water-borne contaminants in sufficient quantities to show measurable differences in the stream. The four indicators examined in this study may provide information to locate buffers in specific positions along streams to meet specific water quality goals. The methods for calculating these indicators use elevation data readily available for most of the United States. These results may be important to producers and agency staff who are planning the location of buffers for one of several water-quality objectives.

Technical Abstract: Digital elevation data and stream-flow records were used to estimate and map four hydrologic variables that influence the optimum location of vegetated riparian buffers; wetness index, baseflow index, sediment-transport index, and discharge index. A discharge index shows that riparian buffers along first order streams can intercept more than an order of magnitude more runoff and groundwater than those occupying a similar reach along larger streams. A wetness index showed that shallow saturated conditions are more frequent along small streams. Unstable bank conditions may be more prevalent along larger streams with steep slopes and large catchment areas as indicated by significantly smaller wetness index values. The baseflow index does not significantly vary among stream orders. Sediment transport index values were significantly smaller along first order streams reducing the potential to trap sediment. Generally, first order streams provide access to larger riparian catchments and a greater range of opportunities to intercept discharge and process contaminants before they enter stream channels. When contaminants are specified, the proposed indices can be used to define optimum locations and number of stream reaches needed to meet water quality improvement goals. Results of research on the water quality response of specific buffer designs can be combined with terrain-derived hydrologic variables to estimate the potential water quality improvement produced by buffers in various combinations of stream reaches.