Contour buffer (or filter) strips are strips of perennial vegetation planted along topographic contours, which may be alternated with wider cultivated strips that are farmed on the contour. Contour buffer strips are in-field runoff control practices that use permanent vegetation to decrease the length of slopes along which runoff accumulates, and thereby reduce sheet and rill erosion. They are similar yet complementary to grassed waterways because both use grass vegetation, but contour buffer strips are oriented differently by being placed along topographic contours to intercept flows. This practice can be used in combination with grassed waterways, but the types of grass may differ with stiffer stems being preferred in buffer strips. This typically occurs at lower slope (i.e., footslope) positions. This approach is, in essence, based on recent research in Iowa that has documented benefits of reduced runoff volume and improved water quality derived from installation of contour buffer strips, particularly when placed at footslope positions (Zhou et al., 2014; Hernandez-Santana et al., 2013).

Output buffers strips are smoothed using a PAEK algorithm (Polynomial Approximation with Exponential Kernel) to smooth sharp angles and provide results that should better accommodate farming operations. Note output contour location will usually need to be further modified or smoothed to maintain trafficability for farm implements (that is, results should not be viewed as an actual suggested design/layout for the practice in any given field). A field boundary ID (FBndID) and mean slope is attributed to each contour buffer strip included in the output layer.

Hernandez-Santana, V., X. Zhou, M.J. Helmers, H. Asbjornsen, R. Kolka, and M.D. Tomer. 2013. Native prairie filter strips reduce runoff from hillslopes under annual row-crop system, Iowa USA. Journal of Hydrology. 477:94-103.