MODELING EFFECTIVE FETCH IN A SMALL LINEAR MAN-MADE LAKE USING ARCGIS AND WRPLOT VIEW, SALT FORK LAKE, SOUTHEASTERN OHIO

Effective fetch, which is an important factor in the development of waves, is influenced by wind direction, wind speed and, in the case of small man-made lakes, the morphology of the river valleys. We modeled the affect of long-term weather patterns and their variations on the size of the effective fetch in Salt Fork Lake. Salt Fork Lake, which is located about 10 miles northeast of Cambridge OH, was originally intended to be a water source for the city but has become a major recreation area. The area is part of the unglaciated Allegheny Plateau and has, in general, flattened ridgetops and narrow stream valleys. The local geology which consists of the Pennsylvanian-age Conemaugh and Allegheny Groups influences the shape of the lake which is usually less than 1,200-feet wide. An earthen dam was completed in 1967 creating a 2952 acre lake with approximately 65 miles of shoreline.

Thirty years of wind data from seven regional airports (Columbus, Cleveland, Youngstown, Akron, Pittsburgh, Charleston and Huntington) was analyzed using WRPLOT View. The resultant vector for data from October through March was 245 (west-southwest winds) and the average wind speed was 4.26 m/s. Wind direction percentages, although, varied fairly evenly between due west (270) and due south (180). Effective fetch was modeled using a wind fetch model that follows the procedure of the Shore Protection Manual. The model was adapted for ArcGIS by David Finlayson. Effective fetch was calculated for the following wind directions: 180, 202.5, 225, 247.5 and 270. Arbitrarily using an effective fetch of 4000 feet as a minimum value we calculated the percentage of the total lake area that would have fetches of 4000 feet or more. A wind direction of: 180 yielded 0.67 percent, 202.5 yielded 4.8 percent, 225 yielded 4.5 percent, 247.5 yielded 2.8 percent, and 270 yielded 0.59 percent. These results show the effect of river valley morphology and wind direction variation on the effective fetch.