Basic geologic information is essential to planning flood-control measures in the Upper East Fork Drainage Basin, an area of about 2,300 square miles in east-central Indiana. Principal streams of the basin include the Driftwood, Big Blue, Little Blue, and Flatrock Rivers; Sugar, Clifty, and Sand Creeks; and the upper part of the East Fork of White River, from Columbus downstream to the south line of Bartholomew County. Shelbyville is nearly centrally located within the basin. The present drainage system of the Upper East Fork basin is dominated by a pattern of southwestward-flowing streams. Many of these streams follow inherited valleys that were used by glacial meltwaters during the Wisconsin Age of the Pleistocene Epoch. Preglacial streams, however, flowed in a more westerly direction, generally following the regional slope of the bedrock surface. Although the dip of the bedrock formations is somewhat steeper than the slope of the bedrock surface, the close correspondence in direction between the two clearly indicates that the regional slope is structurally controlled…