Model investigations were conducted to determine the adequacy of a gravity type spillway to be located on the Kiamichi River, Okla., for flood control, water supply, recreation, and fish and wildlife purposes. The investigations of the Hugo Dam spillway were primarily concerned with flow conditions in the approach channel, stilling basin, and exit channel. The model indicated that features of the original design structure were unsatisfactory; however, certain modifications that improved hydraulic performance and reduced construction costs were developed. The capacity of the spillway as determined with the model was greater than that computed. Subsequent modifications to the spillway design to effect economy and eliminate surging at the abutments did not affect the capacity. The performance of the original design stilling basin was satisfactory in the dissipation of all spillway discharges. However, alternate designs were developed to reduce construction costs without impairing hydraulic performance. The size and placement of riprap in the approach and exit channel were determined by model tests. (Author).