Webbers Falls Lock and Dam will comprise a nonnavigable dam of 12 gated spillway bays, a 110- by 600-ft lock on the left bank, and a three-unit powerhouse with a discharge capacity of 35,500 cfs on the right bank. A 1:120- scale fixed-bed model was used to determine flood stages at the dam, navigation conditions in the lock approaches, tendency for sediment deposition in the lower lock approach, and magnitude of surges generated in the upper lock approach canal by lock filling, and to develop modifications required to provide satisfactory conditions. Modifications to the original design required to produce satisfactory navigation conditions in the approaches to the lock were developed and flow conditions through the spillway were improved. In general, results have indicated : Realignment of the entrance to the upper lock approach canal would be required to eliminate hazardous conditions for downbound tows attempting to enter the canal. Ports would be required in the upper guard wall to reduce crosscurrents near the entrance to the upper lock approach canal and to reduce surges resulting from lock filling operations. Surges would develop in the upper lock approach canal from lock filling operations. Magnitude of the surge could be reduced so that it would have no serious effect on navigation with ports in the upper guard wall and a surge basin near the lock. Water-surface elevations at the dam embankment to the left of the lock could be lowered by structures designed to eliminate overbank flow toward the embankment and improve the alignment of currents approaching the spillway. Sediment below the dam would be moved into the lower approach channel and could produce shoaling. Size of the surge basin and length of the upper guard wall could be reduced without any appreciable effect on navigation. The amount of excavation in the approach to the spillway could be reduced appreciably without affecting flow through the spillway.