Red River Waterway, Lock and Dam Number 4. Report 4. Stilling Basin and Riprap Requirements. Spillway Hydraulic Model Study

Lock and Dam No. 4 is proposed for construction in a cutoff canal on the Red River approximately 71 miles below Shreveport, LA. The principal structures consist of a lock with an adjacent gated spillway and overflow weir. The lock, which will be 84 ft wide with 685 ft of usable length, will be located on the left bank line looking downstream and will have a maximum lift of 25 ft. The gated spillway will contain four tainter gates, 60 ft wide by 36 ft high, with a sill elevation of 86.0 ft (elevations (el) are in feet referred to the National Geodetic Vertical Datum), and an overflow weir with three 100-ft-wide hinged gates. The crest of the hinge-gated weir will be at el 115.0, and the top of the hinged gate in its fully raised (closed) position will be at el 122.0. Tests were conducted in a 1:40-scale model of Lock and Dam No. 4 to develop a satisfactory energy dissipator and a stable riprap protection plan. The original crest was lowered to el 85, a fifth tainter gate was added, and the three 100- ft-wide hinge-gated crests were replaced by a single 100-ft-wide baffled chute. Tests were conducted to compare the two designs, and data obtained with both designs are presented in this report. Water-surface profiles were measured for the full range of expected operating conditions. The recommended stilling basin provides adequate energy dissipation for normal flow and for a single gate fully open and half open operating with minimum tailwater. The recommended riprap protection plan in the upstream and downstream areas adjacent to the structure remained stable for these conditions.