DESIGN OF ROCK CHUTES

Rock chute design information is consolidated from several sources to provide a comprehensive design tool. The rock slope stability, boundar y roughness, and outlet stability of rock chutes are each discussed. T ests were performed in three rectangular flumes and in two full size s tructures. Angular riprap with a median stone size ranging from 15 to 278 mm was examined on rock chutes with slopes ranging from 2 to 40%. The typical mode of channel failure is described. An empirical predict ion equation is presented relating the highest stable discharge on a r ock chute to the median stone size and the bed slope. A boundary rough ness relationship is also presented that relates the Manning roughness coefficient to the median stone size and bed slope. These tests also suggest that the riprap size required for stability on the slope will remain stable in the outlet reach even with minimal tailwater. This ar ticle contains information needed to perform a rock chute design.