Kahoma Stream Channel Improvement Project, Maui, Hawaii. Hydraulic Model Investigation

摘要

Tests were conducted on a 1:30-scale model of Kahoma Stream to determine the adequacy of proposed channel improvements for Kahoma Stream and the offshore area. The model reproduced approximately 6,100 ft of Kahoma Stream and approximately a 350-ft-long by 500-ft-wide offshore area. The model was constructed so that the slopes of the high-velocity channel could be adjusted to reproduce various energy gradients equivalent to those resulting from different prototype Manning's n roughness factors. Unsatisfactory flow conditions were observed in the debris basin due to entrance conditions into the debris basin. Large cross waves were also present in the transition just downstream of the debris basin which resulted in pronounced super elevation of the water surface several hundred feet down-stream in the high-velocity channel. A weir and transition design, which consisted of a three-sided weir with a wedge-type transition, was developed that provided satisfactory flow conditions in the transition, but little improvement in flow conditions was observed in the debris basin. Improvements in flow conditions in the debris basin were observed when debris was present in the basin resulting from debris tests or when the invert of the debris basin was unlined.