San Ramon Bypass Channel Overflow Weir Contra Costa County, California. HydraulicModel Investigation

摘要

Tests were conducted on a 1:25-scale model of the San Ramon Bypass Channel,Contra Costa County, California, to develop an overflow weir to remove flows upstream of the covered channel in excess of the 100-year frequency discharge. The overflow weir would remove flows upstream of the covered channel reach to maintain open channel flow conditions through the covered reach and to not exceed channel capacity downstream of the covered reach. The model reproduced approximately 900 ft of the San Ramon Bypass Channel, 100 ft of the Sans Crainte Creek channel, and 400 ft of the catch channel. The model was constructed so that the slopes of the channels could be adjusted to reproduce various energy gradients equivalent to those resulting from different prototype Manning's n roughness factors. The slopes of the model were initially adjusted to produce an energy gradient resulting from a Manning's n roughness factor of 0,012 in the prototype. Based on a initial water-surface profiles measured in the model without the overflow weir installed, the weir height was set at 13.25 ft above the center line invert elevation and the weir length was set at 200 ft. With the overflow weir installed in the model, water-surface profiles and discharges over the weir were recorded with various flow conditions. The weir length was shortened from the upstream end by 25, 50, and 75 feet. Keywords: Hydraulic models. (Author) (KR)