Low-Head Dam Reverse Roller Remediation Options

Abstract

The writers examine possible remediation options to mitigate the dangers found at low-head dams, using computational fluid dynamics and physical model tests. The objective was to identify an option that could be relatively simple to implement, would reduce the strength, or eliminate the dangerous reverse roller found downstream of low-head dams. Two promising options were identified, consisting of (1) ramps spaced along the channel width, or (2) horizontal platforms protruding from the downstream face of the dam. Many designs were investigated, resulting in six that were rigorously tested for flat-topped and ogee-crested weirs. The effectiveness of the options was evaluated based on entrapment times of dummies introduced into the flow. One of the platform designs was the most effective option on both dam shapes. A ramp design also had good results, but was only tested on flat-topped dams.