Incision and width changes caused by dam removal: experiments and data analysis

Abstract

Dam removal may cause severe disruptions to the river, both upstream and downstream of the former location of the dam. The aim of the paper is to study the physical response to dam removal in the former deposit upstream. Specifically, the goal is to analyze bed profile evolution and the associated change in channel width. An experimental investigation has been carried out to study these topics. The experiments consisted of (i) a study of the delta front progradation within the impoundment and (ii) a set of runs in which profile and planform changes caused by dam removal were continuously monitored. All experiments were performed in a tilting flume filled with a non-uniform sediment mixture made of sand and gravel. The dam itself was made of three slats that were sequentially removed, allowing the remaining height to control the response of the river to removal. During the early stages of each removal, a narrowing process was observed while in more advanced phases, channel widening was reported. Narrowingwidening process was linked to bed erosion. The bed degradation process has been satisfactorily reproduced by a set of empirical equations that describe (i) bed erosion through foreset slope evolution and (ii) sediment discharge downstream.