Evaluating Uncertainty in Fluvial Geomorphic Response to Dam Removal

Abstract

Dam removal tends to produce a series of changes in river morphology. Whereas decisions pertaining to dam removal are typically evaluated from a deterministic viewpoint, this study develops a stochastic framework for assessing the effects of hydrological variability on morphological changes in river channels resulting from dam removal. Our approach yields probability distributions for channel responses that can be used in decision-making. Application of the framework to the 25-m-tall Shihgang Dam on the Dajia River in central Taiwan reveals that the area most geomorphically sensitive to removal of the dam lies 1,200–3,600 m downstream of the dam site. We also investigate the influence of flow regime on geomorphic response using indicators of hydrologic alteration (IHA) and find that higher flows result in more pronounced channel evolution and greater thalweg migration.