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Abstract

This study investigated silt movement and the influence of fine sand on downstream ecology during movement by using a small indoor physical model for simulating onsite conditions. The obtained data were analyzed to determine the impact of silt on ecological habitats and can serve as a reference for future onsite and ecology investigations. Before a dam was removed to allow a downstream riverway to restore the initial environment, the riverway stabilized at approximately 960 s, and the dam was removed at approximately 1140 s. After the dam was removed, the silt in each channel section evidently increased, and after a certain time, it gradually stabilized. Before the dam was removed, some of the silt trapped by the dam was moved to the lower reach by flowing water and filled between coarse particles. After the dam was removed, the silt was instantly moved to the lower reach. Consequently, the habitat was critically affected; however, the silt with a constant flow stabilized as time passed. Thus, the habitat was gradually restored. For this study, one half of the dam was removed at the beginning, and the other half was removed subsequently. However, the silt trapped by the remaining half of the dam was limited and, therefore, exerted little impact on the downstream riverway after the remaining half of the dam was removed. The phenomenon observed after the upstream dam was removed was repeated when a 6-cm dam was set downstream.

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