Improving the integration of dams in the natural environment and recovering their storage capacity lost to sedimentation are two topics of growing concern. To address these two issues, the accumulated sediments are being relocated down into the dam's tail water. This process is called sediment replenishment (SR), and has been tested in Japan and other parts of the world. More study is required to enhance its effectiveness, and the present research thus offers a practical method to assess positive outcomes of SR on the downstream ecosystems. It is shown through a 2-D numerical model of Nunome River that SR positively influences the river's morphology by generating riffle-pool structures and sand bars. These patterns increase the channel's global heterogeneity, and create hydraulically favorable habitats for fish and spawning. The habitat quality was quantified by applying suitability indexes to the computed hydraulic variables, and the SR-induced geomorphologies were designed according to field observations of past SR tests and validated by the 2-D model