After the 1999 Chichi earthquake, the site of the Shigang Dam became a knickpoint in the discontinuous riverbed profile. Sediment became blocked by the dam, causing a lack of sediment supply that led to frequent damage to the structures along the river downstream, followed by a series of engineering repairs. For several years,transverse structures such as groundsills were used, and regular reservoir dredging was performed to maintain the water
supply function. However, the river still appears unbalanced, with sediment deposition in the upstream and degradation downstream of the dam. One-dimensional sediment transport simulation indicates that with the current layout the imbalance will likely continue into the future; however, if Shigang Dam is removed, the downstream deposits will gradually return and the continuity of the river will be restored. Therefore, we suggest that administrators should start planning for the removal of Shigang Dam to restore the morphology of the Da-Jia River to a natural state and arranging for an alternative water supply.
Key Words: Shigang Dam, dam removal, river morphology evolution, Dajia River