為解決國寶魚櫻花鉤吻鮭因防砂壩所造成族群隔離、棲息環境惡化以及近親交配等問題，本研究延續去年之研究方法與操作程序對七家灣溪集水區內之防砂壩做適當之開口處理，然而本研究之重點在於探討系列防砂壩改善工程對河床形態與輸砂特性之影響。根據水工模型試驗結果，本研究發現缺口拆除方式對河床之平均淤砂坡度影響不大，而河床之平均淤砂坡度則會隨壩體缺口深度之增加而變大；對於相同之三號壩斷面缺口形狀，一次拆除比分次拆除造成更深的沖刷坑度，而且沖刷坑深度會隨著下游壩體拆除的深度增加而變大；橫斷面的變化與壩體改善的拆除方式並無顯著關係，然而上游淘刷範圍隨壩體缺口深度加深而變大；泥砂排出量與其濃度會隨著缺口深度之增加而增加，而一次拆除的方式之泥砂濃度增率比分次拆除的泥砂濃度增率高約1.5倍，因此分次拆除的壩體改善施工方式對泥砂濃度增率以及下游櫻花鉤吻鮭的棲息地衝擊較小。

　　　　　By partially breaking the dam body or cutting opening appropriately, our experimental studies tried to provide appropriate river rehabilitation measure for Formosan Salmon (Oncorhynchus masu formosanum) in Sheipa National Park. With supports from previous research, this study focused on the effects of improvement engineering of serial check dams on channel morphology from hydraulic model experiment, several results were concluded regarding to the deposit slopes, cross sections, dimension of scouring hole, and sediment discharge of observed channel. The average deposit slope for the observed channel did not change apparently either conducting the dam-conversion simultaneously or gradually, however it increased with the increasing opening depth of dam No.3. With same opening depth applied at dam No.3, deeper scouring hole was found at the downstream channel of dam No.4 when the dam-conversion was conducted simultaneously. Besides, the depth of downstream scouring hole of dam No.4 increased with increasing opening depth at dam No.3. The changes in the channel cross sections between dam No.3 and No.4 mainly related to the opening depth applied at dam No.3 and the scouring range extended with increasing opening depth. Overall, the average deposit slope, changes in cross sections, scouring hole, and sediment discharge of downstream channel of dam No.4 increased with deeper opening depth of dam No.3. however, the effects on those channel morphologic phenomena were milder when the opening-developing procedures were applied gradually.