台灣河道大多坡陡流急，縱向沖刷能力大，為達消減洪水沖刷能力，達到穩定河床，保護跨河、防洪構造物安全及取水供民生、灌溉之目的，設置跌流工、防砂壩或攔河堰等橫向構造物為慣常使用之方法。雖可穩定上游河道，卻因砂石無法向下運送，而淤積於跌水工前河道渠床，導致跌水工上游渠床產生坡度，使水流成超臨界流況沖擊下游渠床，亦是消能工最易受損之處。本研究主要探討跌流工上下游坡度改變之沖擊力、沖擊位置及沖擊角度之理論解通式，並運用坡度效應比δ，以及坡度影響值η探討上下游渠床坡度對投潭水行為對各沖擊水力參數之影響。

Most of Taiwan rivers are rapid and steep with large capacity of vertical erosion. The hydraulic structures crossing the river such as drop structures, check dams and weirs have been widely used to decrease the flood erosion, stabilize riverbed, protect structures crossing the river, and provide civil water and irrigation. The hydraulic structures make upstream channel stable while the sediments cannot be transported downstream and stay in front of riverbed of drop structures on the other way. These structures usually induce the change of upstream slope and super critical flow condition which makes a large impact force on the downstream with the result of destroying energy dissipation structures. This paper aims at studying the theoretical formula of impact force, impact location and impact angle with the variation of upstream and downstream channel slopes. Then, the slope effect ratio δ and slope influence value η are used to study their effects on the above three hydraulic parameters