The Coastal Mountain Range to the east of the Hua-Tung Valley blocks the eroded soil from flowing out to the sea, so it continually accumulates downstream, building up the riverbeds ever higher. Even the railroad tracks are annually displaced by the sand and stone, and must be raised every year.
花東縱谷東邊矗立的海岸山脈，則阻礙沖蝕物流出外海，不斷堆積在下游，河床日益填高，連溪床上的鐵軌也因此每年被砂石淹沒，得年年重新加高。