● Over-development and over-construction on hillsides (erosion) ● Dams (retard the flow of the river, producing silt and sediment) ● Particulates and acid rain.
●山坡地濫墾、濫建（水土流失）。●水壩（使河流速減緩、泥沙淤積）。●落塵、酸雨。