Over the years, uncontrolled logging, construction work on hillsides and the removal of sand and stones from river banks, have all depleted natural drainage and changed river courses.
例如林木濫伐、坡地濫墾、洪氾區違建、河床地耕作、濫採砂石等，多少影響水流的正常發展，使得水無路可走，只好泛濫。