The island of Taiwan lies in the collision area of Eurasian Plate and is characterized by the rugged mountains all over despite of the fact that the area is not very big. Mountains over 1000 meters occupy1/3 of the total area, granting rivers in Taiwan properties of high gradient, swift current, strong destructive power and high silt content.
People were born along the rivers, relying on water resources for daily needs and economic development. However, because of over-exploitation, deficient hill-side conservation and artificial destruction on the conservation of water and soil (e.g. drive ranges, amusement parks, resorts and mining development, etc), when it comes to torrential rain or rainy seasons, a drench of rain pouring into rivers can form swift current, causing the maximum flow (namely flood peak) during the flood period to increase. With the skyrocketing water flow, it is impossible to make the river embankment higher or wider. The issues of flood are created thus.