The Da'an River is a river in northwestern Taiwan. It is the seventh-longest river on the island, it flows through Miaoli County and Taichung City for 105 km. It reaches the Taiwan Strait between the Dajia District and Da'an District, Taichung. The Da'an River was affected by the 1999 Jiji earthquake, where a gorge was formed (called Da'an River Grand Canyon ). In some of the fastest erosion geologists have ever seen, the gorge is being eaten away from its upstream end at a rate of 17 meters per year. They expect the gorge to be erased after 50 years.