Tropical cyclone rainfall influences sediment production and transport in ways that are not reflected in annual mean rainfall. Here we quantify the meteorological and geomorphic impact of Typhoon Toraji, which struck Taiwan in July 2001 and was the first major tropical cyclone to affect the island after the 1999 Chichi earthquake. Record water and sediment discharge were recorded on the Choshui, Kaoping, and Hualien Rivers. Two meteorological processes controlled sediment discharge on the Kaoping, Choshui, and Hualien Rivers. Eyewall processes, enhanced by orographic effects, brought extremely heavy rainfall (>100 mm/h) to the landfall zone in east Taiwan for a short period (about 2 hours), triggering slope failure and the highest sediment concentration ever recorded on the Hualien River. The south-western Central Range received about 10 hours of less intense rainfall (between 10 and 50 mm/h), orographically controlled, that triggered the second highest sediment concentration recorded on the Kaoping River and flushed coseismic debris from storage into the Choshui River system. These results illustrate how tropical cyclone rainfall and its geomorphic consequences are a joint function of tropical cyclone track climatology and topography.

doi:10.1029/2005JF000428