Water and Sediment Discharge from Small Mountainous Rivers, Taiwan: The Roles of Lithology, Episodic Events, and Human Activities

Taiwan’s natural setting creates highly vulnerable watersheds whose rivers discharge disproportionately large quantities of sediment to the coastal ocean. The 16 Taiwanese rivers analyzed in this article discharge∼180 Mt yr-1 ∼ 180 Mt yr - 1 of sediment to the coastal ocean, although totals over the past 20 years have varied between 16 and440 Mt yr-1 440 Mt yr - 1 . The mean annual sediment yield of9500 t km-2 yr-1 9500 t km - 2 yr - 1 for the 16 rivers is 60-fold greater than the global yield of150 t km-2 yr-1 150 t km - 2 yr - 1 , but mean yields for the individual rivers vary by more than 2 orders of magnitude, from 500 to71,000 t km-2 yr-1 71 , 000 t km - 2 yr - 1 . Most sediment erosion and delivery occur in response to typhoon-generated floods, as evidenced by the fact that>75% > 75 % of the long-term flux occurs in