Using Numerical Models for Catchment-Scale Sediment Amount Variation Assessment under Extreme Rainfall Events

Abstract:

Lin-Bien river basin is one of the most sediment hazard-prone river basins in southern Taiwan. Typhoon Morakot in 2009 firstly brought over 2,500mm rainfall in this river basin and caused a large number of sediment in the upstream area. After 2009, large sediment disasters occurred annually and damaged or buried community located in the middle and upstream areas, especially one of the most serious events in 2010. However, more sediment occurred and affected meddle and downstream area during 2010 event than the one in 2009 even though more precipitation in 2009. In order to clarify the sediment amount changes in this river basin, author aims to focus on landslide and debris flow in the upstream area. To estimate the sediment amount by landslide and debris flow, TRIGRS and Flo-2D were used. TRIGRS is for landslide and Flo-2D is for debris flow. The sediment amount changes during 2009 and 2013 were analyzed and the total sediment amount was estimated by landslide volume, debris flow volume by part of landslide. In order to have more reliable and precisely sediment estimation amount under continuous typhoon events scenario, topographic changes were analyzed by history disaster data, image data, and landslide inventory.

Finally, the author also collects data by field investigation. The sediment variation estimation model is finally constructed by the two numerical models. By this model, it is possible to estimate the probable sediment amount under climate change scenario. This is also significant results to discuss the long-term variation of sediment amount in a small catchment.