ANALYSIS OF CLIMATE CHANGE IMPACTS ON RUNOFF AND SEDIMENT YIELD IN CENTRAL TAIWAN

摘要

Numerous typhoons and torrential rains have confronted Taiwan over the years due to climate change. Severe floods and sediment related disasters have been a norm. What levels of change we can expect for runoff and sediments from climate change remains critical and is a significant challenge for the disaster prone island. Not only will the challenge be on disaster mitigation measures, but also the entire water resources management sector. Several models have been developed and applied; however, most have limited accuracy due to their inability to factor in spatial changes for both hydrologic and physiographic factors. In the present study, a physiographic soil erosion deposition (PSED) model is employed to simulate runoff and sediment yields during storm events. The PSED model is integrated with Geographic Information System (GIS) making it capable of handling enormous data. It also entails rainfall-runoff model and a basin scale erosion-deposition model. PSED model is validated using discharge and sediment data from Chou-shui river basin during two typhoon events. Simulated flow hydrographs and sediment transport rates are in good agreement with observed data. A one-day and a two-day storm for baseline (1980-1999) and climate change scenario A1B (2020-2039) for 2, 5, 10, 25, 50, 100 and 200-year return are applied to predict future sediment yields. Results indicate that for one-day storm events, sediment yield decreases for return periods 2, 5 and 10. Sediment yield shows an increasing trend for all return periods during two-day storm events.