Abstract
Soil erosion and landslide triggered by heavy rainfall are serious problems that have threatened water resources in Taiwan watersheds. This study investigated the relationship among streamflow, sediment load, sediment concentration and typhoon characteristics (path and rainfall amount) during 2000–2017 for nine gauging stations in five basins (Tamshui River basin, Zhuoshui River basin, Zengwen River basin, Gaoping River basin, and Hualien River basin) representing the diverse geomorphologic conditions in Taiwan. The results showed that streamflow and sediment load were positively correlated, and the correlation was improved when the sediment load data were grouped by sediment concentration. Among these basins, the Zhuoshui River basin has the highest unit-discharge sediment load and unit-area sediment load. The soil in the upstream was more erodible than the downstream soil during the normal discharge conditions, indicating its unique geological characteristics and how typhoons magnified sediment export. The spatiotemporal variation in sediment loads from different watersheds was further categorized by typhoons of different paths. Although typhoon path types matter, the Zhuoshui and Hualien River basin were usually impacted by typhoons of any path type. The results indicated that sediment concentration, the watershed soil characteristics, and typhoons paths were the key factors for sediment loads. This study can be useful for developing strategies of soil and water conservation implementation for sustainable watershed management.
Highlights
Located at the junction of the Philippine Sea Plate and the Eurasian Plate, the high terrain in Taiwan was formed due to the strong orogeny and frequent earthquakes
This study aims to investigate the correlation between the sediment load and discharge in Taiwan by studying the relationships among streamflow, sediment transport, sediment concentration, and maximum daily typhoon rainfall during 2000–2017 for nine gauges in five basins (Tamshui River basin, Zhuoshui River basin, Zengwun River Basin, Gaoping River basin, and Hualien River basin)
The typical steep hillslopes found in Taiwan result in high streamflow speed, and the sediment exports brought by heavy rainfalls can be significant
Summary
Located at the junction of the Philippine Sea Plate and the Eurasian Plate, the high terrain in Taiwan was formed due to the strong orogeny and frequent earthquakes. Taiwan is the 13th highest precipitation country in the world, with an average annual rainfall of 2500 mm. The rapid flows from steep slopes are difficult to store in rivers. Due to the spatiotemporally uneven rainfall distribution and high population density, the available rainfall per person is less than one-sixth of the world’s average value, which indicates that Taiwan is the 18th high water-deficient country in the world [1]. Reservoirs have been built in middle and upper reaches of rivers for water storage. Typhoons invade Taiwan with heavy rainfall that wash hillslopes, causing landslides and debris flow into downstream areas. Many of the sediment disasters are caused by serious scouring of siltation in rivers, such as large-scale constructions in
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