Fluvial transportation and sedimentation of the Fu-shan small experimental catchments

Abstract

The Fu-shan long-term ecological site is one of Taiwan's mid-altitude forest drainage basins. This study provides an estimation of the denudation rate for two small catchments within that site. Data upon which the estimation is based include topographic maps, site surveys, and measurements on bed, dissolved, and suspended loads over the period from 1998 to 2000. The result indicates that typhoons and storm rainfalls, as well as geomorphic and ancestral conditions, have major impacts on hydrological and sediment regimes of these drainage basins. The total sediment output measured at Weir No. 1 indicates a denudation rate of ∼2.7 mm per year, which is 53% of the figure calculated from the data measured at Weir No. 2. Since the geological settings in these basins are similar, the result is a demonstration of the nonlinear relationship between basin areas and sediment production. In Basin No. 1, 90% of the total sediment output is dissolved load. However, this figure plunges to 42% in Basin No. 2, in contrast with the fact that the runoff per unit area in Basin No. 2 is 35% higher than that in Basin No. 1. The denudation rates of these two drainage basins are relatively high in comparison with those from other areas around the world.