A Study on the characteristics of sediments particles and rock strength along a bedrock river channel. - Case of in Dong River(Upper Han River), Korea
Abstract
Bedrock river channels mainly incised by the transporting sediment particles, through abrasion, plucking and hydrowedging processes. The quantity and size of sediment particles eroding the channel bed is the crucial to the erosive forces to the channel bed. But also the difference in strength of eroding sediments and bedrock channel bed could strongly affects the erosion rates.
To find the grain size characteristics of river sediments and the rock strengths of bedrock and sediment particles, sediment particles and bedrocks are investigated for a reach of the Dong River, upstream part of the Han River, Korea. 7 sampling points were selected based on the availability of sediment and bedrock outcrops. The bedrock of the study area is various limestone belonging to the Paleozoic Choseon limestone group, and Mesozoic sandstone and conglomerate occur in some areas. Samples size and rock strength values were measured at the fields and lithologies were identified. Rock strength measured using Schmidt hammer. More than 70% of these sediments are identified as sandstone and conglomerate, rather than limestone which forms the basis of the valley. Sediment particles seem to have been supplied upstream of the study area rather supplied from the channel bed or nearest slope, could supplied by landslide or rockfall. The particle sizes of the upstream section are decreasing in the downstream direction. However, at the DG3,where the downstream of confluence with a tributary, particle size are increased. The largest mean particle size found from DG4 and it may be influenced by the influx of tributaries, but it also can be supposed as the impact of the large flood in 2002. In the downstream parts, the particle size decreases exponentially with distance. It is difficult to find the statistically significant difference in the shape of the sediment particles of limestones and non-limestones. However, limestones has platy forms rather than block forms, it can be assumed that the limestone was supplied from the surrounding valley wall and transported over a short distance. The sediments of limestone were decreased in grain size more rapidly than those of limestone sediments. Limestone showed lower rebound strength than non-limestone regardless the size and shape of samples.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP53F2225K
- Keywords:
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- 1813 Eco-hydrology;
- HYDROLOGY;
- 1824 Geomorphology: general;
- HYDROLOGY;
- 1825 Geomorphology: fluvial;
- HYDROLOGY;
- 1826 Geomorphology: hillslope;
- HYDROLOGY