Debris flow erosion and deposition in Jiangjia Gully, Yunnan, China |
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Authors: | J Chen Y P He F Q Wei |
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Institution: | (1) Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu, 610041, China;(2) Department of Hydraulic and Hydro-electrical Engineering, Tsinghua University, Beijing, 100084, China |
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Abstract: | The erosion and deposition of debris flows at Jiangjia Gully in Dongchuan section of Yunnan province, southwestern China,
was surveyed at 12 cross sections from 1999 to 2003. Deposition occurred in most sections because of the low debris-flow magnitude.
The result was an increase in their elevations except for two sections at D17 and D19, where the channel was diverted in September
1999. As the annual sediment discharge of debris flow increased, the deposited volume decreased in the upper channel and increased
in the lower channel. In each debris flow event, the erosion or deposition at the upper and the lower channel were different,
but the eroded/deposited volume and the trend of erosion or deposition were similar between the neighboring sections. The
average elevation change of all cross sections between consecutive surveys can reasonably represent the debris flow influence
on the channel. Its relationship with the total sediment discharge between two surveys follows a three-stage pattern: when
debris flow magnitude is small, deposition in the channel increases with the magnitude. When the magnitude reaches a certain
level, the deposition begins to decrease and eventually erosion takes place. In three typical cross sections which had similar
channel width, the debris flow showed a clear trend that the deposited volume decreased, while the eroded volume increased
as the discharge of debris flow sediments increased. |
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Keywords: | Debris flow Erosion and deposition Jiangjia Gully China |
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