The influence of the ratio of forested area on suspended sediment discharge in the upper part of the Agatsuma River basin
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- NAMBA Yohe
- Graduate School of Agricultural and Life Sciences, The university of Tokyo Graduate School of Agricultural and Life Sciences, The university of Tokyo
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- HOTTA Norifumi
- Graduate School of Agricultural and Life Sciences, The university of Tokyo
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- SUZUKI Masakazu
- Graduate School of Agricultural and Life Sciences, The university of Tokyo
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- SHUIN Yasuhiro
- Faculty of Agriculture, Utsunomiya University
Bibliographic Information
- Other Title
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- 吾妻川上流域におけるsuspended sedimentの流出に対する森林率の影響
- アガツマガワ ジョウリュウイキ ニ オケル suspended sediment ノ リュウシュツ ニ タイスル シンリンリツ ノ エイキョウ
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Abstract
The relationship between the ratio of forested area (F) and suspended sediment (SS) discharge was examined after eliminating the influence of geography as represented by the average slope gradient in a basin (G). The research area comprised 75 basins nested in the upper part of the Agatsuma River basin (707.9 km2). Using manual sampling, 617 samples were collected between 1994 and 1998, and SS concentrations were determined using the gravimetric method. Water discharge was measured at the time of sampling to estimate SS discharge. After classifying all the data into 3 and 4 groups according to F and G, respectively, sediment rating curves for each group were obtained using the least squares method. By comparing the sediment rating curves, the SS discharge in the basins was found to decrease with higher F, even with scattered data, while no clear relationship was found between SS discharge and G, which means that the forested area had a stronger influence on SS discharge than the geographic characteristics of the research area. Furthermore, we ascertained that the SS concentration converged on a lower value where F was near 1, resulting in especially low SS discharge in wholly forested basins. From these results, we conclude that it is difficult to evaluate SS discharge emphasizing only F, although F is one of the important factors that strongly affects SS discharge. The difficulty, we think, is caused by the existence of fields, which have a strong negative correlation with F in these basins, and which generate SS according to their local geographic characteristics. It is also possible that the relationship between sediment yields and geographic characteristics, which has often been highlighted in previous reports, can be applied only in basins where F is sufficiently high, because most of the research areas in such studies have been limited to upper mountain areas.
Journal
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- Sabo Gakkaishi
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Sabo Gakkaishi 59 (6), 14-24, 2007
Japan Society of Erosion Control Engineering
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Details 詳細情報について
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- CRID
- 1390282679043938304
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- NII Article ID
- 130004296370
- 10018907974
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- NII Book ID
- AN0012035X
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- NDL BIB ID
- 8774720
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- ISSN
- 02868385
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- Data Source
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- JaLC
- NDL
- CiNii Articles
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- Abstract License Flag
- Disallowed