Slope denudation and the supply of debris to cones in Langtang Himal, Central Nepal Himalaya

被引:28
作者
Watanabe, T [1 ]
Dali, L
Shiraiwa, T
机构
[1] Hokkaido Univ, Grad Sch Environm Earth Sci, Sapporo, Hokkaido 0600810, Japan
[2] Hokkaido Univ, Inst Low Temp Sci, Sapporo, Hokkaido 0600819, Japan
关键词
debris flow cone; denudation rate; cone volume; sedimentation rate; toe incision; Langtang Himal;
D O I
10.1016/S0169-555X(98)00058-0
中图分类号
P9 [自然地理学];
学科分类号
0705 ; 070501 ;
摘要
The onset and termination of the formation of debris cones and the rate of denudation of source areas were studied in the Langtang Valley, central Nepal Himalaya. A stereo photogrammetric analysis was employed to map a detailed topography of debris cones, through which the volume of 19 cones was calculated. Debris cones were classified into four types (types 1-4) based on the criteria, such as incision of a toe, sizes of a cone and surface boulders, altitudinal distributions and vegetation cover. Cones of types 1-3 had been formed after deglaciation following the Langtang stage (3310 years BP). Type 1 cones are characterized by incision of toes by glaciers of the Lirung and Yala stages. The formation of the type 1 cones terminated well before 2000 years BP, Radiocarbon dates of charcoal fragments and buried soils show the major period of formation of the type 2 cones from 3300 to 2000 years BP. The rate of sedimentation calculated near the toe of cone 3 has been reduced in the last 5 centuries from 30.0 cm/100 years to 5.5 cm/100 years. The large amount of denudation of source areas (116.9-132.5 m) indicates that slope failures initiated the formation of type 3 cones. The development of type 4 cones made less of a contribution to landscape evolution in the valley. The rates of denudation for source areas were calculated except for those above type 3 cones. The average rates are 15.6-6.2 mm/year (above type 1 cones), 3.2 mm/year (type 2 cones) and 3.4 mm/year (type 4 cones). Debris cones of types 2 and 3 are located on the valley floors which are completely deglaciated. Those of types 1 and 4, on the other hand, are located by the large valley glaciers with debris cover. The formation of type 1 cones is important especially in terms of debris supply to moraines and supra-glacial debris in the upper valley. (C) 1998 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:185 / 197
页数:13
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