Sources and destinations of sediment in the Huang He and Changjiang basins of China  - article ; n°567 ; vol.101, pg 541-552
13 pages
English

Découvre YouScribe en t'inscrivant gratuitement

Je m'inscris

Sources and destinations of sediment in the Huang He and Changjiang basins of China - article ; n°567 ; vol.101, pg 541-552

-

Découvre YouScribe en t'inscrivant gratuitement

Je m'inscris
Obtenez un accès à la bibliothèque pour le consulter en ligne
En savoir plus
13 pages
English
Obtenez un accès à la bibliothèque pour le consulter en ligne
En savoir plus

Description

Annales de Géographie - Année 1992 - Volume 101 - Numéro 567 - Pages 541-552
La charge sédimentaire élevée du Fleuve Jaune est à l'origine de dépôts volumineux entre les berges artificielles de la plaine du Nord de la Chine. Pour éviter les inondations, il faut contrôler l'érosion des sols du plateau lœssique. Trois types de sources alimentent les sédiments du Yangtse (Changjiang) : l'érosion des terrains lœssiques au Nord du bassin du Jialin Jiang ; les coulées boueuses du Yunnan et du Sud du Se-Tchouen ; et l'érosion active des terrains cultivés sur des pentes raides.
The high sediment yield on the Yellow River (Huang He) leads to aggradation of the potentially instable lowland channel. To avoid flood risk action must be taken to prevent soil erosion on the lœss plateau. The Yangtse (Changjiang) has three major sediment sources : lœss areas at the head of the Jialin Jiang catchment ; debris flows in Yunnan and southern Sichuan ; and severe erosion of steeply sloping agricultural land.
12 pages
Source : Persée ; Ministère de la jeunesse, de l’éducation nationale et de la recherche, Direction de l’enseignement supérieur, Sous-direction des bibliothèques et de la documentation.

Informations

Publié par
Publié le 01 janvier 1992
Nombre de lectures 10
Langue English
Poids de l'ouvrage 1 Mo

Extrait

Ian Douglas
Sources and destinations of sediment in the Huang He and
Changjiang basins of China
In: Annales de Géographie. 1992, t. 101, n°567. pp. 541-552.
Résumé
La charge sédimentaire élevée du Fleuve Jaune est à l'origine de dépôts volumineux entre les berges artificielles de la plaine du
Nord de la Chine. Pour éviter les inondations, il faut contrôler l'érosion des sols du plateau lœssique. Trois types de sources
alimentent les sédiments du Yangtse (Changjiang) : l'érosion des terrains lœssiques au Nord du bassin du Jialin Jiang ; les
coulées boueuses du Yunnan et du Sud du Se-Tchouen ; et l'érosion active des terrains cultivés sur des pentes raides.
Abstract
The high sediment yield on the Yellow River (Huang He) leads to aggradation of the potentially instable lowland channel. To
avoid flood risk action must be taken to prevent soil erosion on the lœss plateau. The Yangtse (Changjiang) has three major
sediment sources : lœss areas at the head of the Jialin Jiang catchment ; debris flows in Yunnan and southern Sichuan ; and
severe erosion of steeply sloping agricultural land.
Citer ce document / Cite this document :
Douglas Ian. Sources and destinations of sediment in the Huang He and Changjiang basins of China . In: Annales de
Géographie. 1992, t. 101, n°567. pp. 541-552.
doi : 10.3406/geo.1992.21109
http://www.persee.fr/web/revues/home/prescript/article/geo_0003-4010_1992_num_101_567_21109Gèo. no 567 1992 Ann
Sources and destinations
of sediment in the Huang He
and Changjiang basins of China
University lan of DOUGLAS Manchester
Although the Huang He Yellow River is well known for its extre
mely high sediment yield the larger Changjiang Yangtse River dis
charges far more water and also carries great tonnage of sediment
The combination of terrain and climate in these two great basins creates
particular sediment sources which in many cases are among the most
extreme such situations on any continent Fig Although glaciers
exist in the highest parts of their catchments the climate of their
headwaters is so arid that unlike many other continental river systems
these rivers receive far less runon from their upland and mountain than from their middle and lower course tributaries Ho
wever both past and present tectonic and climatic geomorphic in
fluences in the upland headwaters cause severe natural problems for
river management and water resource use The geologically rapid uplift
of the plateau has created great gorge sections through unstable terrain
on both the Huang He and Chang Jiang within which occur some of
the most spectacular debris flows and rockslides experienced anywhere
in the world State Commission of Science and Technology 1988 In
the north the vast spreads of ss accumulated in every Pleistocene
cold period provide depths of up to 400 of highly erodible material
which is eroded into some of the elaborate ravine terrain to be found
anywhere Liu 1988 On to these naturally spectacular and unstable
landscapes have moved people who use agricultural land more densely
and intensively than most others Population pressure on the land
intensifies the erosion problem but also creates new demands for water
Three broad categories of sediment source thus operate in these two
great basins erosion of ss terrain sediment supply by debris flows
and rapid soil on intensively occupied agricultural land DE OGRAPHIE ANNALES SOURCES AND DESTINATIONS OF SEDIMENT 543
TABLE
Characteristics of Major Chinese Rivers after Yen et al. 1986
Note These data differ slightly from those used to compile table
The reliability of the two sources is difficult to ascertain
Average Average Average annual Average tidal Length Drainage area sediment annual runoff River sediment load range at mouth IO3 km2 concentration km IO9 m3 IO6 mg
6300 808.5 928 486 470 4.66 Changjiang
Huang He 5464 752.4 44 120 25200 0.2
Zhu Jiang 2210 442.6 336 230 1.26 83
Li 1390 219.0 14.5 18 6860 2.3
Hai 1090 263.0 23.3 38 1060 2.48
14 Huai 1000 261.0 45.9 460
62.1 130 Min 584 60.9 4.5
410 49.9 38.2 200 5.45 Qintang
The basic contrast between the two rivers is that the runoff per
unit area in the Changjiang catchment is nine times that of the Huang
He catchment table The Huang He problem is water defi
ciency while in the Changjiang it is that of population pressure on the
land and associated land degradation and erosion
The overall pressure on the land is well described by Wu Chuan-
Jun 1990
In China over long period of time land has been used gratis occupied
at will with destruction and waste consequently intensifying the problem
of land shortage Whilst upholding the socialist public ownership of land
and adapting the law of socialist planned commodity economy the system
of paid utilization of land is to be implemented both in urban and rural
areas Those lands already disturbed or left abandoned by extraction and
mining are to rehabiltated for appropriate use
The Huang He Yellow River
With mean suspended sediment concentration of 25200mg l1
and sediment table of 490t km2 y1 the Huang He is rightly
considered the muddiest river table Of this sediment load
90 comes from the ss plateau region in the middle course of the
river Up to 25 of the sediment delivered to the head of the alluvial
fan at Xiaolangdi is subsequently deposited between the dikes restrai
ning the river along its course across the North China Plain Fig
Deposition is rapid enough to raise the channel bed 10cm y1 and
consequently the channel flow is now generally between and 544 ANNALES DE OGRAPHIE
TABLE
Characteristics of the Huang He and Changjiang 1955-1985
Average Mean annual Mean annual Catchment area River annual flow sediment load sediment yield IO3 km2 m3 km2 m3 km2 IO6
Huang He 0.002 1640 752 1490
1.808 0.018 480 280 Changjiang
and in places 10m above the plain outside the dikes Douglas 1989
Deposition in the delta adds some 23.5 km2 of new land every year
with the delta growing seaward by about 0.42km y1 Gao Jiacai
1989)
The basin sediment system of the Huang He is at critical stage
where constant effort to evacuate peak water and sediment flows
through the endiked channel across the alluvial fan depositional tract
may be disrupted by any major natural or people-caused events ups
tream affecting peak discharges or sediment loads Huang Bingwei
1988 has described the problem succinctly
Simply stated embankment strengthening alone is doomed to failure in
the race against channel siltation Should the river break at its most
dangerous locality the resulting flood would directly assect an area with
more than 150 million inhabitants The only dependable remedy for this
problem is soil conservation on the ss highlands for if the lower Yellow
River is not so heavily silt-laden our engineers can easily grapple with
the problem of river control
The key to silt reduction in the ss highlands is to protect the surface
against raindrop impact and detachment Active gully enlargement is
almost ubiquitous on the ss plateau where sediment concentrations
in run off reach 100 000 mg erosion rates of 18 600 km2 y1 being
recorded parts of Shaanxi Derbyshire 1990 Raindrop splash
rilling gullying slurry flow and sliding of ss blocks combine to
produce persistently high sediment yields that of the Dali River in
Shaanxi averaging 19600t km2 y1 from 1959-1969 However much of
the actual soil loss occurs from within the gully systems in the Wuding
river system 30 to 62 of the erosion occurs on the interfluves between
gullies but 38 to 70 within the gullies Jiang et al. 1981 Determi
nations of caesium 137 levels in soils indicate similar proportions to
20 of the eroded material coming from interfluves and 74 to 93
from the gullies Zhang et al. 1989 Although revegetation of actively
eroding is difficult maintenance of good plant cover on the
interfluves not only reduces erosion there but encourages infiltration
and so lowers the runoff to gullies and thus the potential for erosion
with gullies Huang Bingwei 1988 Much of the eroded sediment is SOURCES AND DESTINATIONS OF SEDIMENT 545
trapped behind darns or erosion control works within the catchment
but nevertheless flood flows with extremely high sediment concentra
tions are carried into the endiked plains section of the river where the
coarse particles of more than 005 mm diameter account for more than
half the accretion within the dikes Zeng and Zhou 1989)
Despite the importance of watershed management and soil conser
vation north China often is short of water and multi-purpose reservoir
construction has long been part of the strategy for managing the Huang
He The main stem of the river is regulated by chain of reservoirs
from the Longyang Gorge Dam upstream in Qinghai province to the
Sanmenexia Dam with ninth at Lijia Gorge in Henan under construc
tion and tenth the Xiaolangdi Dam on the lower river now under
construction The Yihe and Louhe tributaries in Henan which at times
contribute up to 50 of the flow of the Huang He across the plain
are dammed the Guxian Reservoir on the Lohe being due for comple
tion in 1992 Yuan Jiang 1991 The

  • Univers Univers
  • Ebooks Ebooks
  • Livres audio Livres audio
  • Presse Presse
  • Podcasts Podcasts
  • BD BD
  • Documents Documents