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Research Needs and Applications to Reduce Erosion and Sedimentation in Tropica! Stceplands (Proceedings of the Fiji Symposium, June 1990): IAHS-AISH Publ. No.192,1990.

Soil erosion in dry-hot valleys of tropics and subtropics in southwest China LIU SUQING, TANG BANGXING, LI J IAN, SHANG XIANGCHAO Institute of Mountain Disasters S Environment, Chinese Academy of Sciences

Abstract

Environment is degrading, soil seriously eroded and soil and water losses intensifying in dry valleys of Southwest China. Notable is the in­tensive gravitational erosion, which accelera­tes environment degradation and activates ha­zardous debris flows. Debris flows are the re­sult of the formation and development process of dry valleys. As a common natural disaster in dry valleys, debris flows' occurrence and acti­vity intensifies environment degradation of• dry valleys, which have a favourable environment for their occurrence and activity. In particu­lar, there are rich natural resources (forest, minerals, hydropower, land, light and heat) in dry valleys. With the development of agricultu­ral and industrial production and the growth of population in mountainous areas, large-scale exploitation and extraction of biological ener­gy destroy the ecological environment and lead to environment degradation and debris flow in­tensification.

INTRODUCTION

Soil erosion is serious in the dry valleys of Southwest China, espe­cially in the dry valleys of the Jinsha River Basin and the Minjiang River Basin. There are extremely complicated factors in the formation of dry valley environment of Southwest China, where the most promi­nent problem is the basic destruction of virgin forests which find expression in secondary texture predominated by drought-resistant shrubs and grasses. Desertification can be seen in some places with an intensified debris and sedimentation process. Furthermore, fre­quent human economic activities accelerate the occurrence and deve­lopment of soil erosion. In this area, red earth and brown soil are most intensely eroded. Moderate soil erosion occurs in low mountains and hills, while gravitational erosion is very strong and active in water erosion of rocky mountains, especially in the form of debris flow and landslide.

The authors have conducted priority studies on gravitational erosion in the dry valleys of Southwest China, particularly systematic inves­tigations, analyses and researches on debris flow - a special erosion phenomenon, which not only disturbs natural environment and accelera­tes the env i r o n m e nt degradation and the debris and sedimentation

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process of dry valleys, but also makes a great damage and threat, even disaster, to local economic development, industrial and agricul­tural production and people's lives and properties. At the same time, studies and implementation of countermeasure systems are carried out, and remarkable benefits have been achieved so far.

DRY VALLEY ENVIRONMENT

Dry valleys of China are mainly distributed in western mountainous areas. Rich in natural resources, they have the importance in Chinese national economy. But in the past slow economic development, iira-tional productivity distribution, and excessive development of na­tural resources led to the frequency of natural disasters and great damage of debris flows, causing the degradation of valley environment desertification of farmland, and endangerment of towns and villages. For this reason, studying the dry valley environment and debris flow is of great practical value in developing effective counterneasures improving the degrading natural environment, and controlling debris flows. Since dry valleys are widely distributed in China, this paper only makes a preliminary analysis and exploration on the western Sichuan and northwestern Yunnan Provinces.

Dry valleys are mainly distributed in western Hengduan Mountain region, between 260 - 33° north latutude and 95°30' - 103°30' east longitude, including Tanianta Mountain, Nu Mountain, Ningjing Moun­tain, Yunling Mountain, Shaluli Mountain, Daxue Mountain, Pionglai mountain and Longmen Mountain, as well as most or some sections of the middle and upper reaches of Minjiang River, Dadu river, Anning River, Yalong River, Jinsha River, Lancang River and Nujiang River in western Sichuan, northwestern Yunnan and eastern Tibet. In this re­gion mountains alternate with rivers, extending from south to north; valleys are widely distributed in large areas. For example, most dry valleys of Lancang River, Jinsha River, Yalong River, Anning River, Dadu River and Minjiang River in Sichuan and Yunnan cover an area of more than 30 thousand km2.

I. Characteristics of Dry Valley Environment

1. Active Geological Structure

Most dry valleys develop in tectonic fracture zones, or controlled by tectonism. There are not only strong neotectonic movement, but also active seismisity. Many dry valleys are located in seismic zones, such as the Songpan seismic zone of the upper reaches of Minjiang River, the Anning River seismic zone, the Xianshui River seismic zone, the Mabian seismic zone on the middle and lower reaches of Jinsha River, the Yongshandaguan seismic zone, the Xiaojiang River and Yuanzhi River seismic zone, the Yalong River and Ganzi seismic zone and the Longmen Mountain seismic zone etc.

2.Young Geomorphological Development

Dry valleys have a short history of development, and most of them have young geomorphological characteristics: steep gradient river bed cur-

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ved upward, with many steps and rapids, such as the middle and upper reaches of Jinsha River, the upper and middle reaches of Yalong River the upper reaches of Minjiang River, and the upper and middle reaches of Dadu River. Most valleys are V-shaped with many gorges, such as the Futiao Gorge of Jinsha River, which is flanked by mountains 3500-5000 m above sea level, 1000-2000 m at the relative height, and with slopes over 35°, where unstability leads to intense contemporary geomorphological processes, active landslides and collapses.

3. Complex Strata

The strata that comprise dry valleys are complicated and varied, inc­luding clastic rock, sandstone, shale, slate, phyllite, limestone and igneous rock. In particular, sandstone, slate and phyllite have a widest distribution; they can be found in Jinsha River, Yalong River, Dadu River and Minjiang River etc. Under the influence of geo-tecto-nic movement, earthquake, physical and chemical weathering, the stra­ta are very broken, and gravitational geomorphic phenomena (debris avalanche and talus) are active. A specially droughty scene occurs in the valleys.

4. Climatic Differentiation

In comparison with their counterparts, the dry valleys have a ten-denciously dry and differential climate. 1) Temperature. Two zones can be distinguished horizontally: dry hot valleys of the south and southeast; dry temperate valleys of the north and northwest. For example, the average annual temperature of the lower reaches of Jinsha River Valley is about 20°C, while the average annual tempera­ture of the upper reaches of the valley is below 10°C. Vertically, the bottom of the valleys is dry and hot, but with the increase in altitude, the temperature decreases, and the climate becomes dry warm or dry temperate. Temporally, the annual difference of temperature is little, while the daily difference is large. It is very dry and warm in the winter-spring half year. 2) Sunshine. Sunshine is so plentiful that the annual sunshine is over 1200 hours. It is more than 2000-2200 hours in Jinsha River Valley and Yalong River valley, especially in winter and spring. 3) Precipitation. It is characterized by disti­nct dry season and wet season, and great regional difference in precipitation. Generally there is more rainfall on windward slopes, and less rainfall in rainshadow zones. Moreover, the annual distribu­tion of precipitation is so uneven that the winter is dry and the summer is wet. The precipitation during May to October accounts for 75-90% of the annual, while the precipitation during November to April is so low that it is 10% in Jinsha River, and 25% in Dadu River and Minjiang River. Southwestwardly, the more obvious the characte­ristic is. 4) Evaporation. Evaporation rate is 3 or 4 times as much as precipitation in dry valleys. For example, annual evaporation is 2798 mm and 1867 mm in Dukou and Batang respectively corresponding to 3.7 and 3.9 times as much as the annual precipitation locally. In winter and spring evaporation is 10 times more than precipitation. Annual relative humidity is usually 50-70% ( 50% in Jinsha River; 70% in Anning River). It changes from humid and sub-humid in the south and southeast to semi-arid and arid in the north and northwest.

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5. Low and Spinal Vegetation

Low and spinal vegetation is sparsely distributed. The geographical position where dry valleys are located used to belong to the subtro­pical belt where evergreen broad-leaf forest, and deciduous mixed forest, and broad-leaf and needle-leaf mixed forest grew. As climate became dry, hygrophilous plants evolved into siccocolous plants. Consequently many low, spinal, fleshy desert species appeared, and horizontal zonality and vertical zonality of vegetation distribution were changed. The evolution model is: primeval needle-leaf and broad-leaf mixed forest - bush - arid bush - sparse grassland - semi-desert.

The vertical distribution of dry-valley vegetation is characterized by upward movement of forest and downward intrusion of bush and grassland. The distance of both movements is about 200-300 m.

6. Dry Soils Poor in Water Content and Solidity, and Subject to Erosion

Under the influence of the dry valley climate, vegetation has evolved into semi-arid and potentially desertified. Soil typology is unitary and can be classified into two groups: brown soil and red earth. The Minjiang River Basin, the Dadu River Basin, the middle and upper reaches of Yalong River and Jinsha River, and the dry valleys of Lancang River and Nujiang River are covered with mountain brown soil and gray brown soil; the dry valleys on the lower reaches of Yalong River, Jinsha River and Anning River with red brown soil; and the dry valleys on the lower reaches of the Anning River and Jinsha River, and downstream Liuku of the Nujiang River with dry red earth.

The common properties of brown soil and red earth are that most soils are coarse-grained and ill-textured with thin and dry layers charac­terized by poor permeability, water conservation, water capacity and high evaporation in top horizons. Moreover, the two types of soil contain clay mineral components that are water-absorbing and expan­sible. They are prone to water erosion due to their deep-weathered and broken mother materials, so favourable for the occurrence of deb­ris flows.

The arid environment of dry valleys disturb the original horizontal distribution and vertical differentiation of vegetation. After the occurrence of dry valleys, their vegetation evolves into a self-complete and special system. As a result, non-zonal arid communities grow, reflecting non-zonal characteristic soils. For instance, the soils characteristic of the subtropics are yellow earth and red earth; after the destruction of the subtropics, they become red-brown soil and dry red earth.

Recent irrational human economic activities have some influence on the occurrence and development of soils and the destruction of soil structure, such as steep-slope cultivation, ill-devised irrigation canals, slash-and-burn farming and overgrazing etc., which make a damage to mountain stability, soil structure and soil occurrence and development, and accelerate soil and water losses and the occurrence

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of landslides and collapses.

The ill-formed soils in dry valleys become poorer and poorer, worse and worse due to irrational human utilization. This provides favoura­ble conditions for the occurrence, development and frequent activity of debris flows in dry valleys.

II. Factors in the Formation of Dry Valleys

The formation of dry valleys are the result of the combining effect of natural and anthropic factors. Geological, geomorphological and meteorological conditions are the leading factors, while human econo­mic activities play an accelerative and aggravating role, and they are the main cause for the degradation of local environment.

1. Geological and Geomorphological Conditions

Geologically and geomorphologically, the strong upheaval of the Qinghai-Tibet Plateau is the leading facyor in the formation of dry valleys. Since Upper Pleistocene the Qinghai-Tibet Plateau has exten­sively uprisen. In Middle and Late Quaternary the uplift range reach­ed 3000-4000 m, giving birth to the highest large plateau on earth. It constitutes a giant heat source which alters the pattern of atmos­pheric circulation (west wind circulation)., cuts off the Indian Ocean humid air-current from penetrating into the heartland, affects the redistribution of hydrothermal conditions, thus leading to the occurrence and development of dry valleys.Particularly, the nature and intensity of the neotectonic movement have control, both intensi­fying and restraining, over the formation and development of dry valleys. Moreover, a strong uplift predominates in the neotectonic movement of the Quaternary, not only characterized by a high rise of mountains, but also accompanied by the occurrence of a series of NNW and SN fracture structures, along which rivers develop and undercut by erosion, producing SN and NNW high mountains and narrow valleys. Such mountain structures constitute a climatic screen and result in rain-shadow zones, reducing temperature, humidity and precipitation from south to north or northwest and from the basin rim to the peri­pheral mountains, a characteristic of changing from warm humid th­rough semihumid and semiarid to arid. For example, the lower reaches of Jinsha River have a hot and dry climate with an annual precipita­tion of 800 mm, while the zone to the north only has 300-400 mm of rain to fall in valleys each year, a well-known rain-shadow zone in the Hengduan Mountain. 2. Meteorological Differentiation From the viewpoint of atmospheric circulation, after the formation of the Qinghai-Tibet Plateau, this region is located in the air-current radiation lowering zone at the periphery of the Tibet high air-pressure, the dominant west wind circulation of south branch in wint­er half year makes the zone less rain, dry and windy, especially in the deep-cut valleys where the increase in temperature and decrease in moisture of the lowering air-current, and the marked foehn effect give an extremely dry climate to the winter half year. In summer half year the west wind circulation of the south branch recedes northward, and the subtropical high pressure of the south strengthens, and con-

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trois the Hengduan Mountain region, ending the dry season gradually from south to north. When the rainy season begins, the shielding effect of high mountains, the increase in temperature and decrease in noisture of air-current as it goes downhill will result in high air temperature, little precipitation and dry hot climate, which is typi­cal of the valleys. Obviously, the atmospheric circulation is the direct cause for the formation of dry valleys.

3. Human Factor

Human irrational economic activities are one of the causes to facili­tate and accelerate the formation of dry valleys. According to lite­rature record, the main branches of the upper reaches of Minjiang River in the region were historically covered by forest vegetation, and had a good forest ecological system. After random deforestation of many dynasties, the forest coverage lost 50% in the Yuan Dynasty. In the 12th year of Hongwu Emperor of the ming Dynasty 1380 A.D.) the forest was extensively felled to build the Songpan Town. Before the liberation of New China exploitive deforestation had happened time and time, reducing the forest cover to 30% or less. After liber­ation, the development of economic construction, population growth and shortage of biological energy in the mountain region resulted in chaotic cutting of forest, farming on steep slopes and clearing land from forest, decreasing the forest coverage to about 18%. During recent years, in Diqing and Lijiang, Yunnan Province, forestland has been shrinking by 1 million mu, and timber reserves by 3 million m3

each year. As the forest coverage shrank, timber line moved up, meadow intruded down, and the range of dry valley expanded, the vall­ey became even drier. The places which used to be rich in forest and water are droughty for lack of water. Under the influence of serious erosion and frequent debris flows the present typical dry valley landscape has evolved. Worse than all, the role of forest in water source protection and soil and water conservation is weakened, thus intensifying soil erosion and natural disasters.

SOIL EROSION IN DRY VALLEYS

The soil -eroded area of the southwest China is more than 450 thousand km2, accounting for 33% of the total region.

At present, Sichuan ranks first in soil erosion among the 3 provinces in Southwest China (the other two are Yunnan and Guizhou). Of the to­tal 567 thousand km2 land area, 247 thousand km2 suffer from water erosion, 43.5% of the total land area. The average annual amount of waqter erosion is 1.6 billion T. In addition, gravitational erosion (debris flow and landslide) is serious in Sichuan. In the dry valley areas of Southwest China, the most intense zones include Jinsha River Basin, Nujiang River and Dadu River; the intense zones are Minjiang River, Yalong River and Lancang River.

In this region, water erosion is the most serious of soil erosion, i.e., intense soil and water losses, while gravitational erosion (debris flow, landslide and collapse, which also can be regarded as special phenomena of soil and water losses in rocky mountains) is

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extremely frequent and hazardous. As one type of water gravitational erosion, debris flow is the most serious of soil erosions in dry valleys of Southwest China. As a result of both natural and human factors, it has following characteristics:

I. Special Origins

The natural environment peculiar to dry valleys possesses plentiful solid materials, steep topography and concentrated high-intensity rainstorms, which are the leading factors to debris flow occurrence. Irrational human economic activities, however, accelerate and tempt debris flow to occur. In one word, the dry valley environment favours the formation of debris flow. Accordingly, debris flows in this region are characterized by wide distribution, frequent activity and severe damage, and also they are one of the important factors for the development of dry valley desertification. Take the Derong County in the drought centre of Sichuan as an example, where a debris flow triggered by a rainstorm that lasted 20 minutes with 10 mm of rain­fall in 10 minute intensity killed 7 people and incurred a loss of more than 6 million RMB Yuan. 110 thousand m3 of solid materials were carried out and 277.9 m3 of soil washed away from the farmland at the ravine head. Debris flows have the following origins:

1. Plenty of Loose Materials

Most dry valleys are situated in active fault zones or seismic zones where numerous joints and cracks exist, earthquakes frequently occur, and rock is extremely broken. In addition, vegetation is so poor that many bare strata can be seen on the surface. Intense physical weathering and contemporary geomorphic effect give rise to a lot of landslides, rockfall talus and debris avalanches, which supply plen­tiful materials to debris flows and constitute the prominent favoura­ble conditions for debris flow occurrence in dry valleys.

2. Steep Topography

Dry valleys are characterized by active contemporary tectonic move­ment, severe river erosion, and steep topography. The height diffe­rence between mountain and valley is 800-1000 m; the steepness of slopes is 30-50°; the longitudinal gradient of valley bed is 100-300%. The valley slope is poorly stable. This topography favours water collection, which affords favourable dynamic conditions for debris flow formation.

3. Concentrated High-Intensity Precipitation

The high-intensity precipitation during May to October makes up over 75% of the annual. It is not only the water source, but also the triggering factor for debris flows. Accordingly, the occurrence of debris flows in dry valleys largely depends on precipitation that is to say, if only precipitation is enough, debris flows may come. Observations show that when daily precipitation is 30 mm, and 10-minute precipitation is 10mm, debris flows are most likely to occur (Table 1). Therefore, since 1981 all local rainstorms have brought

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Table 1. Statistics of Rainstorms and Debris Flows in 1981 - 1984

Time

June 24 1981

July 9, 1981

July 1, 1983

June 23, 1983

June 24, 1983

June 25, 1983

1983

August 1978

June 24, 1983

June 23, July 25, Sep.8, 1983

July 20, 1983

July 18, 1984

August 11, 1984

Place

Miyf, Huili

Liziyida, Ganlo

Xide Zone

Puge

Ningnan

Meigu

Liuku

Kangding

Jinchuan

Dechang

Heishui

Nanping

1 Derong

Precip (mm

24 hrs

102

100

70.9

85.1

104

46.6

48

30

20

37.3

13.0

itation ) 10 m.

105

60-70 Ohr)

26.09

5.21

15

20

16.4

10

10

Debris flow ravines

30+

1

20+

17

20+

20+

16

1

10+

7

1

4

31

Damage

Farmland

Bridge, vehicles

Town, farm­land, road

Hydropower station

Road, town

Road

Houses, road

Town

Road, 2 death

Road

Farmland, houses, 2 injuries

15 million Yuan

Houses

about debris flows in the dry valleys of west Sichuan; usually they occur in several ravines or even tens simultaneously.

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II. Frequent Activity

Recent debris flows are active in dry valleys. During mid-1970s and early 1980s debris flows have frequently occurred in the vast area from Minjiang River on the east to Nujiang River on the west. Not only widely distributed, they are also numerously concentrated in zones, such as the lower reaches of Sunshui River of Anning River, the upper reaches of Dadu River, Heishui River and Xiaojiang River whre a rainstorm caused tens or even more than 100 debris flows in 1983. Also, debris flows occurred in 381 ravines of 29 counties which are located in dry valleys of west Sichuan in 1981, and in more than 100 ravines of 5 counties along Nujiang River in 1976 and 1979. Another example is the Gongmiao Ravine and Zhila Ravine of the Bai-shui River, and the Rizu Ravine of the Zagu River and the Luhua Ra­vine of the Heishui River where more than ten debris flows occurred in 1984. The activity of debris flows is seasonal. Most debris flows occur during May to October every year. For the rainfall of dry va­lleys during the summer half year is double-humped, there are two upsurges in debris flow occurrence during the summer half year, i.e., June, July and September.

III. Heavy Damage

The most serious phenomenon of soil and water losses in dry valleys of southwest China is debris flows, which destroy farmland, houses, highways and railways, and incur casualties and great economic losses in the rainy season every year. Sichuan Province suffers hundreds of casualties and more than 6 million Yuan from debris flows each year. In 1981, the most disastrous year, 710 people were killed and an economic loss of about 350 million Yuan incurred.

Table 1. shows that between 1981 and 1984 disastrous debris flows occurred in 200 ravines, of which the largest took place at the Guanmiao Ravine, Nanping County, Sichuan Province and the Liziyida Ravine along the Chengdu-Kunming Railway. The former is a specially large debris flow of 200 year recurrence, which dammed the Baishui River with an economic loss of 15 million Yuan and a death toll of 26. The latter destroyed a railway bridge and washed 2 locomotives, 1 freight carriage and 2 passenger carriages into the Dadu River, killing more than 200 people.

Debris flows are the most hazardous of soil and water losses in dry valleys. That is why this paper pays more attention to them. The ordinary soil and water losses are less damaging, and mostly caused by irrational farming, so they are relative easy to control. But dis­astrous debris flows occur unexpectedly and catastrophically. They are difficult and costly to cure; great attention should be given to them.

REGI0NALIZATI0N OF OF SOIL EROSION IN DRY VALLEYS

Soil erosion has become a concern of experts and officials worldwide. It is the same in China, where a certain sum is earmarked and special agencies set up to control it. The southwest region is the timber

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production base of China; the dry valleys are the producer of food and cash crops. Owing to over-production and land abuse, dry valleys are degrading, and soil erosion is intensifying. To control these problems properly, an erosion regionalization (mainly water erosion regionalization) is done in this area.

Based on the erosion intensity of dry valleys, 4 zones are distin­guished:

I. Light erosion zone in northwest Sichuan Plateau and broad valleys;

II. Debris flow, landslide and collapse erosion zone in the high mountains and canyons on the upper reaches of Jinsha River, Lancang River and Nujiang River;

III. Debris flow, landslide and collapse erosion zone on the middle and upper reaches of Nujiang River, Lancang River and Jinsha River;

IV. Debris flow, landslide and collapse erosion zone in the middle and upper reaches of Dadu River and Minjiang River.

Again, according to the intensity of debris flow, landslide, collapse (i.e., gravitational erosion) and soil and water losses, 4 zones are discriminated:

1. Extremely intense erosion zone of debris flow, landslide and collapse;

2. Intense erosion zone of debris flow, landslide and collapse;

3. Moderate erosion zone of debris flow, landslide and ordinary soil and water losses;

4. Light erosion zone of debris flow, landslide and ordinary soil and water losses (Fig.1);

COUNTERMEASURES

Ordinary soil and water losses should be prevented and controlled mainly by vegetative measures, supplemented by small-scale soil and water conservation works. As for landslide and collapse, structural measures are the mainstay with attention to mountain protection in construction to prevent new landslide and collapse from taking place. Here, emphasis is put on the measures against debris flows.

The formation of debris flows in dry valleys has its internal physi­cal factors, buL the recent frequent activity of debris flows and their damage are mainly attributed to irrational human economic activities, which facilitate the generation and development of debris flows, and accelerate the desertification of dry valleys, endangering the safety of towns and villages, submerging farmland, interrupting transport, polluting and blocking rivers, damaging industrial faci-

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Fig.1. Regionalization of Soil Erosion in Dry Valleys

1. Extremely intense erosion zone of debris flow, landslide and collapse;

2. Intense erosion zone of debris flow, landslide and collapse;

3. Moderate erosion zone of debris flow, landslide and soil and water losses;

4. Light erosion zone of debris flow, landslide and soil and water losses.

I. Light erosion zone in southwest Sichuan Plateau and broad valleys;

II. Debris flow, landslide and collapse erosion zone in high mountains and canyons on the upper reaches of Nujiang, Lancang and Jinsha Rivers;

III. Debris flow, landslide and collapse erosion zone on the middle and upper reaches of Nujiang, Lancang and Jinsha Rivers;

IV. Debris flow, landslide and collapse erosion zone on the middle and upper reaches of Dadu and Minjiang Rivers.

lities, silting or destroying reservoirs and canals, causing casual­ties and washing away domestic animals.

Some experts concerned made a multidisciplinary approach to the deg­radation of dry valley environment and countermeasures against debris flows, and worked out the following measures to ameliorate the dry valley environment.

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I. I. Recover the forest ecological system to form a new eco­logical balance, comprehensively manage agriculture, forestry and animal husbandry with emphasis on forestry; intensify afforestation and reserve mountain areas.

II. Fully and rationally utilize natural resources of dry valleys; properly develop agriculture, forestry and animal husbandry, seek a better solution to the conflict between forestry and animal husbandry.

III. Improve the backward farming practices; special treatment should be made to landslides and broken mountains where irrigation canals pass through lest materials be supplied for debris flow occurrence.

IV. Proper measures should be taken in case of road construction and mining; refuse be appropriately disposed to avoid landslide, collapse and debris flow activities.

V. Villages, industrial installations and city expansion should keep away from debris flow hazard zones to save the troubles given by them.

VI. In population centres that suffer heavily from debris flow, in case of energy shortages, biological energy need to be developed and fast-growing firewood forest planted to protect hillslope vegetation.

VII. In towns, transport mains and key factories and mines plagued by serious debris flow hazards, an integrated control program is specially required to combine vegetative neasures with structural ones; structural treatment is mainly for the short term, and vegetative one for the long term.

The countermeasures against soil erosion in China have developed into a complete preventive and control system, which adopts structural, vegetative and social measures, including legislation, administrative orders, unified management, economic development and living standard improvement etc.