Economic Benefit Evaluation of Nanxi Debris Flow Prevention Project in Chenzhou City, Hunan Province

I. Overview of Nanxi Debris Flow Prevention Project

(A) Nanxi debris flow environmental geological conditions

Nanxi is located in the seat of Nanxi Township Government in Beihu District, Chenzhou City. From 7: 00 pm on August 7, 2002 to 8: 00 am the next day, the rainfall less than 10 hour was 230mm, of which the rainfall from 8: 00 pm to 0: 00 pm was 1 160mm, which caused serious economic losses in hospitals, credit cooperatives, grain depots, nursing homes and handicraft associations.

Nanxi is located at the intersection of two gullies, surrounded by steep slopes and thick weathered debris, which is a prone area for landslides and mudslides.

Nanxi landform belongs to a mountainous area with low degree of structural erosion, and the terrain is an intermountain valley. The terrain is generally high in the east and low in the west. The elevation of the highest point nearby is 947.8m, the elevation of the lowest point is about 660.0m, and the slope is about 40.

The average annual rainfall in the region is 1528mm, and the maximum annual rainfall is 2247.6 mm The rainfall is unevenly distributed during the year. April-June is the rainy season, and there are usually heavy rains and heavy rains from June to August.

Gullies are developed in this area, and the overall flow direction of surface water is from east to west. Nanxi is located in the alluvial fan area where two gullies meet. On the north side, the discharge of Xiadongxi is small, the gully slope is 0. 10, and the catchment area is 4.7km2 On the south side, the discharge of Shangdongxi is large, the gully slope is 0. 16, and the catchment area is10.0km2.. Based on the comprehensive analysis of geological, hydrological, meteorological and geomorphological conditions, it is found that Xiadongxi and Shangdongxi are gullies prone to debris flow, and the gullies along the line are the debris flow-prone areas where the slope of Nanxi section is gentle and the terrain is relatively open, which becomes a local accumulation area of debris flow. On August 7, 2002, Nanxi produced debris flow deposits with a thickness of about 1.0m and an area of 1500m2, with a maximum particle size of 0.5m. ..

The rocks in the area are mainly medium-grained porphyritic amphibole biotite syenite (adamellite), with weathering depth of 5 ~ 20m, developed fractures and broken rocks. The surface residual slope is about 2.0m thick, which is sandy clay, loose, with strong water permeability and poor stability after saturation. It is easy to cause landslides and damage slopes, and it also provides material conditions for mudslides.

(II) Overview of Nanxi Debris Flow Prevention Project

Sand bars and river dredging are used to control debris flow gullies. Build sand dams on Upper East Stream and Lower East Stream to intercept sand and gravel, slow down gully slope and reduce the intensity of debris flow; Dredging rivers and building dikes in Nanxi section can ensure the smooth flow of streams and divert debris flows.

Retaining walls, intercepting ditches and drainage ditches are used to control landslides, improve the stability of slopes and protect the lives and property of residents under slopes.

Second, the economic benefit evaluation of Nanxi debris flow control project

(A) the basic data of economic evaluation

In the maximum damage range of Nanxi debris flow, the main disaster-bearing body is Dongxi Village, Nanxi Township. Stations are 1 1 institutions, 14 1 households, 1568 residents and 200 floating population. The resident fixed assets are 56 million yuan, including 30 shops. Aimin New Village has built 59 private houses; 15 vehicles, including 6 buses and 72 motorcycles; Township hospitals 1, township middle schools1; Credit cooperatives deposit 6 million yuan; The output value of animal husbandry is 300,000 yuan; The output value of planting industry is 320,000 yuan. Highway 1000m, arch bridge 1 seat, 2 small hydropower stations, with an installed capacity of 500kW and an output value of 2.6 million yuan.

(2) Calculation of social benefits

According to the data of 23 people killed, 3 seriously injured and 5 10 slightly injured in Nanxi mudslide on August 7, 2002, the population security vulnerability of Nanxi mudslide is calculated as 0.015.

The maximum number of possible deaths is 1768× 0.0 15 = 27.

(3) Calculation of economic benefits

The accumulation of debris flow in Nanxi is 6,543,8+500,000 m3, which belongs to medium debris flow. According to the field investigation data, refer to the summary table of vulnerability experts' opinions to determine the vulnerability of each disaster-bearing body. Calculate the possible maximum economic losses of various disaster-bearing bodies.

Table 3-4-2 Unit Price Table of Geological Disaster Carrier in Chenzhou City, Hunan Province

(1) Housing for urban residents: A1= 56 million yuan, V1= 0.5397c1= 56 million yuan × 0.5397 = 30,223,200 yuan.

(2) Household articles for urban residents: A2 = 10,000 yuan/household ×14/kloc-0 = 3.525 million yuan, V2 = 0.9297 C2 = 352.5 million yuan × 0.9297 = 3.2772 million yuan.

(3) Housing for rural residents: A3 = 1.5 million yuan/building× 59 building = 8.85 million yuan, V3 = 0.7044c3 = 88,500 yuan× 0.7044 = 6.234 million yuan.

(4) Household articles for rural residents: A4 = 1.3 million yuan/household× 68 households = 884,000 yuan, V4 = 0.8853 C4 = 884,000 yuan× 0.8853 = 782,600 yuan.

(5) Livestock assets: A5 = 300,000 yuan, V5 = 0.9301C5 = 300,000 yuan × 0.9301= 279,000 yuan.

(6) Agricultural net assets: A6 = 320,000 yuan, V6 = 0.5096C6 = 320,000 yuan × 0.5096 = 163 1 10,000 yuan.

(7) Transport property: A7 = 80,000 yuan/vehicle× 9 vehicles+50,000 yuan/vehicle× 6 vehicles+05,000 yuan/vehicle× 72 vehicles = 654.38 million yuan, V7 = 0.5 169, C7 = 1.38 million yuan× 0.50.

(8) Commercial property: A8 = 1 10,000 yuan/set× 30 = 300,000 yuan, V8 = 0.4944c8 = 300,000 yuan× 0.4944 =1.483 million yuan.

(9) Financial unit property: A9 = 600 million yuan, V9 = 0.5515c9 = 6 million yuan × 0.5515 = 3.309 million yuan.

(10) Property of institutions and units: A10 = 20,000 yuan/unit ×1= 220,000 yuan, V10 = 0.5515c10 = 220,000 yuan ×

(1 1) medical and health property: a11= 200,000 yuan, v11= 0.5037c1= 200,000 yuan.

(12) school property: a12 = 200,000 yuan, v12 = 0.5706c12 = 200,000 yuan × 0.5706 =1..

(13) highway: A 13 = 1000 yuan/m×1000 million yuan =1000 million yuan, v13 = 0.9469c/kloc.

(14) Small hydropower station: A14 = 2.6 million yuan, V14 = 0.5066c14 = 2.6 million yuan × 0.5066 =13/kloc-0.

Total value of maximum possible economic loss of disaster-bearing body:

c = c 1+C2+C3+C4+C3+C6+C7+c8+C9+c 10+c 12+c 13+c 14。

Investment budget of debris flow prevention and control project in Nanxi: According to the expected workload of exploration and control, the required funds are budgeted according to the relevant national cost standards, and the required funds are 6.5438+0.5064 million yuan, including 62,000 yuan for exploration and 6.5438+0.444 million yuan for control (Table 3-4-3).

Table 3-4-3 Budget Table for Exploration and Treatment of Debris Flow in Nanxi

The capital profit and tax rate of debris flow prevention and control project is as follows

b =(C-D)/D =(4773.05- 150.64)/ 150.64 = 3068.5%

The direct economic benefit of the prevention and control project: C-D = 46.2238+0 million yuan.

Input-output ratio =150.64: 4773.05 =1:31.69.

Three. conclusion

Nanxi debris flow in Chenzhou City, Hunan Province is a moderately dangerous debris flow, and the prevention project is designed according to the standard of once every 20 years. After the implementation of the project management, all kinds of disaster-bearing bodies within the range of 0.3 124km2 (Nanxi Village, where Nanxi Township Government is located) can protect the personal safety of 1768 people and reduce the number of possible deaths by 27 people; Reduce possible economic losses by 47.7305 million yuan. The direct economic benefit of project management is 4624 1 10,000 yuan, the capital profit and tax rate is 3068.5%, and the input-output ratio is 1: 3 1.69. It can be seen that the social and economic benefits of Nanxi debris flow prevention project are enormous.