Evaluation of Disaster Reduction Benefit of Landslide Prevention and Control Project in Qukou Town, Kaixian County, Chongqing City

1. Overview of landslide control project in Qukou Town, Kaixian County

Qukou Town, Kaixian County, is a resettlement town for the Three Gorges immigrants. It is located at the Qukou landslide at the intersection of Pengxi River and Puli River. Above, the new site of Qukou Town is located in the Xinglongqiao-Hejiapang-Juping area, with an elevation of 200-295m and an area of ??0.36km2. The port is arranged on the north and south bank slopes of Shuanghezhai. The population is more than 4,000 and the land size is 21.2hm2. Since 1997, resettlement housing and relocation housing are under construction, with a completed housing area of ??approximately 10,000 m2, 650m and 450m of roads (including main and secondary roads), and considerable construction of electricity, water supply, communications, and drainage. scale.

The ancient landslide in Qukou Town is located on the west bank of the Pengxi River, starting from the Pengxi River in the east, to Wangjiayuan in the west, to Gangou in the north, and to Xinglongqiaogou in the south. The landslide is 1700m long in the longitudinal direction and 620m wide in the transverse direction. 1100m, with a plane distribution area of ??1.18km2, and a total landslide volume of approximately 47.11 million m3. The landslide has a "tongue" shape in appearance, with an obvious "armchair" topography at the trailing edge. The front edge elevation is about 147m, the trailing edge elevation is 410m, the height difference is 263m, and the overall slope is about 10°. The Baishuwan landslide is a secondary landslide based on the ancient landslide in Qukou Town. The landslide has clear boundaries, about 395m long, 428m wide, an area of ??169,000 m2, and a volume of 3.04 million m3. The overall shape is a wide "tongue" shape, the elevation of the trailing edge of the landslide is about 270m, the elevation of the front edge is 147-180m, the maximum height difference is about 90m, the overall slope is 13°, and the slope of the landslide front edge is large, about 30°. With good air access conditions, after the Three Gorges Reservoir is impounded, the stability of the landslide will be greatly reduced, and the overall situation will be basically stable or unstable.

The Qukou Town landslide control project was included in the "Overall Plan for Geological Disaster Prevention and Control in the Three Gorges Reservoir Area", and the Chongqing Municipal Development and Planning Commission approved the project. According to the preliminary design plan approved by the Chongqing Municipal Land and Housing Administration Bureau, the landslide was treated as a whole, using the "anti-slide pile support + drainage" treatment plan. The construction scale is: the landslide area is 169,000 m2 and the volume is 3.04 million m3. Main project volume: 13,000m3 of earth and stone excavation, 258m3 of filling volume, 3637m3 of stone strips (blocks), 9795m3 of concrete, and 723t of steel bars.

The approved investment budget is 11.57 million yuan. Among them: the main project cost of control is 7.87 million yuan (slip prevention project 6.82 million yuan, slope protection project 100,000 yuan, drainage project 830,000 yuan, other projects 20,000 yuan, monitoring project 100,000 yuan), temporary project cost 160,000 yuan, engineering Other expenses are 3 million yuan (including design fee of 540,000 yuan, engineering survey fee of 1.85 million yuan, including supplementary survey fee of 300,000 yuan), and basic preparation fee of 540,000 yuan.

Table 3-4-1 Preliminary design investment budget table for the landslide control project in Qukou Town, Kaixian County Unit: 10,000 yuan

II. Basic data for disaster reduction benefit assessment

The main physical indicators on the landslide and in the affected area include the following aspects:

(1) The Kaiwan Secondary Highway is 1.0km long, connecting Kaixian and Wanxian, and is an important outbound highway in Kaixian. The main road of the market town is 650m and the secondary road is 450m.

(2) The population is more than 3,700 people and the housing area is about 100,000 m2. The investment amount is more than 30 million yuan, and the family property is more than 15 million yuan. There are more than 1,500 people on the landslide, and the housing area is about 40,000 m2. Houses are built for relocation units and relocated immigrants. The main relocation units include the town government, primary and secondary school teaching buildings, Broadcasting station, construction management office, family planning building, etc.

(3) Qukou Port is located on the north and south slopes of Shuangzhai River. Qukou Port is one of the important passenger transportation and cargo distribution centers in Kaixian County. According to the overall plan of Kaixian New County, the construction scale of the port area It has an annual passenger volume of 100,000 passengers and an annual freight volume of 600,000 tons.

(4) The national defense optical cable passes through the front edge of the landslide, with a total length of about 1.6km.

(5) The total cultivated land area is about 700 acres, including more than 400 acres of paddy fields; there are many trees and fruit trees, which have great economic value.

The landslide is adjacent to the Pengxi River. When the water level rises to 176.76m, if a sudden disaster occurs and a large-scale landslide occurs, the river will be blocked, directly threatening the new county and the new immigrant market town. Dam failure will seriously affect Zhaojia Town and other places downstream.

3. Disaster Reduction Benefit Calculation

(1) Social Benefit Calculation

Social benefit evaluation mainly evaluates the impact of the implementation of landslide control projects on people and ensures that people Life safety. Multiply the population in the landslide hazard range by the population safety vulnerability value to obtain the maximum possible number of casualties. This is used to evaluate the number of casualties that landslide control projects can reduce.

The population security vulnerability value to geological disasters in the Three Gorges Reservoir area. According to statistics from counties and districts in the Three Gorges Reservoir area, 400 people died due to geological disasters. The total population of the reservoir area at that time was 102,758. Based on these two items The ratio of parameters serves as population security vulnerability, with a value of 0.004.

The maximum number of possible deaths is 3,700 × 0.004 = 15 people.

(2) Calculation of economic benefits

Calculate the value of various disaster-bearing bodies based on the basic data of the survey. The values ??of various disaster-bearing bodies can be obtained by checking the summary table of expert opinions on vulnerability. Vulnerability, the two are multiplied to obtain the maximum possible loss value of various disaster-bearing bodies.

(1) Urban residential housing: A1=300 yuan/m2×100000m2=30 million yuan, v1=0.8029 C1=30 million yuan×0.8029=24.087 million yuan

(2 ) Household supplies for urban residents: A2 = 15 million yuan, v2 = 0.8809 C2 = 15 million yuan × 0.8809 = 13.2135 million yuan

(3) Cultivated land: A3 = 2,000 yuan × 700 = 1.4 million yuan, v3 ＝0.8993 C3＝1.4 million yuan×0.8993＝1.259 million yuan

(4) Highway: A4＝2000 yuan×1001000 yuan×1100＝3.1 million yuan, v4＝0.8257 C4＝3.1 million yuan× 0.8257＝2.5597 million yuan

(5) National defense optical cable: A5＝100,000 yuan×1.6＝140,000 yuan, v5＝0.7015 C5＝160,000 yuan×0.7015＝112,240 yuan

The maximum possible total loss of the disaster-bearing body: C＝C1+C2+C3+C4+C5＝41.2314 million yuan

The fund profit rate of the landslide prevention and control project: B＝（C-D）/D＝（ 4123.14-1157)/1157=256.4%

Net economic income of the prevention and control project=4123.14-1157=29.6614 million yuan

Input-output ratio=1157:4123.14=1:3.56

(3) Calculation of environmental benefits

The ecological service value of environmental resources is calculated using 20 years × (number of protected land resources × ecological service value of land resources): C = 20 × 169000 × 1.52 yuan/m2=5.1376 million yuan.

(4) Comprehensive evaluation of disaster reduction benefits

The landslide control project in Qukou Town, Kaixian County has protected the life safety and normal life of 1,500 people on the Baishu Bay landslide; it can reduce the maximum number of deaths by 15 People have played a role in calming people's hearts and promoting social stability and healthy development. Resettling 3,700 immigrants ensured the economic development of the immigration area.

The landslide control project in Qukou Town, Kaixian County ensured the property safety of the resettled market town and reduced the possible economic losses caused by geological disasters by 41.2314 million yuan; the net economic income of the project control was 29.6614 million yuan; the capital profit The tax rate is 256.4%; the input-output ratio is 1:3.56, which has significant economic benefits.

The environmental benefits after the implementation of the landslide control project are reflected in: first, the 169,000m2 land resources on the landslide body were protected from damage, which is equivalent to increasing the ecological service value of land resources by 5.1376 million yuan; second, reducing the The 3.04 million m3 of water and soil loss caused by the landslide caused siltation in the Three Gorges Reservoir area, ensuring the effective storage capacity, flood control capacity and service life of the reservoir.