Research on land use planning of resettlement area based on CAD platform

School of Economics and Management, Southwest University, Chongqing, 4007 16)

By analyzing the relationship between elevation, soil suitability and slope and land use planning, taking Sangangping resettlement area in Luding County, Sichuan Province as an example, with the support of CAD platform, the elevation map, slope map and soil suitability evaluation map are extracted respectively, and finally superimposed on the land use planning map. The results of land planning analysis are more in line with the actual situation and operable, which can be used as support for the government and owners' immigration decision.

Keywords: resettlement area; Land use planning; Superposition analysis; CAD platform

The quality of land planning in resettlement areas will affect whether the production and living standards of immigrants can reach or exceed the original level after relocation, and then indirectly affect the stability of local social and economic development. There are many factors that affect the land planning of resettlement areas, which can be roughly divided into socio-economic factors and natural factors. Socio-economy mainly includes indigenous people's production habits, traffic conditions, local agricultural policies, etc. Natural factors are mainly considered from the aspects of altitude, soil, slope and land use mode in the resettlement area. This study investigates the relationship between natural factors and land use planning in resettlement areas.

This paper takes Sangangping resettlement area in Luding County, Sichuan Province as an example. The resettlement area is located in groups 1 and 3 of Li Zan Village, Luqiao Town, Luding County, with the back of Li Zan Houshan and on the right bank of Dadu River, with the latitude of 29 48 ′14 ″ and the longitude of 29 49 ′ 08 ″. The elevation of the selected resettlement area is between 1500 ~ 1700 m, the length from north to south is about 2 150m, and the width from east to west is about 850m m. The total land area of the resettlement area is 12238.6 mu, and the current land use is mainly grassland with a small amount of dry land. 745 immigrants will be resettled in Sangangping resettlement area, accounting for 30% of the number of immigrants flooded by Luding Reservoir. It is one of the larger resettlement areas in the local area, and its land use planning will affect the enthusiasm of local immigrants and the stability of large-scale hydropower construction in the country. This paper attempts to use CAD software and based on CAD platform to analyze the relationship between land use planning and elevation, slope and soil suitability evaluation in resettlement areas, and deeply understand the relationship between various natural factors and land use planning. The purpose is to find a more scientific basis for land use planning in resettlement areas.

1 Establishment of land planning model

1. 1 Selection of factors and determination of weights

From a natural point of view, the factors that affect the land use pattern in resettlement areas are mainly as follows. The first is altitude. According to the report of planting division in Luding County, altitude 1600 m is the dividing line of agricultural production, and the planting patterns are quite different. Below 1600 m, it is a low mountain valley area, where rice, vegetables and fruits are mainly planted; above 1600 m, it is a middle and high mountain area, where alpine crops such as potato and medicinal materials are mainly planted. The second is the slope of the land. On the one hand, slope affects the cost of land development, on the other hand, it also affects the result of land planning. The third is the evaluation result of soil suitability. Soil suitability evaluation is the basis of land use planning and scientific and reasonable land planning. The fourth is the way of land use. Generally speaking, land planning should be carried out on the premise of respecting the original land way and not changing the original way. The fifth is the geological situation. The stability of geological conditions will also bring many factors that need to be considered in planning.

There are no faults and fracture zones in Sangangpingchang area. The hydrogeological conditions of the site are simple, the overall stability of the hillside is good, and there are no adverse geological phenomena such as large-scale slope deformation, landslide and debris flow. The main land use status of resettlement area is mainly grassland, with a small amount of dry land, but it still contains a lot of gravel, and land consolidation is still needed. The geological and land use patterns are relatively simple and consistent, and there is no big difference. Therefore, geology and land use patterns are not considered as planning influencing factors.

According to the specific situation of Sangangping resettlement area, the evaluation results of elevation, slope and soil suitability are mainly selected as the influencing factors of land planning. Through the study of agricultural production in Luding County, the grading weight of altitude, slope and suitability evaluation results was determined by comprehensive analysis. See table 1, table 2 and table 3 for details.

Table 1 Weight Table of Sangangping Elevation Classification

Table 2 Weight Table of Sanggangping Slope Grade Division

Table 3 Grading Weight Table of Soil Suitability Evaluation in Sangangping

1.2 planning objectives

According to the original planting habits of immigrants and the planning objectives of immigrants, it is planned to plan four land use types: paddy field, irrigated land (vegetable field), garden land and dry land. In this study, the comprehensive index method is used for classification, and the comprehensive index of each plot is determined according to the following formula:

Comprehensive index = elevation value × slope value × soil evaluation value

It should be noted that the comprehensive index range only has the right of priority planning, that is, within this range, priority planning is given to land types, not absolute planning. See Table 4 for details.

Table 4 Classification Table of Sangangping Land Use Planning

1.3 Analysis of land planning process in Sangangping

According to the above planning analysis, the land planning process of Sangangping is comprehensively determined. See figure 1 for details.

Figure 1 Land Planning Process of Sangangping

Application of 2 CAD in land use planning

2. 1 data acquisition

The total station was used to survey the resettlement area of Sangangping, and the topographic map of Sangangping 1∶2000 was obtained. On the basis of 1∶2000 topographic map, the attribute data such as altitude, land slope and soil suitability evaluation of resettlement area are input and vectorized.

2.2 Extraction of elevation, slope and soil evaluation map

With the support of CAD platform, the slope map, soil suitability evaluation map and elevation classification map of Sangangping resettlement area are extracted respectively according to the above altitude, slope and soil suitability evaluation classification indicators, as shown in Figure 2 ~ Figure 4.

Fig. 2 Slope map of Sangangping

Fig. 3 Soil evaluation map of Sangangping

Fig. 4 Elevation view of Sangangping

3 Results and analysis

In this study, only the slope of < 25 is statistically analyzed, and the area of > 25 will be reclaimed according to the national policy of returning farmland to forest and grassland. In the area less than 25 degrees, the slope map, soil suitability evaluation map and elevation map are superimposed and classified, and four types of plots suitable for planning are counted according to the above classification principles.

Figure 5 Overall Land Planning of Sangangping

Figure 6 Scale Map of Sangangping Land Planning

As can be seen from Figures 5 and 6, the paddy field area suitable for planning is 509 mu, accounting for 42%; This part of the area is mainly distributed in the area with an altitude of 1400 ~ 1500m and a slope below 15, and belongs to the best land. Although most of the soil suitability evaluation belongs to the fourth-grade land, it is the land suitability evaluation before transformation. After the transformation of the outer soil, the soil removal and fertilization project will probably go to the secondary land. Therefore, paddy fields should be given priority in this part of land to ensure stable grain production and bumper harvest after resettlement. Suitable planning vegetable area is 333 mu, accounting for 27%; This part of the land is mainly distributed in the area of 1500 ~ 1550 m, and the slope is less than 15. The evaluation result of soil suitability is Grade IV (foreign soil will reach Grade II after transformation). As an area to increase the income of immigrants, this part of the land mainly grows cash crops such as vegetables to increase the income of immigrants. The suitable planning garden area is 174 mu, accounting for14%; This part of the land is mainly distributed in the area of 1550 ~ 1600 m, with a slope of about 15, and the evaluation result of soil suitability is Grade III. As an economic tree planting area for immigrants, this part of the land mainly grows citrus. , thus generating income for immigrants. The suitable planning area of dry land is 206 mu, accounting for17%; This part of the land is mainly distributed in the area of 1600 ~ 1700 m, with a slope of15 ~ 25, and the evaluation result of soil suitability is Grade III. As the main grain producing area of immigrants, this part of the land mainly grows corn, sweet potato and other food crops to ensure the food security of immigrants.

From the above statistical analysis, it can be seen that the overall land planning map obtained by superimposing and analyzing different layers on the CAD platform takes all natural factors into account, which is operable in actual operation and can be used as a reference for government and owner departments to plan.

4 problems and suggestions

Although statistical analysis by overlaying layers has certain reference value, there are still three problems in the actual planning process:

(1) This paper analyzes the relationship between natural factors and land planning, but in fact, natural factors are not the only conditions that affect land use types. Especially in the study area, socio-economic factors, such as traffic conditions and development policies, will definitely affect the land use planning in this area. It is suggested that according to the actual situation in this area, restrictive factors or dominant factors should be selected as influencing factors, and then each factor layer should be extracted for superposition analysis, so as to obtain more accurate land planning data.

(2) Selection of influencing factors and distribution of weights. The influencing factors not only have different degrees of influence on the same land use type under different conditions, but also have different degrees of influence on different land use types under the same conditions, so the final grading standards of land use types are also different. This study refers to land grading and assigns values according to the actual situation. In different regions and different situations, the choice of factors and the distribution of weights will be different.

(3) The particularity of land planning in resettlement areas. This paper takes the resettlement area as an example. The author has a deep understanding of immigration planning. Planning must respect the production habits of immigrants. If some immigrants mainly plant citrus before moving, then the planning of the garden must be given priority. If some of them used to rely on traffic conditions to grow vegetables as their main business, they must plan vegetable fields under convenient traffic conditions. In a word, it is suggested that in the land planning of resettlement areas, we should not only analyze the conditions of resettlement itself, but also expand the scope, investigate the production habits of indigenous people, and investigate their skills and preferences. Only in this way can we make a feasible land planning. Immigrants will not be poor because of the gap in production habits after relocation, and gradually guide them to become rich through production.