Comprehensive research and judgment method and system for water and soil conservation rate

Abstract

The invention provides a water and soil conservation rate comprehensive research and judgment method and system. The method comprises the following steps: acquiring basic information of a research area, and analyzing and generating attribute data mat files of different soil erosion types, different provincial regions, different water and soil conservation three-level partitions and different land utilization types; encoding the water and soil loss research and judgment rule of the research area in the specified period; according to the attribute data mat file and the water and soil loss research and judgment rule coding data, water and soil loss research and judgment result mat files of different evaluation periods, different three-level partitions and different land utilization types are generated; according to the water and soil loss study and judgment result mat file, respectively taking the provincial region, the three-level partition and the land utilization type as statistical calibers, and performing statistical summation to obtain a corresponding water and soil loss condition mat file; and according to the water and soil loss condition mat file, respectively taking the provincial region and the three-level subregion as statistical calibers, summarizing to obtain the total area and the water and soil loss area of different land utilization types, and calculating the water and soil conservation rate of different statistical calibers.

Description

Technical Field

[0001] The present invention relates to the technical field of soil and water conservation, and in particular to a method and system for comprehensively evaluating soil and water conservation rates. Background Art

[0002] The soil and water conservation rate refers to the proportion of the area with good soil and water conservation conditions (non-soil and water loss area) in the region to the area of ​​the region. It is a macro-management indicator that reflects the overall situation of soil and water conservation, and is a comprehensive reflection of the effectiveness of soil and water loss prevention and control and the natural endowment soil and water conservation function at a spatial scale. Its calculation formula is (the current land area with mild soil erosion intensity in the region / regional land area) × 100%. At present, the Chinese Soil Loss Equation (CSLE) is mostly used to calculate soil erosion intensity. This model has a distributed structure. When calculating soil erosion intensity, many types of data are required (such as rainfall erosivity factor, soil erodibility factor, slope length factor, cover and biological measures factor, engineering measures factor and tillage measures factor), and the data processing process is relatively complicated. In addition, the model faces the problem of generating complex scenarios in the future in the prediction and evaluation period in terms of future soil and water loss prediction. Therefore, the workload and difficulty of judging the soil and water conservation rate in different periods in the future are relatively large. Summary of the invention

[0003] In order to solve the problems of the large number of data types required for calculating the soil and water conservation rate, the complex data processing process and the difficulty in generating future soil and water loss prediction scenarios, the present invention provides a comprehensive soil and water conservation rate analysis method and system.

[0004] In one aspect, the present invention provides a method for comprehensive assessment of soil and water conservation rate, comprising:

[0005] Step 1: Obtain basic information of the study area, including soil erosion type and intensity data, land use type data, slope data, and vegetation coverage data;

[0006] Step 2: Based on the basic information of the study area, parse and generate attribute data mat files of different erosion types, different provinces and regions, different soil and water conservation three-level zones, and different land use types;

[0007] Step 3: Obtain soil and water loss judgment rules for different erosion types and land use types in the study area during a specified period, and encode the soil and water loss judgment rules;

[0008] Step 4: Generate soil and water loss assessment result mat files for different assessment periods, different soil and water conservation three-level zones, and different land use types based on the attribute data mat file and soil and water loss assessment rule coding data;

[0009] Step 5: According to the soil and water loss assessment result mat file, the province, the three-level soil and water conservation zone and the land use type are used as statistical calibers, and the corresponding soil and water loss status mat file is obtained by statistical summation;

[0010] Step 6: According to the soil and water loss status mat file, the province and the three-level soil and water conservation zones are used as statistical calibers, the total area and soil and water loss area of ​​different land use types are summarized, and the soil and water conservation rates of different statistical calibers are calculated.

[0011] Furthermore, step 2 specifically includes:

[0012] Step 2.1: Process the four types of data contained in the basic information respectively to obtain raster layers corresponding to each type of data;

[0013] Step 2.2: spatially overlay the raster layers of various data to generate a multi-factor composite layer, and generate attribute information data of the multi-factor composite layer, which is used to indicate the slope grade, erosion type, erosion intensity grade, vegetation coverage grade and land use type of each three-level zone of soil and water conservation in the study area;

[0014] Step 2.3: Parse the attribute information data of the multi-factor composite layer into attribute data tables of different erosion types, different provinces and regions, different three-level soil and water conservation zones, and different land use types, and save them separately as data files of the mat type.

[0015] Furthermore, in step 3, the soil and water loss assessment rules are encoded, specifically including:

[0016] Each soil and water conservation three-level zone uniquely corresponds to a three-level zone code identifier, and each land use type uniquely corresponds to a land type code identifier; each soil and water conservation three-level zone includes multiple land use types;

[0017] For each three-level soil and water conservation zone, at least one composite code is assigned to each land use type under the three-level soil and water conservation zone, and the composite code is used to indicate the slope grade, erosion intensity grade and vegetation coverage grade required for the area of ​​the land use type to transform from soil erosion to non-soil erosion under the corresponding erosion type.

[0018] Furthermore, step 4 specifically includes:

[0019] For each land use type area under each three-level soil and water conservation zone, find the synthetic code corresponding to the assessment period judgment rule. If there is only one synthetic code and the erosion type of the area meets the erosion type indicated by the synthetic code, compare them according to the preset judgment process to obtain the final soil and water loss judgment result; if there are multiple synthetic codes, after obtaining the soil and water loss judgment result corresponding to each synthetic code, find the union of the soil and water loss judgment results of all synthetic codes as the final soil and water loss judgment result;

[0020] Among them, the preset analysis and judgment process includes: setting the value of the ones digit of the composite code to represent the vegetation coverage level that needs to be achieved. When the vegetation coverage of the area is greater than this level, it is determined that there is no soil erosion in the corresponding area; setting the value of the tens digit of the composite code to represent the soil erosion intensity level that needs to be achieved. When the soil erosion intensity of the area is less than or equal to this level, it is determined that there is no soil erosion in the corresponding area; setting the value of the hundreds digit of the composite code to represent the slope level that needs to be achieved. When there is only one composite code and the slope of the area is less than or equal to this level, or when there are multiple composite codes and the slope of the area is equal to this level, it is determined that there is no soil erosion in the corresponding area; setting the value of the thousands digit of the composite code to represent the soil erosion type applicable to the composite code. If the erosion type of the corresponding area meets the requirements, the composite code is applicable, otherwise it is not applicable; if the values ​​from the ones digit to the hundreds digit of the composite code are 0, it indicates that the corresponding analysis and judgment condition does not exist.

[0021] In another aspect, the present invention provides a soil and water conservation rate comprehensive evaluation system, comprising:

[0022] A judgment rule coding module is used to obtain the soil and water loss judgment rules for different erosion types and land use types in the study area during a specified period, and to encode the soil and water loss judgment rules;

[0023] An information acquisition module is used to acquire basic information of the study area, wherein the basic information includes soil erosion type and intensity data, land use type data, slope data and vegetation coverage data;

[0024] The data processing module is used to parse and generate attribute data mat files of different erosion types, different provinces and regions, different soil and water conservation three-level zones, and different land use types based on the basic information of the study area;

[0025] The judgment module is used to generate a mat file of soil and water loss judgment results for different assessment periods, different three-level soil and water conservation zones, and different land use types according to the attribute data mat file and soil and water loss judgment rule coding data;

[0026] The first statistical module is used to obtain the corresponding soil and water loss status mat file by taking the province, the three-level soil and water conservation district and the land use type as the statistical caliber according to the soil and water loss assessment result mat file;

[0027] The second statistical module is used to use the province and the three-level soil and water conservation zones as statistical calibers according to the soil and water loss status mat file, summarize the total area and soil and water loss area of ​​different land use types, and calculate the soil and water conservation rates of different statistical calibers.

[0028] Beneficial effects of the present invention:

[0029] The present invention encodes the judgment rules for the judgment conditions in different periods, and then adopts spatial information fusion and multi-condition comprehensive judgment methods to achieve effective judgment of soil and water loss conditions in large-scale regions in the medium and long term in the future. It has the characteristics of relatively small data volume, relatively low data processing difficulty, scientific and reasonable technical route, simple and efficient calculation process, etc., which can meet the actual needs of the country for the judgment of soil and water conservation rates in different periods in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of a flow chart of a method for comprehensive assessment of soil and water conservation rate provided by an embodiment of the present invention;

[0031] Figure 2 The judgment rules for some three-level zones in 2050 provided by the embodiment of the present invention;

[0032] Figure 3 The judgment rule coding of some three-level partitions in 2050 provided by the embodiment of the present invention;

[0033] Figure 4 A schematic diagram of the analysis and judgment results provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] like Figure 1 As shown, the embodiment of the present invention provides a method for comprehensive assessment of soil and water conservation rate, comprising the following steps:

[0037] S101: Obtain basic information of the study area, wherein the basic information includes soil erosion type and intensity data, land use type data, slope data, and vegetation coverage data;

[0038] Specifically, the data used in this embodiment are the vector boundaries of the Northwest Loess Plateau, the vector boundaries of relevant provinces and regions (Shanxi, Shaanxi, Qinghai, Ningxia, Inner Mongolia, and Gansu), the vector boundary data of the secondary and tertiary soil and water conservation zones in the region, the 2018 soil erosion intensity classification data, land use data, and the 250m resolution NDVI data of MODIS and the 12.5m resolution DEM data of ALOS PALSAR from 2008 to 2017 on the USGS data platform.

[0039] S102: According to the basic information of the study area, the attribute data mat files of different erosion types, different provinces and regions, different soil and water conservation three-level zones, and different land use types are parsed and generated;

[0040] Specifically, the data are preprocessed according to the soil and water conservation rate assessment requirements. This includes the following sub-steps:

[0041] S1021: performing data processing on the four types of data included in the basic information respectively to obtain raster layers corresponding to the various types of data;

[0042] Specifically, the processing process of soil erosion intensity and land use type data is as follows: Taking the soil erosion intensity data as raster data stored at a resolution of 10m by county in 2018, and the land use type data as high-precision vector data stored by county as an example, first, the county-level administrative area corresponding to each three-level zone is determined according to the vector range of each three-level soil and water conservation zone, and then imported into ArcGIS for splicing, and then the vector data is converted into raster data to obtain the raster layers of soil erosion intensity and land use type of each three-level zone.

[0043] The slope data processing process is as follows: according to the range of each three-level partition, the corresponding DEM data is obtained by splicing and cropping, and then the slope tool is used to obtain the slope, and the slope is graded (<5°, 5-8°, 8-15°, 15-25°, 25-35°, >35°) to obtain the slope classification raster layers of each three-level partition.

[0044] The vegetation coverage data processing process is as follows: (1) The 250-m resolution NDVI of MODIS in the Loess Plateau from 2008 to 2017 was synthesized to obtain the NDVI of each month, and the vegetation coverage (FVC) of each month was calculated; (2) The average value of vegetation coverage during the growing season from June to September was taken as the vegetation coverage for soil and water loss prevention and control in that year; (3) The difference in vegetation coverage between years is the interannual variation rate of vegetation coverage, and the interannual variation rate of vegetation coverage from 2008 to 2017 was calculated. (4) Based on this change rate and the regional vegetation coverage recovery threshold, the vegetation coverage of forests and grasslands in 2025, 2030, 2035 and 2050 was predicted; (5) The vegetation coverage was divided into five levels (<30%, 30%-45%, 45%-60%, 60%-75%, >75%) to obtain the vegetation coverage classification data layer of the Northwest Loess Plateau, which was clipped using the vector boundaries of the three-level soil and water conservation zones to obtain the vegetation coverage classification raster layers of each three-level zone.

[0045] S1022: spatially overlaying the raster layers of various data to generate a multi-factor composite layer, and generating attribute information data of the multi-factor composite layer, wherein the attribute information data is used to indicate the slope grade, erosion type, erosion intensity grade, vegetation coverage grade and land use type of each three-level soil and water conservation zone in the study area;

[0046] Specifically, the data layers of land use, slope and vegetation coverage were resampled to generate 10m resolution data with the same soil erosion intensity. The four raster layers were loaded into ArcGIS for spatial overlay to obtain a multi-factor composite layer. Twenty patch areas were used to perform mask extraction on the four layers, and attribute table information (txt file) was generated after extraction.

[0047] As an implementable method, the method of superimposing attribute information data of each layer is as follows:

[0048] The attribute information data of the land use type layer remains unchanged. This embodiment encodes 26 land use types, such as Figure 2 As shown, it is 9-84.

[0049] The attribute information data of the vegetation coverage layer is multiplied by 100; before superposition, the attribute information data of vegetation coverage is 1-5, a total of 5 levels; after superposition, the attribute information data of vegetation coverage becomes 100-500;

[0050] The attribute information data of the erosion type and intensity layer is multiplied by 1000; before superposition, the attribute information data of the erosion type is 1-3, a total of 3 types (such as water erosion, wind erosion and freeze-thaw erosion), and the attribute information data of the erosion intensity is 1-6, a total of 6 levels; after superposition, the attribute information data of the erosion type and intensity becomes 11000-36000;

[0051] The attribute information data of the slope layer is multiplied by 100000; before superposition, the attribute information data of the slope is 1-6, a total of 6 slope levels, and after superposition, the attribute information data of the slope becomes 100000-600000.

[0052] For example, if the attribute information data of the multi-factor composite layer is 111113, it means: the slope level is 1, the erosion type is 1, the erosion intensity level is 1, the vegetation coverage level is 1, and the land use type is 13.

[0053] S1023: Parse the attribute information data of the multi-factor composite layer into attribute data tables of different erosion types, different provinces and regions, different three-level soil and water conservation zones, and different land use types, and save them separately as data files of the mat type.

[0054] Specifically, the purpose of parsing the attribute information data into a mat-type data file is to facilitate the subsequent analysis and calculation process. Each mat data file is a 5×36 matrix containing 6 slope levels, and each slope level is a 5×6 attribute information matrix, that is, 5 erosion intensity levels and 6 vegetation coverage levels.

[0055] Taking erosion type as the statistical caliber as an example, according to the different erosion types that need to be counted, the MAT data files can be divided into the following three categories: statistical extraction of MAT data files without considering the erosion type, statistical extraction of MAT data files under hydraulic erosion only, and statistical extraction of MAT data files under freeze-thaw erosion only.

[0056] S103: Obtaining soil and water loss assessment rules for different erosion types and land use types in the study area during a specified period, and encoding the soil and water loss assessment rules;

[0057] Specifically, based on the comprehensive consideration of the impact of land use type, vegetation coverage and slope on soil erosion, the soil erosion surface erosion classification index table in the "Soil Erosion Classification and Grading Standard (SL 190-2007)" of the Ministry of Water Resources is shown in Table 1, and the wind erosion intensity classification table is shown in Table 2. Given that freeze-thaw action is difficult to control, the existing freeze-thaw erosion area is all included in the soil and water loss area at different times.

[0058] Table 1 Surface corrosion classification index table

[0059]

[0060] Table 2 Wind erosion intensity classification table

[0061]

[0062]

[0063] The water erosion and wind erosion assessment conditions may be different in different assessment periods. Figure 2 Shown are the conditions for assessing water erosion and wind erosion in 2050.

[0064] It can be seen from the above content that the soil and water loss judgment rules are relatively complex, and the original judgment rule format is not conducive to the automation of the judgment calculation process, resulting in low judgment calculation efficiency of the soil and water conservation rate. Therefore, in order to improve the judgment calculation efficiency of the soil and water conservation rate, this embodiment encodes the soil and water loss judgment rules. As an implementable method, the encoding method specifically includes:

[0065] Each third-level zone uniquely corresponds to a third-level zone code identifier, and each land use type uniquely corresponds to a land type code identifier; each third-level zone includes multiple land use types;

[0066] For each three-level soil and water conservation zone, at least one composite code is assigned to each land use type under the three-level soil and water conservation zone. The number of codes is consistent with the number of conditions in the judgment rule. The composite code is used to indicate the slope level, erosion intensity level and vegetation coverage level required for the area of ​​the land use type to change from soil erosion to non-soil erosion under the corresponding erosion type. It should be noted that in the embodiment of the present invention, mild and above erosion intensity is defined as soil erosion, and slight erosion intensity is defined as non-soil erosion, that is, there is no soil erosion in the corresponding area.

[0067] As an implementable method, the coding order is: three-level soil and water conservation zoning, land type, and year. Among them, the year has four evaluation dimensions, namely erosion type, slope, erosion intensity, and vegetation coverage. For example, Figure 3 As shown, the fifth column is the coding identifier of the third-level zoning, the sixth column is the land type coding identifier of the land use type, and the seventh column is the judgment conditions corresponding to the year, involving a total of 4 judgment dimensions.

[0068] Coding initialization: Assign an initial value of 0 to the composite code of each land use type under the three-level partition, where 0 represents that there are no constraints on the three-level partition, the land type, the year, or the assessment dimension.

[0069] Judgment logic: The synthetic code of the judgment rule represents the corresponding conditions and judgment thresholds through different digits and values. The ones digit represents the vegetation coverage, and the value is the vegetation coverage level (level 1-5). When the vegetation coverage is greater than this level, it is judged that the soil erosion intensity has changed to slight, and there is no soil and water loss in the corresponding area; the tens digit represents the soil erosion intensity, and the value is the soil erosion intensity level (level 1-6). When the soil erosion intensity is less than or equal to this level, it is judged that the soil erosion intensity has changed to slight, and there is no soil and water loss in the corresponding area; the hundreds digit represents the slope, and the value is the slope level (level 1-6). When the slope is less than or equal to this level (there is only one synthetic code) or the slope is equal to this level (there are multiple synthetic codes), it is judged that the soil erosion intensity has changed to slight, and there is no soil and water loss in the corresponding area; the thousands digit represents the soil erosion type, and the value is the soil erosion type (1 water erosion, 2 wind erosion, 3 freeze-thaw), as the applicable erosion type of the judgment rule, if the corresponding area is the specified erosion type, the synthetic code is applicable; the values ​​from the ones digit to the hundreds digit are 0, indicating that the corresponding judgment condition does not exist.

[0070] S104: Generate a mat file of soil and water loss assessment results for different assessment periods, different three-level soil and water conservation zones, and different land use types according to the attribute data mat file and the soil and water loss assessment rule coding data;

[0071] S105: According to the soil and water loss assessment result mat file, the province, the three-level soil and water conservation zone and the land use type are respectively used as statistical calibers, and the corresponding soil and water loss status mat file is obtained by statistical summation;

[0072] S106: Based on the soil and water loss status mat file, the province and the three-level soil and water conservation zones are used as statistical calibers, and the total area and soil and water loss area of ​​different land use types are summarized, and then the soil and water conservation rates of different statistical calibers can be calculated, such as Figure 4 shown.

[0073] Example 2

[0074] In order to implement the above method, an embodiment of the present invention provides a comprehensive soil and water conservation rate analysis system, including an analysis rule encoding module, an information acquisition module, a data processing module, an analysis module, a first statistical module and a second statistical module.

[0075] The analysis and judgment rule encoding module is used to obtain the soil and water loss analysis and judgment rules for different erosion types and land use types in the study area during a specified period, and encode the soil and water loss analysis and judgment rules; the information acquisition module is used to obtain the basic information of the study area, and the basic information includes soil erosion type and intensity data, land use type data, slope data and vegetation coverage data; the data processing module is used to parse and generate attribute data mat files of different erosion types, different provinces and regions, different three-level soil and water conservation zones, and different land use types according to the basic information of the study area; the analysis and judgment module is used to analyze and generate attribute data mat files of different erosion types, different provinces and regions, different three-level soil and water conservation zones, and different land use types according to the attribute data mat files and soil and water loss The analysis and judgment rule encoding data is used to generate soil and water loss analysis and judgment result mat files for different assessment periods, different three-level soil and water conservation zones, and different land use types; the first statistical module is used to use the province, the three-level soil and water conservation zone, and the land use type as the statistical caliber according to the soil and water loss analysis and judgment result mat file, and obtain the corresponding soil and water loss status mat file by statistical summation; the second statistical module is used to use the province and the three-level soil and water conservation zone as the statistical caliber according to the soil and water loss status mat file, and obtain the total area and soil and water loss area of ​​different land use types, and calculate the soil and water conservation rate of different statistical calibers.

[0076] It should be noted that the embodiment of the present invention is to implement the above method, and its specific functions can be referred to the above method embodiment, which will not be repeated here.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A comprehensive method for evaluating soil and water conservation rate, characterized in that: include: Step 1: Obtain basic information of the study area, including soil erosion type and intensity data, land use type data, slope data, and vegetation coverage data; Step 2: Based on the basic information of the study area, parse and generate attribute data mat files of different erosion types, different provinces and regions, different soil and water conservation three-level zones, and different land use types; Step 3: Obtain soil and water loss judgment rules for different erosion types and land use types in the study area during a specified period, and encode the soil and water loss judgment rules; Step 4: Generate soil and water loss assessment result mat files for different assessment periods, different soil and water conservation three-level zones, and different land use types based on the attribute data mat file and soil and water loss assessment rule coding data; Step 5: According to the soil and water loss assessment result mat file, the province, the three-level soil and water conservation zone and the land use type are used as statistical calibers, and the corresponding soil and water loss status mat file is obtained by statistical summation; Step 6: According to the soil and water loss status mat file, the province and the three-level soil and water conservation zones are used as statistical calibers, the total area and soil and water loss area of ​​different land use types are summarized, and the soil and water conservation rates of different statistical calibers are calculated.

2. A comprehensive soil and water conservation rate evaluation method according to claim 1, characterized in that: Step 2 specifically includes: Step 2.1: Process the four types of data contained in the basic information respectively to obtain raster layers corresponding to each type of data; Step 2.2: spatially overlay the raster layers of various data to generate a multi-factor composite layer, and generate attribute information data of the multi-factor composite layer, which is used to indicate the slope grade, erosion type, erosion intensity grade, vegetation coverage grade and land use type of each three-level zone of soil and water conservation in the study area; Step 2.3: Parse the attribute information data of the multi-factor composite layer into attribute data tables of different erosion types, different provinces and regions, different three-level soil and water conservation zones, and different land use types, and save them separately as data files of the mat type.

3. A comprehensive soil and water conservation rate evaluation method according to claim 2, characterized in that: In step 3, the soil and water loss assessment rules are encoded, specifically including: Each soil and water conservation three-level zone uniquely corresponds to a three-level zone code identifier, and each land use type uniquely corresponds to a land type code identifier; each soil and water conservation three-level zone includes multiple land use types; For each three-level soil and water conservation zone, at least one composite code is assigned to each land use type under the three-level soil and water conservation zone, and the composite code is used to indicate the slope grade, erosion intensity grade and vegetation coverage grade required for the area of ​​the land use type to transform from soil erosion to non-soil erosion under the corresponding erosion type.

4. A comprehensive soil and water conservation rate evaluation method according to claim 3, characterized in that: Step 4 specifically includes: For each land use type area under each three-level soil and water conservation zone, find the synthetic code corresponding to the assessment period judgment rule. If there is only one synthetic code and the erosion type of the area meets the erosion type indicated by the synthetic code, compare them according to the preset judgment process to obtain the final soil and water loss judgment result; if there are multiple synthetic codes, after obtaining the soil and water loss judgment result corresponding to each synthetic code, find the union of the soil and water loss judgment results of all synthetic codes as the final soil and water loss judgment result; Among them, the preset analysis and judgment process includes: setting the value of the ones digit of the composite code to represent the vegetation coverage level that needs to be achieved. When the vegetation coverage of the area is greater than this level, it is determined that there is no soil erosion in the corresponding area; setting the value of the tens digit of the composite code to represent the soil erosion intensity level that needs to be achieved. When the soil erosion intensity of the area is less than or equal to this level, it is determined that there is no soil erosion in the corresponding area; setting the value of the hundreds digit of the composite code to represent the slope level that needs to be achieved. When there is only one composite code and the slope of the area is less than or equal to this level, or when there are multiple composite codes and the slope of the area is equal to this level, it is determined that there is no soil erosion in the corresponding area; setting the value of the thousands digit of the composite code to represent the soil erosion type applicable to the composite code. If the erosion type of the corresponding area meets the requirements, the composite code is applicable, otherwise it is not applicable; if the values ​​from the ones digit to the hundreds digit of the composite code are 0, it indicates that the corresponding analysis and judgment condition does not exist.

5. A comprehensive evaluation system for soil and water conservation rate, characterized in that: include: A judgment rule coding module is used to obtain the soil and water loss judgment rules for different erosion types and land use types in the study area during a specified period, and to encode the soil and water loss judgment rules; An information acquisition module is used to acquire basic information of the study area, wherein the basic information includes soil erosion type and intensity data, land use type data, slope data and vegetation coverage data; The data processing module is used to parse and generate attribute data mat files of different erosion types, different provinces and regions, different soil and water conservation three-level zones, and different land use types based on the basic information of the study area; The judgment module is used to generate a mat file of soil and water loss judgment results for different assessment periods, different three-level soil and water conservation zones, and different land use types according to the attribute data mat file and soil and water loss judgment rule coding data; The first statistical module is used to obtain the corresponding soil and water loss status mat file by taking the province, the three-level soil and water conservation district and the land use type as the statistical caliber according to the soil and water loss assessment result mat file; The second statistical module is used to use the province and the three-level soil and water conservation zones as statistical calibers according to the soil and water loss status mat file, summarize the total area and soil and water loss area of ​​different land use types, and calculate the soil and water conservation rates of different statistical calibers.

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