Method for monitoring and evaluating water and soil loss of rocky desertification slope in situ

Abstract

The application discloses a method for monitoring and evaluating soil and water loss of a rocky desertification slope in situ, which comprises the following steps: planning a test plot and building an assembled blocking structure; leveling and laying a source of cohesive soil for observing soil and water loss on the slope surface of the test plot; excavating a horizontal observation ditch along the boundary of the bottom of the test plot, and building a multi-stage layered collection pipe groove; laying a vacuum film with a certain strength on the surface of the rocky desertification slope after soil and water loss of the test plot, laying the source of cohesive soil on the vacuum film to a preset thickness before the test, and then slowly rolling up the vacuum film to obtain the total soil loss amount on the rocky desertification slope; and combining the measured soil loss amount in the slope runoff and the soil loss amount in the soil flow to obtain the soil underground leakage amount of the rocky desertification slope. The application further provides a method for comprehensively evaluating soil and water loss of the rocky desertification slope. The application provides a fast, simple, accurate and practical method for monitoring and evaluating the complex space-time effect of soil and water surface loss and underground leakage of the rocky desertification slope.

Description

Technical Field

[0001] This invention belongs to the field of observation and evaluation of soil and water loss on rocky desertification slopes, specifically involving a comprehensive on-site monitoring and evaluation method for soil and water loss on rocky desertification slopes. Background Technology

[0002] Rocky desertification slopes or areas undergoing ecological degradation both experience surface and groundwater erosion, leading to a series of complex and serious problems related to surface water and soil loss and groundwater leakage. Currently, the complex water and soil erosion issues arising from rocky desertification and ecological degradation continue to constrain the sustainable development of rocky desertification areas. On the one hand, the main factors and evaluation indicators affecting water and soil erosion on rocky desertification slopes are complex and numerous, including rocky desertification area, degree of rocky desertification, bedrock exposure rate, karst landforms, underground porosity, topographic relief, micro-topography, slope length, slope gradient, lithological combination, soil texture in the surface karst zone, soil macropore morphology (exposed, shallowly buried, deeply buried), soil layer thickness, slope underlying surface, vegetation type, vegetation cover, rainfall intensity, rainfall duration, rainfall amount, rainfall erosiveness, water conservation measures, soil and water conservation measures, biodiversity maintenance measures, allowable soil loss, and allowable surface soil erosion. On the other hand, soil erosion on rocky desertification slopes exhibits complex spatiotemporal effects. Currently, there are no efficient and practical methods for comprehensive, three-dimensional monitoring of rocky desertification slopes, and some observation indicators are almost entirely lacking. Furthermore, soil erosion on rocky desertification slopes involves not only surface runoff and interflow, but also underground seepage (leakage) unique to karst regions. Conducting comprehensive, three-dimensional on-site monitoring of soil erosion on rocky desertification slopes is a crucial foundation for researching the causes, characteristics, influencing factors, evaluation methods, and ecological protection technologies related to complex soil erosion. The data obtained from such monitoring is more scientific and convincing than simulation results from model experiments.

[0003] In the research on comprehensive evaluation methods and indicators for soil erosion on karst slopes, the scientific validity and effectiveness of existing technologies still need improvement. For example, according to my country's current "Classification and Grading Standards for Soil Erosion" (SL190-2007), using only the annual average soil erosion modulus as the sole criterion for judging the intensity of soil erosion on karst slopes is clearly incomplete and unreasonable, and easily underestimates the severity of local soil erosion. The "Technical Standards for Comprehensive Management of Soil and Water Loss in Karst Areas" (SL461-2009) comprehensively considers factors such as carbonate rock formation rate, lithological combination, and allowable loss to maintain sustainable soil fertility, based on the original single standard of soil erosion modulus, thus improving the scientific validity of my country's soil erosion classification and grading standards for karst areas. The most widely used evaluation method for soil erosion on karst slopes is the revised general soil loss equation, namely the RUSLE model, which can be used to evaluate the sensitivity of soil erosion in karst areas. The evaluation indicators used in this model method include rainfall and runoff erosivity factors, soil erodibility factors, slope length factors, slope gradient factors, vegetation cover management factors, and soil and water conservation measures factors. Based on actual observation data and combined with mathematical statistics, the amount of slope erosion or annual average soil loss is estimated. Referring to the RUSLE model, some researchers have introduced dimensionless factors such as shallow gully erosion, biological measures, engineering measures, and tillage measures, and improved the topographic factor algorithm, further establishing the CSLE model for soil and water loss assessment in my country. However, due to the unique underground leakage mechanism in karst regions, these models still have certain errors when assessing soil erosion in karst areas, especially on rocky desertification slopes with severe underground leakage, requiring correction and improvement.

[0004] Another method for assessing soil erosion is the physical process prediction model. Based on the fundamental physical processes of erosion and sediment production, it utilizes the principles of hydraulics, sediment dynamics, and other related disciplines to generalize complex erosion and sediment production phenomena. It then uses actual observation data to establish mathematical models and obtain parameters, such as the WEPP model, GUEST model, and EUROSEM model. This method is well-suited for loess regions, red soil hilly regions, Northeast black soil regions, and Southwest purple soil regions. However, for rocky desertification areas with limited total soil volume and complex soil erosion processes, where, in extreme cases, the surface is almost entirely devoid of soil cover, the soil erosion data obtained by this physical process prediction model is extremely low. Furthermore, the acquisition of measured data and the selection of parameters are difficult, making it impossible to accurately reflect the current state of soil erosion on rocky desertification slopes. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a comprehensive on-site monitoring and evaluation method for soil and water loss on rocky desertification slopes. This method offers a rapid, simple, accurate, and practical approach to the complex spatiotemporal effects of surface water and soil loss and underground leakage on rocky desertification slopes, thereby improving the accuracy and relevance of forecasts and providing theoretical support and guidance for promoting soil and water conservation and ecological protection in rocky desertification areas.

[0006] This invention was proposed with the support of the National Natural Science Foundation of China, the Guangxi Transportation Industry Key Science and Technology Project, and the Sichuan Provincial Key Research and Development Fund Project.

[0007] The present invention provides a method for comprehensive on-site monitoring and evaluation of soil erosion on rocky desertification slopes, including the following: (1) Select test plots for comprehensive three-dimensional observation of soil and water loss in the field; dig isolation trenches on the upper side and left and right sides of the selected test plots, place vertical isolation membranes along the isolation trenches, bury the lower part of the isolation membranes in the trenches, and make the upper part of the isolation membranes stand upright outside the isolation trenches. Build a fence around the boundary of the test plots with small anchor rods and crossbars, and lean the vertical isolation membranes against the crossbars to form a prefabricated fence structure. (2) Spread the source clay soil for soil erosion observation along the slope of the experimental plot and level it to the set thickness of the experiment. This material is used as the source material for soil erosion during rainfall and is also the matrix material for ecological protection of vegetation on rocky desertification slopes. (3) A transverse observation trench was excavated along the boundary of the bottom of the experimental plot slope for three-dimensional observation of soil and water loss in the geological section. After the long-term observation is completed, it will be used as a planting trench for ecological protection of soil and water loss. Along the depth direction of the transverse observation trench, grid baffles were placed at the depths corresponding to different soil layers. A collection pipe trench was placed on each grid baffle to realize multi-level layered collection and observation of soil and water loss corresponding to each rock and soil layer of the rocky desertification slope. Drainage membranes corresponding to each collection pipe trench in the transverse observation trench were set on the slope and each soil layer of the geological section of the experimental plot to divert the soil and water loss caused by runoff and interflow to each collection pipe trench. A slope guide pipe was connected to the same end of each collection pipe trench. The outlet of the slope guide pipe was connected to the respective soil and water collection bucket or soft pipe bag to collect the soil and water loss of each layer of the geological section. (4) Use sedimentation buckets to separate the soil and water collected from the slope runoff and interflow at each level by sedimentation method, in order to count and calculate the amount of sediment (silt) produced by the slope surface runoff and the amount of sediment produced by the interflow, and observe the sediment process of the slope runoff and the interflow. Observe once after each rainfall. (5) After soil erosion occurs due to rainfall, a vacuum membrane with a certain strength is laid on the surface of the rocky desertification slope in the test area. After the edges are sealed and compacted with soil, the air covered under the membrane is extracted. The vacuum membrane is then pressed tightly onto the soil erosion gullies and small hills on the rocky desertification slope after soil erosion. The same leveling method as in step (2) is used on the vacuum membrane (meaning that the leveled slope soil before and after erosion should be the same, such as the same leveling thickness, density, water content, void ratio, and compaction degree). The cohesive soil source is laid flat to the original set thickness of the slope cover on the rocky desertification slope. Then the vacuum membrane is slowly rolled up to obtain the total amount of soil loss on the rocky desertification slope. Combined with the measured amount of soil loss in the slope runoff and interflow, the amount of soil leakage in the rocky desertification slope is obtained. (6) Rain gauges and evapotranspiration devices were distributed at multiple points on the rocky desertification slope of the experimental area in advance. The total amount of precipitation and its process, the amount of water evaporation during the evaporation stage and its process were obtained through manual observation. Based on the measured rainfall duration, the rainfall intensity on site was calculated, and the temperature and humidity on site were tracked and measured online in real time.

[0008] Furthermore, the test plots can be set up in multiple tiers from top to bottom according to the size of the test area and the slope classification, forming a complete test system.

[0009] Furthermore, in step (1), the selection of the experimental planning plot is to select an area on the rocky desertification slope with a relatively flat horizontal slope and relatively uniform slope and soil conditions.

[0010] Further, in step (1), a topographic map of the site is obtained using photography and image processing techniques, and the area, degree, and bedrock exposure rate of the rocky desertification slope are calculated. Within the experimental planning area, the slope length, slope gradient, soil texture, soil macropore morphology, and soil layer thickness on the surface karst zone are measured to assess the degree of rocky desertification development on the slope before monitoring, preliminarily determine the degree of soil erosion, and provide a basis for calculating the amount and thickness of the source clay soil used for soil erosion observation on the slope in subsequent steps. The rocky desertification slope requires vegetation restoration, and the source clay soil is also used as a planting substrate. Before soil erosion observation, a layer of soil is laid on the rocky desertification slope to level it for comparative observation of soil erosion. This leveling soil layer is also used for vegetation restoration.

[0011] Furthermore, in step (1), the lower part of the erected isolation membrane is fixed by filling the isolation trench with soil or sealing the isolation trench with solidifying materials.

[0012] Furthermore, in step (1), at least two small anchor rods are arranged at both ends of the upper and lower boundaries of the experimental plot as supports for the horizontal bar and as reference objects (settlement markers) for observing and comparing the topography and geomorphology of the slope before and after soil erosion. The horizontal bar and the small anchor rods are tied together with wire or cable ties. After each heavy rain, the distance from the top of the small anchor rod to the eroded slope is observed, and the soil erosion thickness of the rocky desertification slope is calculated.

[0013] Furthermore, in step (3), the grid baffle has a certain slope along the length of the observation ditch, preferably a slope of 0.3% to 3%, so that the stratified collection trough also has the same slope, so that the collected water-soil mixture can be more smoothly transported to the downslope guide pipe connected to its end. If the consistency is high, a broom scraper can be used to assist in sliding the guide pipe.

[0014] Furthermore, in step (3), the width of the grid baffle is preferably slightly larger than the width of the transverse observation ditch, so that the grid baffle can be tilted and placed into the observation ditch, naturally leaning against the two side walls of the ditch, thus fixing the position of the grid baffle. The grid baffle is inclined in the transverse observation ditch, supporting the pipe groove above it, and at the same time serving as a barrier against dead branches, fallen leaves, debris, or large pieces of debris sliding down the slope with the runoff, preventing them from falling into the pipe groove or disturbing the pipe groove; the grid baffle is a plastic grid plate or an anti-corrosion bamboo raft.

[0015] Furthermore, in step (3), a membrane pad is laid in the collection trench. If the water-soil mixture has a high consistency, it is used to lift and remove the silt deposited in the trench, improving the accuracy of subsequent calculations, and the membrane pad is then replaced. Preferably, the membrane pad is a plastic film with a certain strength.

[0016] Further, in step (3), each layer of the drainage membrane is buried (stuffed) into the slope soil on one side of the slope surface and slope body (each soil layer within the geological cross-section), using the slope soil to hold it in place, while the other side extends into the transverse pipe trench, smoothly diverting the runoff and soil erosion caused by interflow into the collection pipe trench. Preferably, the drainage membrane is an ordinary plastic film with a certain strength, and its length is the same as that of the collection pipe trench.

[0017] Furthermore, in step (3), when installing the slope-guided flow pipe, a trench is dug perpendicularly to the end of the transverse observation trench and downwards towards the slope to install the slope-guided flow pipe (since the terrain is low in the direction of the slope, only a small section of trench needs to be dug, and most of the pipe body can be supported on the slope with soil bags or bricks). Using the slope-guided flow pipe, the slope runoff and interflow collected by the multi-stage collection trench are transported to their respective water and soil collection buckets or soft pipe bags.

[0018] Furthermore, the soft tubular bag mentioned in step (3) is a long tubular bag made of soft plastic, so that the soft bag can be segmented, tied in sections and measured during the collection process to realize the collection of soil and water loss at different time periods.

[0019] Furthermore, the layered collection trench in step (3) and the crossbar in step (1) are preferably made of PVC half-pipes, obtained by cutting off half of the pipe body along the length of the PVC pipe; the slope guide pipe for transporting water and soil, the collection trench in the transverse observation ditch, and the half-pipe barrier at the boundary of the test plot are connected at the joints with tee or two-way half-pipe joints respectively. Preferably, when used as a barrier for the test plot, the PVC half-pipe is placed with the concave side of the half-pipe facing inward, so that the erected isolation membrane can be fixed by filling the groove with soil.

[0020] Furthermore, when the test plot is located at the toe of a slope, it is not necessary to excavate a transverse observation trench. Instead, the collection trench can be placed below the toe of the slope, with supporting measures such as installing small anchors behind the trench. Since the collection trench is much lower than the toe of the slope, it would generally be damaged by immersion at the toe. Therefore, it is best to have an upright transverse bamboo raft between the toe of the slope and the trench for support, filtration, and isolation. The drainage membrane can be inserted into the soil at the toe of the slope through the horizontal gaps between the bamboo rafts.

[0021] In the above-described scheme of the present invention, further, to facilitate the experiment being conducted at any time, and to simulate the runoff from rainfall eroding the slope for experimental observation, the preferred operation is as follows: an overflow trough is fixed to the top of the experimental plot against the slope, and the foundation of the overflow trough is leveled to generate uniform overflow. The estimated overflow volume should be equivalent to the rainfall runoff volume. Preferably, an anti-erosion diversion membrane is laid under the overflow trough to prevent the overflow from eroding the adjacent slope soil below the trough.

[0022] In the above-described scheme of this invention, after obtaining relevant soil and water loss data, the following evaluation indicators are used to calculate the surface runoff coefficient, erosion area ratio, soil erosion rate, slope runoff rate, slope surface sediment yield, soil infiltration rate, soil sediment yield, groundwater infiltration rate, and groundwater leakage rate of the rocky desertification slope under different rainfall intensities and durations. Furthermore, these indicators are combined with relevant standards and other methods to comprehensively evaluate the soil and water loss status of the rocky desertification slope. The definitions of each evaluation indicator are as follows: The slope surface runoff coefficient is the ratio of the total runoff from rainfall on the slope of a rocky desertification slope test plot to the total rainfall during the same period, i.e., the proportion of rainfall converted into surface runoff. The erosion area ratio is the ratio of the erosion area generated by rainfall on the slope of the rocky desertification test plot to the area of ​​the slope of the test plot; Soil erosion rate is the sum of surface soil erosion and subsurface soil leakage caused by rainfall on the slope surface and below the rocky desertification slope test plot over a period of time. Slope runoff rate is the surface runoff generated by rainfall on the slope of a rocky desertification slope experimental plot over a period of time. The surface sediment yield is the amount of surface soil erosion caused by rainfall on the slope of a rocky desertification test plot over a period of time. The soil infiltration rate is the amount of infiltration along the slope caused by rainfall in the topsoil of the karst zone below the slope of the rocky desertification slope test plot over a period of time. The soil sediment yield rate is the amount of soil erosion caused by downslope seepage in the top karst soil below the slope of the rocky desertification slope test plot over a period of time. The groundwater seepage rate is the amount of groundwater seepage generated by rainfall under the slope surface of a rocky desertification slope test area over a period of time. The underground erosion rate is the amount of soil lost underground due to rainfall in a rocky desertification slope test area over a period of time.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The method described in this invention uses multi-stage prefabricated collection trenches for on-site monitoring of soil and water loss on rocky desertification slopes. This achieves comprehensive, three-dimensional on-site monitoring of soil and water loss on rocky desertification slopes in a rapid, simple, accurate, and practical manner. Using the data observed by this method, a series of new evaluation indicators reflecting the complex spatiotemporal effects of surface water and soil loss and underground leakage on rocky desertification slopes are defined and calculated. This comprehensive evaluation of the soil and water loss status on rocky desertification slopes helps to fully reveal the complex spatiotemporal effects of surface water and soil loss and underground leakage on rocky desertification slopes, improves the accuracy and pertinence of prediction and forecasting, and provides a reference for soil and water conservation and ecological protection on rocky desertification slopes.

[0024] 2. The method described in this invention is specifically designed for rocky desertification slopes in karst regions with severe underground leakage. It further enriches and improves the evaluation system for soil and water loss on rocky desertification slopes. It is simple, easy to implement, low in cost, and effective. It can be directly used to guide the research and application of prevention and control measures for severe surface water and soil loss and underground seepage on rocky desertification slopes, thereby promoting soil and water conservation on rocky desertification slopes. Attached Figure Description

[0025] Figure 1 This is a top view of the experimental planning plot on the rocky desertification slope of the present invention.

[0026] Figure 2 This is a cross-sectional view of the experimental planning plot on the rocky desertification slope of the present invention.

[0027] Figure 3 This is a cross-sectional view of the multi-stage collection pipe trench and the corresponding layers of soil and rock mass for collecting water and soil erosion according to the present invention.

[0028] Figure 4 This is a schematic diagram of the arrangement of the multi-stage collection trough and the slope-guided flow pipe connected to it according to the present invention.

[0029] Figure 5 This is a schematic diagram of the arrangement of the slope guide pipe and water and soil collection bucket of the present invention.

[0030] In the diagram: 1—Experimental plot, 2-1—Topsoil, 2-2—Surface weathering zone or karst zone, 2-3—Bedrock with karst channels, 3—Horizontal bar, 4—Small anchor, 5—Transverse observation trench, 6-0—First layer collection trench, 6-1—Second layer collection trench, 6-2—Third layer collection trench, 7—Membrane cushion layer, 8—Grid baffle, 9—Slope guide pipe, 9-0—First layer slope guide pipe, 9-1—Second layer slope guide pipe, 9-2—Third layer slope guide pipe, 10—T-junction or two-way junction, 11—Soil and water collection bucket, 12—Cohesive soil source area. Detailed Implementation

[0031] The present invention will be further illustrated below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-described invention, and these improvements and adjustments still fall within the scope of protection of the invention.

[0032] Example 1 The present invention provides a method for comprehensive on-site monitoring and evaluation of soil erosion on rocky desertification slopes, including the following: (1) Select a relatively flat area with uniform slope and soil conditions on the rocky desertification slope as the experimental plot 1 for on-site three-dimensional comprehensive observation of soil and water loss; use photography and image processing technology to obtain the on-site topographic map, calculate the area of ​​rocky desertification, degree of rocky desertification, and bedrock exposure rate; measure the slope length, slope, soil texture, soil macropore morphology, and soil layer thickness in the experimental plot to assess the degree of rocky desertification development on the slope before monitoring, preliminarily determine the degree of soil and water loss, and provide a basis for calculating the amount and thickness of source clay soil for soil and water loss observation in subsequent steps. The rocky desertification slope needs vegetation restoration, and the source clay soil is also used as a planting substrate. Before soil and water loss observation, a layer of soil is laid on the rocky desertification slope to level it for comparative observation of soil and water loss. This leveling soil layer is also used for vegetation restoration.

[0033] Isolation trenches were excavated along the upper and left / right boundaries of the experimental plot. Isolation membranes were placed along these trenches, with the lower part buried in the trenches. The lower part of the membranes was then fixed in place by filling the trenches with soil or sealing them with a solidifying material, thus ensuring the membranes stood upright. A perimeter fence was erected around the experimental plot boundaries using small anchor rods 4 and crossbars 3. The upright membranes were then supported against the crossbars, forming a prefabricated barrier structure. The crossbars were made of PVC half-pipes, obtained by cutting off half the length of the PVC pipe. The half-pipe barriers were connected at the intersections of the longitudinal and transverse sections using two-way half-pipe connectors. The concave side of the PVC half-pipes was placed inwards, allowing the erected membranes to be fixed by filling the grooves with soil. At least two small anchor rods were placed at each end of the upper and lower boundaries of the experimental plot as supports for the crossbars and as reference points for comparing the topography before and after slope erosion. The semi-tube barriers and small anchors are tied together with wire or cable ties. After each heavy rain, the height of the top of the small anchor from the eroded slope is observed to calculate the soil erosion thickness of the rocky desertification slope.

[0034] (2) Lay the source clay for soil erosion observation on the slope of the experimental plot, smooth it with a scraper, and lay it with a thickness set according to the experiment. This material is used as the source material for soil erosion during rainfall and is also the matrix material for ecological protection of vegetation on rocky desertification slopes.

[0035] (3) A transverse observation trench 5 is excavated along the boundary of the bottom of the experimental plot slope for three-dimensional observation of soil and water loss at the geological section. After the long-term observation is completed, it will be used as a planting trench for ecological protection against soil and water loss. Along the depth direction of the transverse observation trench, grid baffles 8 are placed at different depths. A PVC half-pipe is placed on each grid baffle as a collection pipe trench (6-0, 6-1, 6-2) to realize multi-level layered collection and observation of soil and water loss corresponding to each rock and soil layer of the rocky desertification slope. The grid baffles have a certain slope along the length of the observation trench, preferably a slope of 0.3% to 3%, so that the layered collection pipe trenches also have the same slope, so that the collected soil and water mixture can be more smoothly transported to the slope guide pipe connected to its end. The width of the grid baffles is preferably slightly larger than the width of the transverse observation trench, so that the grid baffles can be tilted and placed in the observation trench and naturally lean against the two side walls of the trench to fix the position of the grid baffles. The grid baffle is diagonally braced in the transverse observation ditch, supporting the pipe trench above it, and also serving as a barrier against dead branches, fallen leaves, debris, or large pieces sliding down the slope with the runoff, preventing them from falling into the pipe trench or disturbing it; the grid baffle is a plastic grid or anti-corrosion bamboo raft.

[0036] In the experimental plot, drainage membranes corresponding to the collection trenches within the transverse observation trenches are installed on the slope and at each layer of the geological cross-section. One side of the drainage membrane is buried in the slope soil to hold it in place, while the other side extends into the transverse trenches, effectively diverting runoff and interflow-induced soil erosion into the collection trenches. The drainage membrane is a common plastic film with a certain strength, and its length is the same as that of the collection trenches.

[0037] A slope-guided flow pipe 9 is connected to the same end of each collection trench. Each slope-guided flow pipe has its own water and soil collection bucket 11 at its end outlet to collect water and soil loss from each layer of the geological cross section. When installing the slope-guided flow pipe, a trench is dug perpendicularly to the end of the transverse observation trench and downwards to facilitate the installation of the slope-guided flow pipe (since the terrain is lower in the downward direction, only a small section of the trench needs to be dug, and most of the pipe body can be supported on the slope with soil bags or bricks).

[0038] (4) Use sedimentation buckets to separate the soil and water collected from the slope runoff and interflow at each level through sedimentation method, in order to count and calculate the amount of surface sediment (silt) and interflow sediment, and observe the sediment process of slope runoff and interflow. Observe once after each rainfall.

[0039] (5) After soil erosion caused by rainfall, a plastic vacuum membrane with a certain strength was laid on the surface of the rocky desertification slope in the test area. The four sides were sealed with soil. Then, the air covered under the membrane was extracted by a vacuum pump. The vacuum membrane was then pressed tightly onto the soil erosion gullies and small hills on the rocky desertification slope after soil erosion. The same leveling method as before the test was used on the vacuum membrane. The cohesive soil source was laid to the original thickness of the slope cover on the rocky desertification slope. The membrane was smoothed with a scraper. Then, the vacuum membrane was slowly rolled up to obtain the total amount of soil loss on the rocky desertification slope. Combined with the measured amount of soil loss in the slope runoff and interflow, the amount of soil leakage in the rocky desertification slope was obtained. (6) Rain gauges and evapotranspiration devices were pre-arranged at multiple points on the rocky desertification slope of the experimental area. The total amount of precipitation and its process, the amount of water evaporation during the evaporation stage and its process were obtained through manual observation. Based on the measured rainfall duration, the rainfall intensity on site was calculated, and the temperature and humidity on site were tracked and measured online in real time.

[0040] Example 2 The method described in this embodiment differs from that in Embodiment 1 in that: in step (3), a membrane pad is laid inside the collection trench to lift and remove the silted soil accumulated in the trench, thereby improving the accuracy of subsequent collection and calculation. The membrane pad is a plastic membrane with a certain strength. In addition, a soft plastic long tubular bag is connected to the slope guide pipe so that the soft bag can be segmented, tied in sections, and measured during the collection process, thereby realizing the collection of soil erosion at different time periods.

[0041] Example 3 The method described in this embodiment differs from that in Embodiment 1 in that multiple test plots are set up in tiers from top to bottom according to the size of the test area and the slope classification, forming a complete test system. When the test plot is located at the toe of the slope, a transverse observation trench does not need to be excavated. Instead, the collection pipe trench is placed below the toe of the slope, and support measures are set up, such as installing small anchor rods behind the pipe trench. Since the position of the collection pipe trench is much lower than the toe of the slope, it is generally damaged by water immersion at the toe of the slope. Therefore, it is best to have an upright transverse bamboo raft between the toe of the slope and the pipe trench for support, filtration, and isolation. The diversion membrane can be inserted into the soil at the toe of the slope through the horizontal gaps between the bamboo rafts.

[0042] Example 4 The method described in this embodiment differs from that in Embodiment 1 in that, to facilitate the experiment being conducted at any time, and to simulate rainfall runoff to scour the slope for experimental observation, the preferred procedure is as follows: an overflow trough is fixed to the top of the experimental plot against the slope, and the foundation of the overflow trough is leveled to ensure uniform overflow. The estimated overflow volume should be approximately equal to the rainfall runoff volume. A narrow PVC membrane is laid under the overflow trough as a drainage membrane to prevent the overflow from eroding the adjacent slope soil below the trough.

[0043] Example 5 After obtaining relevant soil and water loss data based on the observations in Examples 1-4, the following evaluation indicators were used to calculate the surface runoff coefficient, erosion area ratio, soil erosion rate, slope runoff rate, slope surface sediment yield, soil infiltration rate, soil sediment yield, groundwater infiltration rate, and groundwater leakage rate of rocky desertification slopes under different rainfall intensities and durations. Furthermore, these indicators were combined with relevant standards and methods to comprehensively evaluate the soil and water loss status of the rocky desertification slopes. The definitions of each evaluation indicator are as follows: The slope surface runoff coefficient is the ratio of the total runoff from rainfall on the slope of a rocky desertification slope test plot to the total rainfall during the same period, i.e., the proportion of rainfall converted into surface runoff. The erosion area ratio is the ratio of the erosion area generated by rainfall on the slope of the rocky desertification test plot to the area of ​​the slope of the test plot; Soil erosion rate is the sum of surface soil erosion and subsurface soil leakage caused by rainfall on the slope surface and below the rocky desertification slope test plot over a period of time. Slope runoff rate is the surface runoff generated by rainfall on the slope of a rocky desertification slope experimental plot over a period of time. The surface sediment yield is the amount of surface soil erosion caused by rainfall on the slope of a rocky desertification test plot over a period of time. The soil infiltration rate is the amount of infiltration along the slope caused by rainfall in the topsoil of the karst zone below the slope of the rocky desertification slope test plot over a period of time. The soil sediment yield rate is the amount of soil erosion caused by downslope seepage in the top karst soil below the slope of the rocky desertification slope test plot over a period of time. The groundwater seepage rate is the amount of groundwater seepage generated by rainfall under the slope surface of a rocky desertification slope test area over a period of time. The underground erosion rate is the amount of soil lost underground due to rainfall in a rocky desertification slope test area over a period of time.

Claims

1. A method for comprehensive on-site monitoring and evaluation of soil erosion on rocky desertification slopes, characterized in that, Includes the following: (1) Select a test plot for on-site three-dimensional comprehensive observation of soil and water loss; dig isolation trenches on the upper side and left and right sides of the test plot, place isolation membranes along the isolation trenches, bury the lower part of the isolation membranes in the trenches, and make the upper part of the isolation membranes stand upright. Build a fence around the boundary of the test plots with small anchor rods and crossbars, and lean the upright isolation membranes against the crossbars to form a prefabricated fence structure. The test plots are set up in multiple steps from top to bottom according to the size of the test area and the slope classification, forming a complete test system. For the test plots located at the toe of the slope, the collection pipe trench is placed below the toe of the slope, and small anchor rods are installed behind the pipe trench. Horizontally erected bamboo rafts are set between the toe of the slope and the pipe trench as support, filter and isolation. The drainage membrane is inserted into the soil at the toe of the slope through the gap between the bamboo rafts. The experimental planning plots were selected from areas on rocky desertification slopes that were relatively flat laterally and had relatively uniform slope and soil conditions. At least two small anchor rods are arranged at both ends of the upper and lower boundaries of the experimental plot to serve as supports for the crossbars and as references for observing and comparing the topography and geomorphology before and after soil erosion on the slope. (2) Spread the cohesive soil for soil erosion observation along the slope of the experimental plot and level it to the set thickness for the experiment. This soil will serve as the source material for soil erosion during rainfall and will also be the matrix material for ecological protection of vegetation on rocky desertification slopes. (3) A transverse observation trench was excavated along the boundary of the bottom of the experimental plot slope for three-dimensional observation of soil and water loss in the geological section. After the long-term observation is completed, it will be used as a planting trench for ecological protection of soil and water loss. Along the depth direction of the transverse observation trench, grid baffles were placed at the depths corresponding to different soil layers. A collection pipe trench was placed on each grid baffle to realize multi-level layered collection and observation of soil and water loss corresponding to each rock and soil layer of the rocky desertification slope. Drainage membranes corresponding to each collection pipe trench in the transverse observation trench were set on the slope and each soil layer of the geological section of the experimental plot to divert the soil and water loss caused by runoff and interflow to each collection pipe trench. A slope guide pipe was connected to the same end of each collection pipe trench. The outlet of the slope guide pipe was connected to the respective soil and water collection bucket or soft pipe bag to collect the soil and water loss of each layer of the geological section. The grid baffle has a slope of 0.3% to 3% along the length of the observation ditch; the width of the grid baffle is greater than the width of the transverse observation ditch, so that the grid baffle can be tilted and placed into the observation ditch and naturally lean against the two side walls of the ditch, thereby fixing the position of the grid baffle. A membrane pad is laid inside the collection trench to lift and remove the silt and mud accumulated in the trench, thereby improving the accuracy of subsequent measurement and calculation. The drainage membrane is buried in the slope soil on one side of the slope and inside the slope body, and the slope soil is used to hold it down. The other side extends into the collection trench to smoothly divert the water and soil loss caused by the slope runoff and interflow into the collection trench. (4) Use sedimentation buckets to separate the soil and water collected from the slope runoff and interflow at each level by sedimentation method, in order to count and calculate the surface sediment yield and interflow sediment yield, observe the sediment process of slope runoff and interflow, and observe once after each rainfall. (5) After soil erosion occurs due to rainfall, a vacuum membrane with a certain strength is laid on the surface of the rocky desertification slope in the experimental plot. After the edges are sealed and compacted with soil, the air covered under the membrane is extracted. The vacuum membrane is then pressed tightly onto the soil erosion gullies and small hills on the rocky desertification slope after soil erosion. The same leveling method as in step (2) is used on the vacuum membrane to lay the source clay soil to the original set thickness of the slope cover on the rocky desertification slope. Then the vacuum membrane is slowly rolled up to obtain the total amount of soil loss on the rocky desertification slope. Combined with the measured amount of soil loss in the slope runoff and interflow, the amount of soil leakage in the rocky desertification slope is obtained. (6) Rain gauges and evapotranspiration devices were distributed at multiple points on the rocky desertification slope of the experimental area in advance. The total amount of precipitation and its process, the amount of water evaporation during the evaporation stage and its process were obtained through manual observation. Based on the measured rainfall duration, the rainfall intensity on site was calculated, and the temperature and humidity on site were tracked and measured online in real time. After obtaining relevant soil and water loss data, the soil and water loss status of rocky desertification slopes is comprehensively evaluated based on the following evaluation indicators: The slope surface runoff coefficient is the ratio of the total runoff from rainfall on the slope of a rocky desertification slope test plot to the total rainfall during the same period, i.e., the proportion of rainfall converted into surface runoff. The erosion area ratio is the ratio of the erosion area generated by rainfall on the slope of the rocky desertification test plot to the area of ​​the slope of the test plot; Soil erosion rate is the sum of surface soil erosion and subsurface soil leakage caused by rainfall on the slope surface and below the rocky desertification slope test plot over a period of time. Slope runoff rate is the surface runoff generated by rainfall on the slope of a rocky desertification slope experimental plot over a period of time. The surface sediment yield is the amount of surface soil erosion caused by rainfall on the slope of a rocky desertification test plot over a period of time. The soil infiltration rate is the amount of water that flows downhill in the topsoil of the karst zone beneath the slope of a rocky desertification slope test plot over a period of time. The soil sediment yield rate is the amount of soil erosion caused by downslope seepage in the top karst soil below the slope of the rocky desertification slope test plot over a period of time. The groundwater seepage rate is the amount of groundwater seepage generated by rainfall under the slope surface of a rocky desertification slope test area over a period of time. The underground erosion rate is the amount of soil lost underground due to rainfall in a rocky desertification slope test area over a period of time.

2. The method according to claim 1, characterized in that, In step (1), the on-site topographic map is obtained by taking pictures and image processing technology, and the area of ​​rocky desertification, degree of rocky desertification, and bedrock exposure rate of the slope are calculated. The slope length, slope, soil texture, soil macropore morphology, and soil layer thickness on the surface karst zone are measured in the experimental planning area to assess the degree of rocky desertification development of the slope before monitoring, preliminarily determine the degree of soil erosion, and provide a basis for calculating the amount and thickness of source clay soil for soil erosion observation on the slope in subsequent steps.

3. The method according to claim 1, characterized in that, The soft tube bag mentioned in step (3) is a long tubular bag made of soft plastic, so that the soft tube bag can be segmented, tied in sections and measured during the collection process to realize the collection of soil and water loss at different time periods.

4. The method according to claim 1, characterized in that, The experiment observed the scouring of the slope by simulated rainfall runoff: an overflow trough was fixed to the top of the experimental plot and a drainage membrane was laid under the overflow trough. The foundation of the overflow trough was leveled to generate uniform flow. The estimated overflow volume was comparable to the rainfall runoff.

Images