A multi-stage ecological slope protection system for reservoir area and a design method thereof

Abstract

The application discloses a multi-stage ecological slope protection system for reservoir area suitable for reservoir regulation and storage and a design method thereof. The system comprises a longitudinal segmentation module, a vertical layering module and an ecological slope protection configuration module. The longitudinal segmentation module divides the reservoir area into multiple river sections according to the backwater length corresponding to the characteristic water level of the reservoir. The vertical layering module divides the bank slope of each river section into an interval above the maximum characteristic water level, an interval from the minimum characteristic water level to the maximum characteristic water level and an interval below the minimum characteristic water level. The ecological slope protection configuration module sets ecological lattice protection or ecological bag protection in different intervals and configures arbor-shrub-grass vegetation, Reynolds protection pad or gabion stone protection and configures flood-tolerant shrubs and emergent herbaceous vegetation and natural pebble belt and submerged vegetation. The application realizes dynamic design of multi-stage ecological slope protection in the longitudinal direction and the vertical direction of the reservoir area by extracting the characteristic water level of the reservoir regulation and storage, significantly improves the slope protection stability and the vegetation survival rate, and gives consideration to engineering safety and ecological benefits.

Description

Technical Field

[0001] This invention relates to the field of ecological slope protection in reservoir areas, specifically a multi-level ecological slope protection system adapted to reservoir regulation and its design method. Background Technology

[0002] The operation of large reservoirs has fundamentally altered the annual distribution pattern of natural water levels in the reservoir area, with water level rises and periodic fluctuations being particularly prominent. This anthropogenic hydrological change poses a continuous challenge to the pre-reservoir flood control standards and bank stability, directly threatening bank safety and potentially impacting the surrounding ecosystem and human life. To ensure the stability of the drawdown zone banks and enhance the flood control capacity of the backwater area, ecological slope protection, as a green engineering technology that balances protection and ecological value, has been widely applied in various reservoirs. It plays a crucial role in reinforcing banks, curbing erosion, enhancing carbon sequestration, restoring ecosystems, and optimizing the landscape, and is one of the core technologies for green water conservancy construction. Without ecological slope protection in the drawdown zone, soil erosion is highly likely. Exposed bank soil is lost in large quantities under the combined effects of rainwater erosion and water level fluctuations, accelerating bank degradation, exacerbating siltation, polluting water quality, destroying aquatic habitats, and damaging the integrity of the reservoir ecosystem.

[0003] However, during the normal operation of reservoirs, the longitudinal backwater range and vertical inundation zone of the reservoir area dynamically change with the rise and fall of water levels. Their evolution is mainly influenced by factors such as water level control in front of the dam and seasonal precipitation, exhibiting complex periodic characteristics. Traditional ecological slope protection adopts a static design with fixed elevations, failing to fully consider dynamic water level changes and making it difficult to adapt to the actual hydrological conditions of the reservoir area. This easily leads to problems such as low vegetation survival rates, slope protection failure, and mismatched protection ranges, failing to fully realize its effectiveness and value. Simultaneously, the ecological slope protection is mismatched with the hydrological rhythm of the reservoir area, and the vegetation's flood tolerance characteristics are not coordinated with the actual inundation duration, resulting in a high vegetation mortality rate. The decomposition of a large amount of dead vegetation releases carbon dioxide, increasing carbon emissions in the drawdown zone, weakening carbon sink benefits, and violating the concept of green and low-carbon development. Therefore, it is urgent to base a dynamic design method for multi-level ecological slope protection across the entire reservoir area, based on actual reservoir operation and combined with water level control patterns and hydrological characteristics. This method should scientifically configure differentiated flood-resistant vegetation communities and slope protection structures for different reservoir sections and different inundation levels. Summary of the Invention

[0004] This invention provides a multi-level ecological slope protection system for reservoir areas adapted to reservoir regulation and its design method. It can coordinate reservoir regulation and vegetation hydrological adaptability, take into account both regulation and storage needs and ecological benefits, and conform to the concepts of ecological stability, sustainable development and adaptive governance. It provides theoretical support and technical path for clean production and green water conservancy construction in reservoir areas.

[0005] A multi-level ecological slope protection system for reservoir areas adapted to reservoir regulation includes: a longitudinal segmentation module configured to divide the reservoir area longitudinally into multiple river segments based on the backwater length corresponding to multiple characteristic water levels, wherein the characteristic water levels are extracted based on a comprehensive distance index of the water level in front of the reservoir dam and the water level drawdown rate; a vertical stratification module configured to, for each river segment, divide the bank slope of each river segment vertically into multiple strata based on the numerical distribution of the characteristic water levels, wherein the strata include an area above the maximum characteristic water level, an area from the minimum characteristic water level to the maximum characteristic water level, and an area below the minimum characteristic water level; and an ecological slope protection configuration module configured to set up slope protection structures and vegetation community combinations according to each river segment and its vertical strata; wherein the ecological slope protection configuration module includes: in the area above the maximum characteristic water level... The first slope protection unit comprises an ecological grid slope protection or ecological bag slope protection laid on the slope surface, and a composite vegetation community of trees, shrubs and grasses planted on the ecological grid slope protection or ecological bag slope protection; the second slope protection unit comprises a Reno mattress or gabion slope protection laid on the slope surface, a masonry walkway laid laterally along the slope surface, and a composite vegetation community of flood-tolerant shrubs and dry-wet alternating herbaceous plants planted on the Reno mattress or gabion slope protection and the masonry walkway; and the third slope protection unit comprises a non-artificial slope protection structure, comprising a pebble strip naturally placed at the junction of the bank slope and the water body, and a submerged plant community planted on the pebble strip and in the underwater area.

[0006] Furthermore, the longitudinal segmentation module includes: a backwater length calculation unit, configured to establish a quantitative relationship between the backwater length and the operating water level in front of the dam based on the riverbed slope, dam bottom elevation, and riverbed slope angle, and to calculate the backwater length corresponding to each characteristic water level using the quantitative relationship between the backwater length and the operating water level in front of the dam; and a river segment division unit, configured to divide the reservoir area longitudinally into multiple river segments based on the difference in backwater length corresponding to each characteristic water level, wherein the area between the backwater length corresponding to the largest characteristic water level and the backwater length corresponding to the second largest characteristic water level is the reservoir tail segment, and the area between the backwater length corresponding to the smallest characteristic water level and the backwater length corresponding to the second smallest characteristic water level is the dam front segment.

[0007] Furthermore, in the vertical stratification module, the number of vertical levels in each river section increases gradually from the tail section to the dam front section along the longitudinal direction of the reservoir area, with the tail section having the fewest vertical levels and the dam front section having the most.

[0008] Furthermore, in the first slope protection unit: the ecological grid slope protection is a rhomboid concrete grid or a masonry grid, and the grid is backfilled with planting soil; the tree-shrub-grass composite vegetation community includes trees, shrubs and herbaceous plants, wherein the tree spacing is 3-5m, the shrubs are densely planted in the grid or in the gaps on the slope, and the herbaceous plants cover the entire slope; in the first slope protection unit, the area ratio of submerged, emergent and floating plants is 0%, and the area ratio of drought-resistant vegetation is 100%.

[0009] Furthermore, in the second slope protection unit: the porosity of the Reno mattress or gabion slope protection is 30% to 40%, and a geotextile filter layer is set below the gabion in areas with a slope greater than 20°; the masonry walkway is set every 5 to 8 meters along the slope; in the flood-resistant shrub and wet-dry alternating herbaceous composite vegetation community, the shrub spacing is 1 to 2 meters, and the herbaceous plants are densely planted in the gabion pores and on the slope; in the second slope protection unit, the area ratio of submerged plants is 0%, the area ratio of drought-resistant plants is 0%, and the area ratio of emergent plants and shrubs is arranged in a gradient in the vertical direction, wherein the area ratio of emergent plants in the uppermost area is 10% and the area ratio of shrubs is 90%, the area ratio of emergent plants in the lowermost area is 90% and the area ratio of shrubs is 10%, and the area ratio of emergent plants in the middle area increases arithmetically from the upper to the lower layer, while the area ratio of shrubs decreases arithmetically from the upper to the lower layer.

[0010] A multi-level ecological slope protection design method for reservoir areas adapted to reservoir regulation includes the following steps:

[0011] Step S1: Extract characteristic water levels under reservoir regulation: Obtain daily water level data in front of the reservoir dam, calculate the daily water level drawdown rate, standardize the water level in front of the dam and the water level drawdown rate respectively, and construct a scatter plot with the standardized water level in front of the dam as the horizontal axis and the standardized water level drawdown rate as the vertical axis; calculate the comprehensive distance index between each point in the scatter plot and other points, the comprehensive distance index representing the representativeness of the water level characteristics to the reservoir operation mode; draw a contour map of the comprehensive distance index with the water level in front of the dam as the horizontal axis and the water level drawdown rate as the vertical axis, extract the comprehensive distance index sequence of the horizontal axis profile, and statistically analyze its cumulative frequency distribution, and extract multiple characteristic water levels corresponding to multiple preset cumulative frequency values;

[0012] Step S2: Divide the reservoir area into longitudinal river segments and vertical levels based on characteristic water levels: Establish a quantitative relationship between backwater length and operating water level in front of the dam based on the riverbed slope, dam bottom elevation, and river slope angle; calculate the backwater length corresponding to each characteristic water level; divide the reservoir area into multiple river segments longitudinally based on the difference in backwater length corresponding to each characteristic water level; divide the bank slope of each river segment into multiple levels vertically based on the numerical distribution of each characteristic water level, including the interval above the maximum characteristic water level, the interval from the minimum characteristic water level to the maximum characteristic water level, and the interval below the minimum characteristic water level.

[0013] Step S3: Configure multi-level ecological slope protection according to river sections and vertical levels: In the section above the maximum characteristic water level of each river section, set up the first slope protection structure and configure a composite vegetation community of trees, shrubs and grasses; In the section from the minimum characteristic water level to the maximum characteristic water level of each river section, set up the second slope protection structure and configure a composite vegetation community of flood-tolerant shrubs and dry-wet alternating herbaceous plants; In the section below the minimum characteristic water level of each river section, do not set up artificial slope protection structures, but naturally place pebbles and configure submerged plant communities.

[0014] Furthermore, in step S1: the formula for calculating the daily water level drop rate is: Where ω is the daily water level drop rate, and Z t+1 and Z t These are the water levels in front of the dam on day t+1 and day t, respectively. This represents the time of water level change.

[0015] The formula for calculating the comprehensive distance index is as follows:

[0016] .

[0017] Where len(t) is the combined distance index between the water level characteristics on day t and the water level characteristics on other dates, Z t 'With Z i 'These are the standardized water levels in front of the dam on day t and day i, respectively. and The standardized water level drop rates in front of the dam are for day t and day i, respectively; the preset cumulative frequency values ​​are 100%, 90%, 75%, 50%, 25%, 10%, and 0%.

[0018] Furthermore, in step S2: the quantitative relationship between the backwater length and the operating water level upstream of the dam is as follows: Where L is the backwater length, Z is the operating water level in front of the dam, Z0 is the dam bottom elevation, and θ is the river slope angle; the number of the multiple river sections corresponds to the number of the multiple characteristic water levels, the area between the backwater length corresponding to the maximum characteristic water level and the backwater length corresponding to the second maximum characteristic water level is the reservoir tail section, and the area between the backwater length corresponding to the minimum characteristic water level and the backwater length corresponding to the second minimum characteristic water level is the dam front section.

[0019] Furthermore, in step S3: the first slope protection structure is an ecological soil or stone grid slope protection, or an ecological bag stacked slope protection, and is equipped with a drainage ditch at the toe of the slope; the second slope protection structure is a Reno mattress or gabion slope protection, and is equipped with a masonry stone walkway along the slope surface; when vegetation is configured in the range from the minimum characteristic water level to the maximum characteristic water level, the area ratio of emergent plants and shrubs is arranged in a gradient in the vertical direction, wherein the area ratio of emergent plants in the uppermost area is 10% and the area ratio of shrubs is 90%, the area ratio of emergent plants in the lowermost area is 90% and the area ratio of shrubs is 10%, and the area ratio of emergent plants in the middle area increases arithmetically from the upper to the lower layer, while the area ratio of shrubs decreases arithmetically from the upper to the lower layer.

[0020] Furthermore, after step S3, the following steps are also included: Step S4, optimizing the slope protection form in combination with the reservoir area topography: adopting a gradual transition design for the slope protection structure in the area where the slope gradient changes, with a transition section length of 5 to 8 meters; optimizing the vertical connection between the drainage ditch and the horse path according to the changes in topographic elevation to ensure that the slope runoff is discharged straight.

[0021] Compared with existing technologies, the multi-level ecological slope protection system and its design method for reservoir areas adapted to reservoir regulation provided by this invention have the following beneficial effects:

[0022] (1) This invention constructs a comprehensive distance index of the water level in front of the dam and the water level drop rate, extracts the characteristic water level under reservoir regulation, and divides the reservoir area longitudinally with the backwater length corresponding to the characteristic water level, so that the protection range of the ecological slope protection is precisely matched with the actual operation mode of the reservoir, overcomes the defect of traditional fixed elevation static design that is difficult to adapt to dynamic changes in water level, and significantly improves the pertinence and effectiveness of slope protection project.

[0023] (2) Based on the longitudinal segmentation, this invention further divides each river section into vertical levels according to the characteristic water level, and sets up differentiated slope protection structures and vegetation community combinations in the intervals above the maximum characteristic water level, the intervals from the minimum characteristic water level to the maximum characteristic water level, and the intervals below the minimum characteristic water level, forming a multi-level ecological slope protection system of "longitudinal segmentation and vertical stratification". This system fully considers the spatiotemporal heterogeneity of the reservoir area's hydrological situation and realizes the coordinated adaptation of the slope protection structure and the hydrological rhythm.

[0024] (3) In the core drawdown zone from the minimum characteristic water level to the maximum characteristic water level, the present invention adopts a composite structure of Reno mattress or gabion slope protection combined with transverse walkway, and gradient configuration of flood-resistant shrubs and emergent herbaceous vegetation, which not only enhances the stability of the slope protection structure, but also significantly improves the survival rate of vegetation, realizing the organic unity of engineering protection, ecological restoration and landscape enhancement, and providing reliable technical support for green water conservancy construction. Attached Figure Description

[0025] Figure 1This is a flowchart of a design method for a multi-level ecological slope protection system for reservoir areas adapted to reservoir regulation, according to the present invention.

[0026] Figure 2 This is a schematic diagram showing the relationship between the backwater length and the operating water level in front of the dam under the reservoir operation mode established in an embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram illustrating the principle of configuring multi-level ecological slope protection according to the characteristic water level of the reservoir area in an embodiment of the present invention.

[0028] Figure 4 This is a schematic diagram illustrating the water level change process in front of a reservoir dam from 2002 to 2020, according to an embodiment of the present invention.

[0029] Figure 5 This is a schematic diagram of the comprehensive distance index distribution of water level characteristics of a reservoir from 2009 to 2020, according to an embodiment of the present invention.

[0030] Figure 6 This is a schematic diagram of the characteristic water level distribution of a reservoir from 2009 to 2020, according to an embodiment of the present invention.

[0031] Figure 7 This is a schematic diagram of the design of an ecological slope protection project for a typical section of a reservoir dam in an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Please see Figure 1 This invention provides a design method for a multi-level ecological slope protection system adapted to reservoir regulation, comprising the following steps:

[0034] (1) Establish a quantitative relationship between the backwater length of the reservoir and the operating water level in front of the dam.

[0035] Based on the riverbed slope, dam bottom elevation, and riverbed slope angle, establish the relationship between the backwater length and the operating water level upstream of the dam. For example... Figure 2 As shown.

[0036] (1)

[0037] Where L is the backwater length (m), Z is the operating water level in front of the dam (m), Z0 is the dam bottom elevation (m), and θ is the river slope angle (°).

[0038] (2) Construct a scatter plot of the water level in front of the reservoir dam and the rate of water level drop.

[0039] The daily water level drop rate is calculated using the daily water level data from the reservoir's hydrological stations.

[0040] (2)

[0041] Where ω is the daily water level drop rate (m / d), Z t+1 and Z t The values ​​are the water levels (m) in front of the dam on day t+1 and day t, respectively. This represents the time of water level change; here it is 1 day.

[0042] Draw a scatter plot of the reservoir's regulation and storage methods, with the water level in front of the dam as the horizontal axis and the daily water level drop rate as the vertical axis.

[0043] (3) Use the comprehensive distance index to extract the characteristic water level of the reservoir area.

[0044] By calculating the comprehensive distance index corresponding to each water level in the scatter plot (water level in front of the dam, water level drawdown rate), and combining it with its characteristic frequency, the characteristic water level of the reservoir area under the reservoir's regulation and storage effect is determined. The specific steps are as follows:

[0045] ① The daily water level sequence in front of the dam and the water level drawdown rate sequence were both standardized.

[0046] (3)

[0047] Where x t ' represents the standardized value of the t-th data point in the sequence, μ is the sequence mean, and σ is the sequence standard deviation.

[0048] ② Calculate the comprehensive distance index between each point and other points in the scatter plot (water level in front of the dam, water level drop rate);

[0049] (4)

[0050] len(t) is the combined distance index of the water level characteristics on day t and the water level characteristics on other days. and These are the standardized water levels in front of the dam on day t and day i, respectively. and denoted as the standardized drawdown rates of the water level in front of the dam on day t and day i, respectively.

[0051] As shown in equation (4), when there are many similar days for a specific water level characteristic (water level size and drawdown rate) and the differences between them are small, the larger the comprehensive distance index, the stronger the representativeness of the water level characteristic to the reservoir operation mode. Conversely, when a specific water level characteristic differs greatly from the water level characteristics of other dates, the smaller the comprehensive distance index, the less representative the water level characteristic is. Therefore, the comprehensive distance can be used to characterize the characteristic water level of the reservoir operation mode.

[0052] ③ Draw a contour map of the comprehensive distance index and extract the profile of the horizontal axis (y=0).

[0053] Using the water level in front of the reservoir dam as the horizontal axis and the daily water level drop rate as the vertical axis, and assigning scatter values ​​to the comprehensive distance index, a contour map is drawn. Using the horizontal axis (y=0) of the contour map as a reference, the profile line of the comprehensive distance index is obtained.

[0054] Since reservoir operation must meet the principle of water balance, the positive and negative values ​​of the water level fluctuation relationship in front of the dam satisfy the symmetrical distribution characteristics. The maximum value of the comprehensive distance index corresponding to the water level fluctuation of 0 m / d is the horizontal axis profile value in the contour map. Therefore, the horizontal axis profile value in the contour map can characterize the representativeness of the water level conditions for the reservoir operation mode.

[0055] ④Based on the cumulative frequency distribution of the comprehensive distance index on the horizontal axis profile, the characteristic water level of the reservoir area is determined.

[0056] By combining the comprehensive distance index sequence of the horizontal axis profile of the contour map, the cumulative frequency distribution characteristics are statistically analyzed. The comprehensive distance index corresponding to the cumulative frequency of 100%, 90%, 75%, 50%, 25%, 10%, and 0% is calculated. Based on the contour map in step ③ above, the corresponding characteristic water level of the reservoir area is further clarified.

[0057] (4) Divide the vertical levels of different river sections according to the characteristic water level.

[0058] Based on the characteristic operating water levels of the reservoir obtained above, the corresponding backwater lengths are calculated sequentially, and the reservoir area is longitudinally segmented according to the relationship between the backwater lengths. The technical principle is described in [link to technical details]. Figure 3 :

[0059] ① Divide the river into longitudinal sections based on characteristic water levels.

[0060] Using formula (1), the backwater length corresponding to the characteristic dam inlet water level is calculated. The difference in backwater length is used to divide the reservoir area longitudinally into multiple segments. The seven characteristic water levels divide the reservoir area into seven longitudinal river segments. The longitudinal river channel from the maximum characteristic water level (100% cumulative frequency) to the second characteristic water level (75% cumulative frequency) is the reservoir tail segment (L1). The longitudinal river segment corresponding to the minimum characteristic water level to the second-to-last minimum characteristic water level is the dam inlet segment (L7). The remaining river segments correspond to their respective interval maximum characteristic water levels (L...). n ).

[0061] ② Statistical vertical stratification is performed for different river sections.

[0062] Depend on Figure 3 It can be seen that the vertical hierarchy of different river sections decreases with the increase of backwater distance. The reservoir tail section (L1) has only 2 layers: the section above the maximum water level and the section from the maximum water level to the characteristic water level Z1 (90% cumulative frequency); the river section L1 contains 3 layers: the section above the maximum water level, the section from the maximum water level to the characteristic water level Z1 (90% cumulative frequency), and the section from the characteristic water level Z1 (90% cumulative frequency) to the characteristic water level 2 (75% cumulative frequency); and so on, the dam front section L7 contains 9 layers.

[0063] (5) Multi-level ecological slope protection is configured vertically in different sections of the reservoir area.

[0064] Based on the longitudinal segmentation of the reservoir area and the vertical stratification of the river section, a flexible combination of vegetation and slope protection is adopted, and ecological slope protection is configured in multiple stages and segments:

[0065] ① The area above the maximum characteristic water level:

[0066] 1) Characteristics of the area: It is not affected by water level inundation, and is only affected by natural rainfall and slope runoff. The soil moisture content of the bank slope is stable and the hydrological impact is minimal. It serves as the upper barrier for ecological slope protection in the reservoir area, and has both landscape and slope soil and water conservation functions.

[0067] 2) Slope protection structure: Ecological soil / stone grid slope protection (such as rhomboid concrete grid, masonry grid, with planting soil backfilled in the grid) is adopted. Simple masonry drainage ditch is set at the toe of the slope to divert slope runoff and prevent gully development. In areas with gentle slope (<15°), ecological bag stacking slope protection can be directly adopted to simplify the structure and improve the ecology.

[0068] 3) Vegetation configuration: Select a native drought-resistant and barren-tolerant tree-shrub-grass composite community, with trees as the framework, shrubs as the middle layer, and herbs as the base, taking into account slope stabilization, carbon sequestration and landscape.

[0069] Trees: native riverbank protection trees such as maple, weeping willow, black locust, camphor (southern), and ash (northern), with a spacing of 3-5m between trees;

[0070] Shrubs: Amorpha fruticosa, Vitex negundo, Lespedeza bicolor, Forsythia suspensa, and other shrubs that are tolerant of pruning and have strong soil-fixing ability should be densely planted within the trellis or in the gaps on the slope.

[0071] Herbs: Perennial herbs such as bermudagrass, zoysia grass, ryegrass, and alfalfa can cover the slope and quickly cover the ground.

[0072] Combination form: tree-shrub-grass composite community (trees + shrubs + herbs) + ecological grid slope protection (gentle slope areas are replaced with ecological bag slope protection).

[0073] 4) Vegetation area: Submerged, emergent, and floating plants account for 0%, and drought-resistant vegetation accounts for 100%.

[0074] ② The range from the minimum characteristic water level to the maximum characteristic water level:

[0075] 1) Section characteristics: The core area affected by reservoir operation is affected by the periodic rise and fall of water level and the alternation of flooding and exposure throughout the year. The rate of water level drop directly affects soil permeability and vegetation survival rate. It has the strongest hydrological impact and is the core protection section of ecological slope protection. It is necessary to take into account flood resistance, exposure resistance, and slope stability.

[0076] 2) Slope Protection Structure: An erosion-resistant composite ecological slope protection system is adopted, balancing structural stability with vegetation growth space. Its core principle is a combination of a "hard foundation + ecologically flexible structure."

[0077] 3) Main structure: Reno mattress / gabion slope protection (filled with pebbles or boulders, with a porosity of 30%~40%, providing attachment space for vegetation). In areas with a slope greater than 20°, a geotextile filter layer is added under the gabion to prevent soil loss from the slope.

[0078] 4) Auxiliary structure: A transverse masonry walkway is set every 5-8m along the slope to reduce the erosion of the slope by the rise and fall of the water level, and at the same time serve as a vegetation planting zone and maintenance passage.

[0079] 5) Vegetation configuration: Select native wetland / emergent herbaceous and shrub communities that are tolerant of flooding and alternating wet and dry conditions. Prioritize varieties with well-developed root systems and strong tillering ability. The roots can penetrate deep into the gabion pores to stabilize the slope, and the stems and leaves can adapt to short-term flooding (the flooding duration matches the characteristic water level drawdown cycle of the reservoir).

[0080] Shrubs: Flood-tolerant shrubs such as willow, tamarisk, and water plum should be planted in the gaps between gabions and on horse trails, with a spacing of 1-2 meters between plants;

[0081] Herbs: reeds, rushes, calamus, wild rice, bermudagrass (flood-tolerant varieties), goosegrass, etc., densely planted in the gaps of gabions and on the slope, with emergent herbs planted in the lower part of the flood zone and drought-tolerant herbs planted in the upper part of the flood zone.

[0082] Combination form: community (flood-tolerant shrubs + wet-dry alternating herbaceous plants) + Reno mattress / gabion composite ecological slope protection (with transverse walkway).

[0083] 6) Vegetation area: The submerged vegetation area accounts for 0%, the drought-resistant vegetation area accounts for 0%, and the emergent vegetation area is arranged in a gradient (the uppermost area has 10% emergent vegetation area and 90% shrub area; the lowermost area has 90% emergent vegetation area and 10% shrub area; other areas have an arithmetic progression from upper to lower layers, with the emergent vegetation area increasing and the shrub area decreasing).

[0084] ③ The interval below the minimum characteristic water level:

[0085] 1) Regional characteristics: The area has been continuously submerged for a long time, with weak sunlight conditions and a significant anaerobic soil environment. Vegetation can only grow underwater / at the water's edge. The core requirements for slope protection are to resist water erosion, prevent bank scouring, and take into account the restoration of aquatic ecosystems.

[0086] 2) Slope protection structure: No slope protection is adopted.

[0087] (6) Optimize the design of slope protection form based on the topographic conditions of the reservoir area.

[0088] Based on the typical cross-sectional morphological characteristics of different river sections in the reservoir area, the design of vertical multi-level ecological slope protection was optimized. The optimization principles include:

[0089] ① No artificial slope protection structure is set up in the area below the minimum characteristic water level of all types of bank slopes. Instead, natural topography is used to place pebbles at the junction of the bank slope and the water body to form a natural erosion resistance zone. This is combined with the natural growth of submerged plants (Vallisneria natans, Myriophyllum spicatum) to achieve the self-repair of the aquatic ecosystem.

[0090] ② For areas with gradually changing slopes in the reservoir area, a gradual transition design for the slope protection structure is adopted to avoid stress concentration caused by direct connection between different slope protection forms. The length of the transition section is controlled at 5~8m, and the grid size, gabion particle size and vegetation ratio are gradually adjusted.

[0091] ③ Optimize the vertical connection between drainage ditches and horse trails by taking into account changes in terrain elevation, so as to ensure that runoff from the slope is discharged in a straight manner and avoid water accumulation in low-lying areas, which could lead to soil softening and slope collapse.

[0092] Taking a reservoir as a typical case, the daily water level process of a certain hydrological station (the hydrological station closest to the dam site) is used to quantitatively characterize the operation mode of the reservoir and verify the technical effect of the present invention.

[0093] (1) Analysis of reservoir operation characteristics.

[0094] The process of water level change in front of a reservoir dam from 2002 to 2020 is as follows: Figure 4As shown. Before the reservoir was built, the water level at a certain station fluctuated between 100-130m; after impounding water from 2003 to 2006, the operating water level stabilized at around 140m; from 2007 to 2009, the water level rose further, maintaining an operating level above 145m; after 2009, the reservoir's water level increased from 145m to 175m annually, then dropped back to 145m, with a basically stable operating pattern. This invention uses the water level pattern during the stable operating period after 2009 as a benchmark to dynamically design a multi-level ecological slope protection system for the reservoir area.

[0095] (2) The reservoir is divided into longitudinal and vertical layers.

[0096] Based on water level data from the 2009-2020 operational period, the comprehensive distance index of water level characteristics was calculated and contour lines were drawn to obtain the cumulative frequency distribution of the horizontal axis profile. Figure 5 The minimum water levels corresponding to cumulative frequencies of 90%, 75%, 50%, 25%, and 10% are 173.73m, 169.95m, 163.52m, 158.61m, and 153.32m, respectively. These characteristic water levels correspond to the inflection points of the annual water level curve and can accurately characterize the water level change pattern in the reservoir area.

[0097] Based on the riverbed gradient (0.2‰) and dam base elevation (66m) of a certain reservoir area, the reservoir area was divided into 7 longitudinal river segments (from the reservoir tail to the dam front), achieving precise matching between water level characteristics and river segment space. The longitudinal segments of the reservoir area include: Segment 1 / Reservoir Tail (backwater length 548.7 km - 538.65 km), Segment 2 (backwater length 538.65 km - 519.75 km), Segment 3 (backwater length 519.75 km - 487.60 km), Segment 4 (backwater length 487.60 km - 463.05 km), Segment 5 (backwater length 463.05 km - 436.60 km), Segment 6 (backwater length 436.60 km - 395.00 km), and Segment 7 / Dam Front (395.00 km - 0.00 km). The characteristic water level distribution within different river segments is shown in [reference needed]. Figure 6 Different characteristic water levels correspond to characteristic inflection points of the annual water level process curve, indicating that characteristic water levels can effectively characterize the water level change pattern in the reservoir area.

[0098] (3) Ecological slope protection is configured in a tiered manner in the reservoir area.

[0099] This invention employs a combination of slope protection and vegetation, implementing ecological slope protection measures at different levels for different river sections within the reservoir area, including non-submerged sections, characteristic water level sections, and sections below the minimum water level. Figure 7 shows the design of a typical ecological slope protection project in the dam-front section. It utilizes both theoretical characteristic water level and engineering design water level for dual control, and employs a tiered layout of structures such as frame-and-grass slope protection, pile-slab retaining walls, and waterfront walkways to achieve layered protection and ecological restoration.

[0100] The case study of the Three Gorges Reservoir area demonstrates that this invention has the following advantages and effects compared to traditional design methods:

[0101] (1) This invention calculates the comprehensive distance index based on the water level in front of the dam and the drawdown rate, quantitatively extracts the characteristic water level, and realizes the precise coupling between the slope protection range and the reservoir regulation law, making the design parameters more reliable;

[0102] (2) The present invention constructs a multi-level system of vertical segmentation and vertical stratification, dividing the river section according to the difference of backwater in the reservoir area and stratifying the level according to the inundation characteristics, which solves the problem that traditional technology cannot adapt to the spatiotemporal water level heterogeneity of the reservoir area;

[0103] (3) The present invention adopts a combination of gradient slope protection and gradient vegetation, which significantly improves the erosion resistance and vegetation survival rate, and takes into account engineering safety, ecological restoration, low-carbon landscape and operation and maintenance economy.

[0104] This invention also provides a multi-level ecological slope protection system for reservoir areas adapted to reservoir regulation, comprising:

[0105] The longitudinal segmentation module is configured to divide the reservoir area into multiple river segments along the longitudinal direction based on the backwater length corresponding to multiple characteristic water levels of the reservoir. The characteristic water levels are extracted based on the comprehensive distance index of the water level in front of the reservoir dam and the water level drawdown rate.

[0106] A vertical stratification module is configured to, for each river segment, vertically divide the riverbank slope into multiple levels based on the numerical distribution of the characteristic water levels. These levels include the area above the maximum characteristic water level, the area from the minimum characteristic water level to the maximum characteristic water level, and the area below the minimum characteristic water level.

[0107] The ecological slope protection configuration module is configured to set up slope protection structures and vegetation community combinations according to each river section and its vertical level;

[0108] The ecological slope protection configuration module includes:

[0109] The first slope protection unit is set up in the area above the maximum characteristic water level. The first slope protection unit includes an ecological grid slope protection or ecological bag slope protection laid on the slope surface, and a composite vegetation community of trees, shrubs and grasses planted on the ecological grid slope protection or ecological bag slope protection.

[0110] A second slope protection unit is set up in the range from the minimum characteristic water level to the maximum characteristic water level. The second slope protection unit includes Reno mattresses or gabion slope protection laid on the slope surface, a masonry walkway arranged transversely along the slope surface, and a flood-tolerant shrub and wet-dry alternating herbaceous composite vegetation community planted on the Reno mattresses or gabion slope protection and the masonry walkway; and

[0111] The third slope protection unit is set in the area below the minimum characteristic water level. The third slope protection unit is a non-artificial slope protection structure, which includes a pebble strip naturally placed at the junction of the bank slope and the water body, and a submerged plant community planted in the pebble strip and the underwater area.

[0112] The longitudinal segmentation module includes:

[0113] The backwater length calculation unit is configured to establish a quantitative relationship between the backwater length and the operating water level in front of the dam based on the riverbed slope, dam bottom elevation and riverbed slope angle, and to calculate the backwater length corresponding to each characteristic water level using the quantitative relationship between the backwater length and the operating water level in front of the dam.

[0114] The river segment division unit is configured to divide the reservoir area longitudinally into multiple river segments based on the difference in backwater length corresponding to each characteristic water level. The area between the backwater length corresponding to the maximum characteristic water level and the backwater length corresponding to the second maximum characteristic water level is the reservoir tail segment, and the area between the backwater length corresponding to the minimum characteristic water level and the backwater length corresponding to the second minimum characteristic water level is the dam front segment.

[0115] In the vertical stratification module, the number of vertical levels in each river section increases gradually from the tail section to the dam front section along the longitudinal direction of the reservoir area, with the tail section having the fewest vertical levels and the dam front section having the most.

[0116] In the first slope protection unit:

[0117] The ecological grid slope protection is a rhomboid concrete grid or a masonry grid, and the grid is backfilled with planting soil.

[0118] The tree-shrub-grass composite vegetation community includes trees, shrubs and herbaceous plants, with trees spaced 3-5m apart, shrubs densely planted within the trellis or in the gaps on the slope, and herbaceous plants covering the entire slope.

[0119] In the first slope protection unit, the area of ​​submerged plants accounts for 0%, and the area of ​​drought-resistant vegetation accounts for 100%.

[0120] In the second slope protection unit:

[0121] The porosity of the Reno mattress or gabion slope protection is 30% to 40%, and a geotextile filter layer is set under the gabion in areas with a slope greater than 20°.

[0122] The masonry ramp is set up every 5 to 8 meters along the slope.

[0123] In the aforementioned flood-tolerant shrub and wet-dry alternating herbaceous composite vegetation community, the shrub spacing is 1-2m, and the herbaceous plants are densely planted in the gabion crevices and on the slope.

[0124] In the second slope protection unit, the area ratio of submerged plants is 0%, the area ratio of drought-resistant plants is 0%, and the area ratio of emergent plants and shrubs is arranged in a gradient in the vertical direction. In the uppermost area, the area ratio of emergent plants is 10% and the area ratio of shrubs is 90%. In the lowermost area, the area ratio of emergent plants is 90% and the area ratio of shrubs is 10%. In the middle area, the area ratio of emergent plants increases arithmetically from the upper to the lower layer, and the area ratio of shrubs decreases arithmetically from the upper to the lower layer.

[0125] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-level ecological slope protection system for reservoir areas adapted to water storage and regulation, characterized in that, include: The longitudinal segmentation module is configured to divide the reservoir area into multiple river segments along the longitudinal direction based on the backwater length corresponding to multiple characteristic water levels of the reservoir. The characteristic water levels are extracted based on the comprehensive distance index of the water level in front of the reservoir dam and the water level drawdown rate. The vertical layering module is configured to divide the bank slope of each river segment into multiple layers in the vertical direction according to the numerical distribution of the characteristic water level. The layers include the interval above the maximum characteristic water level, the interval from the minimum characteristic water level to the maximum characteristic water level, and the interval below the minimum characteristic water level. as well as The ecological slope protection configuration module is configured to set up slope protection structures and vegetation community combinations according to each river section and its vertical level; The ecological slope protection configuration module includes: The first slope protection unit is set up in the area above the maximum characteristic water level. The first slope protection unit includes an ecological grid slope protection or ecological bag slope protection laid on the slope surface, and a composite vegetation community of trees, shrubs and grasses planted on the ecological grid slope protection or ecological bag slope protection. A second slope protection unit is set up in the range from the minimum characteristic water level to the maximum characteristic water level. The second slope protection unit includes Reno mattresses or gabion slope protection laid on the slope surface, a masonry walkway arranged transversely along the slope surface, and a flood-tolerant shrub and wet-dry alternating herbaceous composite vegetation community planted on the Reno mattresses or gabion slope protection and the masonry walkway; and The third slope protection unit is set in the area below the minimum characteristic water level. The third slope protection unit is a non-artificial slope protection structure, which includes a pebble strip naturally placed at the junction of the bank slope and the water body, and a submerged plant community planted in the pebble strip and the underwater area.

2. The multi-level ecological slope protection system for reservoir areas adapted to water storage and regulation as described in claim 1, characterized in that, The longitudinal segmentation module includes: The backwater length calculation unit is configured to establish a quantitative relationship between the backwater length and the operating water level in front of the dam based on the riverbed slope, dam bottom elevation and riverbed slope angle, and to calculate the backwater length corresponding to each characteristic water level using the quantitative relationship between the backwater length and the operating water level in front of the dam. The river segment division unit is configured to divide the reservoir area longitudinally into multiple river segments based on the difference in backwater length corresponding to each characteristic water level. The area between the backwater length corresponding to the maximum characteristic water level and the backwater length corresponding to the second maximum characteristic water level is the reservoir tail segment, and the area between the backwater length corresponding to the minimum characteristic water level and the backwater length corresponding to the second minimum characteristic water level is the dam front segment.

3. The multi-level ecological slope protection system for reservoir areas adapted to water storage and regulation as described in claim 1, characterized in that, In the vertical stratification module, the number of vertical levels in each river section increases gradually from the tail section to the dam front section along the longitudinal direction of the reservoir area, with the tail section having the fewest vertical levels and the dam front section having the most.

4. The multi-level ecological slope protection system for reservoir areas adapted to water storage and regulation as described in claim 1, characterized in that, In the first slope protection unit: The ecological grid slope protection is a rhomboid concrete grid or a masonry grid, and the grid is backfilled with planting soil. The tree-shrub-grass composite vegetation community includes trees, shrubs and herbaceous plants, with trees spaced 3-5m apart, shrubs densely planted within the trellis or in the gaps on the slope, and herbaceous plants covering the entire slope. In the first slope protection unit, the area of ​​submerged, emergent, and floating plants accounts for 0%, while the area of ​​drought-resistant vegetation accounts for 100%.

5. The multi-level ecological slope protection system for reservoir areas adapted to water storage and regulation as described in claim 1, characterized in that, In the second slope protection unit: The porosity of the Reno mattress or gabion slope protection is 30% to 40%, and a geotextile filter layer is set under the gabion in areas with a slope greater than 20°. The masonry ramp is set up every 5 to 8 meters along the slope. In the aforementioned flood-tolerant shrub and wet-dry alternating herbaceous composite vegetation community, the shrub spacing is 1-2m, and the herbaceous plants are densely planted in the gabion crevices and on the slope. In the second slope protection unit, the area ratio of submerged plants is 0%, the area ratio of drought-resistant plants is 0%, and the area ratio of emergent plants and shrubs is arranged in a gradient in the vertical direction. In the uppermost area, the area ratio of emergent plants is 10% and the area ratio of shrubs is 90%. In the lowermost area, the area ratio of emergent plants is 90% and the area ratio of shrubs is 10%. In the middle area, the area ratio of emergent plants increases arithmetically from the upper to the lower layer, and the area ratio of shrubs decreases arithmetically from the upper to the lower layer.

6. A multi-level ecological slope protection design method for reservoir areas adapted to reservoir regulation, characterized in that, Includes the following steps: Step S1: Extract characteristic water levels under reservoir regulation: Obtain daily water level data in front of the reservoir dam, calculate the daily water level drawdown rate, standardize the water level in front of the dam and the water level drawdown rate respectively, and construct a scatter plot with the standardized water level in front of the dam as the horizontal axis and the standardized water level drawdown rate as the vertical axis; calculate the comprehensive distance index between each point in the scatter plot and other points, the comprehensive distance index representing the representativeness of the water level characteristics to the reservoir operation mode; draw a contour map of the comprehensive distance index with the water level in front of the dam as the horizontal axis and the water level drawdown rate as the vertical axis, extract the comprehensive distance index sequence of the horizontal axis profile, and statistically analyze its cumulative frequency distribution, and extract multiple characteristic water levels corresponding to multiple preset cumulative frequency values; Step S2: Divide the reservoir area into longitudinal river segments and vertical levels based on characteristic water levels: Establish a quantitative relationship between backwater length and operating water level in front of the dam based on the riverbed slope, dam bottom elevation, and river slope angle; calculate the backwater length corresponding to each characteristic water level; divide the reservoir area into multiple river segments longitudinally based on the difference in backwater length corresponding to each characteristic water level; divide the bank slope of each river segment into multiple levels vertically based on the numerical distribution of each characteristic water level, including the interval above the maximum characteristic water level, the interval from the minimum characteristic water level to the maximum characteristic water level, and the interval below the minimum characteristic water level. Step S3: Configure multi-level ecological slope protection according to river sections and vertical levels: In the section above the maximum characteristic water level of each river section, set up the first slope protection structure and configure a composite vegetation community of trees, shrubs and grasses; In the section from the minimum characteristic water level to the maximum characteristic water level of each river section, set up the second slope protection structure and configure a composite vegetation community of flood-tolerant shrubs and dry-wet alternating herbaceous plants; In the section below the minimum characteristic water level of each river section, do not set up artificial slope protection structures, but naturally place pebbles and configure submerged plant communities.

7. The multi-level ecological slope protection design method for reservoir areas adapted to reservoir regulation as described in claim 6, characterized in that, In step S1: The formula for calculating the daily water level drop rate is: Where ω is the daily water level drop rate, and Z t+1 and Z t These are the water levels in front of the dam on day t+1 and day t, respectively. This refers to the time of water level change. The formula for calculating the comprehensive distance index is as follows: ； Where len(t) is the combined distance index between the water level characteristics on day t and the water level characteristics on other dates, Z t 'With Z i 'These are the standardized water levels in front of the dam on day t and day i, respectively. and denoted as the standardized drawdown rates of the water level in front of the dam on day t and day i, respectively; The preset cumulative frequency values ​​are 100%, 90%, 75%, 50%, 25%, 10%, and 0%.

8. The multi-level ecological slope protection design method for reservoir areas adapted to reservoir regulation as described in claim 6, characterized in that, In step S2: The quantitative relationship between the backwater length and the operating water level upstream of the dam is as follows: Where L is the backwater length, Z is the operating water level upstream of the dam, Z0 is the dam bottom elevation, and θ is the river channel slope angle. The number of the multiple river sections corresponds to the number of the multiple characteristic water levels. The area between the backwater length corresponding to the maximum characteristic water level and the backwater length corresponding to the second maximum characteristic water level is the reservoir tail section, and the area between the backwater length corresponding to the minimum characteristic water level and the backwater length corresponding to the second minimum characteristic water level is the dam front section.

9. The multi-level ecological slope protection design method for reservoir areas adapted to reservoir regulation as described in claim 6, characterized in that, In step S3: The first slope protection structure is an ecological soil or stone grid slope protection, or an ecological bag stacked slope protection, and is equipped with a slope toe drainage ditch. The second slope protection structure is a Reno mattress or gabion slope protection, and a masonry walkway is set laterally along the slope surface; When vegetation is configured in the range from the minimum characteristic water level to the maximum characteristic water level, the area ratio of emergent plants and shrubs is arranged in a gradient in the vertical direction. In the uppermost area, the area ratio of emergent plants is 10% and the area ratio of shrubs is 90%. In the lowermost area, the area ratio of emergent plants is 90% and the area ratio of shrubs is 10%. In the middle area, the area ratio of emergent plants increases arithmetically from the upper to the lower layers, and the area ratio of shrubs decreases arithmetically from the upper to the lower layers.

10. The multi-level ecological slope protection design method for reservoir areas adapted to reservoir regulation as described in claim 6, characterized in that, Step S3 is followed by: Step S4: Optimize the slope protection method based on the reservoir area's topography: In areas where the slope gradient changes gradually, adopt a slope protection structure with a gradual transition design, with a transition section length of 5-8m; optimize the vertical connection between the drainage ditch and the horse path according to the changes in topographic elevation to ensure that the slope runoff is discharged straight; do not set up artificial slope protection structures in all areas below the minimum characteristic water level, but only naturally place pebbles at the junction of the slope and the water body to form a natural erosion resistance zone.

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