CN117513229A - A technology for ecological restoration of river systems in mountain canyon areas - Google Patents

Abstract

The invention provides an ecological restoration technology aiming at a river system in a mountain gorge valley area, which comprises river bed management measures, bank slope protection measures and river flood beach restoration measures, wherein the river bed management measures are used for longitudinally managing a river bed by constructing a ladder system; the bank slope protection measures adopt a fiber roll foreign soil planting method to establish a arbor zone parallel to a river bank line; the river flood restoration measures imitate natural forms to trim the river flood into sand waves, the gabion is utilized to buffer flood impact, and the river flood ecological restoration species are designed according to ecological investigation results. The technology can weaken water flow erosion power to stabilize a river course, control loss of fine materials on a flood plain, promote soil quality improvement of the flood plain, accelerate ecological system restoration of the flood plain, improve local microclimate environment and comprehensively improve ecological service functions of a river system. The invention also specifically provides a calculation method of the ladder system and the sand wave design parameters, and the stability and the persistence of ecological restoration of the river system are ensured.

Description

A technology for ecological restoration of river systems in mountain canyon areas

Background technique:

Facing the challenge of global climate change, along with the expansion of urbanization brought about by population growth and socioeconomic development, the health of river ecosystems is under tremendous pressure. Human activities such as road projects, water conservancy projects, agricultural projects, and municipal projects have led to varying degrees of habitat changes, intensified hydrological cycles, species invasion, and water quality pollution, resulting in the degradation of most aquatic ecosystems, a significant reduction in freshwater biodiversity, and river restoration. It has now become an important means to improve the ecological functions of river systems. Floodplains are the ecological transition zone between land and water in river systems. They are generally considered to be the center of biodiversity and biological productivity. According to reports, about 80% of animal populations are distributed in floodplains, including 47% of species. Listed as an endangered species; at the same time, floodplains have a profound impact on the regulation of flood peak flows and the migration and storage of sediments, and this is related to the degree of vegetation development. However, some studies have pointed out that the degradation of floodplain ecosystems will destroy the lateral connectivity of river channels, aggravate the dryness of the regional climate, stimulate potential factors for desertification, and accelerate the desertification process. Therefore, the quality of the floodplain ecosystem is related to the sustainability of river ecosystem services and functions. There is an urgent need to protect the existing floodplain ecosystem and restore shoreline vegetation to maintain a certain degree of ecological integrity.

Floodplain ecological restoration first started in Europe, represented by the Danube River ecological restoration project. In the 1990s, Switzerland and Germany proposed the concept of "near-natural river engineering", which became a turning point in river management in some countries. Subsequently, at the end of the 20th century, a global upsurge in river restoration was launched. According to reports, at this stage, Japan More than 23,000 river restoration projects have been launched across the country, and river system ecological restoration technology has also become mature. At present, China's floodplain restoration often focuses on water quality purification, stormwater storage and landscape restoration. For example, CN 207498888 U discloses a design method for a floodplain wetland pit and pond system, which not only improves the hydrological connectivity of the floodplain wetland, but also enhances the Improve the sewage treatment capacity of the wetland system; CN116427342 A uses the "patch-channel-node" model to rearrange the ecological space of the river ecological corridor, solving the problem of how to layout the river ecological corridor, and providing support for restoring the river ecological function; CN 115710879 A proposes a construction method that imitates natural rivers and floodplain wetlands, achieving service functions such as soil conservation, flood storage, and improvement of water environment quality. In contrast, China's river management is still in the development stage, and there are obvious deficiencies in floodplain ecological restoration strategies.

Rivers in mountain canyon areas often have the characteristics of fast flow, large flow, and strong erosion. When floods come, floodplains usually serve as flood channels to share the flow. General flood erosion often leads to a large loss of fine-grained materials on the floodplain, causing floods. After the river retreat, the river floodplain was covered with coarse gravel, the soil was poor, and the ecological function was not strong; and strong erosion caused the river ecosystem to rapidly degrade, accelerating the desertification process, threatening the protection of key species and habitats in some areas (such as Tibet), and affecting local areas. ecological balance. However, it is difficult to repair degraded ecosystems in these areas solely by relying on natural vegetation restoration. The use of ecological engineering measures to restore river systems can accelerate the recovery of degraded ecosystems, improve the local microclimate environment, and rely on plant roots to increase soil cohesion to improve the strength of bank soil and stabilize channels. The interception effect of plants themselves can also be retained floods and relieve the flood control pressure on downstream cities. At the same time, the modification of the original landform through ecological engineering and the use of special structures to dissipate water flow energy can further weaken erosion and protect the river ecosystem. Therefore, inventing effective river system ecological restoration technology to stabilize river channels, improve the ecological restoration potential of coarsened floodplains, speed up the recovery of local ecosystems, and improve local microclimate environments is of great significance to local species protection and ecological balance.

Contents of the invention:

In response to the above problems, the purpose of this invention is to provide an ecological restoration technology for river systems in mountain canyon areas. This technology can weaken the erosion power of water flow, stabilize the river channel, control the loss of fine-grained matter on the floodplain, and can also promote the improvement of floodplain soil quality. , accelerate the restoration of floodplain ecosystems, improve local microclimate environments, and comprehensively enhance the ecological service functions of river systems.

The technical solution adopted by the present invention is as follows: an ecological restoration technology for river systems in mountain canyon areas, including river bed management measures, bank slope protection measures and floodplain repair measures. The riverbed management measures described above weaken the flow energy and limit the lateral erosion of the river through longitudinal management of the river channel. They are characterized by establishing a ladder energy dissipation system. The ladder is composed of stones and has a horizontal or downward reverse slope surface. The height of the ladder is determined by the ladder. Comprehensive control of length and river bed slope. The bank slope protection measures include an arbor belt parallel to the river bank line. The characteristic is that the arbors are planted with guest soil, and the guest soil is wrapped with fiber rolls and then placed in the ditch of the designed size, aiming to improve the survival rate and speed up the development of the bank. Maturity speed. The floodplain restoration measures described above imitate the natural form of modifying the floodplain into sand waves. The sand waves form a certain angle with the river shoreline. They are characterized by shallow ditches and sand ridges connected in a streamlined manner, with a wavy cross-section. Floodplain ecological restoration species are designed based on ecological survey data. Shrubs are planted on the sand ridges and grass seeds are spread among them. Floodplain restoration measures also include the placement of gabions along the river shoreline. The gabions are buried deep and located inside the tree belt.

Preferably, the step energy dissipation system uses machinery to smooth the step surface from downstream to upward. The step surface should be kept horizontal or have a downward reverse slope, and stones with a particle size greater than 0.4m are screened from the excavated gravel to build the steps. Set aside the remainder to fill the gabions;

Preferably, the trees are selected from native tree species with well-developed root systems, cold and waterlogging resistant, and should be cultivated until the tree diameter reaches 3 to 4 cm in diameter. 1 to 2 rows should be planted parallel to the river bank. The guest soil should be mined locally, and the fibers should be mined locally. The rolls are made of shredded coconut or straw, with a diameter of 0.5m. When buried, they should be spaced 0.5m apart from the river bank line to avoid causing severe disturbance to the bank slope;

Preferably, in the floodplain restoration measures, the gabion should be buried 0.4m deep, 0.4m above the ground, and 0.6m wide;

Preferably, the floodplain sand wave should be constructed according to the enlarged design size, by digging shallow trenches and building sand ridges, and connecting them in a streamlined manner, and the sand wave should be 45° to the river bank line, aiming to In order to alleviate the flow rate of floods and induce floods to spread to the periphery of the floodplain; for floodplains with roads as mentioned above, soil ridges should be built again parallel to the embankment at a distance of 2 to 3 meters from the embankment, and drainage ditches should be dug in front of the soil ridges.

Preferably, among the riverbed management measures, bank slope protection measures and floodplain repair measures, if the river is located at the foot of a mountain, only one bank slope and floodplain needs to be repaired and treated; when the river is located in the middle of a canyon, the banks on both sides need to be repaired. The slopes and floodplains are restored and managed, and the restoration patterns on both sides are symmetrical to the river.

The present invention further provides a design method for river bed management measures, bank slope protection measures and floodplain repair measures, including the following steps:

Step 1: Basic data investigation, including:

The river surface width W, river water depth s, river bed slope S, as well as the community, species composition and key species of the local well-developed ecosystem, the key species are judged by calculating the important value of each species;

Step 2: Step system design, mainly designing the step height H and stone particle size d. According to the maximum resistance hypothesis and the congestion effect, the step height H and the stone particle size d satisfy the following relationship:

1<(H/L)/S<2 Formula 1

W/d≤5 Formula 2

In the formula, L is the length of the step, S is the specific drop of the river bed, and W is the width of the river;

Step 3: Bank slope protection measures require the planting of native tree species along the river shoreline. The layout of fiber rolls, burial depth and tree species planting spacing are mainly designed based on existing ecological survey data. The selected tree species must have well-developed root systems, cold and waterlogging resistance. ;

Step 4: Floodplain restoration measures, mainly designing the gabion layout, burial depth, height, and sand wave size, including sand wave height h, sand wave length l, and the angle between the sand wave and the river shoreline. Sand wave height h and sand wave length l are calculated according to the method determined by Julien and Klaasse (1995), which can comprehensively reflect the morphological characteristics of sand waves at the bottom of the river bed during floods. The specific method is as follows:

(1) Median particle size D ₅₀

τ _c =0.15S ^0.25Equation 3

In the formula, τ _c is the Shields coefficient; S is the specific drop of the river bed; R is the hydraulic radius; S _e is the energy slope; S _g is the normalized underwater volume mass of sediment; D ₅₀ is the median diameter of the starting particles.

(2)Height of sand wave

In the formula, r is the flood depth and ε is the empirical coefficient;

(3)Sand wave length

In the formula, γ is the empirical coefficient.

The beneficial effects of the present invention are:

(1) The present invention proposes an ecological restoration method for a river system, decomposes the ecological restoration goals of the river system into various river parts, and designs corresponding countermeasures, including river bed management measures, bank slope protection measures and floodplain repair measures, each of which The countermeasures coordinate and work together to comprehensively improve the ecological service function of the river system;

(2) The present invention controls the river bed longitudinally by constructing a ladder system, and utilizes the efficient energy dissipation characteristics of the ladder system to slow down the flow speed, weaken the water flow dynamics, and control the erosion of the river bed and bank slopes by the river. Trees were planted on the bank, and their root systems were used to increase soil cohesion, further strengthening the stability of the bank slope. The planting method of wrapping soil in fiber rolls not only ensured the survival rate and maturity speed of tree planting, but also utilized fiber rolls. The decay continues to provide nutrients. At the same time, the fiber rolls are connected into a whole and have strong erosion resistance, which can prevent the bank slope from being eroded in the early stage of tree planting, stabilize the river channel, and ensure the quality of bank slope protection measures;

(3) This invention imitates the natural river bed shape of the flood impact river, and modifies the floodplain land into sand waves. When the flood comes, it provides the most stable bed surface with large shape resistance for the flood flowing on the floodplain, reducing the flood risk. It can erode river floodplain materials and intercept fine-grained materials through shallow ditches after floods recede, improving soil conditions and accelerating the recovery of local ecosystems. In addition, gabions are permeable and can spread water to the floodplain when the flood level is low; when the water level is high, they can buffer the flood impact and store floods together with the restored vegetation on the floodplain, reducing the flood risks faced by downstream cities. ;

(4) The present invention designs floodplain ecological restoration species based on ecological survey data, improves the survival rate of ecological restoration species, and ensures the stability of ecological restoration communities. After restoring the vegetation community on the river floodplain, it can preserve soil and fix sand, improve the dryness of the local climate, and plant shrubs in the sand ridges to form plant sand barriers, further preventing the formation of desertification and slowing down the desertification process;

(5) The present invention further provides calculation methods for ladder system and sand wave design parameters, ensuring the stability and sustainability of ecological restoration of the river system.

Description of drawings

Figure 1 is a comprehensive model diagram of a river system ecological restoration technology;

Figure 2 is a floor plan for implementing ecological restoration of the river system on one side;

Figure 3 is a cross-sectional view of the ladder energy dissipation system;

Figure 4 is a cross-sectional view of bank slope protection measures;

Figure 5 is a cross-sectional view of the floodplain sand wave.

In the drawings, the parts represented by each number are listed as follows:

1. Ladder, 2. Tree, 3. Soil, 4. Fiber roll, 5. Gabion, 6. Drainage ditch, 7. Ridge, 8. Shallow ditch, 9. Shrub, 10. Sand ridge, 11. Hemp Rope, 12. Original floodplain ground.

Detailed ways:

The preferred embodiments of the present invention will be further described below with reference to the accompanying drawings.

The Gyirong Zangbo Canyon is located on the southern slope of the Himalayas. The altitude rises from 1,700m to 5,600m. A unique vertical ecosystem system is formed in the canyon, spanning 6 years from the subtropical evergreen broad-leaved forest ecosystem to the alpine meadow ecosystem. The large ecosystem system and huge differences in natural zones make the Gyirong Zangbo Canyon area home to many rare species of animals and plants. The Gyirong Zangbo Valley is also located in the middle of the Himalayas and is an important part of the Everest National Nature Reserve. The animal and plant species and ecosystems protected by the Everest Reserve are widely distributed in the Gyirong Zangbo Valley. Therefore, the strength of the ecosystem function of the Gyirong Zangbo Canyon is related to regional ecosystem protection. However, the riverbed in the middle reaches of the Gyirong Zangbo River has declined significantly, coarse gravels are scattered on the floodplain, the ecosystem has been seriously degraded, and the existing ecological functions are not strong. Moreover, the middle reaches of the Longzangbo River have a dry and hot climate, a fragile environmental matrix for land desertification, and a high inherent risk of desertification.

A specific ecological restoration plan is now designed for the river system in the middle reaches of the Zangbo River in Gyirong.

1. Obtain basic parameters

By measuring the physical parameters of the river and combining multiple floodplain ecosystem surveys, the following basic data were obtained:

River width W = 2m; river depth s = 1m; river bed slope S = 10%;

Ecosystem types include meadow ecosystems and shrub ecosystems; the species compositions of the two types of ecosystems are different. The meadow ecosystem includes dwarf sageweed, Echinacea aurantia, straight astragalus, baicalensis, and flowerhead. Lepidium, Echinacea, Caragana, Echinacea microphylla, Artemisia frigata, dandelion, the shrub ecosystem includes Elymus, Artemisia frigid, Lepidium capitatum, Clematis goldenrod, Tamarix, sea buckthorn.

Key species are distinguished according to their importance values. The top two important species in the meadow ecosystem are dwarf sageweed and Echinacea. The top two important species in the shrub ecosystem are Tamarix and Seabuckthorn.

2. Ladder system design

According to existing survey data, the step height H and stone particle size d in the river step system in the design section should meet:

0.1<H/L<0.2

d≥0.4m

Furthermore, while ensuring the convenience of construction, in order to ensure a smooth connection between the riverbed in the treatment section and the original riverbed, this design adopts a step length L = 10m, a step height H = 1m, and a stone particle size greater than 0.4m. The recommended engineering measure is to use machinery to level the step surface from the downstream upwards. The step surface should be kept horizontal or have a downward reverse slope, and the gravel with a particle size larger than 0.4m should be screened from the gravel excavated when leveling the step surface to build the steps 1 , the rest are reserved for filling the gabion 5; after smoothing out a step surface with a length of L = 10m in the horizontal direction, continue to trim the next step surface at a height of 1m from the current step surface. In addition, in order to ensure the stability of the ladder system, a shallow trench with a width of 2m and a depth of 0.5m should be dug downward at the location of the ladder construction, and then the stones should be stacked to form a ladder with a trapezoidal cross-section.

3. Bank slope protection measures

Bank slope protection measures use vegetation roots to increase soil cohesion and improve river bank strength. The selected tree species are required to be native tree species with well-developed root systems, cold and waterlogging resistance. Based on the existing survey data, tree 2 was selected to be planted in the river bank tree belt as Salix salix. The tree diameter of the Salix planted requires a tree diameter of 3 to 4cm, and the spacing between Salix plantings is 0.8m. When the height of the tree reaches 2.0m, "topping" is performed to reduce the impact of wind load on the vegetation, and thinning is required for proper tending. During specific planting, in order not to damage the stability of the bank slope and ensure the survival rate and maturity speed of the salix, a planting method of wrapping soil 3 in fiber rolls 0.5m away from the bank slope is adopted: first, excavate 0.5m away from the bank slope. A shallow trench with a width of 0.5m and a depth of 0.5m is then laid perpendicularly to the bottom of the trench every 2m with hemp rope 11 of suitable length for subsequent fastening of the fiber rolls. At the same time, the fiber rolls are unfolded and laid flat in the shallow trench. The joints of the rolls are staggered, and the fiber rolls are filled with soil. After planting the salix in it, tie the hemp rope tightly. The surface of the fiber rolls should be covered with sand and gravel.

4. Floodplain restoration measures

Floodplain restoration measures include gabion placement and sand wave preparation. Gabion 5 is located behind the vegetation zone of bank slope protection measures. The specific arrangement method is: first, excavate a shallow trench 0.6m wide and 0.4m deep 0.5m away from the vegetation zone, and then fill the gabion with gravel and place it in the shallow trench. Inside, the gabion is 0.8m high and 0.6m wide.

The determination process of sand wave height h and sand wave length l is as follows:

(1) Median particle size D ₅₀

According to the existing survey data, the riverbed specific drop S = 0.1; the hydraulic radius is replaced by water depth, R = 1.2m; the energy slope is replaced by the initial riverbed specific drop, S _e = 0.1; S _g = 1650kg/m ³ ; brought-in formula 3. Formula 4:

τ _c =0.15S ^0.25 =0.084

(2)Height of sand wave

Take ε = 2.5 and substitute it into Equation 5;

(3)Sand wave length

Take γ = 1.5 and substitute it into equation 6;

In order to deposit more fine-grained materials on the floodplain after the flood recedes, the sand wave height is designed to be enlarged. The design sand wave height h=0.8m and the sand wave length l=4.5m. The sand wave forms an angle of 45° with the river shoreline, aiming to slow down the flow of floods and induce floods to spread to the periphery of the floodplain. When building sand waves in the floodplain by trimming the land, the recommended engineering measures are: use machinery to dig 0.4m deep shallow trenches 80% of the wave troughs at intervals of 4.5m in the repair section of the floodplain, and place the excavated soil, sand and gravel in the middle of the two shallow trenches. The sand ridge 10 is piled up, which is the wave crest; then the ditch and ridge surface are trimmed mechanically or manually, so that the shallow ditch 8 and the sand ridge 10 are connected in a streamlined manner, and finally a sand wave is built. When there is a road built on the floodplain, a trench 6 needs to be dug 3m away from the embankment for drainage. The trench is 1m wide and 0.4m deep. The excavated soil, sand and gravel are piled on one side and compacted into a ridge 7 with a height of 0.8m. Finally, spread grass seeds evenly on the river floodplain. The grass seeds are Acanthus truncatula, Scutellaria erectus, Elymus elegans, and Dwarf sedge. The shrub species are Tamarix and Seabuckthorn. Tamarix and Seabuckthorn need to be cultivated until the tree diameter reaches 1cm. Plant in sand ridges with a planting spacing of 0.5m.

According to the ecological restoration plan for the river system, when the river is close to the foot of the mountain, only one side of the floodplain needs to be prepared according to the above design; when the river is located in the center of the valley, the floodplains on both sides need to be prepared, sand waves and sand wave designs The program remains consistent.

Finally, it should be noted that the above are only preferred implementation examples, and are not intended to limit this patent. Although detailed descriptions are made with reference to the aforementioned cases, those skilled in the art can still make use of the aforementioned implementation examples. Modify or combine the technical solutions described, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this patent shall be included in the protection scope of this patent. Within.

Claims (6)

1. An ecological restoration technology for river systems in mountain gorges and valley areas is characterized in that: comprises river bed treatment measures, bank slope protection measures and river flood beach restoration measures;

the river bed treatment measures weaken water flow energy through longitudinal treatment of a river channel, limit transverse erosion of the river, and are characterized in that a step energy dissipation system is established, a step (1) is formed by block stones and provided with a step surface with a horizontal or downward reverse slope, and the step height is comprehensively controlled by the step length and the river bed slope;

the bank slope protection measure is provided with a arbor belt parallel to a river bank line, and is characterized in that the arbor (2) is planted by adopting foreign soil, the foreign soil is wrapped by a fiber roll (4) and then is arranged in a ditch with a designed size, so that the survival rate is improved, and the maturation speed is accelerated;

the river flood beach repairing measure is characterized by comprising shallow grooves (8) and sand ridges (10), wherein the sand waves and the river shorelines form a certain included angle, the cross sections of the sand waves are wavy, ecological restoration species of the river flood beach are designed through ecological investigation data, shrubs are planted on the sand ridges (10), grass seeds are sowed in the middle of the sand ridges, the river flood beach repairing measure further comprises gabions (5) arranged along the river shorelines, and the gabions (5) are buried deep and are positioned on the inner sides of arbor zones.

2. The step energy dissipation system of claim 1, wherein: the step surface is mechanically flattened from downstream to upstream, the step surface is kept horizontal or has a downward counter slope, the step (1) is built by screening the excavated gravel with a particle size greater than 0.4m, and the rest is left for standby so as to fill the gabion (5).

3. The bank slope protection measure according to claim 1, characterized in that: the arbor (2) is used for selecting a rural tree species with developed root system, cold resistance and waterlogging tolerance, the tree species should be cultivated until the tree diameter reaches 3-4 cm thick, 1-2 rows of tree species are planted parallel to the river shoreline, the foreign soil (3) should be mined locally, the fiber roll (4) is woven by coconut shreds or straws, the diameter is 0.5m, and the tree species should be corresponding to the river shoreline interval of 0.5m when being buried, so that severe disturbance to the river shoreline is avoided.

4. The flood bank repair procedure of claim 1, wherein: the gabion (5) should be buried 0.4m deep, 0.4m above ground and 0.6m wide.

5. The river flood beach sand wave of claim 1, wherein: building according to the amplified size, building by digging shallow grooves (8) and building sand ridges (10), and connecting in a streamline shape, wherein sand waves are 45 degrees to the direction of a river shoreline, so as to relieve the flow rate of flood and induce the flood to spread to the periphery of the river flood; and constructing soil ridges (7) again at the position 2-3 m away from the embankment and parallel to the embankment, and digging drainage ditches (6) in front of the soil ridges (7).

6. The river bed remediation procedure, bank slope protection procedure, and flood bank repair procedure of claim 1, wherein: if the river is positioned on the mountain foot, repairing and treating are only needed on one side of the bank slope and the flood bank; when the river is positioned in the middle of the canyon, the bank slopes and the flood lands at the two sides are required to be repaired and treated, and the repair modes at the two sides are symmetrical to the river.