A method for constructing a natural river channel and floodplain wetland

Abstract

The application provides a construction method of a natural river channel and overbank wetland, comprising the following steps: S1: constructing a natural river channel and three-stage overbank in a riverbed according to historical daily flow statistical characteristics, so as to adapt to river channel flow characteristics under different rainfall scenarios; and S2: constructing overbank wetlands with different characteristics according to selected overbank types. The application relies on overbank wetlands to comprehensively improve the ecological service function of the river channel; in a non-rainfall scenario, the service functions of landscape, soil conservation, wind prevention and sand fixation are realized; and in a rainfall scenario, the service functions of reducing non-point source pollution, storing flood, and improving water environmental quality are mainly played.

Description

Technical Field

[0001] This invention belongs to the field of ecological engineering technology, and in particular relates to a method for constructing simulated natural river channels and floodplain wetlands. Background Technology

[0002] Water shortage is a widespread problem in northern my country. While socio-economic development consumes a large amount of water resources, it also encroaches on ecological water use, resulting in the shrinkage or even drying up of many natural rivers.

[0003] In normal circumstances, these natural river channels have only a small amount of water remaining on the surface, while most of the riverbed is exposed. This not only eliminates their original ecological service functions, such as pollution protection and biodiversity maintenance, but also turns them into potential sources of pollution. During rainfall events, floodwaters fill the river channels, rendering the previously exposed riverbeds unable to provide ecological services. Furthermore, pollutants deposited on the riverbed may be resuspended, and large amounts of endogenous pollutants are released, severely impacting the quality of the river's water environment. Therefore, it is necessary to construct an ecological river channel that can provide ideal ecological services both during the rainy season and the dry season, comprehensively improving the quality of the river's water environment. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for constructing simulated natural river channels and floodplain wetlands, which comprehensively enhances the ecological service functions of river channels by relying on floodplain wetlands. In non-rainfall scenarios, it provides services such as landscape enhancement, soil conservation, and windbreak and sand fixation. In rainfall scenarios, it primarily serves to reduce non-point source pollution, retain floodwater, and improve water quality.

[0005] To achieve the above objectives, the present invention provides a method for constructing simulated natural river channels and floodplain wetlands, comprising the following steps:

[0006] S1: Based on the historical daily average flow statistics, a simulated natural river channel and three-level floodplain are constructed within the riverbed to adapt to the river flow characteristics under different rainfall scenarios;

[0007] S2: Construct floodplain wetlands with different characteristics based on the selected floodplain type.

[0008] Preferably, in step S1, the method for constructing a simulated natural river channel and a three-tiered floodplain within the riverbed based on historical daily average flow statistics is as follows:

[0009] S11: Transform the existing river channel in the riverbed into a meandering shape to serve as a water flow channel in non-rainfall scenarios. The meandering river channel has the characteristic of being prone to flooding and overflowing the banks.

[0010] S12: Construct a first-level floodplain for the high-frequency floodplain area around the meandering river channel; construct a second-level floodplain for the medium-frequency floodplain area around the meandering river channel; construct a third-level floodplain for the low-frequency floodplain area around the meandering river channel; the high-frequency floodplain area, the medium-frequency floodplain area, and the low-frequency floodplain area are determined based on research and analysis.

[0011] Preferably, the concave bank of the meandering river channel should be constructed with an ecological revetment that has the ability to prevent erosion, and the convex bank of the meandering river channel should be constructed with a gentle slope to facilitate the flow of river water out of the channel and onto the floodplain.

[0012] Preferably, the primary floodplain is located on the inner side of the convex bank of the meandering river channel, and is the most frequent floodplain area and the main sediment deposition area; the matrix of the primary floodplain is composed of a coarse sand layer and a gravel layer from top to bottom, and the total thickness of the matrix layer is consistent with or slightly greater than the depth of the meandering river channel; emergent plants are planted on the primary floodplain to construct a primary floodplain wetland.

[0013] Preferably, the secondary floodplain is located on both sides close to the meandering river channel. The secondary floodplain matrix consists of a coarse sand layer, a pea gravel layer, and a gravel layer from top to bottom. The total thickness of the matrix layer is consistent with or slightly greater than the depth of the meandering river channel. Herbaceous plants are planted on the secondary floodplain to construct a secondary floodplain wetland.

[0014] Preferably, the tertiary floodplain is located on both sides away from the meandering river channel, the substrate of the tertiary floodplain is the original riverbed, and herbaceous plants are planted on the tertiary floodplain to construct a tertiary floodplain wetland.

[0015] This invention discloses the advantages and technical effects:

[0016] 1) This invention is based on the transformation of exposed riverbeds to form a simulated natural complex riverbed with a "main channel-multi-level floodplain" structure. It organically combines in-situ water purification technology, vegetation buffer zone technology, habitat improvement technology and aquatic biological functional group construction technology. It does not require the occupation of land outside the river channel and does not affect the flood discharge of the river channel. It can significantly improve the ecological service function of the river channel under different flow scenarios, and has huge environmental, economic and social benefits.

[0017] 2) In non-rainfall scenarios, river flow is relatively low, and water flows in the main channel. The varied hydrological conditions within the meandering river provide habitats for various aquatic organisms, while floodplain wetlands at all levels serve functions such as soil conservation, windbreak and sand fixation, and landscaping.

[0018] 3) During periods of moderate to light rainfall, river flow is moderate, and water occasionally flows out of the main channel into the primary floodplain wetland. During periods of heavy flow, water flows into the secondary floodplain wetland. Emergent plants in the primary floodplain wetland intercept particulate matter in the floodplain water and make it a source of nutrients for the floodplain wetland; the secondary floodplain wetland regulates and purifies floodwaters; and the tertiary floodplain wetland effectively reduces the inflow of non-point source pollutants from both banks of the riverbed.

[0019] 4) During periods of heavy rainfall, river flows are large, and water overflows the riverbanks, sometimes even filling the entire riverbed. First, second, and third-level floodplain wetlands comprehensively serve functions such as flood retention, reduction of non-point source pollution, and improvement of water quality. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 This is a schematic diagram of the structure of the simulated natural river channel and floodplain wetland of the present invention.

[0022] Attached diagram descriptions: 1-Meandering river channel; 2-Primary floodplain; 3-Secondary floodplain; 4-Tertiary floodplain; 5-Convex bank of the meandering river channel; 6-Concave bank of the meandering river channel; 7-Existing riverbank protection. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0025] according to Figure 1 As shown, the present invention provides a method for constructing simulated natural river channels and floodplain wetlands, comprising the following steps:

[0026] S1: Based on the historical daily average flow statistics, a simulated natural river channel and three-level floodplain are constructed within the riverbed to adapt to the river flow characteristics under different rainfall scenarios;

[0027] S2: Construct floodplain wetlands with different characteristics based on the selected floodplain type.

[0028] Specifically, based on historical daily average flow statistics, the method for constructing a simulated natural river channel and a three-tiered floodplain within the riverbed is as follows:

[0029] S11: Transform the existing river channel in the riverbed into a meandering shape to serve as a water flow channel in non-rainfall scenarios. The meandering river channel has the characteristic of being prone to flooding and overflowing the banks.

[0030] S12: Construct a first-level floodplain for the high-frequency floodplain area around the meandering river channel; construct a second-level floodplain for the medium-frequency floodplain area around the meandering river channel; construct a third-level floodplain for the low-frequency floodplain area around the meandering river channel; the high-frequency floodplain area, medium-frequency floodplain area, and low-frequency floodplain area are determined based on research and analysis.

[0031] In this embodiment, 1) the statistical characteristics of the historical daily average flow after the river surface area has been greatly reduced are analyzed, and key frequency characteristic values ​​such as P=50%, P=40%, P=20%, and P=10% are determined.

[0032] 2) Hydrological simulation based on the MIKE model: Taking the daily average flow of P=50% without leaving the channel within the meandering channel 1 as the standard, the morphology, width, depth and other characteristics of the meandering channel 1 are determined; the area submerged by the daily average flow of P=40% is used as the high-frequency floodplain area to determine the first-level floodplain 2 construction area; the area submerged by the daily average flow of P=20% is used as the medium-frequency floodplain area to determine the second-level floodplain 3 construction area; and the area submerged by the daily average flow of P=10% is used as the low-frequency floodplain area to determine the third-level floodplain 4 construction area.

[0033] 3) Construction of the meandering river channel 1. The existing river channel in the riverbed is transformed into a meandering shape to serve as a water flow channel in non-rainfall scenarios. The meandering river channel 1 has the characteristic of being prone to flooding and overflowing the channel during floods. The meandering river channel 1 is constructed based on the planar shape, width, and depth determined by model simulation. The bank protection of the meandering river channel adopts flexible natural bank protection. The concave bank 6 of the meandering river channel is filled with stones to form an ecological bank protection to prevent erosion. The slope of the convex bank 5 of the meandering river channel is reduced to promote the outflow of river water.

[0034] 4) Construction of the primary floodplain wetland. The primary floodplain 2 is located on the inner side of the convex bank of the meandering river channel 1, and is the most frequent floodplain area and the main sediment deposition area. The primary floodplain wetland matrix consists of a coarse sand layer and a pea gravel layer with a particle size of 5-10 mm, arranged from top to bottom. The total thickness of the matrix layer is consistent with or slightly greater than the depth of the meandering river channel, and the thickness ratio of the coarse sand layer to the pea gravel layer should be 1:1 to 1:2. Emergent plants are mainly planted in the primary floodplain 2 area. The emergent plants selected are species with well-developed root systems and tall plants, such as: reeds, cattails, loosestrife, water onions, calamus, and rush.

[0035] 5) Construction of the secondary floodplain wetland. The secondary floodplain 3 is located on both sides near the meandering river channel 1. From top to bottom, the secondary floodplain 3 consists of a coarse sand layer, a 5-10mm gravel layer, and a 10-20mm gravel layer. The total thickness of the matrix layer is consistent with or slightly greater than the depth of the meandering river channel 1. The recommended thickness ratio of the coarse sand layer, the gravel layer, and the gravel layer is 1:1:2. Local native herbaceous plants are planted on the surface of the secondary floodplain 3 area.

[0036] 6) Construction of the three-level floodplain wetland. The three-level floodplain 4 is located on both sides away from the meandering river channel 1. The three-level floodplain 4 area basically maintains the original riverbed appearance and is planted with local native herbaceous plants.

[0037] This invention is based on the transformation of exposed riverbeds and existing riverbank protection to form a simulated natural complex riverbed with a "main channel-multi-level floodplain" structure. It organically combines in-situ water purification technology, vegetation buffer zone technology, habitat improvement technology, and aquatic biological functional group construction technology. It does not require the occupation of land outside the river channel and does not affect the flood discharge of the river channel. It can significantly improve the ecological service function of the river channel under different flow scenarios, and has huge environmental, economic and social benefits.

[0038] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for constructing simulated natural river channels and floodplain wetlands, characterized in that, Includes the following steps: S1: Based on the historical daily average flow statistics, a simulated natural river channel and three-level floodplain are constructed within the riverbed to adapt to the river flow characteristics under different rainfall scenarios; S2: Construct floodplain wetlands with different characteristics based on the selected floodplain type; In S1, the method for constructing a simulated natural river channel and a three-tiered floodplain within the riverbed based on historical daily average flow statistics is as follows: S11: Transform the existing river channel in the riverbed into a meandering river channel to serve as a water flow channel in non-rainfall scenarios. The meandering river channel has the characteristic of being prone to flooding and overflowing the banks. S12: Construct a first-level floodplain for the high-frequency floodplain area around the meandering river channel; construct a second-level floodplain for the medium-frequency floodplain area around the meandering river channel; construct a third-level floodplain for the low-frequency floodplain area around the meandering river channel; the high-frequency floodplain area, the medium-frequency floodplain area, and the low-frequency floodplain area are determined based on research and analysis; The concave bank of the meandering river is constructed with an ecological revetment that has the ability to prevent erosion, and the convex bank of the meandering river is constructed with a gentle slope to facilitate the flow of river water out of the channel and onto the floodplain. In non-rainfall scenarios, the river flow is small, and the water flows in the main channel. The varied hydrological conditions in the meandering river channel provide habitats for various aquatic organisms, while the floodplain wetlands at all levels play a role in soil conservation, windbreak and sand fixation, and landscape services. In scenarios of light to moderate rainfall, the river flow is moderate, and water occasionally flows out of the main channel into the primary floodplain wetland. When the flow is heavy, it flows into the secondary floodplain wetland. Emergent plants in the primary floodplain wetland intercept particulate matter in the floodplain water and make it a source of nutrients for the floodplain wetland. The secondary floodplain wetland regulates and purifies the floodplain floodwater. The tertiary floodplain wetland effectively reduces the inflow of non-point source pollutants from both banks of the river. During periods of heavy rainfall, river flows are large, and water overflows the riverbanks and may even fill the entire riverbed. First, second, and third-level floodplain wetlands comprehensively serve to retain floodwater, reduce non-point source pollution, and improve water quality. 1) Analyze the historical daily average flow statistics after the significant reduction in river surface area, and determine the key frequency characteristic values ​​of P=50%, P=40%, P=20%, and P=10%. 2) Hydrological simulation based on the MIKE model: Using the standard that the average daily flow of P=50% does not leave the channel in the meandering river, the morphology, width, and depth characteristics of the meandering river are determined; The area inundated by the average daily flow of P=40% is used as the high-frequency floodplain area to determine the first-level floodplain construction area; the area inundated by the average daily flow of P=20% is used as the medium-frequency floodplain area to determine the second-level floodplain construction area. The area inundated by the average daily flow of P=10% is used as a low-frequency floodplain area to determine the three-level floodplain construction area; 3) Construction of primary floodplain wetlands: The primary floodplain is located on the inner side of the convex bank of the meandering river channel and is the most frequent floodplain area and the main sediment deposition area. The primary floodplain wetland matrix consists of a coarse sand layer and a pea gravel layer with a particle size of 5-10 mm from top to bottom. The total thickness of the matrix layer is consistent with or slightly greater than the depth of the meandering river channel, and the thickness ratio of the coarse sand layer to the pea gravel layer is 1:1 to 1:

2. Emergent plants are mainly planted in the primary floodplain area. The emergent plants selected are species with well-developed root systems and tall plants, including: reeds, cattails, loosestrife, water onions, calamus, and rush. 4) Construction of secondary floodplain wetlands: The secondary floodplain is located on both sides close to the meandering river channel. The secondary floodplain consists of a coarse sand layer, a pea gravel layer with a particle size of 5-10 mm, and a gravel layer with a particle size of 10-20 mm, arranged from top to bottom. The total thickness of the matrix layer is consistent with or slightly greater than the depth of the meandering river channel. The recommended thickness ratio of the coarse sand layer, pea gravel layer, and gravel layer is 1:1:

2. Local native herbaceous plants are planted on the surface of the secondary floodplain area. 5) Construction of three-level floodplain wetlands: The three-level floodplains are located on both sides away from the meandering river channel. The three-level floodplain areas maintain the original riverbed features and are planted with local native herbaceous plants.

Images