A method for adjusting and reconstructing tidal flow of a tidal river

Abstract

The present application relates to a kind of tidal river tidal flow regulation and reconstruction method, including being set in the tidal river city area river section downstream near estuary region regulation dam;When tide rises, regulation dam is in dam rising operation state, maintain its upstream landscape water level, when regulation dam downstream water level rises to consistent with its upstream landscape water level, regulation dam collapses dam operation;When tide falls, falling tide flow overflows air shield dam and flows downstream, and river water level gradually drops, when regulation dam upstream water level falls to consistent with its landscape water level, regulation dam rises dam, continue to maintain its landscape water level;On the basis of maintaining the function of tidal river landscape water level and ecological environment, the method most reduces the influence on the natural rise and fall tidal movement law of tidal river, water body connection, water exchange, migratory fish upstream, shipping and other functions still normally play, also have the function of inhibiting salt tide upstream.

Description

Technical Field

[0001] This invention relates to a method for regulating and modifying tidal currents in tidal rivers, belonging to the field of river management technology. Background Technology

[0002] Tidal flow is a natural characteristic of tidal rivers. To meet people's needs for freshwater resources, flood control, and salinity prevention, tide gates have been built at the mouths of many tidal rivers, playing a positive role in tide control, freshwater storage, flood discharge, drainage, and landscaping. However, the construction of tide gates also obstructs ocean currents, altering the natural tidal movement of tidal rivers, and bringing adverse effects including:

[0003] (1) It disrupted the connectivity of the water body;

[0004] (2) A reservoir is formed upstream of the sluice gate, the river flow velocity decreases, the water body’s self-purification capacity decreases, and pollution is easily caused.

[0005] (3) It hinders the migration of fish and crabs in the river and cuts off the biological communication pathways;

[0006] (4) The original navigation function of the river has disappeared.

[0007] It should also be noted that in some rivers with large tidal ranges and low low tide levels, the water in the riverbed almost disappears completely at low tide, exposing the entire riverbed. In urban river sections, the riverbed is often black and smelly due to human activities, which is quite detrimental to the river's ecological environment and urban landscape.

[0008] Therefore, it is necessary to take appropriate measures to regulate the flow of water in order to maintain the normal ecological environment and landscape function of the river. Summary of the Invention

[0009] The purpose of this invention is to provide a method for regulating and modifying tidal currents in tidal rivers, so as to solve the problems mentioned in the background art.

[0010] The technical solution of the present invention is as follows:

[0011] 1. A method for modifying tidal river channels, comprising the following steps:

[0012] On-site surveys and analysis were conducted to obtain topographic data and tidal level change data for the tidal channel.

[0013] A regulating dam will be constructed in the main channel of the tidal river near the estuary in the downstream area of ​​the urban section of the river.

[0014] When the regulating dam is raised, the dam crest elevation is lower than the elevation of the beach areas on both sides of the dam site, lower than the average high tide level of the dam site, and lower than the water level control level for flooding in the riverbank areas.

[0015] Preferably, the regulating dam is an air-shield dam, and the length of the air-shield dam is equal to the width of the main channel at the dam site.

[0016] Preferably, the air shield dam is arranged with a single hole or multiple holes.

[0017] Preferably, the elevation of the top of the air-supported dam is its landscape water level elevation; the elevation of the bottom of the air-supported dam is consistent with the riverbed elevation.

[0018] Preferably, the air-supported dam includes a gate dam section, an upstream paving section, a downstream stilling basin section, a downstream apron section, and an upstream-downstream connecting section.

[0019] Preferably, the air shield dam gate piers are set on both sides of the main channel of the river. The upstream connecting section retaining wall is arranged upstream along the air shield dam gate piers, and its length is the same as the length of the apron, and it is smoothly connected to the beach on both sides of the main channel of the tidal river. The downstream connecting section retaining wall is arranged downstream along the lower edge of the air shield dam gate piers, and its length is the same as the length of the stilling basin and the sea, and it is smoothly connected to the beach on both sides of the main channel of the tidal river.

[0020] Preferably, an inspection well is set up outside the gate pier. The air inlet and outlet pipes of the airbag at the bottom of the air shield dam are led to the ground through the inspection well and laid along the tidal river beach to the control room. The air inlet and outlet pipes are fitted with PVC sleeves and placed in a pipe trench excavated and constructed on the beach. The pipe trench is buried at a depth of more than 0.5m and is covered with a cover plate. The top of the cover plate is backfilled to the original beach elevation.

[0021] A method for regulating the tidal flow of a tidal channel, used in conjunction with a method for modifying a tidal channel;

[0022] This includes setting up regulating dams in the downstream area of ​​the urban section of tidal river near the river mouth;

[0023] During high tide, the regulating dam is in the raised dam operation state to maintain the upstream landscape water level. When the downstream water level of the regulating dam rises to the same level as the upstream landscape water level, the regulating dam is in the collapsed dam operation state.

[0024] At low tide, the ebb current flows downstream over the air shield dam, and the river level gradually drops. When the water level upstream of the regulating dam drops to match its landscape water level, the regulating dam is raised to maintain its landscape water level.

[0025] Preferably, during floods, the regulating dam is operated by collapsing in advance to release floodwaters; after the flood has passed, the regulating dam is restored to its normal operating function.

[0026] Preferably, during the operation of the air-shield dam, the backwater from the upstream river channel will not flood the riverbanks.

[0027] The present invention has the following beneficial effects:

[0028] The water level is maintained at a scenic level throughout the ebb and flow of the tide, forming a scenic water belt that effectively improves the ecological environment of the river and the city's aesthetic appeal.

[0029] While maintaining the landscape water level and ecological functions of tidal channels, this method minimizes the impact on the natural ebb and flow of tidal movements in tidal channels, and ensures that functions such as water connectivity, water exchange, migratory fish migration, and navigation are still functioning normally.

[0030] It also has the function of inhibiting the upstream intrusion of saltwater. During high tide, the saltwater wedge is located at the bottom of the river channel, and the regulating dam is located in the main channel, which can block the saltwater wedge. Attached Figure Description

[0031] Figure 1 This is a cross-sectional view of the tidal channel of the present invention. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0033] Example:

[0034] The riverbed of a certain tidal river in its middle and lower reaches is mostly silted up, and the width and height of the riverbank beaches are relatively large. During high tide, the silt on the riverbed is carried to the beaches on both sides by the tide, and during low tide, the silt on the riverbed and beaches is exposed. This not only has a certain impact on the water quality of the tidal river, but also causes the area of ​​natural vegetation and bird habitat to decrease year by year, and the riverbank environment to deteriorate.

[0035] Determine a suitable site for the regulating dam. The regulating dam should ideally be located downstream of the urban section of the tidal river, near the estuary, to ensure a good water level for the urban section. Furthermore, the dam's placement should also consider factors such as river topography, geology, river-related engineering works, construction diversion, and the layout of temporary facilities. Before any modifications are carried out, observe the average tidal level and average high tidal level of the river channel, and measure the river's topography.

[0036] A regulating dam should be set up in the main channel of the tidal river dam site section. The regulating dam should preferably be an air shield dam.

[0037] The air-supported dam is located in the main channel of the tidal river, and can be arranged in a single-span or multi-span configuration. The length of the air-supported dam (width along the river channel cross-section) is equal to the width of the main channel at the dam site. The elevation of the dam base should ideally match the original riverbed elevation to facilitate a smooth connection between the upstream and downstream riverbeds and reduce the area occupied by the dam. The elevation of the dam crest is its landscape water level. The design considers that the normal water level will not submerge the riverbanks after channel reshaping and ecological restoration, and ensure water storage in the main channel. It also considers that most high tide levels will allow for tidal intake without affecting the normal drainage of the downstream banks.

[0038] The following aspects are considered when determining the landscape water level of the air-supported dam:

[0039] ① Elevation of the riverbanks on both sides of the dam site cross-section. The riverbanks refer to the first-level riverbanks adjacent to the main channel. The landscape water level of the air shield dam should not be higher than the elevation of the riverbanks on both sides of the dam site cross-section.

[0040] ② The elevation of the riverbanks on both sides of the upstream river and the landscape water level of the air shield dam are determined. When the air shield dam is operating at its landscape water level, it should ensure that the main channel of the river is filled with water, and the upstream backwater should not submerge the riverbanks on both sides of the river so as not to affect the original ecological landscape effect of the riverbanks.

[0041] ③ The average high tide level of the river section at the dam site should not be higher than the average high tide level of the dam site section, so as to ensure that the tide can continue to be drawn in during high tide.

[0042] ④ The water level for flood control in the riverbanks upstream of the air-supported dam should be lower than the water level for flood control in the riverbanks when the air-supported dam is operating at its landscape water level, so as not to affect the normal drainage of the riverbanks upstream of the air-supported dam.

[0043] The regulating dam consists of a gate dam section, an upstream paved section, downstream energy dissipation and scour prevention facilities, and upstream and downstream connecting sections. The upstream connecting section retaining wall extends upstream along the gate piers of the air-shield dam, with a length equal to the length of the apron, smoothly connecting to the beaches on both sides of the main channel of the tidal river. The downstream connecting section retaining wall extends downstream along the lower edge of the gate piers of the air-shield dam, with a length equal to the length of the stilling basin and the seawall, smoothly connecting to the beaches on both sides of the main channel of the tidal river.

[0044] The regulating dam is located on the main channel of the tidal river. It is an air-shield dam, primarily composed of a base dam, gate structure, embedded components, airbags, and a pneumatic system. The gate's water-retaining surface is constructed of a row of reinforced steel plates, with airbags supporting the downstream side of these plates. The inflation and deflation of the airbags control the gate's undulations and support its water-retaining function.

[0045] The dam adopts a single-span layout with an opening size of 120.0 × 4.0 m (width × height). The bottom elevation of the dam is -1.50 m, and the top elevation of the dam is 2.50 m. When the dam is raised, overflow occurs from the top; when it collapses, an open-type broad-crested weir is used for discharge. The dam section is 11.50 m long and 120.0 m wide in the direction of water flow, and is a C35 reinforced marine concrete structure. The bottom slab of the dam is 2.0 m thick and 120.0 m wide, with a 0.3 m thick sand and gravel cushion layer and a 0.1 m thick plain concrete cushion layer at the bottom. A settlement joint with a width of 20 mm is installed every 30 m on the bottom slab, and a copper sheet waterstop is installed upstream and downstream. The joints are filled with closed-cell foam board.

[0046] The dam has piers on both sides with a width of 1.0m and a top elevation of 3.50m. A maintenance well is set on the outer side of the left bank pier. The air intake and exhaust pipes of the bottom airbag are led to the ground through the maintenance well. Considering that the regulating dam is located in the main channel of the tidal river, the control room needs to be located outside the riverbank. Therefore, the air intake and exhaust pipes are led to the ground through the maintenance well and then laid along the tidal riverbank to the control room. To facilitate future maintenance, the air intake and exhaust pipes are placed in a C35 reinforced concrete trench through two D400 PVC sleeves. The trench dimensions are 1.0m × 0.5m (width × height). A 0.20m thick reinforced concrete cover plate is installed on the top. To avoid scouring of the trench by the tidal river flood discharge, the trench is buried at a depth of 0.5m. The top of the trench is filled with cohesive soil to the elevation of the riverbank.

[0047] Upstream paving section:

[0048] Upstream of the air-supported dam, there is a 10.0m long and 0.6m thick C35 reinforced marine concrete paving, under which is a 0.10m thick plain concrete cushion layer and a 0.30m sand and gravel cushion layer. The top elevation of the paving bottom plate is -1.50m. A settlement joint with a width of 0.20m is set every 30.0m along the vertical direction of water flow, and the joint is filled with closed-cell foam board.

[0049] Downstream stilling basin section:

[0050] Downstream of the air-supported dam, there is a 5.0m long and 0.80m thick C35 reinforced marine concrete stilling basin, with a 0.10m thick plain concrete cushion layer and a 0.30m sand and gravel cushion layer. The top elevation of the stilling basin bottom slab is -2.0m, the top elevation of the outlet is -1.50m, the basin depth is 0.5m, and the width is 120.0m. A settlement joint with a width of 0.20m is set every 30.0m along the vertical direction of water flow, and the joint is filled with closed-cell foam board.

[0051] Downstream abutment section:

[0052] Downstream of the stilling basin, there is a 10.0m long and 1.0m thick C20 plain concrete abutment, with a 0.10m thick plain concrete cushion layer and a 0.30m sand and gravel cushion layer. The top elevation of the abutment is -1.50m and the width is 120.0m. A settlement joint with a width of 0.20m is set every 30.0m along the direction perpendicular to the water flow, and the joint is filled with closed-cell foam board.

[0053] Upstream and downstream connection sections:

[0054] The upstream connecting section retaining wall extends upstream along the dam abutments, with a length equal to that of the apron. It smoothly connects to the production dikes on both sides of the main channel of the tidal river. The upstream connecting section retaining wall is a C20 plain concrete gravity structure with a top elevation of 3.50m. Expansion joints, 20mm wide, are provided every 8m to 15m along the retaining wall, filled with closed-cell foam board. The retaining wall foundation is soft soil, and its bearing capacity does not meet the requirements for the superstructure's foundation surface; therefore, the foundation needs reinforcement.

[0055] The downstream connecting section retaining wall extends downstream along the lower edge of the dam's side abutments, with a length identical to that of the stilling basin and the seawall. It smoothly connects to the production dikes on both sides of the main channel of the tidal river. The downstream connecting section adopts a C20 reinforced concrete cantilever structure with a sidewall thickness of 0.8m and a top elevation of 3.50m. The retaining wall foundation is soft soil, and the bearing capacity of the foundation does not meet the requirements for the foundation surface of the superstructure; therefore, the foundation needs to be reinforced.

[0056] During normal operation, at high tide, the air-supported dam is in a raised dam operation state, maintaining its upstream landscape water level (the crest elevation of the air-supported dam). When the downstream water level of the air-supported dam rises to match its upstream landscape water level, the air-supported dam collapses, and the high tide flows over the air-supported dam and continues to advance upstream, gradually raising the river level until it subsides. At low tide, the low tide flows over the air-supported dam and flows downstream, gradually lowering the river level. When the upstream water level of the air-supported dam falls to match its landscape water level, the air-supported dam rises, continuing to maintain its landscape water level. Thereafter, until the next high tide when the downstream water level of the air-supported dam rises to match its upstream landscape water level, the air-supported dam remains in a raised dam operation state.

[0057] During floods, the air-supported dam collapses in advance based on weather forecasts to release floodwaters, thus ceasing to maintain its landscape function. Its normal operation will be restored after the floods have passed.

[0058] Existing tide gates are used to prevent tides from rising and to cut off rivers, but they cannot achieve the natural rise and fall of tides in tidal channels.

[0059] Rubber dams and steel gates, which are commonly used to maintain water levels in landscapes, are not suitable for watersheds with a lot of floating debris and loose rocks; flap gate dams are not suitable for watersheds with frequent floods, rapid flow, and a lot of floating debris; rubber dams are not suitable for watersheds with large flow variations, a lot of floating debris and loose rocks, and frequent ice jams.

[0060] Tidal gates (which have the same structure as tide barriers but operate differently, allowing tides to rise in. When the open sea level is higher than the water level above the gate, the tide is drawn in, and the gate is closed when the water level reaches the control level) require large investments, the gate piers affect flood control, and they cannot solve the problem of saltwater intrusion.

[0061] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for regulating tidal currents in tidal channels, characterized in that: Includes the following steps: On-site surveys and analysis were conducted to obtain topographic data and tidal level change data for the tidal channel. A regulating dam will be constructed in the main channel of the tidal river near the estuary in the downstream area of ​​the urban section of the river. When the regulating dam is raised, the dam crest elevation is lower than the elevation of the beach areas on both banks of the dam site, lower than the average high tide level of the dam site, and lower than the water level control level for flooding in the riverbank areas. During high tide, the regulating dam is in the raised dam operation state to maintain the upstream landscape water level. When the downstream water level of the regulating dam rises to the same level as the upstream landscape water level, the regulating dam is in the collapsed dam operation state. At low tide, the ebb current flows downstream past the regulating dam, and the river level gradually drops. When the water level upstream of the regulating dam falls to match its landscape water level, the regulating dam is raised to maintain its landscape water level.

2. The tidal flow regulation method for tidal channels as described in claim 1, characterized in that: The regulating dam is an air-shield dam, and the length of the air-shield dam is equal to the width of the main channel at the dam site.

3. The tidal flow regulation method for tidal channels as described in claim 2, characterized in that: The air-supported dam is arranged with single or multiple openings.

4. The tidal flow regulation method for tidal channels as described in claim 2, characterized in that: The elevation of the top of the air-supported dam is its landscape water level elevation; the elevation of the bottom of the air-supported dam is consistent with the riverbed elevation.

5. The tidal flow regulation method for tidal channels as described in claim 2, characterized in that: The air-supported dam includes a gate dam section, an upstream paving section, a downstream stilling basin section, a downstream apron section, and an upstream-downstream connecting section.

6. The method for regulating tidal currents in a tidal channel as described in claim 5, characterized in that: The air-supported dam gate piers are set on both sides of the main channel of the river. The upstream connecting section retaining wall is arranged upstream along the air-supported dam gate piers, and its length is the same as the length of the apron, and it is smoothly connected to the beach on both sides of the main channel of the tidal river. The downstream connecting section retaining wall is arranged downstream along the lower edge of the air-supported dam gate piers, and its length is the same as the length of the stilling basin and the sea, and it is smoothly connected to the beach on both sides of the main channel of the tidal river.

7. A method for regulating tidal currents in a tidal channel as described in claim 6, characterized in that: A maintenance well is set up on the outside of the gate pier. The air inlet and outlet pipes of the airbag at the bottom of the air shield dam are led to the ground through the maintenance well and laid along the tidal river beach to the control room. The air inlet and outlet pipes are fitted with PVC sleeves and placed in a pipe trench excavated on the beach. The pipe trench is buried at a depth of more than 0.5m and is covered with a cover plate. The top of the cover plate is backfilled to the original beach elevation.

8. The method for regulating tidal currents in a tidal channel as described in claim 1, characterized in that: During floods, the regulating dam is operated in advance by collapsing to release floodwaters; after the flood has passed, the regulating dam is restored to its normal operating function.

9. A method for regulating tidal currents in a tidal channel as described in claim 2, characterized in that: During the operation of the air-supported dam, the backwater from the upstream river will not flood the riverbanks.

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