A numerical simulation method and system for water and sediment ecological geomorphological evolution considering wave-current coupling, extreme weather, and two-way feedback from vegetation dynamics.

Abstract

This invention belongs to the field of marine engineering technology and discloses a numerical simulation method and system for water and sediment ecological geomorphological evolution considering wave-current coupling, extreme weather, and bidirectional feedback of vegetation dynamics. The method includes: constructing a multi-module coupled model of hydrodynamics-wave-sediment-vegetation-topography, and setting an initial vegetation field; introducing vegetation parameters into each governing equation to characterize their influence on water flow resistance, wave dissipation, and sediment transport; introducing wave-current coupling and extreme weather forcing to simulate typhoon storm surge processes, and outputting the spatiotemporal distribution of hydrodynamic and environmental factors; updating suspended sediment transport, erosion and subsidence, and topographic evolution accordingly; simulating vegetation colonization, growth, competition, death, and lodging processes driven by hydrodynamic environmental factors; bidirectionally feeding back vegetation changes and topographic updates to each module to form a closed loop; and iteratively calculating to the termination condition to realize the simulation of the entire process of water and sediment ecological geomorphological evolution.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology, specifically relating to a numerical simulation method and system for water and sediment ecological geomorphological evolution that considers wave-current coupling, extreme weather and vegetation dynamics bidirectional feedback. Background Technology

[0002] Estuaries, deltas, and coastal wetlands are complex systems highly coupled with hydrodynamic, wave, sediment transport, aquatic environment, and vegetation processes. Their evolution is simultaneously controlled by multiple factors, including tidal currents, wind waves, storm surges, and vegetation distribution. To simulate the water, sediment, and geomorphological evolution characteristics of these areas, various numerical models have been proposed and applied. Among existing technologies, models targeting single or localized processes are relatively mature. For example, existing models can describe the impact of vegetation on water flow resistance, or simulate the wave-dissipating effect of vegetation on wave propagation and energy attenuation by introducing vegetation dissipation terms. Studies have also considered the capture and adhesion of suspended sediment by vegetation in sediment transport models. Furthermore, in ecological or water quality models, the influence of environmental factors such as nutrients and salinity on vegetation growth and survival has been characterized to some extent.

[0003] However, most of the aforementioned models focus on describing single processes or weak couplings, lacking a holistic integration of wave-current coupling, sediment transport, water environment conditions, and vegetation dynamics within a unified framework. This makes it difficult to reflect the bidirectional feedback relationships between multiple processes. Especially under extreme weather conditions such as typhoons, strong winds, high waves, and storm surges can cause damage to vegetation in a short period, such as lodging, breakage, or uprooting, significantly weakening its flow-blocking and wave-dissipating capabilities, and further affecting hydrodynamic, wave, and sediment transport processes. Current technologies lack effective methods for characterizing short-term vegetation damage and its reverse effects under extreme weather conditions.

[0004] Furthermore, the drastic changes in hydrodynamics and sediment processes under extreme weather conditions can, in turn, affect vegetation survival and recovery. Existing models often employ static or simplified vegetation parameter descriptions, making it difficult to reflect such rapid feedback mechanisms. At the same time, the coupling consideration of water environment factors such as salinity and nutrients between water-sediment models and vegetation dynamic models is relatively insufficient.

[0005] Therefore, there is an urgent need for a numerical simulation method for water and sediment ecological geomorphological evolution that can integrate wave-current coupling, extreme weather, sediment transport, water environment conditions and vegetation dynamics under a unified numerical framework, and characterize the short-term vegetation destruction and its two-way feedback process under extreme weather effects. Summary of the Invention

[0006] To address the challenges of existing numerical models for water and sediment geomorphological evolution, which struggle to integrate wave-current coupling, extreme weather, sediment transport, water environment conditions, and vegetation dynamics within a unified framework, and which fail to characterize short-term vegetation damage under extreme weather events such as typhoons and their inverse effects on hydrodynamics, waves, and sediment processes, this invention provides a numerical simulation method and system for water and sediment ecological geomorphological evolution that considers two-way feedback from wave-current coupling, extreme weather, and vegetation dynamics. This method enables strong coupling simulation of multiple processes within the same numerical framework, improving the ability to simulate the evolution of areas such as estuaries, tidal flats, and coastal wetlands under both normal and extreme weather conditions.

[0007] To achieve the above objectives, the present invention provides the following solution: A numerical simulation method for water-sediment ecological geomorphological evolution considering wave-current coupling, extreme weather, and two-way feedback from vegetation dynamics, the method comprising: S1. Construct a multi-module coupled model that includes hydrodynamics, waves, sediment transport, vegetation dynamics and bed topography evolution, and set an initial vegetation field, which includes at least the spatial distribution of vegetation height, density or coverage. S2. The initial vegetation field is introduced as a control condition into the hydrodynamic, wave and sediment transport module to characterize the influence of vegetation on water flow resistance, wave energy dissipation and sediment transport process, and to serve as the initial input condition for subsequent coupled calculations. S3. Introduce wave-current coupling mechanism and extreme weather forcing in the hydrodynamic and wave module to simulate typhoon wind field and storm surge process. Under the influence of vegetation, solve the evolution process of hydrodynamic-sediment system and simultaneously calculate and output the spatiotemporal distribution of flow velocity, water depth, bottom shear stress, wind speed, salinity and nutrient concentration. S4. Based on the hydrodynamic, wave and sediment calculation results obtained in S3, update the suspended sediment transport, erosion and settlement processes and bed topography evolution. S5. Using the flow velocity, water depth, bed shear stress, wind speed, salinity and nutrient concentration output by S3 as external influencing factors of vegetation dynamic evolution, a vegetation dynamic evolution module is constructed to simulate the colonization, growth, expansion, competition, death and lodging or uprooting of vegetation. S6. Feedback the changes in vegetation height, density or coverage caused by the dynamic changes in vegetation to the hydrodynamic, wave and sediment transport modules, and synchronously feed back the environmental change results to the vegetation dynamic evolution module, forming a two-way coupled cyclical renewal mechanism between hydrodynamics, waves, sediment, vegetation and topography. S7. Repeat steps S3 to S6 until the time termination condition is met to complete the numerical simulation of the water and sediment ecological geomorphological evolution process.

[0008] Preferably, the initial vegetation field is synchronously introduced into the hydrodynamic, wave, and sediment transport modules. The initial impact of vegetation on water flow, wave propagation, and sediment transport processes is characterized through resistance terms, wave dissipation terms, or sediment source-sink terms. Specifically: The hydrodynamic module solves for water depth and flow velocity based on two-dimensional shallow water equations. The governing equations are: ; ; ; In the formula, ▽ is the Hamiltonian operator; h For water depth; t U is time; u is the depth-averaged velocity vector; g It is the acceleration due to gravity; S The source term includes Coriolis force, bottom friction, and vegetation friction; or Water level; n The momentum diffusion coefficient; S T As a tracer, it includes salinity and temperature; n T The tracer diffusion coefficient is... T For temperature; The wave module describes wave propagation under unsteady sea states based on the wave action spectrum equation considering source and sink terms. The governing equation is: ; In the formula, N is the wave action spectral density; V is the wave propagation velocity vector; Q For source and sink terms, it represents the generation, dissipation, and redistribution of wave energy, including wave energy dissipation caused by vegetation. Q veg ; degree x,k Two-dimensional physical space x and wavenumber space k Gradient operators in a jointly constructed four-dimensional phase space; Suspended concentration C The equation is given by convection-diffusion, which also includes settling velocity. w s With turbulent diffusion coefficient n t Impact: ; In the formula, U , V The components of the depth-averaged flow velocity in the x and y directions; e s The turbulent diffusion coefficient of sediment; E For erosion flux; The variation in bed elevation is described by the Exner equation, with the source term being the deposition flux. D With erosion flux E The formula is: ; In the formula, r s The dry density of the sediment; Q mb The sediment transport rate per unit width; z b The elevation of the bed surface; q Porosity; Vegetation resistance term Source terms added to the momentum equation S Among them l This is the vegetation resistance coefficient. , C D This is the vegetation drag coefficient. m Plant density, d The diameter of the plant; The impact of vegetation on waves is through wave energy dissipation caused by vegetation. Q veg This is used to describe the feedback effect of vegetation on the wave propagation and attenuation process. α represents the relative submergence of vegetation. The mean wave number, The average natural angular frequency, m 0 The zeroth moment of the wave energy spectrum, F ( s , i () represents the two-dimensional wave energy density spectrum, which is the frequency... s and the direction of wave propagation i The function; The sediment transport module modifies the source and sink terms in the sediment transport control equation by introducing terms related to the capture and adhesion of suspended sediment by vegetation. , e For adhesion rate, u The magnitude of the flow velocity; simultaneously considering the effects of sediment gradation, sediment content, and salinity on the settling modulation effect of cohesive sediment, the settling velocity... w s Settling velocity formula for cohesive sediment , w nonco For non-cohesive sediment settling velocity, β The coefficients representing the influence of sand content and gradation are given. , ϕ v This represents the volume fraction of suspended sediment. α clayThis refers to the volume content of particles with a diameter less than 10 μm. S a This is the salinity influence coefficient. , s Salinity.

[0009] Preferably, the governing equation for the vegetation dynamic evolution module is: ; ; in, P For vegetation density, H The height of the vegetation; P est The density of vegetation resulting from planting. H estini The initial height for vegetation establishment; P growth and H growth These represent the increased density and height of vegetation due to growth, respectively. P diff The increased density of vegetation due to lateral expansion. H diff The height increase due to the lateral expansion of vegetation; P annual and H annual This represents the reduction in density and height of vegetation due to mortality during the off-season. P flow The density of vegetation reduced due to death caused by excessive water flow velocity. P inu The density of vegetation decreased due to death from prolonged flooding. P wind This refers to the reduction in vegetation density due to death caused by excessive wind speed.

[0010] Preferably, the expression for the reduction in vegetation density due to death caused by wind speed exceeding a preset value is: ; in, w wind For ambient wind speed, w death The wind speed threshold that causes vegetation death. m The attenuation coefficient; The expression for vegetation establishment is: ; in, seed This represents the probability of vegetation establishment. P 0 The initial planting density, H 0This is the initial planting height. f This is a function of environmental pressure; Mdim , Ndim ) represents the terrain grid dimension. H estini The initial height for vegetation establishment; The expression for vegetation growth is: ; ; in, dP growth and dH growth These represent the increase in vegetation density and height due to growth within the coupling time step, respectively. r 1 , r 2 These are the stable growth rates of density and height, respectively. K 1 , K 2 These are the maximum density and height, respectively. P Planting density, H For planting height, C inter This represents the vegetation competition coefficient. The expression for vegetation expansion is: ; ; In the formula, dP diff This represents the increase in vegetation density due to lateral expansion within the coupling time step. D diff This represents the vegetation expansion coefficient. dH diff The height increase of vegetation due to lateral expansion within the coupling time step.

[0011] This invention also provides a numerical simulation system for water and sediment ecological geomorphological evolution that considers wave-current coupling, extreme weather, and bidirectional feedback of vegetation dynamics. The system is used to implement the aforementioned method and includes: a model construction and vegetation initialization module, a vegetation field introduction and influence characterization module, a wave-current coupling and storm process simulation module, a sediment transport and topography renewal module, a vegetation dynamic evolution simulation module, a multi-module bidirectional feedback coupling module, and an iterative calculation and simulation termination module. The model building and vegetation initialization module is used to build a multi-module coupled model that includes hydrodynamics, waves, sediment transport, vegetation dynamics and bed topography evolution, and to set the initial vegetation field, which includes at least the spatial distribution of vegetation height, density or coverage. The vegetation field introduction and influence characterization module is used to introduce the initial vegetation field as a control condition into the hydrodynamic, wave and sediment transport module to characterize the influence of vegetation on water flow resistance, wave energy dissipation and sediment transport process, and to serve as the initial input condition for subsequent coupled calculations. The wave-current coupling and storm process simulation module is used to introduce wave-current coupling mechanism and extreme weather forcing into the hydrodynamic and wave module to simulate typhoon wind field and storm surge process. Under the influence of vegetation, it solves the evolution process of hydrodynamic-sediment system and simultaneously calculates and outputs the spatiotemporal distribution of flow velocity, water depth, bottom shear stress, wind speed, salinity and nutrient concentration. The sediment transport and topography update module is used to update suspended sediment transport, erosion and settlement processes and bed topography evolution based on the hydrodynamic, wave and sediment calculation results obtained from the wave-current coupling and storm process simulation module. The vegetation dynamic evolution simulation module is used to construct a vegetation dynamic evolution module by using the flow velocity, water depth, bed shear stress, wind speed, salinity and nutrient concentration output by the wave-current coupling and storm process simulation module as external influencing factors of vegetation dynamic evolution, and to simulate the colonization, growth, expansion, competition, death and lodging or uprooting of vegetation. The multi-module bidirectional feedback coupling module is used to feed back the changes in vegetation height, density or coverage caused by the dynamic changes in vegetation to the hydrodynamic, wave and sediment transport module, and to synchronously feed back the environmental change results to the vegetation dynamic evolution module, forming a bidirectional coupling cyclical update mechanism between hydrodynamics, waves, sediment, vegetation and topography. The iterative calculation and simulation termination module is used to repeatedly execute the wave-current coupling and storm process simulation module to the multi-module bidirectional feedback coupling module until the time termination condition is met, thereby completing the numerical simulation of the water and sediment ecological geomorphological evolution process.

[0012] Preferably, the initial vegetation field is synchronously introduced into the hydrodynamic, wave, and sediment transport modules. The initial impact of vegetation on the water flow, wave propagation, and sediment transport processes is characterized by equivalent roughness, resistance, wave dissipation, or sediment source-sink terms. Specifically: The hydrodynamic module solves for water depth and flow velocity based on two-dimensional shallow water equations. The governing equations are: ; ; ; In the formula, ▽ is the Hamiltonian operator; h For water depth; t U is time; u is the depth-averaged velocity vector; g It is the acceleration due to gravity; S The source term includes Coriolis force, bottom friction, and vegetation friction; orWater level; n The momentum diffusion coefficient; S T As a tracer, it includes salinity and temperature; n T The tracer diffusion coefficient is... T For temperature; The wave module describes wave propagation under unsteady sea states based on the wave action spectrum equation considering source and sink terms. The governing equation is: ; In the formula, N is the wave action spectral density; V is the wave propagation velocity vector; Q For source and sink terms, it represents the generation, dissipation, and redistribution of wave energy, including wave energy dissipation caused by vegetation. Q veg ; degree x,k Two-dimensional physical space x and wavenumber space k Gradient operators in a jointly constructed four-dimensional phase space; Suspended concentration C The equation is given by convection-diffusion, which also includes settling velocity. w s With turbulent diffusion coefficient n t Impact: ; In the formula, U , V The components of the depth-averaged flow velocity in the x and y directions; e s The turbulent diffusion coefficient of sediment; E For erosion flux; The variation in bed elevation is described by the Exner equation, with the source term being the deposition flux. D With erosion flux E The formula is: ; In the formula, r s The dry density of the sediment; Q mb The sediment transport rate per unit width; z b The elevation of the bed surface; q Porosity; Vegetation resistance term Source terms added to the momentum equation S Among them l This is the vegetation resistance coefficient. , CD This is the vegetation drag coefficient. m Plant density, d The diameter of the plant; The impact of vegetation on waves is through wave energy dissipation caused by vegetation. Q veg This is used to describe the feedback effect of vegetation on the wave propagation and attenuation process. α represents the relative submergence of vegetation. The mean wave number, The average natural angular frequency, m 0 The zeroth moment of the wave energy spectrum, F ( s , i () represents the two-dimensional wave energy density spectrum, which is the frequency... s and the direction of wave propagation i The function; The sediment transport module modifies the source and sink terms in the sediment transport control equation by introducing terms related to the capture and adhesion of suspended sediment by vegetation. , e For adhesion rate, u The magnitude of the flow velocity; simultaneously considering the effects of sediment gradation, sediment content, and salinity on the settling modulation effect of cohesive sediment, the settling velocity... w s Settling velocity formula for cohesive sediment , w nonco For non-cohesive sediment settling velocity, β The coefficients representing the influence of sand content and gradation are given. , ϕ v This represents the volume fraction of suspended sediment. α clay This refers to the volume content of particles with a diameter less than 10 μm. S a This is the salinity influence coefficient. , s Salinity.

[0013] Preferably, the governing equation for the vegetation dynamic evolution module is: ; ; in, P For vegetation density, H The height of the vegetation; P est The density of vegetation resulting from planting. H estini The initial height for vegetation establishment; P growth andH growth These represent the increased density and height of vegetation due to growth, respectively. P diff The increased density of vegetation due to lateral expansion. H diff The height increase due to the lateral expansion of vegetation; P annual and H annual This represents the reduction in density and height of vegetation due to mortality during the off-season. P flow The density of vegetation reduced due to death caused by excessive water flow velocity. P inu The density of vegetation decreased due to death from prolonged flooding. P wind This refers to the reduction in vegetation density due to death caused by excessive wind speed.

[0014] Preferably, the expression for the reduction in vegetation density due to death caused by wind speed exceeding a preset value is: ; in, w wind For ambient wind speed, w death The wind speed threshold that causes vegetation death. m The attenuation coefficient; The expression for vegetation establishment is: ; in, seed This represents the probability of vegetation establishment. P 0 The initial planting density, H 0 This is the initial planting height. f The environmental stress function is denoted by (Mdim, Ndim), which represents the terrain grid dimension, and Hestini represents the initial height of vegetation establishment. The expression for vegetation growth is: ; ; in, dP growth and dH growth These represent the increase in vegetation density and height due to growth within the coupling time step, respectively. r 1 , r 2 These are the stable growth rates of density and height, respectively. K 1 ,K 2 These are the maximum density and height, respectively. P Planting density, H For planting height, C inter This represents the vegetation competition coefficient. The expression for vegetation expansion is: ; ; In the formula, dP diff This represents the increase in vegetation density due to lateral expansion within the coupling time step. D diff This represents the vegetation expansion coefficient. dH diff The height increase of vegetation due to lateral expansion within the coupling time step.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention integrates wave-current coupling, extreme weather, sediment transport, aquatic environmental conditions, and vegetation dynamics, enabling the characterization of vegetation's feedback to hydrodynamic, wave, and sediment processes. Furthermore, it considers short-term vegetation damage and its reverse effects under extreme weather conditions, achieving bidirectional coupling simulation between multiple processes. This method is applicable to estuaries, deltas, tidal flats, and coastal wetlands, significantly improving the completeness and reliability of water and sediment ecological geomorphological evolution simulations under both normal and extreme weather conditions. Attached Figure Description

[0016] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a numerical simulation method for water and sediment ecological geomorphological evolution that considers wave-current coupling, extreme weather and vegetation dynamics bidirectional feedback, according to an embodiment of the present invention. Figure 2 These are ideal tidal flat topographic maps and initial vegetation distribution maps of embodiments of the present invention, wherein (a) is an initial topographic diagram and (b) is an initial vegetation distribution diagram; Figure 3 This is a comparison diagram of vegetation density changes before and after a typhoon according to an embodiment of the present invention, wherein (a) is a schematic diagram before the typhoon and (b) is a schematic diagram after the typhoon. Figure 4 This is a diagram of siltation after a typhoon, according to an embodiment of the present invention. Detailed Implementation

[0018] 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, and 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.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Example 1 This invention provides a numerical simulation method for hydro-sediment ecological geomorphological evolution considering wave-current coupling, extreme weather, and two-way feedback from vegetation dynamics. The method is applicable to areas such as estuaries, deltas, tidal flats, and coastal wetlands, and is used to simulate the evolution of the vegetation-hydrodynamic-sediment-topography system under normal and extreme weather conditions. The method includes: S1. Construct a multi-module coupled model that includes hydrodynamics, waves, sediment transport, vegetation dynamics and bed topography evolution, and set an initial vegetation field, which includes at least the spatial distribution of vegetation height, density or coverage. S2. The initial vegetation field is introduced as a control condition into the hydrodynamic, wave and sediment transport module to characterize the influence of vegetation on water flow resistance, wave energy dissipation and sediment transport process, and to serve as the initial input condition for subsequent coupled calculations. S3. Introduce wave-current coupling mechanism and extreme weather forcing in the hydrodynamic and wave module to simulate typhoon wind field and storm surge process. Under the influence of vegetation, solve the evolution process of hydrodynamic-sediment system and simultaneously calculate and output the spatiotemporal distribution of flow velocity, water depth, bottom shear stress, wind speed, salinity and nutrient concentration. S4. Based on the hydrodynamic, wave and sediment calculation results obtained in S3, update the suspended sediment transport, erosion and settlement processes and bed topography evolution. S5. Using the flow velocity, water depth, bed shear stress, wind speed, salinity and nutrient concentration output by S3 as external influencing factors of vegetation dynamic evolution, a vegetation dynamic evolution module is constructed to simulate the colonization, growth, expansion, competition, death and lodging or uprooting of vegetation. S6. Feedback the changes in vegetation height, density or coverage caused by the dynamic changes in vegetation to the hydrodynamic, wave and sediment transport modules, and synchronously feed back the results of environmental changes such as water depth and flow velocity to the vegetation dynamic evolution module, forming a two-way coupled cyclical renewal mechanism between hydrodynamics, waves, sediment, vegetation and topography. S7. Repeat steps S3 to S6 until the time termination condition is met to complete the numerical simulation of the water and sediment ecological geomorphological evolution process.

[0021] like Figure 1 As shown, the specific implementation process is as follows: S1. Construct a multi-module coupled model that includes hydrodynamics, waves, sediment transport, vegetation dynamics, and bed topography changes, and set an initial vegetation field, which includes at least spatial distribution information of vegetation height, density, or coverage. In the multi-module coupled model, the direct interaction between the hydrodynamic module and the wave module achieves bidirectional dynamic coupling of wave-current interaction: within each computation time step, the hydrodynamic module updates the current flow velocity (U,V) and water depth (U,V) at the current time step. h The data is transmitted to the wave module; the wave module uses the received flow velocity and water depth as background field conditions to solve the wave action conservation equation. The wave module calculates the wave driving force acting on the water flow (wave radiation stress gradient F). x ,F y The updated wave-driving force is then used as a momentum source term and passed back to the control equations of the hydrodynamic module.

[0022] The hydrodynamic module, wave module, and vegetation dynamic evolution module are bidirectionally coupled: hydrodynamic parameters (flow velocity, submerged water depth) and wave parameters (wave height) are input to the vegetation dynamic evolution module to determine the physical damage, lodging, or extinction status of vegetation and update vegetation parameters (vegetation height). H and vegetation density P The updated vegetation morphology parameters are converted into fluid drag force and fed back as a drag term into the momentum equation of the hydrodynamic module, thus achieving the vegetation's impediment to the water flow. Simultaneously, the vegetation parameters are synchronously transmitted to the wave module, which calculates the vegetation energy dissipation term when solving the wave action conservation equation. Q veg Quantify the attenuation of wave energy by vegetation.

[0023] The maximum bed shear force under the combined action of wave and current is calculated from the bottom velocity of the wave and the bottom velocity of the current. The data is input to the sediment transport module. This module calculates the suspended sediment concentration field by solving the suspended sediment convection-diffusion equation. Simultaneously, it calculates the vegetation sediment sink term based on updated vegetation parameters input from the vegetation evolution module, and also considers the bed shear force. The relationship with the critical initiation shear stress of sediment is used to calculate the scour flux and sedimentation flux of sediment, as well as the bedload transport rate. The bed elevation change is updated using the Exner topographic evolution equation and fed back to the hydrodynamic and wave modules to solve for the wave field and flow field in the next time step.

[0024] S2. At the initial moment of the model, the initial field of vegetation is synchronously introduced into the hydrodynamic, wave and sediment transport module. The initial influence of vegetation on the process of water flow, wave propagation and sediment transport is characterized by means of resistance term, wave dissipation term or sediment source and sink term. The hydrodynamic module solves for water depth and flow velocity based on two-dimensional shallow water equations. The governing equations are as follows: In the formula, ▽ is the Hamiltonian operator; h For water depth; t U is time; u is the depth-averaged velocity vector; g It is the acceleration due to gravity; S The source term includes Coriolis force, bottom friction, vegetation friction, etc. or Water level; n The momentum diffusion coefficient; S T As a tracer, such as salinity, temperature, etc.; n T The tracer diffusion coefficient is... T For temperature.

[0025] The wave module describes wave propagation under unsteady sea states based on the wave action spectrum equation considering source and sink terms. The governing equations are as follows: In the formula, N is the wave action spectral density; V is the wave propagation velocity vector; Q For source and sink terms, it represents the generation, dissipation, and redistribution of wave energy, including wave energy dissipation caused by vegetation. Q veg ; degree x,k Two-dimensional physical space x and wavenumber space k Gradient operators in a four-dimensional phase space formed by the joint operation.

[0026] Suspended concentration C The equation is given by convection-diffusion, which also includes settling velocity. w s With turbulent diffusion coefficient n t Impact: In the formula, U , V The components of the depth-averaged flow velocity in the x and y directions; e s The turbulent diffusion coefficient of sediment;E For erosion flux, the Partheniades formula is used for calculation as follows: ,in M To flush the Kron-Paternades law constant, t b The shear stress on the bed surface. t ce The critical erosion shear stress of the bed surface; D For siltation flux, ,in w s For sediment settling speed, C Zref This is the reference concentration of sediment near the bottom.

[0027] The variation in bed elevation is described by the Exner equation, with the source term being the deposition flux. D With erosion flux E The Krone and Partheniades formulas are used respectively: In the formula, r s The dry density of the sediment; Q mb The sediment transport rate per unit width; z b The elevation of the bed surface; q Porosity.

[0028] The vegetation resistance term Source terms added to the momentum equation S Among them l This is the vegetation resistance coefficient. , C D This is the vegetation drag coefficient. m Plant density, d The diameter of the plant.

[0029] The impact of vegetation on waves is through wave energy dissipation caused by vegetation. Q veg This is used to describe the feedback effect of vegetation on the wave propagation and attenuation process. α represents the relative submergence of vegetation. The mean wave number, The average natural angular frequency, m 0 The zeroth moment of the wave energy spectrum, F ( s , i () represents the two-dimensional wave energy density spectrum, which is the frequency... s and the direction of wave propagation iThe function.

[0030] The sediment transport module modifies the source and sink terms in the sediment transport control equation by introducing terms related to the capture and adhesion of suspended sediment by vegetation. , e For adhesion rate, u The magnitude of the flow velocity is considered. The settling modulation effect of cohesive sediment, influenced by sediment gradation, sediment content, and salinity, is also taken into account. w s Settling velocity formula for cohesive sediment , w nonco For non-cohesive sediment settling velocity, β The coefficients representing the influence of sand content and gradation are given. , ϕ v This represents the volume fraction of suspended sediment. α clay This refers to the volume content of particles with a diameter less than 10 μm. S a This is the salinity influence coefficient. , s Salinity.

[0031] S3. Introduce wave-current coupling mechanism and extreme weather forcing conditions into the hydrodynamic and wave module to simulate typhoon waves and storm surge processes. The hydrodynamic module calculates and outputs the spatiotemporal distribution of environmental variables such as flow velocity, water depth, bed shear stress, wind speed, salinity and nutrient concentration. The wave-current coupling effect is as follows: within each computation time step, the hydrodynamic module updates the current flow velocity (U,V) and water depth (U,V) at the current time step. h The data is transmitted to the wave module; the wave module uses the received flow velocity and water depth as background field conditions, and solves the wave action conservation equation using the method of characteristics and the finite element method. Based on the obtained two-dimensional directional wave spectrum, and combined with linear wave theory, the wave module obtains the wave momentum flux per unit horizontal area by integrating the frequency and wave direction across the entire frequency band and in all directions, and then applies it to... x Taking the spatial partial derivative in the y-direction, we obtain the wave driving force acting on the water flow (wave radiation stress gradient F). x ,F y The updated wave-driving force is then used as a momentum source term and passed back to the control equations of the hydrodynamic module.

[0032] The extreme weather forcing condition is to use the strong wind field during typhoon waves and storm surges as the driving force for the hydrodynamic module and wave module, which is reflected in the wind resistance term of the momentum equation and the wind and wave generation source term of the wave control equation, respectively.

[0033] The expression for wind resistance is: In the formula, Fx and Fy These represent wind resistance in the x and y directions, respectively. pair air density; Density of water; awind The wind drag coefficient; Uwind and Vwind These are the wind speed vectors in the x and y directions, respectively.

[0034] The expression for the source term of wind and waves is: In the formula, Q in For the generation of wind and waves; s The angular frequency of the wave; e The air-to-water density ratio; β The dimensionless wind and wave growth coefficient; u The speed of wind friction; C The wave phase velocity; z a This is the empirical offset.

[0035] S4. Based on the calculation results of step S3, the suspended sediment concentration is calculated in the sediment transport module according to the suspended sediment convection diffusion equation, the sedimentation flux and erosion flux are calculated, the suspended sediment transport, erosion and deposition processes are updated, and the bed topography evolution is calculated through the Exner equation to achieve the coordinated updating of hydrodynamic-wave-sediment-topography processes. S5. Using the flow velocity, water depth, bed shear stress, wind speed, salinity, and nutrient concentration output from step S3 as external influencing factors for vegetation dynamic evolution, a vegetation dynamic evolution module is constructed based on population dynamics to simulate processes such as vegetation colonization, growth, expansion, competition, death, and lodging or uprooting. The vegetation dynamic evolution module is modulated by an environmental pressure function, which includes a salinity function, a nutrient function, and an interspecific competition coefficient, used to comprehensively characterize the constraining effect of environmental conditions on the vegetation evolution process. The expression for the salinity function is as follows: In the formula, s The average salinity of the water column. v sop For optimal growth salinity, v scr This is the critical coefficient for salinity stress.

[0036] The nutrient function expression is as follows: In the formula, bNP The concentrations of ammonium salts and phosphates, v kNP is the half-saturation constant of ammonium salts and phosphates in vegetation.

[0037] The expression for the interspecific competition coefficient is as follows: In the formula, C inter This represents the vegetation competition coefficient. C light The light competition coefficient, a These are vegetation shape parameters. AL For effective light intensity, b The minimum light intensity required for vegetation; C resource This is the spatial competition coefficient. d 2 The vegetation sensitivity coefficient, f r To determine the proportion of effective resources, c It is the half-saturation constant.

[0038] The governing equations for the vegetation dynamics evolution module are as follows: in, P For vegetation density, H The height of the vegetation; P est The density of vegetation resulting from planting. H estini The initial height for vegetation establishment; P growth and H growth These represent the increased density and height of vegetation due to growth, respectively. P diff The increased density of vegetation due to lateral expansion. H diff The height increase due to the lateral expansion of vegetation; P annual and H annual This represents the reduction in density and height of vegetation due to mortality during the off-season. P flow The density of vegetation reduced due to death caused by excessive water flow velocity. P inu The density of vegetation decreased due to death from prolonged flooding. Pwind This refers to the reduction in vegetation density due to death caused by excessive wind speed.

[0039] When the flow velocity or the bed shear stress calculated from it exceeds the vegetation tolerance threshold, the vegetation damage, lodging or uprooting criteria are triggered, and the vegetation height or coverage in the corresponding area is reduced; when the water depth exceeds the vegetation tolerance water depth threshold and continues for more than a preset time, the vegetation submersion and death process is triggered.

[0040] Under extreme weather conditions, when the wind speed exceeds the vegetation wind resistance threshold, the dynamic evolution of vegetation simultaneously triggers the process of vegetation lodging or uprooting, and in turn affects hydrodynamic resistance, wave dissipation and sediment transport processes through changes in vegetation parameters.

[0041] The expression for the decrease in vegetation density due to death caused by excessive wind speed is: In the formula, w wind For ambient wind speed, w death The wind speed threshold that causes vegetation death. m This is the attenuation coefficient.

[0042] The expression for vegetation establishment is: In the formula, seed This represents the probability of vegetation establishment. P 0 The initial planting density, H 0 This is the initial planting height. f For environmental pressure function, ( Mdim , Ndim ) represents the terrain grid dimension. H estini The initial height for planting vegetation.

[0043] The expression for vegetation growth is: In the formula, dP growth and dH growth These represent the increase in vegetation density and height due to growth within the coupling time step, respectively. r 1 , r 2 These are the stable growth rates of density and height, respectively. K 1 , K 2These are the maximum density and height, respectively. P Planting density, H This refers to the planting height.

[0044] The expression for vegetation expansion is: In the formula, dP diff This represents the increase in vegetation density due to lateral expansion within the coupling time step. D diff This represents the vegetation expansion coefficient. dH diff The height increase of vegetation due to lateral expansion within the coupling time step.

[0045] S6. Input the changes in vegetation height, density, and spatial distribution caused by the dynamic evolution of vegetation into the hydrodynamics, wave, and sediment transport modules, and update the vegetation resistance term in the momentum equation. Fv Vegetation dissipation term in wave control equations Q veg Vegetation adhesion item in sediment transport module D trap Continue to perform hydrodynamic, wave, and sediment calculations for new coupled time steps, and synchronously feed back environmental pressure change data such as water depth, flow velocity, salinity, nutrients, and wind speed to the vegetation dynamic evolution module to form a two-way coupled cyclical update mechanism between hydrodynamics, waves, sediment, vegetation, and topography. S7. Repeat steps S3 to S6 until the time termination condition is met to complete the numerical simulation of the water and sediment ecological geomorphological evolution process.

[0046] Specifically, such as Figure 1 As shown, this embodiment specifically includes the following steps: Step (1): Construct a two-dimensional numerical model of the computational domain, set the computational grid, initial topography and tidal dynamic boundary conditions, set the wind field that changes over time, and establish a coupled computational module for hydrodynamics, waves, sediment transport and bed topography evolution. Step (2) Set up the initial vegetation field, which includes vegetation species and vegetation distribution, and is used to correct the equivalent roughness, resistance term, wave dissipation term and sediment source and sink. Step (3) introduces a wave-current coupling mechanism to simulate wind waves, storm surges and tidal currents under extreme weather conditions such as typhoons, solves hydrodynamic and wave control equations, and obtains the spatiotemporal distribution of flow velocity, water level, water depth and wave elements. Step (4): Based on the hydrodynamic and wave calculation results of step (3), calculate the sediment transport process, update the suspended sediment concentration, erosion and deposition flux, and update the bed topography simultaneously. At the same time, calculate and output environmental variables such as bed shear stress, wind speed, salinity and nutrient concentration until a coupling time step is completed, and exchange data with the vegetation dynamic evolution module. Step (5): Using the environmental variables output in step (4) as environmental pressure influencing factors, calculate the vegetation establishment, growth, lateral expansion, interspecific competition and mortality processes based on population dynamics. Step (6) introduces vegetation damage criteria under extreme weather conditions in step (5). When the flow velocity or bed shear stress exceeds the vegetation tolerance threshold, the vegetation damage, lodging or uprooting process is triggered; when the water depth exceeds the vegetation tolerance water depth threshold and continues for more than a preset time, the vegetation submersion and death process is triggered; when the wind speed exceeds the vegetation wind resistance threshold, the vegetation lodging or uprooting process is triggered, and the vegetation height, density or spatial distribution of the corresponding area is updated. Step (7) feeds back the updated vegetation parameters to the hydrodynamic, wave and sediment transport module, and feeds back the results of bed topography changes to the vegetation dynamic evolution module. Step (8) determines whether the time termination condition is met. If it is met, the calculation ends; if it is not met, the time advances to the next coupled time step and returns to step (3) to form a two-way coupled cyclic update process of hydrodynamics-waves-sediment-vegetation-topography.

[0047] The hydrodynamic module is used to output information on flow velocity, water depth, salinity and nutrient concentration; the wave module is used to output wave elements; the sediment transport module is used to output suspended sediment concentration and erosion deposition; and the vegetation dynamic evolution module is used to output the spatiotemporal distribution of vegetation height and density.

[0048] In this embodiment, the influence of vegetation on hydrodynamics is characterized by the equivalent roughness or drag coefficient, the influence of vegetation on waves is characterized by the wave energy dissipation term, and the influence of vegetation on sediment is characterized by the source and sink terms in the sediment transport control equation.

[0049] This implementation uses an ideal rectangular tidal flat as an example to specifically describe a numerical simulation method for water and sediment ecological geomorphological evolution that considers wave-current coupling and bidirectional feedback between extreme weather and vegetation dynamics, as follows: The ideal rectangular tidal flat is set as a regular rectangular calculation region, and the initial bed topography is set as approximately flat or gently sloping terrain. Tidal dynamic boundary conditions are applied at the boundary of the calculation region, and a wind field that varies with the typhoon process is set to simulate the tidal current, wind waves, and storm surge processes during typhoon landfall or nearshore impact. An initial vegetation field is set for the tidal flat area, which includes vegetation species and their spatial distribution characteristics. This initial vegetation field is introduced into the hydrodynamic, wave, and sediment transport calculation process to correct for equivalent roughness, drag, wave dissipation, and sediment source and sink. The model calculates a continuous short-term process before and after the typhoon's impact. Within each coupled time step, it solves the hydrodynamic and wave control equations through wave-current coupling calculations to obtain the spatiotemporal evolution characteristics of current velocity, water level, water depth, and wave elements in the tidal flat area during the typhoon process. Based on the hydrodynamic and wave calculation results during the typhoon, it simultaneously calculates the sediment transport process, updates suspended sediment concentration, erosion and deposition fluxes, and bed topography, and outputs environmental variables such as bed shear stress, wind speed, salinity, and nutrient concentration, exchanging data with the vegetation dynamic evolution module. The dynamic evolution module uses the environmental variables as environmental pressure influencing factors to characterize the short-term response processes of vegetation damage and uprooting during typhoons, and calculates vegetation state changes within the short timescale. Under extreme weather conditions such as typhoons, when the flow velocity or bed shear stress exceeds the vegetation tolerance threshold, vegetation damage, lodging, or uprooting processes are triggered; when the water depth exceeds the vegetation tolerance water depth threshold and persists for more than a preset time, vegetation submersion and death processes are triggered; when the wind speed exceeds the vegetation wind resistance threshold, vegetation lodging or uprooting processes are triggered, and the vegetation height in the tidal flat area is updated accordingly. The vegetation parameters obtained after the typhoon are updated are fed back to the hydrodynamic, wave, and sediment transport modules, and the results of the bed topography change are simultaneously fed back to the vegetation dynamic evolution module to correct the hydrodynamic resistance, wave dissipation, and sediment transport during the typhoon and its subsequent short-term processes. After one coupled time step is completed, the time is advanced to the next time step, and the above calculation process is repeated until the preset typhoon process time termination condition is met, thereby completing the short-term water-sediment-vegetation-topography coupled evolution numerical simulation of the ideal rectangular tidal flat during the typhoon.

[0050] The initial topography and initial vegetation field of an ideal tidal flat, such as Figure 2 As shown, the simulation results are as follows Figure 3-4 As shown.

[0051] Figure 3 This is a comparison of the spatial distribution of vegetation density before and after a typhoon in an embodiment of the present invention. Figure 3It is evident that the vegetation distribution and density within the study area underwent significant changes after the typhoon. Specifically, areas with deeper waters near the coast experienced prolonged high water levels and severe flooding during the typhoon, resulting in significant submersion pressure on the vegetation. Vegetation density decreased markedly in some areas, and vegetation even disappeared in others. Simultaneously, the strong winds (in this embodiment, a time-varying uniform wind field was used to simulate the typhoon wind field) subjected the vegetated areas to substantial wind loads, leading to vegetation lodging or damage, thus causing an overall reduction in vegetation density compared to before the typhoon. Figure 4 This presents the results of bed erosion and deposition evolution in the study area after the typhoon. Figure 4 It is evident that under the influence of strong winds, waves, and enhanced hydrodynamics caused by the typhoon, the seabed in the study area was primarily characterized by scouring. Significant differences in scouring and deposition characteristics were observed across different regions, and alterations in vegetation further impacted the scouring and deposition patterns. The nearshore area, affected by strong currents and waves, exhibited particularly pronounced scouring in areas where vegetation had disappeared. Conversely, areas with less vegetation damage showed deposition characteristics due to the wave-damping and flow-blocking effects of the vegetation.

[0052] Example 2 This invention also provides a numerical simulation system for water and sediment ecological geomorphological evolution that considers wave-current coupling, extreme weather, and bidirectional feedback of vegetation dynamics. The system is used to implement the method described in Embodiment 1. The system includes: a model construction and vegetation initialization module, a vegetation field introduction and influence characterization module, a wave-current coupling and storm process simulation module, a sediment transport and topography renewal module, a vegetation dynamic evolution simulation module, a multi-module bidirectional feedback coupling module, and an iterative calculation and simulation termination module. The model building and vegetation initialization module is used to build a multi-module coupled model that includes hydrodynamics, waves, sediment transport, vegetation dynamics and bed topography evolution, and to set the initial vegetation field, which includes at least the spatial distribution of vegetation height, density or coverage. The vegetation field introduction and influence characterization module is used to introduce the initial vegetation field as a control condition into the hydrodynamic, wave and sediment transport module to characterize the influence of vegetation on water flow resistance, wave energy dissipation and sediment transport process, and to serve as the initial input condition for subsequent coupled calculations. The wave-current coupling and storm process simulation module is used to introduce wave-current coupling mechanism and extreme weather forcing into the hydrodynamic and wave module to simulate typhoon wind field and storm surge process. Under the influence of vegetation, it solves the evolution process of hydrodynamic-sediment system and simultaneously calculates and outputs the spatiotemporal distribution of flow velocity, water depth, bottom shear stress, wind speed, salinity and nutrient concentration. The sediment transport and topography update module is used to update suspended sediment transport, erosion and settlement processes and bed topography evolution based on the hydrodynamic, wave and sediment calculation results obtained from the wave-current coupling and storm process simulation module. The vegetation dynamic evolution simulation module is used to construct a vegetation dynamic evolution module by using the flow velocity, water depth, bed shear stress, wind speed, salinity and nutrient concentration output by the wave-current coupling and storm process simulation module as external influencing factors of vegetation dynamic evolution, and to simulate the colonization, growth, expansion, competition, death and lodging or uprooting of vegetation. The multi-module bidirectional feedback coupling module is used to feed back the changes in vegetation height, density or coverage caused by the dynamic changes in vegetation to the hydrodynamic, wave and sediment transport module, and to synchronously feed back the environmental change results to the vegetation dynamic evolution module, forming a bidirectional coupling cyclical update mechanism between hydrodynamics, waves, sediment, vegetation and topography. The iterative calculation and simulation termination module is used to repeatedly execute the wave-current coupling and storm process simulation module to the multi-module bidirectional feedback coupling module until the time termination condition is met, thereby completing the numerical simulation of the water and sediment ecological geomorphological evolution process.

[0053] In this embodiment, the initial vegetation field is synchronously introduced into the hydrodynamic, wave, and sediment transport modules. The initial impact of vegetation on the water flow, wave propagation, and sediment transport processes is characterized by equivalent roughness, resistance, wave dissipation, or sediment source-sink terms. Specifically: The hydrodynamic module solves for water depth and flow velocity based on two-dimensional shallow water equations. The governing equations are: ; ; ; In the formula, ▽ is the Hamiltonian operator; h For water depth; t U is time; u is the depth-averaged velocity vector; g It is the acceleration due to gravity; S The source term includes Coriolis force, bottom friction, and vegetation friction; or Water level; n The momentum diffusion coefficient; S T As a tracer, it includes salinity and temperature; n T The tracer diffusion coefficient is... T For temperature; The wave module describes wave propagation under unsteady sea states based on the wave action spectrum equation considering source and sink terms. The governing equation is: ; In the formula, N is the wave action spectral density; V is the wave propagation velocity vector; Q For source and sink terms, it represents the generation, dissipation, and redistribution of wave energy, including wave energy dissipation caused by vegetation. Qveg ; degree x,k Two-dimensional physical space x and wavenumber space k Gradient operators in a jointly constructed four-dimensional phase space; Suspended concentration C The equation is given by convection-diffusion, which also includes settling velocity. w s With turbulent diffusion coefficient n t Impact: ; In the formula, U , V The components of the depth-averaged flow velocity in the x and y directions; e s The turbulent diffusion coefficient of sediment; E For erosion flux; The variation in bed elevation is described by the Exner equation, with the source term being the deposition flux. D With erosion flux E The formula is: ; In the formula, r s The dry density of the sediment; Q mb The sediment transport rate per unit width; z b The elevation of the bed surface; q Porosity; Vegetation resistance term Source terms added to the momentum equation S Among them l This is the vegetation resistance coefficient. , C D This is the vegetation drag coefficient. m Plant density, d Where is the diameter of the plant, and u is the water flow velocity; The impact of vegetation on waves is through wave energy dissipation caused by vegetation. Q veg This is used to describe the feedback effect of vegetation on the wave propagation and attenuation process. α represents the relative submergence of vegetation. The mean wave number, The average natural angular frequency, m 0 The zeroth moment of the wave energy spectrum, F ( s , i() represents the two-dimensional wave energy density spectrum, which is the frequency... s and the direction of wave propagation i The function; The sediment transport module modifies the source and sink terms in the sediment transport control equation by introducing terms related to the capture and adhesion of suspended sediment by vegetation. , e For adhesion rate, u The magnitude of the flow velocity; simultaneously considering the effects of sediment gradation, sediment content, and salinity on the settling modulation effect of cohesive sediment, the settling velocity... w s Settling velocity formula for cohesive sediment , w nonco For non-cohesive sediment settling velocity, β The coefficients representing the influence of sand content and gradation are given. , ϕ v This represents the volume fraction of suspended sediment. α clay This refers to the volume content of particles with a diameter less than 10 μm. S a This is the salinity influence coefficient. , s Salinity.

[0054] In this embodiment, the control equation for the vegetation dynamic evolution module is: ; ; in, P For vegetation density, H The height of the vegetation; P est The density of vegetation resulting from planting. H estini The initial height for vegetation establishment; P growth and H growth These represent the increased density and height of vegetation due to growth, respectively. P diff The increased density of vegetation due to lateral expansion. H diff The height increase due to the lateral expansion of vegetation; P annual and H annual This represents the reduction in density and height of vegetation due to mortality during the off-season. P flow The density of vegetation reduced due to death caused by excessive water flow velocity. P inu The density of vegetation decreased due to death from prolonged flooding.P wind This refers to the reduction in vegetation density due to death caused by excessive wind speed.

[0055] In this embodiment, the expression for the reduction in vegetation density due to death caused by wind speed exceeding a preset value is: ; in, w wind For ambient wind speed, w death The wind speed threshold that causes vegetation death. m The attenuation coefficient; The expression for vegetation establishment is: ; in, seed This represents the probability of vegetation establishment. P 0 The initial planting density, H 0 This is the initial planting height. f This is a function of environmental pressure; Mdim , Ndim ) represents the terrain grid dimension. H estini The initial height for vegetation establishment; The expression for vegetation growth is: ; ; in, dP growth and dH growth These represent the increase in vegetation density and height due to growth within the coupling time step, respectively. r 1 , r 2 These are the stable growth rates of density and height, respectively. K 1 , K 2 These are the maximum density and height, respectively. P Planting density, H For planting height, C inter This represents the vegetation competition coefficient. The expression for vegetation expansion is: ; ; In the formula, dP diff This represents the increase in vegetation density due to lateral expansion within the coupling time step. Ddiff This represents the vegetation expansion coefficient. dH diff The height increase of vegetation due to lateral expansion within the coupling time step.

[0056] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A numerical simulation method for water and sediment ecological geomorphological evolution considering wave-current coupling and bidirectional feedback between extreme weather and vegetation dynamics, characterized in that, The method includes: S1. Construct a multi-module coupled model that includes hydrodynamics, waves, sediment transport, vegetation dynamics and bed topography evolution, and set an initial vegetation field, which includes at least the spatial distribution of vegetation height, density or coverage. S2. The initial vegetation field is introduced as a control condition into the hydrodynamic, wave and sediment transport module to characterize the influence of vegetation on water flow resistance, wave energy dissipation and sediment transport process, and to serve as the initial input condition for subsequent coupled calculations. S3. Introduce wave-current coupling mechanism and extreme weather forcing in the hydrodynamic and wave module to simulate typhoon wind field and storm surge process. Under the influence of vegetation, solve the evolution process of hydrodynamic-sediment system and simultaneously calculate and output the spatiotemporal distribution of flow velocity, water depth, bottom shear stress, wind speed, salinity and nutrient concentration. S4. Based on the hydrodynamic, wave and sediment calculation results obtained in S3, update the suspended sediment transport, erosion and settlement processes and bed topography evolution. S5. Using the flow velocity, water depth, bed shear stress, wind speed, salinity and nutrient concentration output by S3 as external influencing factors of vegetation dynamic evolution, a vegetation dynamic evolution module is constructed to simulate the colonization, growth, expansion, competition, death and lodging or uprooting of vegetation. S6. Feedback the changes in vegetation height, density or coverage caused by the dynamic changes in vegetation to the hydrodynamic, wave and sediment transport modules, and synchronously feed back the environmental change results to the vegetation dynamic evolution module, forming a two-way coupled cyclical renewal mechanism between hydrodynamics, waves, sediment, vegetation and topography. S7. Repeat steps S3 to S6 until the time termination condition is met to complete the numerical simulation of the water and sediment ecological geomorphological evolution process.

2. The method according to claim 1, characterized in that, The initial vegetation field is synchronously introduced into the hydrodynamic, wave, and sediment transport modules. The initial impact of vegetation on water flow, wave propagation, and sediment transport processes is characterized through resistance terms, wave dissipation terms, or sediment source-sink terms. Specifically: The hydrodynamic module solves for water depth and flow velocity based on two-dimensional shallow water equations. The governing equations are: ； ； ； In the formula, ▽ is the Hamiltonian operator; h For water depth; t U is time; u is the depth-averaged velocity vector; g It is the acceleration due to gravity; S The source term includes Coriolis force, bottom friction, and vegetation friction; η Water level; ν The momentum diffusion coefficient; S T As a tracer, it includes salinity and temperature; ν T The tracer diffusion coefficient is... T For temperature; The wave module describes wave propagation under unsteady sea states based on the wave action spectrum equation considering source and sink terms. The governing equation is: ； In the formula, N is the wave action spectral density; V is the wave propagation velocity vector; Q For source and sink terms, it represents the generation, dissipation, and redistribution of wave energy, including wave energy dissipation caused by vegetation. Q veg ; grad x,k Two-dimensional physical space x and wavenumber space k Gradient operators in a jointly constructed four-dimensional phase space; Suspended concentration C The equation is given by convection-diffusion, which also includes settling velocity. w s With turbulent diffusion coefficient ν t Impact: ； In the formula, U , V The components of the depth-averaged flow velocity in the x and y directions; ε s The turbulent diffusion coefficient of sediment; E For erosion flux; The variation in bed elevation is described by the Exner equation, with the source term being the deposition flux. D With erosion flux E The formula is: ； In the formula, ρ s The dry density of the sediment; Q mb The sediment transport rate per unit width; z b The elevation of the bed surface; q Porosity; Vegetation resistance term Source terms added to the momentum equation S Among them λ This is the vegetation resistance coefficient. , C D This is the vegetation drag coefficient. m Plant density, d The diameter of the plant; The impact of vegetation on waves is through wave energy dissipation caused by vegetation. Q veg This is used to describe the feedback effect of vegetation on the wave propagation and attenuation process. α represents the relative submergence of vegetation. The mean wave number, The average natural angular frequency, m 0 The zeroth moment of the wave energy spectrum, F ( σ , θ () represents the two-dimensional wave energy density spectrum, which is the frequency... σ and the direction of wave propagation θ The function; The sediment transport module modifies the source and sink terms in the sediment transport control equation by introducing terms related to the capture and adhesion of suspended sediment by vegetation. , ε For adhesion rate, u The magnitude of the flow velocity; simultaneously considering the effects of sediment gradation, sediment content, and salinity on the settling modulation effect of cohesive sediment, the settling velocity... w s Settling velocity formula for cohesive sediment , w nonco For non-cohesive sediment settling velocity, β The coefficients representing the influence of sand content and gradation are given. , ϕ v This represents the volume fraction of suspended sediment. α clay This refers to the volume content of particles with a diameter less than 10 μm. S a This is the salinity influence coefficient. , s Salinity.

3. The method according to claim 2, characterized in that, The governing equations for the vegetation dynamics evolution module are: ； ； in, P For vegetation density, H The height of the vegetation; P est The density of vegetation resulting from planting. H estini The initial height for vegetation establishment; P growth and H growth These represent the increased density and height of vegetation due to growth, respectively. P diff The increased density of vegetation due to lateral expansion. H diff The height increase due to the lateral expansion of vegetation; P annual and H annual This represents the reduction in density and height of vegetation due to mortality during the off-season. P flow The density of vegetation reduced due to death caused by excessive water flow velocity. P inu The density of vegetation decreased due to death from prolonged flooding. P wind This refers to the reduction in vegetation density due to death caused by excessive wind speed.

4. The method according to claim 3, characterized in that, The expression for the reduction in vegetation density due to death caused by wind speed exceeding a preset value is: ； in, w wind For ambient wind speed, w death The wind speed threshold that causes vegetation death. m The attenuation coefficient; The expression for vegetation establishment is: ； in, seed This represents the probability of vegetation establishment. P 0 The initial planting density, H 0 This is the initial planting height. f This is a function of environmental pressure; Mdim , Ndim ) represents the terrain grid dimension. H estini The initial height for vegetation establishment; The expression for vegetation growth is: ； ； in, dP growth and dH growth These represent the increase in vegetation density and height due to growth within the coupling time step, respectively. r 1 , r 2 These are the stable growth rates of density and height, respectively. K 1 , K 2 These are the maximum density and height, respectively. P For planting density, H For planting height, C inter This represents the vegetation competition coefficient. The expression for vegetation expansion is: ； ； In the formula, dP diff This represents the increase in vegetation density due to lateral expansion within the coupling time step. D diff This represents the vegetation expansion coefficient. dH diff The height increase of vegetation due to lateral expansion within the coupling time step.

5. A numerical simulation system for water and sediment ecological geomorphological evolution considering wave-current coupling, extreme weather, and bidirectional feedback of vegetation dynamics, said system being used to implement the method described in any one of claims 1-4, characterized in that, The system includes: a model building and vegetation initialization module, a vegetation field introduction and impact characterization module, a wave-current coupling and storm process simulation module, a sediment transport and terrain renewal module, a vegetation dynamic evolution simulation module, a multi-module bidirectional feedback coupling module, and an iterative calculation and simulation termination module. The model building and vegetation initialization module is used to build a multi-module coupled model that includes hydrodynamics, waves, sediment transport, vegetation dynamics and bed topography evolution, and to set the initial vegetation field, which includes at least the spatial distribution of vegetation height, density or coverage. The vegetation field introduction and influence characterization module is used to introduce the initial vegetation field as a control condition into the hydrodynamic, wave and sediment transport module to characterize the influence of vegetation on water flow resistance, wave energy dissipation and sediment transport process, and to serve as the initial input condition for subsequent coupled calculations. The wave-current coupling and storm process simulation module is used to introduce wave-current coupling mechanism and extreme weather forcing into the hydrodynamic and wave module to simulate typhoon wind field and storm surge process. Under the influence of vegetation, it solves the evolution process of hydrodynamic-sediment system and simultaneously calculates and outputs the spatiotemporal distribution of flow velocity, water depth, bottom shear stress, wind speed, salinity and nutrient concentration. The sediment transport and topography update module is used to update suspended sediment transport, erosion and settlement processes and bed topography evolution based on the hydrodynamic, wave and sediment calculation results obtained from the wave-current coupling and storm process simulation module. The vegetation dynamic evolution simulation module is used to construct a vegetation dynamic evolution module by using the flow velocity, water depth, bed shear stress, wind speed, salinity and nutrient concentration output by the wave-current coupling and storm process simulation module as external influencing factors of vegetation dynamic evolution, and to simulate the colonization, growth, expansion, competition, death and lodging or uprooting of vegetation. The multi-module bidirectional feedback coupling module is used to feed back the changes in vegetation height, density or coverage caused by the dynamic changes in vegetation to the hydrodynamic, wave and sediment transport module, and to synchronously feed back the environmental change results to the vegetation dynamic evolution module, forming a bidirectional coupling cyclical update mechanism between hydrodynamics, waves, sediment, vegetation and topography. The iterative calculation and simulation termination module is used to repeatedly execute the wave-current coupling and storm process simulation module to the multi-module bidirectional feedback coupling module until the time termination condition is met, thereby completing the numerical simulation of the water and sediment ecological geomorphological evolution process.

6. The system according to claim 5, characterized in that, The initial vegetation field is synchronously introduced into the hydrodynamic, wave, and sediment transport modules. The initial impact of vegetation on water flow, wave propagation, and sediment transport processes is characterized using equivalent roughness, resistance terms, wave dissipation terms, or sediment source-sink terms. Specifically: The hydrodynamic module solves for water depth and flow velocity based on two-dimensional shallow water equations. The governing equations are: ； ； ； In the formula, ▽ is the Hamiltonian operator; h For water depth; t U is time; u is the depth-averaged velocity vector; g It is the acceleration due to gravity; S The source term includes Coriolis force, bottom friction, and vegetation friction; η Water level; ν The momentum diffusion coefficient; S T As a tracer, it includes salinity and temperature; ν T The tracer diffusion coefficient is... T For temperature; The wave module describes wave propagation under unsteady sea states based on the wave action spectrum equation considering source and sink terms. The governing equation is: ； In the formula, N is the wave action spectral density; V is the wave propagation velocity vector; Q For source and sink terms, it represents the generation, dissipation, and redistribution of wave energy, including wave energy dissipation caused by vegetation. Q veg ; grad x,k Two-dimensional physical space x and wavenumber space k Gradient operators in a jointly constructed four-dimensional phase space; Suspended concentration C The equation is given by convection-diffusion, which also includes settling velocity. w s With turbulent diffusion coefficient ν t Impact: ； In the formula, U , V The components of the depth-averaged flow velocity in the x and y directions; ε s The turbulent diffusion coefficient of sediment; E For erosion flux; The variation in bed elevation is described by the Exner equation, with the source term being the deposition flux. D With erosion flux E The formula is: ； In the formula, ρ s The dry density of the sediment; Q mb The sediment transport rate per unit width; z b The elevation of the bed surface; q Porosity; Vegetation resistance term Source terms added to the momentum equation S Among them λ This is the vegetation resistance coefficient. , C D This is the vegetation drag coefficient. m Plant density, d The diameter of the plant; The impact of vegetation on waves is through wave energy dissipation caused by vegetation. Q veg This is used to describe the feedback effect of vegetation on the wave propagation and attenuation process. α represents the relative submergence of vegetation. The mean wave number, The average natural angular frequency, m 0 The zeroth moment of the wave energy spectrum, F ( σ , θ () represents the two-dimensional wave energy density spectrum, which is the frequency... σ and the direction of wave propagation θ The function; The sediment transport module modifies the source and sink terms in the sediment transport control equation by introducing terms related to the capture and adhesion of suspended sediment by vegetation. , ε For adhesion rate, u The magnitude of the flow velocity; simultaneously considering the effects of sediment gradation, sediment content, and salinity on the settling modulation effect of cohesive sediment, the settling velocity... w s Settling velocity formula for cohesive sediment , w nonco For non-cohesive sediment settling velocity, β The coefficients representing the influence of sand content and gradation are given. , ϕ v This represents the volume fraction of suspended sediment. α clay This refers to the volume content of particles with a diameter less than 10 μm. S a This is the salinity influence coefficient. , s Salinity.

7. The system according to claim 6, characterized in that, The governing equations for the vegetation dynamics evolution module are: ； ； in, P For vegetation density, H The height of the vegetation; P est The density of vegetation resulting from planting. H estini The initial height for vegetation establishment; P growth and H growth These represent the increased density and height of vegetation due to growth, respectively. P diff The increased density of vegetation due to lateral expansion. H diff The height increase due to the lateral expansion of vegetation; P annual and H annual This represents the reduction in density and height of vegetation due to mortality during the off-season. P flow The density of vegetation reduced due to death caused by excessive water flow velocity. P inu The density of vegetation decreased due to death from prolonged flooding. P wind This refers to the reduction in vegetation density due to death caused by excessive wind speed.

8. The system according to claim 7, characterized in that, The expression for the reduction in vegetation density due to death caused by wind speed exceeding a preset value is: ； in, w wind For ambient wind speed, w death The wind speed threshold that causes vegetation death. m The attenuation coefficient; The expression for vegetation establishment is: ； in, seed This represents the probability of vegetation establishment. P 0 The initial planting density, H 0 This is the initial planting height. f The environmental stress function is denoted by (Mdim, Ndim), which represents the terrain grid dimension, and Hestini represents the initial height of vegetation establishment. The expression for vegetation growth is: ； ； in, dP growth and dH growth These represent the increase in vegetation density and height due to growth within the coupling time step, respectively. r 1 , r 2 These are the stable growth rates of density and height, respectively. K 1 , K 2 These are the maximum density and height, respectively. P For planting density, H For planting height, C inter This represents the vegetation competition coefficient. The expression for vegetation expansion is: ； ； In the formula, dP diff This represents the increase in vegetation density due to lateral expansion within the coupling time step. D diff This represents the vegetation expansion coefficient. dH diff The height increase of vegetation due to lateral expansion within the coupling time step.

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