Evaluation Methods and Systems for the Impact of Water-Related Projects on Sediment Flux into the Sea

Abstract

This invention relates to the field of estuarine water environment assessment, and in particular to a method and system for assessing the impact of water-related projects on sediment flux into the sea. Using a pre-defined extreme flood scenario (such as a once-in-a-century flood) as a benchmark, a numerical model capable of simulating hydrodynamics and suspended sediment transport processes in the estuary region is established and validated. The model simulates and calculates sediment flux into the sea under four scenarios: no flood and before project construction, flood and before project construction, no flood and after project construction, and flood and after project construction. Furthermore, through specific calculation relationships, the additional contribution ratio of water-related projects to sediment flux into the sea during flood events is quantified. Based on a preset contribution ratio threshold, the degree of project impact is assessed, providing a decision-making basis for project optimization and offering crucial technical support for estuarine ecological environment protection, water-related project planning and design, and scheme optimization.

Description

Technical Field

[0001] This invention relates to the field of estuarine water environment assessment, and in particular to an assessment method and system for the impact of water-related projects on sediment flux into the sea. Background Technology

[0002] With the continuous development of society and the economy, estuaries, as key areas where human activities interact with the natural environment, are facing increasing pressure from engineering development. Frequent water-related engineering activities such as dam construction, land reclamation, and waterway improvement, while bringing economic benefits, have also profoundly altered the hydrodynamic conditions and sediment transport processes in estuaries, significantly impacting the ecological environment, shoreline evolution, and water quality of estuaries and nearshore areas. Therefore, scientifically and accurately quantifying the impact of water-related projects on the estuarine environment has become an urgent and practically significant task in the fields of water resource management and ecological environmental protection.

[0003] Currently, assessment methods for the impact of estuarine water environment can be mainly divided into two categories. The first category is qualitative descriptive methods based on historical cases and expert experience. These methods rely on the subjective judgment of experts and analogical analysis of similar projects, and are suitable for scenarios with scarce data, low analytical requirements, or those requiring rapid preliminary assessment. The second category is methods that evaluate the magnitude of flux changes based on mathematical models verified by measured data. Because flood volumes vary in different estuaries, this method cannot determine a uniform magnitude of flux changes caused by engineering construction during the flood season, and therefore is only applicable to scenarios with multi-year average runoff.

[0004] Against the backdrop of global climate change, extreme weather events are becoming more frequent, leading to an increasing frequency and intensity of floods in rivers flowing into the sea. Numerous studies have shown that the flood season is the primary period for river sediment transport to the ocean, and the amount of sediment flux entering the sea has a decisive impact on the shaping of river deltas, nearshore sediment distribution, and nutrient cycling in water bodies. Current technologies lack objective indicators for evaluating the impact of water-related projects on changes in sediment flux into the sea during the flood season, the main period of river sediment input. Therefore, there is an urgent need to develop a method that can compare the effects of water-related projects on sediment flux into the sea across estuaries with different flood volumes and quantify the impact of such projects to address this problem. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for evaluating the impact of water-related engineering projects on sediment flux into the sea, in order to solve the problem in the existing technology that it is difficult to scientifically and quantitatively evaluate the combined effects of extreme flood events and water-related engineering construction activities on sediment flux into the sea and its environmental impact, especially the lack of a method to quantify the contribution of engineering projects by using extreme flood events as a baseline scenario.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for evaluating the impact of water-related projects on sediment flux into the sea includes the following steps:

[0008] S1. Obtain relevant background field data and historical hydrological data for the estuary area, and determine a baseline flood scenario representing extreme events based on long-term hydrological statistics;

[0009] S2. Establish and validate a three-dimensional hydrodynamic-sediment transport coupled numerical model applicable to the target estuary;

[0010] S3. Simulate and calculate the sediment flux into the sea under four scenarios: no flood and before project construction, flood and before project construction, no flood and after project construction, and flood and after project construction.

[0011] S4. Calculate the contribution ratio of water-related projects to the change in sediment flux into the sea under the baseline flood scenario, compare the calculated contribution ratio with the preset impact threshold, and determine the degree of impact of water-related projects on sediment flux into the sea under the baseline flood scenario.

[0012] Furthermore, the background field data and historical hydrological data in step S1 include, but are not limited to:

[0013] Daily flow and sediment concentration data from historical hydrological stations;

[0014] Spatiotemporal distribution data of salinity, temperature, and suspended sediment concentration in the sea area;

[0015] Water depth and topographic data for the study area;

[0016] Meteorological and hydrological forcing data.

[0017] Furthermore, the process for determining the baseline flood scenario is as follows:

[0018] Based on the annual maximum flow sequence of hydrological stations over the past 50 years, frequency analysis was performed using the P-III type extreme value distribution to calculate the extreme flood flow with a return period of 100 years, and this flow was determined as the baseline flood scenario.

[0019] A typical historical flood event was selected as a prototype, and the flood process line was generated by scaling it up proportionally.

[0020] The multi-year average runoff of the study area was calculated.

[0021] Furthermore, step S3 includes the following processes:

[0022] S31. Simulate and calculate the sediment flux T into the sea under the baseline flood scenario without engineering conditions. flood_natural ;

[0023] S32. Simulate and calculate the sediment flux T into the sea under the baseline flood scenario with engineering conditions. flood_engineered ;

[0024] S33. Simulate and calculate the sediment flux T into the sea under the conditions of multi-year average runoff at the estuary (i.e., no flood), without engineering conditions. avg_natural ;

[0025] S34. Simulate and calculate the sediment flux T into the sea under the conditions of multi-year average runoff at the estuary (i.e., no flood), with engineering conditions. avg_engineered .

[0026] Furthermore, step S4 includes the following processes:

[0027] S41. Calculate the sediment flux ΔT caused by the engineering construction activities themselves under the aforementioned baseline flood scenario. judge Change, that is:

[0028] ΔT judge = T flood_engineered - T flood_natural ;

[0029] When ΔT judge If the value is greater than 0, it means that the engineering construction activities have increased the amount of sediment entering the sea, then proceed to steps S42 to S43;

[0030] When ΔT judge If the value is less than 0, it means that the engineering construction activities have reduced the amount of sediment entering the sea, and then S44 to S45 shall be implemented.

[0031] S42. Calculate the background value ΔT of the change in sediment flux into the sea caused by the combined effects of the estuary reference flood and engineering construction. background ,Right now:

[0032] ΔT background = T flood_engineered - T avg_natural ;

[0033] S43. Calculate the change ΔT in the sea-entering sediment flux caused by the engineering construction activities themselves under the aforementioned baseline flood scenario. engine ,Right now:

[0034] ΔT engine = T flood_engineered - T flood_natural ;

[0035] S44. Calculate the background value ΔT of the change in sediment flux into the sea caused by the combined effects of estuary baseline flood and engineering construction. background ,Right now:

[0036] ΔT background = Tflood_natural - T avg_engineered ;

[0037] S45. Calculate the change in sediment flux into the sea caused by the engineering construction activities themselves under the aforementioned baseline flood scenario, i.e.:

[0038] ΔT engine = T flood_natural - T flood_engineered ;

[0039] S46. Calculate the contribution ratio η of engineering construction activities to the change in sediment flux into the sea under the baseline flood scenario, i.e.:

[0040] η=ΔT engine / ΔT background ;

[0041] S47. Compare the calculated contribution ratio η with the preset impact threshold to determine the degree of impact of the water-related project on the sediment flux into the sea under the baseline flood scenario.

[0042] An evaluation system for the impact of water-related engineering projects on sediment flux into the sea based on the aforementioned evaluation method includes:

[0043] The data acquisition and input module is used to acquire multi-source heterogeneous data from the target estuary area;

[0044] The baseline scenario generation module is connected to the data acquisition and input module and is used to determine the baseline flood scenario based on historical hydrological data.

[0045] The numerical simulation calculation module is connected to the data acquisition and input module and the baseline scenario generation module. It is used to construct and run a three-dimensional hydrodynamic-sediment transport coupled numerical model and output the sediment flux into the sea under various scenarios.

[0046] The contribution quantification and analysis module, connected to the numerical simulation calculation module, is used to quantify the contribution ratio of water-related projects to the change in sediment flux into the sea based on the simulation results.

[0047] The decision support output module, connected to the contribution metric analysis module, is used to output evaluation results and provide decision recommendations.

[0048] Furthermore, the data acquisition and input module includes:

[0049] The hydrological and meteorological data interface unit establishes a communication connection with an external hydrological database to acquire historical and real-time time series data.

[0050] The marine environmental data interface unit is used to acquire background field data;

[0051] Geographic information data storage unit, used to store digital elevation models, nautical chart topographic data and shoreline vector data;

[0052] The engineering data input unit is used to receive digital design parameters for water-related engineering projects input by users and convert these parameters into structural files that the model can recognize.

[0053] Furthermore, the baseline scenario generation module includes:

[0054] The extreme value statistical analysis unit has a built-in P-III type extreme value distribution statistical model, which is used to perform frequency analysis on the input annual maximum flow sequence and calculate the flood peak flow for a specified return period.

[0055] The flood hydrograph generation unit is used to generate a complete baseline flood flow hydrograph by scaling up the peak flow rate of the flood based on a typical historical flood process; at the same time, it calculates and outputs the multi-year average runoff of the estuary area.

[0056] Furthermore, the numerical simulation calculation module includes:

[0057] The model mesh generation unit is used to generate unstructured triangular meshes that fit complex boundaries based on stored terrain and shoreline data, and can adaptively refine the mesh in the engineering area and near the waterway as defined by the user.

[0058] The model solver unit is an integrated hydrodynamic-sediment coupled numerical model, responsible for receiving boundary conditions, initial field, and engineering structure parameters, and performing numerical simulation calculations;

[0059] The sediment flux calculation unit is used to extract and calculate the average sediment flux into the sea during a complete full tidal cycle through a preset estuary gate section.

[0060] Furthermore, the decision support output module includes:

[0061] The threshold comparison unit has a built-in preset influence threshold, which is used to compare the calculated contribution ratio with the influence threshold.

[0062] The results visualization and report generation unit is used to visualize and render simulation results, seabed sediment flux data, and contribution ratios, and generate structured assessment reports.

[0063] The early warning and optimization suggestion unit is used to trigger an early warning signal when the contribution ratio exceeds the impact threshold and to provide a list of preset engineering optimization suggestions.

[0064] The advantages of this invention are as follows: It is the first to propose using extreme flood events (such as a once-in-a-century event) as a baseline scenario to quantify the incremental contribution of water-related projects to sediment flux into the sea, providing a scientific method for assessing the environmental impact of projects under extreme conditions. By constructing a validated three-dimensional hydrodynamic-sediment model, it can more realistically simulate the water and sediment movement processes in complex estuarine areas during flood season, with and without engineering conditions. Furthermore, it defines a judgment mechanism for the proportion of engineering contribution (η) and a preset impact threshold, providing a clear and quantitative decision-making basis for engineering environmental impact assessment. This provides important technical support for estuarine ecological environmental protection, and the planning, design, and optimization of water-related projects. Attached Figure Description

[0065] Figure 1 This is a flowchart illustrating the evaluation method for the impact of water-related projects on the sediment flux into the sea, as shown in the embodiments.

[0066] Figure 2 This is a block diagram of the evaluation system for the impact of water-related projects on the sediment flux into the sea, as shown in the embodiment. Detailed Implementation

[0067] like Figure 1 As shown in this embodiment, an evaluation method for the impact of water-related projects on sediment flux into the sea is proposed. The core concept is as follows: using a set extreme flood scenario (such as a once-in-a-century flood) as a benchmark, a numerical model capable of simulating the hydrodynamic and suspended sediment transport processes in the estuary area is established and verified. The sediment flux into the sea is simulated and calculated under four scenarios: no flood and before project construction, flood and before project construction, no flood and after project construction, and flood and after project construction. Then, through specific calculation relationships, the additional contribution ratio of water-related projects to sediment flux into the sea during flood events is quantified, and the degree of project impact is assessed based on a preset contribution ratio threshold, providing a decision-making basis for optimizing project schemes. The method includes the following steps.

[0068] Step S1. Data Acquisition and Baseline Flood Determination:

[0069] Background field data for the estuary area and adjacent sea areas will be collected, including but not limited to: daily flow and sediment concentration data from historical hydrological stations; spatiotemporal distribution data of salinity, temperature, and suspended sediment concentration in the sea area (which can be obtained through on-site mobile observation, satellite remote sensing inversion, etc.); detailed water depth and topographic data of the study area; and meteorological and hydrological forcing data such as tide level, tidal current, and wind field.

[0070] Based on the annual maximum discharge series of hydrological stations over the past 50 years, frequency analysis was performed using the P-III type extreme value distribution to calculate the extreme flood discharge of a 100-year return period. This discharge was determined as the baseline flood scenario for this assessment. Furthermore, a typical historical flood event was selected as a prototype and scaled up to generate a flood hydrograph. Simultaneously, the multi-year average runoff for the region was calculated.

[0071] Step S2. Construction and Validation of Estuarine Sediment Transport Model:

[0072] Mature 3D hydrodynamic-sediment coupling models such as FVCOM or MIKE 3 were selected as simulation tools. The model's computational domain should cover the entire estuary system from all tidal sections of the river downstream to the coastal area outside the estuary. The model settings are as follows:

[0073] Grid and Topography: Curved grids or unstructured triangular grids are used to better fit the complex shoreline of the estuary. The grid resolution is refined to no more than 100 meters in the engineering area and near the waterway, ensuring at least three complete rows of triangular grids in the transverse direction of the river channel. In open sea areas, the resolution can be gradually widened to 1-2 kilometers. Water depth data is fused with nautical charts and the latest survey maps.

[0074] Boundary conditions: Harmonic constants for the eight major tidal constituents (M2, S2, N2, K2, K1, O1, P1, Q1) obtained by assimilation from global tidal models such as TPXO and NAO.99b are applied to the open boundary to simulate tidal forcing. The upstream river boundary input is the baseline flood discharge or multi-year average discharge and the corresponding sediment concentration time series determined in step S1.

[0075] Sediment parameters: Set key parameters such as settling velocity, critical resuspension shear stress, and flocculation effect. These parameters need to be calibrated using field and laboratory data.

[0076] Model Validation: A validation period was selected that included spring, mid-, and neap tides (all tides) as well as flood and dry seasons. The simulated tidal levels, current velocities, current directions, salinity, and suspended sediment concentrations were compared with synchronous measured data. Quantitative evaluation was conducted by calculating indicators such as correlation coefficients and root mean square errors to ensure that the model achieved acceptable accuracy in both hydrodynamic and sediment simulation aspects.

[0077] Step S3. Simulation calculation of sediment flux under multiple scenarios:

[0078] Run the validated and reliable model to calculate the average sediment flux into the sea over a full tidal cycle (unit: tons / day) through the estuary barrier sand section under the following four scenarios.

[0079] S31. Simulate a 100-year flood flow rate under no-engineering conditions and obtain T. flood_natural .

[0080] S32. Simulate the engineering conditions (incorporating precise structures of waterway improvement projects, such as groynes and guide dikes, into the model), input a 100-year flood flow, and obtain T. flood_engineered .

[0081] S33. Simulate the state without engineering work, input the multi-year average runoff, and obtain T. avg_natural .

[0082] S34. Simulate the engineering conditions, input the multi-year average runoff, and obtain T. avg_engineered .

[0083] Step S4. Measurement and assessment of engineering impact contribution:

[0084] S41. First, assess and calculate the direct impact of the engineering construction activities themselves on the flood:

[0085] ΔT judge = T flood_engineered - T flood_natural ;

[0086] When ΔT judge If the value is greater than 0, it means that the engineering construction activities have increased the amount of sediment entering the sea, then proceed to steps S42 to S43.

[0087] When ΔT judge If the value is less than 0, it means that the engineering construction activities have reduced the amount of sediment entering the sea, and the S44 to S45 path will be executed.

[0088] After the execution of path S42 to S43 or path S44 to S45 is completed, path S46 to S47 will be executed.

[0089] S42. Calculate the background change value, which represents the change in the combined effects of "extreme floods" and "engineering construction" relative to the "natural average state." It includes the mixed effects of the flood itself and the engineering construction:

[0090] ΔT background = T flood_engineered - T avg_natural ;

[0091] S43. Calculate the individual impact value of the project, which represents the change in sediment flux caused purely by the project construction under the same extreme flood conditions:

[0092] ΔT engine = T flood_engineered - T flood_natural (This is ΔT in S41) judge );

[0093] S44. Calculate the background value ΔT of the change in sediment flux into the sea caused by the combined effects of estuary baseline flood and engineering construction. background ,Right now:

[0094] ΔT background = T flood_natural - T avg_engineered ;

[0095] S45. Calculate the change in sediment flux into the sea caused by the engineering construction activities themselves under the aforementioned baseline flood scenario, i.e.:

[0096] ΔT engine = T flood_natural - T flood_engineered ;

[0097] S46. Core quantitative step: Calculate the contribution ratio η of engineering construction activities to the total background change value.

[0098] η=ΔT engine / ΔT background ;

[0099] S47. Impact assessment and decision-making: The preset impact threshold can be set according to the sensitivity of regional environmental protection.

[0100] If the contribution ratio calculated through the S42-S43 path exceeds the impact threshold, it indicates that the channel improvement project has a significant impact on increasing the sediment flux into the sea. Decision-makers should pay close attention to this result and consider optimizing the project plan, such as adjusting the length of the guide dike, modifying the dike head structure, and adding ecological buffer zones to mitigate its environmental impact. The optimized plan can be re-evaluated using this methodology until the impact level falls below the threshold. The contribution ratio calculated through the S44-S45 path is also compared using the same logic to determine whether the water-related project has a significant impact on the sediment flux into the sea.

[0101] In summary, this embodiment, through rigorous numerical simulation and an original branch quantification formula, successfully separates the impact of extreme flood events and engineering construction on the sediment flux into the sea, and provides an objective and quantitative decision-making indicator, effectively solving the scientific problem that existing technologies struggle to assess the additional contributions of engineering projects under extreme conditions.

[0102] like Figure 2As shown, this embodiment, based on the above method, also provides an evaluation system for the impact of water-related projects on sediment flux into the sea. It integrates data management, high-performance computing, and intelligent decision support functions. Its core lies in efficiently and automatically executing complex model simulation and quantitative analysis processes through hardware modularization. The system includes a data acquisition and input module, a baseline scenario generation module, a numerical simulation calculation module, a contribution quantification and analysis module, and a decision support output module. These modules are interconnected and work collaboratively via a system bus.

[0103] The data acquisition and input module is used to automatically acquire and receive multi-source heterogeneous data required for implementing the quantization method. This module includes:

[0104] The hydrological and meteorological data interface unit is used to establish communication connections with external hydrological databases (such as the Ministry of Water Resources hydrological stations and meteorological bureau databases) and automatically acquire historical and real-time time series data such as river flow, sediment concentration, wind speed, and wind direction.

[0105] The marine environmental data interface unit is used to receive background field data such as salinity, temperature, and suspended sediment concentration from platforms such as marine buoys, monitoring vessels, and satellite remote sensing.

[0106] The geographic information data storage unit is a built-in high-capacity storage device (such as an SSD array) used to store the detailed digital elevation model (DEM), nautical chart topographic data, and shoreline vector data of the study area;

[0107] The engineering data input unit is used to receive digital design parameters of water-related projects (such as the geometric dimensions, spatial coordinates, and slope of groynes and guide dikes) input by users, and convert these parameters into structural files that the model can recognize.

[0108] A baseline scenario generation module, connected to the data acquisition and input module, is used to determine extreme flood baseline scenarios based on long-term hydrological data. This module includes:

[0109] The extreme value statistical analysis unit has a built-in P-III type extreme value distribution statistical model, which can perform frequency analysis on the input annual maximum flow sequence and automatically calculate the peak flow of floods with a specified return period (such as once in a hundred years).

[0110] The flood hydrograph generation unit is used to generate a complete baseline flood flow hydrograph by scaling up the peak flow rate based on a typical historical flood process. At the same time, this unit calculates and outputs the multi-year average runoff of the estuary area.

[0111] The numerical simulation calculation module, the core computing unit of the system, is connected to the baseline scenario generation module and the data acquisition and input module. It is used to construct and run the estuarine sediment transport numerical model. This module includes:

[0112] The model mesh generation unit is used to automatically generate unstructured triangular meshes that fit complex boundaries based on stored terrain and shoreline data, and can adaptively refine the mesh in the engineering area and near the waterway as defined by the user.

[0113] The model solver unit is an integrated high-performance hydrodynamic-sediment coupling numerical model (such as the solver kernel of FVCOM and MIKE 3), responsible for receiving boundary conditions, initial field, and engineering structure parameters, and performing numerical simulation calculations under the four scenarios (no flood and no engineering, flood and no engineering, no flood and engineering, flood and engineering).

[0114] The sediment flux calculation unit is used to automatically extract and calculate the average sediment flux (T) into the sea during a complete full tidal cycle (including a complete spring tide, mid-tide, and neap tide) through a preset estuary section after the model simulation is completed. flood_natural T flood_engineered T avg_natural T avg_engineered ).

[0115] A contribution quantification and analysis module, connected to the numerical simulation calculation module, is used to quantify the engineering contribution based on simulation results. This module includes:

[0116] The influence direction determination unit is used to calculate ΔT. judge = T flood_engineered - T flood_natural It automatically determines the sign of the result, thereby determining the subsequent calculation path;

[0117] The contribution ratio calculation unit selects the appropriate algorithm branch to calculate ΔT based on the result of the judgment unit. background and ΔT engine And finally calculate the contribution ratio η=ΔT of the engineering construction activities. engine / ΔT background .

[0118] A decision support output module, connected to the contribution quantification analysis module, is used to output evaluation results and provide decision recommendations. This module includes:

[0119] The threshold comparison unit has a built-in preset influence threshold (such as η). critical = 0.1), used to automatically compare the calculated contribution ratio η with the influence threshold;

[0120] The results visualization and report generation unit is used to visualize and render simulation results (such as flow field and sediment load distribution), flux data, and contribution ratio η in the form of charts, contour maps, etc., and automatically generate structured evaluation reports.

[0121] Early warning and optimization suggestion unit, if η>η critical If the unit triggers an early warning signal (such as a warning box popping up on the human-computer interaction interface), it can provide a list of preset engineering optimization suggestions (e.g., "It is recommended to shorten the length of the east guide dike by 100 meters to reduce the impact").

[0122] Through the modular hardware design described above, the system automates and intelligently transforms the complex manual modeling, simulation, and analysis processes of the aforementioned evaluation methods, greatly improving the efficiency and accuracy of the assessment work and providing a powerful dedicated tool for environmental impact assessment of water-related projects.

[0123] The above embodiments are only used to explain the concept of the present invention, and are not intended to limit the protection of the present invention. Any non-substantial modifications made to the present invention using this concept should fall within the protection scope of the present invention.

Claims

1. A method for evaluating the influence of a waterway project on the sediment flux into the sea, characterized by, Comprising the following steps: S1. Obtain the background field data and historical hydrological data related to the estuary area, and determine a benchmark flood scenario representing an extreme event based on long-term hydrological statistics; the determination process of the benchmark flood scenario is as follows: Based on the annual maximum flow sequence of the hydrological station in the past 50 years, frequency analysis is carried out by using P-III type extreme value distribution, and the extreme flood flow with a return period of 100 years is calculated, which is determined as the benchmark flood scenario; Select a typical historical flood process as a prototype, and generate a flood hydrograph by scaling up; Calculate the multi-year average runoff of the study area; S2. Establish a three-dimensional hydrodynamic-sediment transport coupling numerical model suitable for the target estuary, and verify it; S3. Simulate and calculate the sediment flux into the sea under four scenarios: no flood and before construction, with flood and before construction, no flood and after construction, and with flood and after construction; S31. Simulate the sediment flux T into the sea without engineering under the reference flood scenario flood_natural ; S32. Simulate the calculation of the sediment flux T into the sea under the reference flood scenario with the engineering state flood_engineered ; S33. Simulate the sediment flux into the sea under the condition of the average annual runoff of the estuary without the project T avg_natural ; S34. The simulated annual average runoff conditions in the estuary, there are engineering state of sediment flux into the sea T avg_engineered ; S4. Calculate the contribution ratio of the water-related project to the change of sediment flux into the sea under the benchmark flood scenario, and compare the calculated contribution ratio with the preset impact threshold to determine the impact degree of the water-related project on the sediment flux into the sea under the benchmark flood scenario; S41. Calculate the sediment flux ΔT caused by the engineering construction activities themselves under the baseline flood scenario judge i.e.: ΔT judge = T flood_engineered - T flood_natural ; When ΔT judge If the engineering construction activity increases the sediment flux into the sea, then steps S42 to S43 are executed. When ΔT judge is less than 0, indicating that the construction activity causes the sediment flux into the sea to decrease, S44 to S45 are executed. S42. Calculate the background value of the change of sediment flux into the sea caused by the joint action of the estuary datum flood and the engineering construction ΔT background That is: ΔT background = T flood_engineered - T avg_natural ; S43. Calculate the change of sediment flux into the sea ΔT caused by the construction activity itself under the baseline flood scenario engine i.e.: ΔT engine = T flood_engineered - T flood_natural ; S44. Calculate the background value of the change of sediment flux into the sea caused by the joint action of the estuary datum flood and the engineering construction ΔT background That is: ΔT background = T flood_natural - T avg_engineered ; S45. Calculate the change of sediment flux into the sea caused by the construction activity itself under the benchmark flood scenario, that is: ΔT engine = T flood_natural - T flood_engineered ; S46. Calculate the contribution ratio η of the construction activity to the change of sediment flux into the sea under the benchmark flood scenario, that is: η = ΔT engine / ΔT background ; S47. Compare the calculated contribution ratio η with the preset impact threshold to determine the impact degree of the water-related project on the sediment flux into the sea under the benchmark flood scenario.

2. The method of claim 1, wherein the waterway project is a dam. The background field data and historical hydrological data in step S1 include but are not limited to: Daily flow and sediment concentration data of historical hydrological stations; The spatial and temporal distribution data of salinity, temperature and suspended sediment concentration in the sea area; Water depth topographic data of the study area; Meteorological and hydrological forcing data.

3. A system for evaluating the influence of a water-crossing project on the sediment flux into the sea based on the evaluation method according to any one of claims 1 to 2, characterized in that Comprise: Data acquisition and input module for acquiring multi-source heterogeneous data of target estuary area; Benchmark scenario generation module connected with the data acquisition and input module for determining the benchmark flood scenario based on historical hydrological data; Numerical simulation calculation module connected with the data acquisition and input module and the benchmark scenario generation module for constructing and running a three-dimensional hydrodynamic-sediment transport coupling numerical model, and outputting the sediment flux into the sea under multiple scenarios; Contribution quantification analysis module connected with the numerical simulation calculation module for quantifying the contribution ratio of the water-related project to the change of sediment flux into the sea according to the simulation results; Decision support output module connected with the contribution quantification analysis module for outputting evaluation results and providing decision suggestions.

4. The system for evaluating the influence of a water engineering project on the sediment flux into the sea according to claim 3, characterized in that, The data acquisition and input module comprises: Hydro-meteorological data interface unit, which establishes communication connection with external hydrological database to obtain historical and real-time time series data; Ocean environmental data interface unit for obtaining background field data; Geographic information data storage unit for storing digital elevation model, chart topographic data and shoreline vector data; Engineering data input unit for receiving user input of digital design parameters of water-related projects, and converting these parameters into model recognizable structure files.

5. The system for evaluating the influence of a water engineering project on the sediment flux into the sea according to claim 4, characterized in that, The reference scenario generation module comprises: a statistical extreme value analysis unit, which internally stores a P-III type extreme value distribution statistical model, is used for frequency analysis on the input annual maximum flow sequence, and calculates the flood peak flow of a specified return period; a flood hydrograph generation unit, which is used for proportional amplification according to the flood peak flow, generates a complete reference flood flow hydrograph taking the historical typical flood process as a prototype, and simultaneously calculates and outputs the multi-year average runoff of the estuary area.

6. The system for evaluating the influence of a water engineering project on the sediment flux into the sea according to claim 5, wherein The numerical simulation calculation module comprises: a model grid generation unit, which is used for generating a non-structured triangular grid fitting a complex boundary according to stored terrain and coastline data, and can perform grid adaptive encryption near the user-set engineering area and channel; a model solver unit, which is an integrated hydrodynamic-sediment coupling numerical model, is responsible for receiving boundary conditions, initial fields and engineering structure parameters, and performing numerical simulation calculation; a sediment flux calculation unit, which is used for extracting and calculating the average sediment flux into the sea through a complete full-tide cycle of a pre-set estuary mouth section.

7. The system for evaluating the influence of a water engineering project on the sediment flux into the sea according to claim 6, characterized in that, The decision support output module comprises: a threshold comparison unit, which internally stores a pre-set influence threshold, is used for comparing the calculated contribution proportion with the influence threshold; a result visualization and report generation unit, which is used for visualizing and rendering the simulation results, the sediment flux into the sea data and the contribution proportion, and generating a structured evaluation report; a warning and optimization suggestion unit, which is used for triggering a warning signal when the contribution proportion exceeds the influence threshold, and providing a pre-set list of engineering optimization scheme suggestions.

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