A method and system for calculating sediment transport along a sandy coast

Abstract

The present application relates to the technical field of coastal engineering, and discloses a method and system for calculating sand transport along a sandy coast, which comprises the following steps: obtaining target parameters and initial profile data of the target coast; calculating a profile change item caused by transverse sand transport through a one-dimensional beach evolution model; innovatively introducing an equivalent alongshore distance parameter to quickly estimate the alongshore sand transport gradient; combining the gradient to calculate an elevation change item caused by alongshore sand transport; superimposing the transverse and alongshore change items to obtain complete bottom elevation evolution data; iteratively calibrating the equivalent alongshore distance parameter based on historical topographic data until the simulation result conforms to the measured shoreline change; and finally outputting the calibrated alongshore sand transport impact prediction. The present application can solve the prediction deviation problem caused by the traditional one-dimensional beach evolution model ignoring the alongshore sand transport gradient.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coastal engineering, and particularly relates to a method and system for calculating alongshore sediment transport of sandy coast. BACKGROUND

[0002] The sandy coast is an important region of interaction between the ocean and the land, and is influenced by wave, tidal current and other dynamic factors, so that the morphology of the coastline and the nearshore bed continues to dynamically evolve. The process of beach evolution of the sandy coast is mainly driven by wave, flow and sediment transport, and the prediction accuracy is crucial to the design of coastal protection projects. The traditional one-dimensional beach evolution model (such as the CSHORE model) is based on the continuity equation of the bed sediment, focuses on the transverse sediment transport process, that is, simulates the sediment transport (such as onshore-offshore movement) perpendicular to the coastline. Such one-dimensional beach evolution model assumes that the volume of erosion area is equal to the volume of deposition area (i.e. the "local conservation" assumption) in the range from the land boundary to the closed depth under water. However, actual observations show that most sandy coasts have a persistent coastline recession phenomenon (the erosion volume is significantly greater than the deposition volume), and the coupling relationship between the cross-section elevation change and the alongshore sediment transport is still insufficient. Especially when dealing with non-uniform coastlines or variable topography conditions, the conventional method often ignores the influence of spatial differences in alongshore sediment transport on profile evolution, resulting in limited simulation accuracy.

[0003] Although the two-dimensional numerical model can simulate the alongshore sediment transport gradient, it needs to couple the wave, flow, sediment transport and other multi-physical field equations, and the calculation time is long (usually several hours to several days), the time cost is relatively high, and it is difficult to meet the demand for rapid evaluation and multi-working condition iteration in the preliminary design stage of the project.

[0004] Therefore, there is an urgent need for a method for calculating alongshore sediment transport of sandy coast, which can comprehensively reflect the coupling effect of transverse and longitudinal sediment transport, improve the calculation efficiency, and improve the accuracy of sandy coast evolution simulation. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a method for calculating alongshore sediment transport of sandy coast, which has the advantages of high calculation efficiency, strong adaptability, simple structure, etc., and is particularly suitable for long time series, multi-working condition sand beach response prediction and structure optimization design research.

[0006] The present application provides a method for calculating alongshore sediment transport of sandy coast, comprising the following steps:

[0007] S1, obtaining basic parameters and an initial profile of a target coast;

[0008] S2, inputting the basic parameters and the initial profile into a one-dimensional beach evolution model to obtain a transverse profile change term of the target coast caused by alongshore sediment transport;

[0009] The one-dimensional beach evolution model is a CSHORE model;

[0010] S3, introducing an equivalent alongshore distance parameter, calculating an alongshore sediment transport gradient;

[0011] S4, determining an initial value of the equivalent alongshore distance parameter, inputting the alongshore sediment transport gradient into the one-dimensional beach evolution model, and calculating an alongshore elevation change item of the target coast caused by the alongshore sediment transport;

[0012] S5, superimposing the transverse profile change item and the alongshore elevation change item to obtain complete topographic change data of the target coast caused by the alongshore sediment transport;

[0013] S6, iteratively calibrating the equivalent alongshore distance parameter based on the historical topographic change data of the target coast until the topographic change output by S5 has an error less than a preset threshold value from the historical topographic change data of the target coast;

[0014] S7, inputting the calibrated equivalent alongshore distance parameter and the basic parameters and initial profile of the target coast collected in real time into the one-dimensional beach evolution model, and outputting topographic change data caused by the alongshore sediment transport.

[0015] Further, in S3, the formula of the equivalent alongshore distance parameter is: wherein y e represents the equivalent alongshore distance parameter, q y represents the unit-width alongshore sediment transport rate, and represents the alongshore sediment transport gradient.

[0016] Further, in S1, the basic parameters include a wave incidence angle, a wave height, a wave period, a sediment particle size, a settling velocity, a specific gravity, and a bottom sediment porosity; and the initial profile includes land boundary and bottom elevation data within a closed underwater depth range, and the closed underwater depth is determined by a wave breaking critical condition.

[0017] Further, the initial value of the equivalent alongshore distance parameter is set as an average distance from a wave incidence boundary to a target coastline.

[0018] Further, in S4, the alongshore elevation change item is solved by the following formula:

[0019] ;

[0020] wherein n p represents the bottom sediment porosity; represents an alongshore elevation change amount caused by the alongshore sediment transport; represents a time interval for simulating beach evolution; and Q y represents a unit-width time-averaged volume flux in the alongshore direction. , x m is the cross-section calculation range, q y is the total sediment transport rate per unit width along the coast.

[0021] Further, the S6 specifically comprises:

[0022] S61, collecting target coast historical topographic change data;

[0023] S62, inputting the initial value of the equivalent alongshore distance parameter into the one-dimensional beach evolution model, executing S1-S5, and obtaining complete target coast topographic change data caused by alongshore sediment transport;

[0024] S63, adjusting the equivalent alongshore distance parameter by the same order of magnitude, and repeating S62 until the topographic change and the target coast historical topographic change data error is less than a preset threshold.

[0025] Further, in the S61, the target coast historical topographic change data includes shoreline translation position data, erosion area and deposition area measured values and bottom elevation spatial distribution form data at different time periods.

[0026] In the S62, the target coast topographic change data caused by alongshore sediment transport includes simulated shoreline recession distance, simulated erosion area and simulated deposition area, and simulated bottom elevation spatial distribution form data.

[0027] The present application also provides a sandy coast alongshore sediment transport calculation system for the above-mentioned sandy coast alongshore sediment transport calculation method, comprising:

[0028] A data input module is used to obtain the basic parameters and initial profile of the target coast.

[0029] A lateral profile simulation module is used to input the basic parameters and initial profile into the one-dimensional beach evolution model to obtain the lateral profile change term of the target coast caused by alongshore sediment transport.

[0030] An alongshore sediment transport gradient calculation module is used to introduce the equivalent alongshore distance parameter to calculate the alongshore sediment transport gradient.

[0031] An alongshore elevation simulation module is used to determine the initial value of the equivalent alongshore distance parameter, input the alongshore sediment transport gradient into the one-dimensional beach evolution model, and calculate the alongshore elevation change term of the target coast caused by alongshore sediment transport.

[0032] A topographic change acquisition module is used to superimpose the lateral profile change term and the alongshore elevation change term to obtain complete target coast topographic change data caused by alongshore sediment transport.

[0033] Calibration module: used to iteratively calibrate the equivalent coastal distance parameter based on the historical topographic change data of the target coastline until the error between the topographic change data output by the topographic change acquisition module and the historical topographic change data of the target coastline is less than a preset threshold.

[0034] The results output module is used to input the calibrated equivalent coastal distance parameters and the basic parameters and initial profiles of the target coastline collected in real time into the one-dimensional beach evolution model, and output the topographic change data caused by coastal sediment transport.

[0035] The present invention has the following technical effects:

[0036] This invention efficiently characterizes the non-uniformity of coastal sediment transport in a one-dimensional shoreline evolution model by introducing an equivalent coastal distance parameter and its calculation formula. This innovative design overcomes the physical limitations of traditional models that rely on the assumption of "local conservation"—traditional methods, by ignoring the coastal sediment transport gradient, result in simulations that consistently present a false equilibrium where the erosion area equals the deposition area, failing to explain the actual continuous shoreline retreat. This invention, by quantifying the coastal sediment transport gradient through an equivalent parameter, for the first time reproduces the net loss process where the erosion area significantly exceeds the deposition area within a one-dimensional framework, accurately capturing the shoreline retreat trend. Furthermore, based on the CSHORE model integration scheme, the model retains the computational efficiency advantages of one-dimensional models while avoiding the high computational costs of two-dimensional models, achieving a unification of rapid engineering assessment and long-term evolution prediction. By dynamically optimizing the equivalent coastal distance parameter using historical shoreline data, it can output reliable predictions for complex scenarios such as steep cliff coastlines. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a flowchart of a method for calculating sediment transport along a sandy coastline, provided in an embodiment of the present invention.

[0039] Figure 2 This is a schematic diagram of a steep cliff-type coastal topography and wave incidence provided by an embodiment of the present invention;

[0040] Figure 3 This is a comparison chart of the initial state of the beach profile, the calculation results of the one-dimensional beach evolution model provided in the embodiments of the present invention, and the calculation results of the method of the present invention. Detailed Implementation

[0041] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present application.

[0042] Figure 1 is a flow chart of a sandy coast alongshore sediment transport calculation method provided by an embodiment of the present application. Referring to Figure 1 , the method comprises the following steps:

[0043] S1, obtaining basic parameters and an initial profile of a target coast.

[0044] In some embodiments, in the S1, the basic parameters comprise a wave incidence angle, a wave height, a wave period, a sediment grain size, a settling velocity, a specific gravity and a bottom sediment porosity; and the initial profile comprises a land boundary and bottom elevation data in a range of a closed depth under water, and the closed depth under water is determined by a wave breaking critical condition.

[0045] Specifically, in the sandy coast alongshore sediment transport calculation process, obtaining the basic parameters and the initial profile of the target coast is a core link of model initialization. The selection of the basic parameters needs to comprehensively reflect the coastal dynamic environment and the sediment transport characteristics: the wave incidence angle is used to quantify the component of the wave energy in the alongshore direction, which directly affects the alongshore sediment transport intensity; the wave height and the wave period jointly determine the nearshore wave energy distribution, which controls the sediment starting and suspension ability; the sediment grain size reflects the sediment transport response sensitivity, and the coarse particles need a higher starting flow velocity, and the fine particles are easy to suspend and migrate; the settling velocity is related to the suspended sediment falling and silting process, and affects the beach silting rate; the specific gravity is used for the conversion of the sediment bulk volume, and is used for correcting the sediment volume with the porosity; and the bottom sediment porosity is used for correcting the sediment volume transport amount. The definition of the initial profile needs to cover the complete range from the land boundary to the closed depth under water, the land boundary is usually bounded by the coastal vegetation line or artificial structures, and the closed depth under water is naturally formed by the wave breaking critical condition, the depth far away from the wave energy significantly decays, and the sediment transport activity tends to be static, which constitutes the natural boundary of the transverse calculation domain.

[0046] The initial profile data is usually obtained through field topographic survey and historical data integration. The wave parameters can be inversed through the observation buoy or numerical simulation (such as the SWAN model), and the sediment characteristics are determined through the surface sediment screening experiment and the settling column test.

[0047] S2, inputting the basic parameters and the initial profile into a one-dimensional beach evolution model to obtain a transverse profile variation term of the target coast caused by the alongshore sediment transport.

[0048] In some embodiments, the one-dimensional beach evolution model is a CSHORE model.

[0049] In the present embodiment, after inputting the basic parameters and the initial profile into the one-dimensional beach evolution model, the model first reconstructs the nearshore wave height field distribution based on the wave refraction-diffraction theory. The wave incidence angle and the wave height parameter drive the wave propagation equation to be solved, generating the spatial gradient of wave energy within the breaking zone; the wave period parameter is determined by spectral analysis to determine the flow oscillation frequency, providing periodic characteristic input for bottom shear stress calculation. The initial profile data define the calculation domain boundary: the land boundary is fixed as the backshore or cliff foot position of the beach, and the underwater closed depth boundary is dynamically calibrated according to the wave breaking critical condition, ensuring that the model domain covers all active sediment transport areas.

[0050] The core of the model is to use the bottom sediment continuity equation:

[0051] Equation (1);

[0052] where n p represents the bottom sediment porosity, which is 0.4; z b represents the bottom elevation (m); t represents the geomorphic evolution time; q x represents the total lateral sediment transport rate per unit width (excluding porosity, m 2 / s); q y represents the total onshore sediment transport rate per unit width (excluding porosity, m 2 / s).

[0053] First, calculate the uniform lateral profile evolution (i.e. ), only simulate lateral sediment transport, and obtain the lateral profile change term caused by onshore sediment transport of the target coast. In traditional one-dimensional beach evolution models, the bottom sediment continuity equation is often ignored , which is assumed to be uniform along the coast.

[0054] S3, introduce an equivalent onshore distance parameter to calculate the onshore sediment transport gradient.

[0055] In some embodiments, in S3, the formula of the equivalent onshore distance parameter is: where y e represents the equivalent onshore distance parameter, q y represents the onshore sediment transport rate per unit width, represents the onshore sediment transport gradient.

[0056] In order to effectively calculate the onshore sediment transport gradient, the present application introduces a new parameter: the equivalent onshore distance parameter, which is used to express the range of onshore sediment transport change approximated in the local profile calculation.

[0057] S4, determining an initial value of the equivalent alongshore distance parameter, inputting the alongshore sediment transport gradient into a one-dimensional beach evolution model, and calculating an alongshore elevation change term of the target coast caused by the alongshore sediment transport.

[0058] In some embodiments, the initial value of the equivalent alongshore distance parameter is set as an average distance between the wave incident boundary and the target coastline.

[0059] In the present embodiment, a transverse-alongshore two-way profile coupling calculation strategy is introduced, and a bottom bed elevation change z b of the target coast caused by the alongshore sediment transport is decomposed into a transverse profile change term z x and an alongshore elevation change term z y , i.e. ; and the continuity equation of the bottom bed sediment (i.e. formula 1) is further decomposed into:

[0060] formula (2);

[0061] formula (3).

[0062] Formula (2) can be directly solved by a numerical method; for formula (3), integration is performed in a time period in which the water level and wave conditions are constant, and a unit width alongshore deposition volume change is obtained:

[0063] ; wherein V y represents a unit width alongshore sediment transport volume (i.e. alongshore sediment transport volume), ; , and z

[0064] Q y is defined as a unit width time average volume flux in the alongshore direction (m³ / s), ; V y is an alongshore sediment transport volume (m³) in the entire transverse profile line direction from t to , also referred to as a full cross-section alongshore sediment transport volume, ; and the following relationship can be obtained: ; .

[0065] Assuming that the alongshore sediment transport volume can be represented by an equivalent alongshore distance y e , then ; combined with the formula of z , the alongshore elevation change term in S4 can be solved by the following formula:

[0066] ;

[0067] wherein n p denotes the bottom sediment porosity; denotes the amount of change in the coastal elevation caused by the alongshore sediment transport; denotes the time interval for simulating the beach evolution; Q y denotes the time-averaged volume flux per unit width in the alongshore direction, , x m is the calculation range of the cross section, q y is the total alongshore sediment transport rate per unit width.

[0068] This step compresses the two-dimensional sediment transport gradient effect into a one-dimensional framework by using the equivalent alongshore distance parameter y e The two-dimensional sediment transport gradient effect is compressed into a one-dimensional framework, and the traditional model is broken through to ignore the alongshore non-uniformity.

[0069] S5, superimposing the lateral cross-section variation term and the alongshore elevation change term to obtain complete target coastal terrain change data caused by alongshore sediment transport.

[0070] After the calculation of the lateral cross-section variation term and the alongshore elevation change term, this step generates complete terrain change data by spatial superposition. The lateral cross-section variation term reflects the vertical erosion and deposition response under the action of wave flow, and represents typical landforms such as beach shoulder erosion and foreland deposition. The alongshore elevation change term quantifies the non-uniform transport effect of sediment along the parallel shoreline direction, and reflects the local net erosion or deposition trend.

[0071] S6, iteratively calibrating the equivalent alongshore distance parameter based on the target coastal historical terrain change data until the terrain change output by S5 has an error less than a preset threshold from the target coastal historical terrain change data.

[0072] In some embodiments, the S6 specifically includes:

[0073] S61, collecting target coastal historical terrain change data;

[0074] The target coastal historical terrain change data includes shoreline translation position data, measured erosion area and deposition area values, and bottom elevation spatial distribution form data at different time periods.

[0075] S62, inputting an initial value of the equivalent alongshore distance parameter into the one-dimensional beach evolution model, executing S1-S5 to obtain complete target coastal terrain change data caused by alongshore sediment transport;

[0076] The target coastal terrain change data caused by alongshore sediment transport includes simulated shoreline recession distance, simulated erosion area and simulated deposition area, and simulated bottom elevation spatial distribution form data.

[0077] S63, adjust the equivalent alongshore distance parameter by the same order of magnitude (e.g. increase or decrease by ±10%~20% of the current order of magnitude), and repeat S62 until the error between the terrain change data and the target historical coastal terrain change data is less than the preset threshold.

[0078] S7, input the calibrated equivalent alongshore distance parameter and the basic parameters and initial profile of the target coast collected in real time into a one-dimensional beach evolution model, and output the terrain change data caused by alongshore sediment transport.

[0079] In some embodiments, S7 provides an operation process for actual prediction based on the calibrated model. Specifically, the final calibration value obtained by iteration optimization in S6 is input into the control parameter file of the one-dimensional beach evolution model (such as the CSHORE model) as a fixed parameter. At the same time, the current or predicted hydrodynamic and terrain basic data of the target coast are collected in real time, including the basic parameters such as wave incidence angle, wave height, wave period, sediment particle size, settling velocity, specific gravity, and bottom sediment porosity, as well as the latest initial bottom elevation profile data within the range from the land boundary to the closed depth underwater. The above parameters and the initial profile are collectively input into the model as input parameters to drive the model to perform time evolution calculation. Under the combined action of lateral sediment transport and parameterized alongshore sediment transport gradient, the model outputs the terrain change data of the target coast caused by the imbalance of alongshore sediment transport in a future period of time. The output results include but are not limited to the predicted shoreline recession or advance trend, the profile erosion and deposition spatial distribution, the net sediment loss, and the bottom morphology evolution process. The short-term to medium-term evolution trend of sandy coast is quickly predicted, which is suitable for pre-engineering evaluation, disaster warning, and shoreline management decision support.

[0080] For example, a certain steep cliff-type sandy coast is taken as the application object, which is long-term affected by 30° oblique incident waves. Historical monitoring shows that the annual average shoreline recession rate is significant. In order to analyze the influence of alongshore sediment transport non-uniformity on shoreline evolution, the method of the present application is used to carry out simulation prediction.

[0081] Data input: wave parameters, incidence angle 30°, wave height average value monitored by buoy, period determined by frequency spectrum analysis; sediment characteristics, median particle size obtained by sieve experiment, settling velocity determined by static water settling column; generated based on unmanned aerial vehicle aerial survey and underwater terrain scanning, land boundary is the cliff foot, and the underwater closed depth is calibrated according to the breaking wave critical depth formula.

[0082] As shown in Figure 2 , the x-axis is the vertical direction (i.e. the lateral sediment transport direction), the y-axis is the alongshore direction (i.e. the alongshore sediment transport direction), the blue line is the incident wave, Let be the angle between the incident wave and the vertical direction. A transverse profile line is set at y=5m to evaluate the shoreline retreat rate in the y=4~6m section. Analysis of the experimental data shows that the shoreline sediment transport rate increases rapidly near y=0, while it tends to stabilize in the y=4~6m range. The shoreline retreat is approximately uniform in this range, indicating that the variation in shoreline sediment transport rate is small, satisfying the approximation of local uniformity. The initial value of the equivalent shoreline distance parameter is set as the average distance (7m) between the wave incident boundary and the shoreline.

[0083] Collect historical data, such as the coastline shift over the past 5 years (average annual retreat of 3.2m) and measured erosion / siltation area (erosion accounts for 68%). Initial value y e When the depth is 7m, the simulated erosion area is 15% lower than the measured value; adjust y e After reaching 10m, the simulated erosion area ratio increased to 70%, and the shoreline retreat distance error was <5%; the spatial distribution of bed elevation matched 92%, meeting the convergence conditions.

[0084] like Figure 3 As shown, the blue curve represents the beach profile at the initial moment of calculation; the red curve represents the bed elevation calculated based on the governing equations. The evolution results neglect the coastal sediment transport gradient term. This result corresponds to a traditional one-dimensional shoreline evolution model, which only considers lateral sediment transport, thus exhibiting a "local conservation" characteristic where the areas of erosion and deposition zones are equal. The black curve represents the gradient term of the shoreline sediment transport rate. The inclusion of this parameter in the model calculation reflects the combined effect of lateral sediment transport and coastal sediment transport gradient. In this calculation, the equivalent coastal distance parameter obtained through model experiment calibration is y. e = 10m. Simulation results show that the total erosion area of ​​the profile is significantly larger than the deposition area, indicating that the transverse profile is affected by uneven sediment transport along the coast, resulting in a net erosion process and an overall retreat trend of the shoreline.

[0085] In embodiments involving steep cliff coasts, this invention significantly improves the physical accuracy and engineering practicality of shoreline evolution prediction through the calibration and application of equivalent coastal distance parameters. When a 30° oblique incident wave acts on a steep cliff coast, the traditional one-dimensional model neglects the coastal sediment transport gradient (…). Figure 3 The red curve indicates that the simulation results consistently present a false equilibrium state where the erosion zone and the siltation zone have equal areas, failing to explain the continuous retreat of the measured shoreline. This invention, however, optimizes the equivalent coastal distance parameter to a reasonable range through a dynamic calibration mechanism. Figure 3 The black curve enables the model to accurately quantify the non-uniformity of sediment transport along the coast while retaining one-dimensional computational efficiency. The model successfully reproduces the net loss characteristic where the erosion area is significantly greater than the siltation area, and the error of the shoreline retreat distance is reduced to an extremely low level.

[0086] The application also provides a sandy coast alongshore sediment transport calculation system for the above-mentioned sandy coast alongshore sediment transport calculation method, comprising:

[0087] a data input module for obtaining basic parameters and an initial profile of a target coast;

[0088] a lateral profile simulation module for inputting the basic parameters and the initial profile into a one-dimensional beach evolution model to obtain a lateral profile variation term of the target coast caused by alongshore sediment transport;

[0089] a alongshore sediment transport gradient calculation module for introducing an equivalent alongshore distance parameter and calculating a alongshore sediment transport gradient;

[0090] a alongshore elevation simulation module for determining an initial value of the equivalent alongshore distance parameter, inputting the alongshore sediment transport gradient into the one-dimensional beach evolution model, and calculating a alongshore elevation variation term of the target coast caused by alongshore sediment transport;

[0091] a terrain variation obtaining module for superimposing the lateral profile variation term and the alongshore elevation variation term to obtain complete terrain variation data of the target coast caused by alongshore sediment transport;

[0092] a calibration module for iteratively calibrating the equivalent alongshore distance parameter based on historical bottom elevation variation data of the target coast until the terrain variation output by the terrain variation obtaining module and the historical terrain variation data of the target coast have an error less than a preset threshold value;

[0093] a result output module for inputting the calibrated equivalent alongshore distance parameter and real-time collected basic parameters and initial profile of the target coast into the one-dimensional beach evolution model and outputting terrain variation data caused by alongshore sediment transport.

[0094] It should be noted that the terms used in the present application are only for describing specific embodiments and are not intended to limit the scope of the present application. As shown in the specification of the present application, unless the context clearly indicates otherwise, the words "one", "a", "an", and / or "the" do not specifically refer to the singular, but can also include the plural. The terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method or device including the element.

[0095] It should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like, indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are used only to facilitate the description of the present application and simplify the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise specifically defined and limited, the terms "mount", "connect", "connect" and the like should be broadly understood, for example, can be fixedly connected, can also be detachably connected, or integrally connected; can be mechanically connected, can also be electrically connected; can be directly connected, can also be indirectly connected through an intermediate medium; can be internal communication of two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0096] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present application.

Claims

1. A method of calculating the alongshore transport of sediment at a sandy coast, characterized by, The method comprises the following steps: S1, obtaining basic parameters and an initial profile of a target coast; S2, inputting the basic parameters and the initial profile into a one-dimensional beach evolution model to obtain a horizontal profile variation term of the target coast caused by alongshore sediment transport; The one-dimensional beach evolution model is a CSHORE model; S3, introducing an equivalent alongshore distance parameter to calculate an alongshore sediment transport gradient; The formula of the equivalent alongshore distance parameter is: where y e represents the equivalent alongshore distance parameter, q y represents the alongshore sediment transport rate per unit width, represents the alongshore sediment transport gradient; An initial value of the equivalent alongshore distance parameter is set as an average distance between a wave incident boundary and a target coastline; S4, determining the initial value of the equivalent alongshore distance parameter, and inputting the alongshore sediment transport gradient into the one-dimensional beach evolution model to calculate an alongshore elevation variation term of the target coast caused by alongshore sediment transport; S5, superimposing the horizontal profile variation term and the alongshore elevation variation term to obtain complete topographic variation data of the target coast caused by alongshore sediment transport; S6, iteratively calibrating the equivalent alongshore distance parameter based on historical topographic variation data of the target coast until the topographic variation data output in S5 has an error less than a preset threshold value from the historical topographic variation data of the target coast; S7, inputting the calibrated equivalent alongshore distance parameter and real-time collected basic parameters and an initial profile of the target coast into the one-dimensional beach evolution model to output topographic variation data caused by alongshore sediment transport.

2. The method of claim 1, wherein, In S1, the basic parameters include a wave incident angle, a wave height, a wave period, a sediment particle size, a settling velocity, a specific gravity, and a bottom sediment porosity; and the initial profile includes land boundary and bottom elevation data within a closed underwater depth range, and the closed underwater depth is determined by a wave breaking critical condition.

3. The method of claim 1, wherein, In S4, the alongshore elevation variation term is solved by the following formula: ； where n p represents the porosity of the bottom sediment; represents the amount of change in the coastal elevation due to the coastal sediment transport; represents the time interval for simulating the evolution of the beach; Q y represents the time-averaged volume flux per unit width in the coastal direction, , x m is the calculation range of the cross section, q y is the total sediment transport rate per unit width in the coastal direction.

4. The method of claim 1, wherein, S6 specifically comprises: S61, collecting historical topographic variation data of the target coast; S62, inputting an initial value of the equivalent alongshore distance parameter into the one-dimensional beach evolution model to perform S1-S5 to obtain complete topographic variation data of the target coastline caused by alongshore sediment transport; S63, adjusting the equivalent alongshore distance parameter by an equivalent order, and repeating S62 until the topographic variation data has an error less than a preset threshold value from the historical topographic variation data of the target coast.

5. A method of calculating the sediment transport along a sandy coast according to claim 4, characterized in that, In S61, the historical topographic variation data of the target coast includes shoreline translation position data, measured values of erosion area and deposition area, and bottom elevation spatial distribution form data at different time periods; In S62, the topographic variation data of the target coast caused by alongshore sediment transport includes simulated shoreline recession distance, simulated erosion area and deposition area, and simulated bottom elevation spatial distribution form data.

6. A system for calculating the alongshore sediment transport of a sandy coast, for performing the method for calculating the alongshore sediment transport of a sandy coast according to any one of claims 1 to 5, characterized in that, The method comprises: a data input module for obtaining basic parameters and an initial profile of a target coast; a horizontal profile simulation module for inputting the basic parameters and the initial profile into a one-dimensional beach evolution model to obtain a horizontal profile variation term of the target coast caused by alongshore sediment transport; an alongshore sediment transport gradient calculation module for introducing an equivalent alongshore distance parameter to calculate an alongshore sediment transport gradient; an alongshore elevation simulation module for determining an initial value of the equivalent alongshore distance parameter, and inputting the alongshore sediment transport gradient into the one-dimensional beach evolution model to calculate an alongshore elevation variation term of the target coast caused by alongshore sediment transport; and The terrain change obtaining module is configured to superimpose the lateral profile change term and the alongshore elevation change term to obtain complete terrain change data of the target coast caused by alongshore sediment transport; The calibration module is configured to iteratively calibrate the equivalent alongshore distance parameter based on historical terrain change data of the target coast until the terrain change output by the terrain change obtaining module has an error less than a preset threshold value with the historical terrain change data of the target coast; The result output module is configured to input the calibrated equivalent alongshore distance parameter and the basic parameters and the initial profile of the target coast collected in real time into a one-dimensional beach evolution model to output terrain change data caused by alongshore sediment transport.

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