Method for forecasting navigation capacity of strong erosion-silting estuary for limiting navigation channel

Abstract

The invention provides a method for forecasting the navigation capacity of a strong erosion-silting estuary for limiting a channel, and relates to the technical field of water transportation. Comprising the following steps: S1, collecting related hydrological and topographic data, and collecting weather forecast information of a weather department in future 2 days; s2, predicting the tide level change process of the estuary gate in the next two days by adopting a tide harmonic analysis method; s3, establishing a tidal water flow mathematical model by adopting the latest topographic data, and carrying out real-time calibration work of the tidal water flow mathematical model by utilizing actually measured hydrological data in recent two days; s4, calculating navigation water flow conditions of the channel in the next two days based on the calibrated tidal water flow mathematical model in combination with forecast tide level data; and S5, in combination with ship navigation restrictive elements of forecast weather, water depth and flow velocity, determining a time period in which the ship is allowed to navigate in the next two days. The real-time performance and accuracy of forecasting can be well achieved, decision support is provided for channel management, and navigation safety and efficiency are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of water transport, and in particular to a method for predicting the navigability of a restricted waterway in a heavily eroded and silted estuary. Background Art

[0002] Globally, estuaries with severe erosion and siltation have always been a difficult and key point in the field of waterway management and navigation safety due to their complex hydrodynamics and severe riverbed erosion and siltation. With the growth of global economic integration and trade volume, the stability and navigability of estuaries, as important gateways connecting inland and ocean, are of great value in ensuring smooth maritime transportation and promoting regional economic development. However, estuaries with severe erosion and siltation often face problems such as severe riverbed erosion and siltation, unstable water depth, and variable flow rate. These factors not only affect the navigation safety of ships, but also restrict the passage of large ships, thereby affecting the navigability of the waterway. Traditional waterway design and navigation capacity prediction mainly rely on statistical analysis of historical data to obtain fixed design parameters such as channel bottom elevation, width, and channel depth. This static analysis method is difficult to accurately capture the complexity of the dynamic changes of water and sediment in estuaries with severe erosion and siltation. In recent years, with the improvement of hydrological monitoring, numerical simulation, and computational efficiency, it has become possible to provide real-time monitoring and accurate prediction. In view of the unique environment of estuaries with severe erosion and siltation, developing a method to accurately predict channel restriction conditions is of great and urgent practical significance for ensuring the safety of ship navigation in estuary areas and improving navigation capacity. Summary of the invention

[0003] The purpose of the present invention is to provide a method for predicting the navigability of restricted waterways in heavily eroded and silted estuaries, which can predict the navigable period for ships within the next three days and provide decision support for waterway management and ship scheduling.

[0004] To achieve the above object, the technical solution adopted by the present invention is: A method for predicting the navigability of a restricted channel in a heavily eroded and silted estuary comprises the following steps: S1. Collect relevant hydrological and topographic data, and collect weather forecast information for the next two days provided by the meteorological department; S2. Use tidal harmonic analysis to predict the tidal level changes at the estuary in the next two days; S3. Use the latest terrain data to establish a tidal flow mathematical model, and use the hydrological data measured in the past two days to carry out real-time calibration of the tidal flow mathematical model; S4. Combined with the forecast tide data, the water flow conditions of the channel in the next two days are calculated based on the calibrated tidal flow mathematical model; S5. Based on the forecast weather, water depth, current velocity and other restrictive factors for ship navigation, determine the time periods in the next two days when ships are allowed to navigate normally.

[0005] Furthermore, in step S1: The hydrological data include flow, water level, flow velocity data of fixed hydrological stations around the waterway, and tide level data at the river estuary; the topographic data are the latest river topographic data, and the topographic data are monitored regularly depending on the severity of riverbed scouring and silting. The time interval for topographic measurements in river sections with stable scouring and silting will be relaxed, while the frequency of topographic measurements in river sections with severe scouring and silting needs to be increased; the meteorological forecast information includes wind level and visibility distance elements related to navigation.

[0006] Furthermore, the step S3 includes the following sub-steps: S31. Construct a mathematical model of tidal currents in the estuary area based on triangular grids and perform local encryption on the waterway area; S32, using the runoff data obtained in step S1 as the flow boundary on the upstream side, using the tide level data at the estuary obtained in step S1 as the water level boundary on the downstream side, and calculating the terrain using the latest river terrain obtained in step S1; S33, calibrating the calculation parameters of the tidal current mathematical model according to the measured water level and flow velocity data of the fixed water level stations around the waterway; S34. If the calculation results meet the calibration accuracy requirements for flow velocity and water level in the current technical specifications, the calibration step of the tidal flow mathematical model is completed; if the calculation results do not meet the calibration accuracy requirements in the current technical specifications, adjust the calculation parameters until the calculation results meet the requirements of the current technical specifications.

[0007] Furthermore, the step S4 includes the following sub-steps: S41, using the tide level data predicted in step S2 as the downstream water level boundary condition of the tidal flow mathematical model, and the upstream flow boundary and calculation terrain remain unchanged; S42. Based on the calibrated tidal flow mathematical model, calculate the time-varying process of the water level and flow velocity of the entire channel in the next two days.

[0008] Furthermore, in step S5, the normal navigation period is a period of time in the next two days in which the lateral flow velocity and the longitudinal flow velocity of the entire channel are both less than the navigation velocity threshold, and the water depth of the channel is greater than the navigation depth threshold, and the wind speed is less than the navigation wind speed threshold, and the visibility distance is greater than the navigation visibility distance threshold, then ships are allowed to navigate during this period, otherwise, navigation is not allowed.

[0009] Compared with the prior art, the beneficial effects of the present invention are: 1. Based on the latest hydrological and river topographic data of the waterway, the calculation parameters of the tidal flow model can be calibrated in real time to ensure that the calculation result error meets the requirements of relevant technical specifications; combined with the forecast of offshore astronomical tide processes, the waterway flow conditions in the next two days are predicted based on the tidal flow mathematical model with calibrated calculation parameters, ensuring the real-time and accuracy of the model calculation parameters.

[0010] 2. According to the predicted water flow conditions of the waterway, the real-time water depth change process along the entire waterway is determined. For river sections with severe riverbed erosion and siltation and coupled changes of water level and riverbed, the fixed design bottom elevation used in traditional waterway design is avoided, and the navigation capacity of the restricted waterway is fully tapped.

[0011] 3. Based on the predicted water flow and meteorological conditions, determine the time period in the next two days when ships can sail normally, provide decision support for waterway management, and ensure navigation safety and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Flow chart of the implementation steps of the method of the present invention; Figure 2 It is a schematic diagram of calibration results before and after adjustment of calculation parameters of tidal current model in the embodiment; Figure 3 It is the navigation period allowed when the water flow conditions are met in the embodiment. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0014] like Figure 1 As shown, the present invention provides a method for predicting the navigability of a restricted channel in a heavily eroded and silted estuary, comprising the following steps: S1. Collect relevant hydrological and topographic data, and collect weather forecast information for the next two days provided by the meteorological department; Collect hourly flow data from a power station upstream of the estuary from September 1 to 3, 2019 Q (m 3 / s), the value is 50~815 m 3 / s; Collect the latest measured river topography in the estuary area. The measurement time is from July 15 to 30, 2019, and the measurement scale is 1:10,000. The hourly tide level data of the long-term tide gauge station at the estuary from 2018 to 2019 were collected, with values ​​ranging from -3.33 to 5.89 m, and an average of 0.52 m; Collect the hourly tide level and flow velocity data of the past two days from the fixed hydrological stations around the research channel section. The tide level value is 3.26~6.0m, and the flow velocity value is 0.09~2.55m / s; The wind intensity from September 4th to 5th was collected from an official meteorological website. WF, visibility distance VD (km) distance forecast data.

[0015] S2. Use tidal harmonic analysis to predict the tidal level change process at the estuary in the next two days; specifically, it includes the following sub-steps: S21. Preprocess the tide level data at the estuary from 2018 to 2019, exclude outliers and missing data, and ensure the accuracy and completeness of the data; S22. Identify the main periodic tides in the tidal signal through spectrum analysis, such as M2 (lunar tide), S2 (solar tide), K1, O1, etc.; S23, using the least squares method, calculate the harmonic constant of each tidal component from the observed data and construct a harmonic model; S24. Based on the harmonic constant, the tidal level change process at the estuary from September 4 to 5, 2019 is predicted, and the value is -2.98~5.39m.

[0016] S3. Use the latest terrain data to establish a tidal flow mathematical model, and use the hydrological data measured in the past two days to carry out real-time calibration of the tidal flow mathematical model; specifically, it includes the following sub-steps: S31. Construct a mathematical model of tidal flow in the estuary area based on triangular grids and perform local encryption on the channel area, namely: The mathematical model of tidal flow is constructed based on the shallow water equation. The computational domain is divided by triangular meshes and the channel area is encrypted. The control equation is as follows:

[0017] In the formula, are the vertical average velocity components in the x and y directions respectively ( ); is the water depth ( ); g is the acceleration due to gravity, take 9.81m 2 / s; is the Coriolis force parameter ( , is the latitude, is the Earth's rotation speed); is Xie Cai coefficient, take ; is the roughness coefficient, ranging from 0.005 to 0.03; are the eddy diffusion coefficients in the x and y directions respectively; is the wind stress component in the x and y directions; x, y are rectangular coordinates; t is time.

[0018] S32. The runoff from a power station upstream of the estuary from September 1 to 3, 2019 is used as the upstream flow boundary of the tidal flow mathematical model. The tide level data from the long-term tide gauge station at the estuary from September 1 to 3, 2023 is used as the downstream water level boundary of the tidal flow mathematical model. The latest measured river channel terrain in the estuary area is interpolated to a triangular grid as the terrain for calculation of the tidal flow mathematical model. S33. Based on the tidal flow mathematical model under the initial calculation parameter settings, the flow condition simulation calculation of the channel section from September 1 to 3, 2019 was carried out. The riverbed roughness parameter was taken as 0.01. The calculation results of the fixed hydrological stations around the channel section were extracted and compared with the measured data. Figure 2 In (a), the comparison results show that the tidal flow mathematical model calculates the high tide level too low, the low tide level too high, and the flow velocity too low, and the calculation accuracy does not meet the accuracy requirements of the current technical specifications; S34, reduce the riverbed roughness parameter from 0.01 to 0.008, use the tidal flow mathematical model to simulate the flow conditions of the channel section again, extract the calculation results of the fixed hydrological stations around the channel section and compare them with the measured data, see Figure 2 The comparison in (b) shows that the calculation accuracy is significantly improved after the riverbed roughness parameters are adjusted, meeting the accuracy requirements of current technical specifications.

[0019] S4. Combined with the forecast tide data, the water flow conditions of the channel in the next two days are calculated based on the calibrated tidal flow mathematical model, which specifically includes the following sub-steps: S41, upstream flow boundary is the average flow of 550m from September 1 to 3, 2019 3 / s, and the estuary tidal level forecast data for the next two days in step 2 is used as the downstream water level boundary; S42. Based on the calibrated tidal current mathematical model, the navigation depth and flow velocity conditions from September 4 to 5, 2019 are predicted, and the calculation results are output every half an hour.

[0020] S5, based on the forecast weather, water depth, current speed and restrictive factors for ship navigation, determine the time periods in the next two days when ships are allowed to navigate normally.

[0021] The representative points were selected at intervals of 500 m, and the water level and flow velocity changes at each representative point from September 4 to 5, 2023 were extracted from the calculation results of the tidal current mathematical model. The lateral flow velocity was separated according to the direction of the channel at each representative point. V1 (m / s), longitudinal flow velocity V2 (m / s) change process, the water depth is obtained by subtracting the riverbed elevation from the water level calculated at each representative pointh (m) Change process; According to the existing technical specifications for normal navigation, according to the lateral flow velocity V1 No more than 0.3 m / s, longitudinal flow velocity V2 Not more than 2.0m / s, water depth h Not less than 3.2m, wind level WF Not more than level 6, visibility distance VD The normal navigation threshold of the waterway section is not less than 1.0 km; the maximum lateral velocity, maximum longitudinal velocity, and minimum navigable water depth of each representative point at each time are extracted over time. According to the water flow condition threshold for navigation, the navigation period is 1:15-6:45 and 13:20-18:45 on September 4 and 1:15-6:45 and 13:20-18:45 on September 5. The judgment results are shown in Figure 3 According to the weather forecast, the wind level on September 4-5, 2023 is less than level 6, and the visibility distance from 6:00 to 8:30 on September 5 is VD Less than 1.0km; it is finally determined that the navigation periods on September 4-5, 2023 are 1:15-6:45 and 13:20-18:45 on September 4 and 1:15-6:00 and 13:20-18:45 on September 5.

[0022] The above embodiments and the specific parameters therein are only for clearly describing the invention verification process, and are not intended to limit the patent protection scope of the present invention. The patent protection scope of the present invention shall still be based on its claims. Any equivalent structural changes made using the contents of the description and drawings of the present invention should also be included in the protection scope of the present invention.

Claims

1. A method for predicting the navigability of restricted waterways in heavily eroded and silted estuaries, characterized by: The following steps are involved: S1. Collect relevant hydrological and topographic data, and collect weather forecast information for the next two days provided by the meteorological department; S2. Use tidal harmonic analysis to predict the tidal level changes at the estuary in the next two days; S3. Use the latest terrain data to establish a tidal flow mathematical model, and use the hydrological data measured in the past two days to carry out real-time calibration of the tidal flow mathematical model; S4. Combined with the forecast tide data, the water flow conditions of the channel in the next two days are calculated based on the calibrated tidal flow mathematical model; S5. Based on the forecast weather, water depth, current velocity and other restrictive factors for ship navigation, determine the time periods in the next two days when ships are allowed to navigate normally.

2. The method for predicting the navigability of restricted waterways in heavily eroded and deposited estuaries according to claim 1 is characterized by: In step S1: The hydrological data include flow, water level, flow velocity data of fixed hydrological stations around the waterway, and tide level data at the estuary; The topographic data is the latest river course topographic data. The topographic data is regularly monitored depending on the severity of riverbed scouring and silting. The time interval for topographic measurement in river sections with stable scouring and silting is relaxed, while the frequency of topographic measurement in river sections with severe scouring and silting needs to be increased. The weather forecast information includes wind level and visibility distance elements related to navigation.

3. The method for predicting the navigability of restricted waterways in heavily eroded and silted estuaries according to claim 1 is characterized by: The step S3 includes the following sub-steps: S31. Construct a mathematical model of tidal currents in the estuary area based on triangular meshes, and perform local densification in the channel area; S32, using the runoff data obtained in step S1 as the flow boundary on the upstream side, using the tide level data at the estuary obtained in step S1 as the water level boundary on the downstream side, and calculating the terrain using the latest river terrain obtained in step S1; S33, calibrating the calculation parameters of the tidal current mathematical model according to the measured water level and flow velocity data of the fixed water level stations around the waterway; S34. If the calculation results meet the calibration accuracy requirements for flow velocity and water level in the current technical specifications, the calibration step of the tidal flow mathematical model is completed; if the calculation results do not meet the calibration accuracy requirements in the current technical specifications, adjust the calculation parameters until the calculation results meet the requirements of the current technical specifications.

4. The method for predicting the navigability of restricted waterways in heavily eroded and silted estuaries according to claim 1 is characterized by: The step S4 includes the following sub-steps: S41, using the tide level data predicted in step S2 as the water level boundary condition on the downstream side of the tidal flow mathematical model, and keeping the upstream flow boundary and calculation terrain unchanged; S42, calculating the change process of the water level and flow velocity of the entire channel over time in the next two days based on the calibrated tidal flow mathematical model.

5. The method for predicting the navigability of restricted waterways in heavily eroded and deposited estuaries according to claim 1 is characterized by: In step S5, the time period during which normal navigation is allowed is a period of time in the forecasted entire channel in the next two days when both the lateral flow velocity and the longitudinal flow velocity of the entire channel are less than the navigation velocity threshold, and the channel water depth is greater than the navigation depth threshold, and the wind speed is less than the navigation wind speed threshold, and the visibility distance is greater than the navigation visibility distance threshold, then ships are allowed to navigate during this period, otherwise navigation is not allowed.

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