Method for contrastive analysis of bay hydrodynamic environments of different years

Abstract

The invention discloses a method for contrastive analysis of bay hydrodynamic environments of different years. Basic data such as bay water depth data, coastline data and actually measured tide data of different years are collected, and refined bay ocean hydrodynamic models of different years are established by using a numerical simulation method; in order to accurately compare and analyze numerical simulation results of different years, models of different years are established in the same grid, bay ocean hydrodynamic force changes of different years, such as tide level, tide and tidal capacity changes, are analyzed on the basis of sufficient verification, the influence of historical development on the bay ocean hydrodynamic force is evaluated, and the bay ocean hydrodynamic force is obtained. And predicting the influence of the new bay development plan on the ocean water power.

Description

Technical Field

[0001] The invention relates to the technical field of ocean hydrodynamic environment, in particular to a method for comparative analysis of bay hydrodynamic environments in different eras. Background Art

[0002] In the early 21st century, coastal areas carried out land reclamation activities in order to build industrial development zones, coastal tourist areas, new towns and large-scale infrastructure, alleviate the shortage of urban land, and achieve a balance between the occupation and compensation of cultivated land. Some land reclamation has had an impact on the marine ecological environment, such as the reduction of tidal volume in the bay, the weakening of the self-purification capacity of seawater, and the decline of the self-repair capacity of the marine ecosystem.

[0003] The existing analysis of the evolution of the bay mainly focuses on comparative analysis of the topographic changes and coastline changes in the bay at different times. There is no in-depth analysis and research on the evolution of the hydrodynamic environment brought about by the changes in topography and coastline. How to accurately analyze the evolution of the hydrodynamic environment brought about by the changes in topography and coastline is of great significance to the development and utilization of marine resources.

[0004] At present, by collecting the numerical simulation results of the bay at different ages, we can conduct a comparative analysis of the bay's hydrodynamic environment at different ages. However, since the mathematical models established at different ages are not unified and there are differences in the model grid division, this will inevitably lead to differences in the simulation results, resulting in inaccurate comparative analysis results. Summary of the invention

[0005] The purpose of the present invention is to provide a method for comparative analysis of the hydrodynamic environment of bays in different ages, so as to solve the above technical problems, reduce the differences caused by the model itself, and more accurately compare and analyze the hydrodynamic environment of bays in different ages.

[0006] The technical solution of the present invention is as follows:

[0007] A method for comparative analysis of bay hydrodynamic environments in different eras, comprising the following steps:

[0008] Step 1: Collect water depth data and coastline data of different ages for at least the bay and the offshore areas adjacent to the bay, as well as basic data on measured tide level data in the bay area;

[0009] Step 2: Based on the coastline data of different ages, all the coastline boundaries of different ages to be compared and analyzed are added to the mathematical model pre-processing program, and then gridded into blocks. The common areas in the boundaries of different ages generate block 1, the unique areas of the n1 era generate block 2, the unique areas of the n2 era generate block 3..., and so on, to generate model boundary files containing different ages;

[0010] Step 3: Generate a grid for the n1 era. Block 1 generated by the common area and block 2 generated by the n1 era-specific area generate grids, and no grids are generated for the other blocks; generate a grid for the n2 era. Block 1 generated by the common area and block 3 generated by the n2 era-specific area generate grids, and no grids are generated for the other blocks; and so on, generate grid files for different eras n1, n2, ...;

[0011] Step 4: Import the water depth data of different ages into the generated grid files of corresponding ages, generate corresponding terrain grid files, and set the model hydrological boundaries;

[0012] Step 5: According to the bay conditions and relevant data, the values ​​of the bay bottom roughness and eddy viscosity coefficient are verified and determined through the latest measured hydrological data, and parameter files are prepared for the coefficients whose values ​​change with time or space;

[0013] Step 6: Import the terrain grid file, hydrological boundary conditions and parameter files into the hydrodynamic calculation mathematical model, and start the calculation file to calculate the hydrodynamic characteristics of the bay in different ages;

[0014] Step 7: Analyze and compare the changes in water levels, tidal currents, and tidal volume in the bay in different eras, and conduct an analysis of the evolution of ocean hydrodynamics.

[0015] Furthermore, the mathematical model pre-processing program adopts the MIKE21 software pre-processing program, the mathematical model adopts the MIKE21 hydrodynamic calculation model, and the grid attribute is set to a triangular grid.

[0016] Furthermore, the water depth data includes measured water depth data of the inner bay of the bay, measured elevation data of the outer bay of the bay and charted water depth data of the open sea adjacent to the bay, and the water depth data is interpolated to the horizontal grid points of the model by using the inverse distance weighted interpolation method.

[0017] Furthermore, the model open boundary is located in the open sea, and the model open boundary forcing is set to be tidal driven.

[0018] Furthermore, the hydrological boundary conditions of different ages uniformly adopt the latest measured hydrological data.

[0019] Furthermore, the water level evolution was analyzed by the changes in tidal range during spring tides and neap tides at multiple different stations in the bay in different years.

[0020] Furthermore, the tidal evolution analysis was carried out based on the mean flow velocity of different years at multiple stations in the bay and the distribution of rising and falling rapids in the entire calculation domain.

[0021] Furthermore, the tidal volume is calculated by the following formula:

[0022]

[0023] Where P is the tidal volume; n is the total number of model grids; S i , H 1i , H 2i are the area of ​​the ith grid and the high and low tide levels of the grid respectively.

[0024] Furthermore, a verification step of the hydrodynamic calculation mathematical model is added. When performing water level verification, the measured water level data is compared and verified with the water level simulation results of the model; when performing tidal flow verification, the measured tidal flow data is compared and verified with the tidal flow simulation results of the model.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention provides a method for comparative analysis of the bay hydrodynamic environment at different ages. By collecting basic information such as bay water depth data, coastline data and measured tidal data at different ages, a refined bay ocean hydrodynamic model of different ages is established using a numerical simulation method. In order to accurately compare and analyze the numerical simulation results of different ages, the models of different ages are established in the same set of grids. On the basis of sufficient verification, the changes in bay ocean hydrodynamics at different ages, such as changes in tide level, tidal current and tidal volume, are analyzed. The impact of historical development on bay ocean hydrodynamics is evaluated, and the impact of new bay development plans on ocean hydrodynamics is predicted, so as to contribute to the decision-making of high-quality development of the ocean.

[0027] The model grids of different ages are divided uniformly to ensure the consistency of the model grids in the public area, reduce the differences in simulation results caused by the model itself, and more accurately compare and analyze the bay hydrodynamic environment of different ages. It has good promotion value for evaluating the impact of historical development on the bay's marine hydrodynamics and predicting the impact of new bay development plans on marine hydrodynamics. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0029] Figure 1 This is an overlay comparison of the positions of a certain port shoreline in 1984, 2000 and 2020;

[0030] Figure 2 This is a grid diagram of a port hydrodynamic model in 1984;

[0031] Figure 3 This is a grid diagram of a port hydrodynamic model in 2000;

[0032] Figure 4 This is a grid diagram of a port hydrodynamic model in 2020;

[0033] Figure 5 This is a schematic diagram of water depth distribution of the 1984 model obtained by inverse distance weighted interpolation;

[0034] Figure 6 This is a schematic diagram of the water depth distribution of the 2000 model obtained by inverse distance weighted interpolation;

[0035] Figure 7 This is a schematic diagram of the water depth distribution of the 2020 model obtained by inverse distance weighted interpolation;

[0036] Figure 8 This is a schematic diagram of the change in water depth of a certain port from 2000 to 2020;

[0037] Fig. 9 This is a schematic diagram of the verification results comparing the model results with the water level at water level verification site 1;

[0038] Fig.10 This is a schematic diagram of the verification results of the model results and the water level of the water level verification site 2;

[0039] Fig.11 The model results are compared with the measured tidal current data during spring and neap tides at the C1 site;

[0040] Fig.12 This is a schematic diagram comparing the high tide water levels at point T5 in different years;

[0041] Fig.13 This is a schematic diagram comparing the low tide water levels at point T5 in different years;

[0042] Fig.14 This is a schematic diagram of the flow field during the high tide in 2020;

[0043] Fig.15 This is a schematic diagram of the flow field at the peak of the high tide in 2020;

[0044] Fig.16 This is a schematic diagram of the flow field during the 2020 neap tide.

[0045] Fig.17 This is a schematic diagram of the flow field during the 2020 low tide.

[0046] Fig.18 Schematic diagram of flow velocity comparison in Section 2 in 1984, 2000, and 2020. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments and related drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0048] Let’s take a port on the southeast coast of China as an example.

[0049] 1. Collect basic information about at least one port on the southeast coast:

[0050] Collect basic data including at least the water depth data and coastline data of different ages of the bay and the offshore areas adjacent to the bay, as well as the measured tide level data of the bay area.

[0051] The port of a certain place is southeast-northwest oriented, with an overall narrow and tortuous shape. There are many mountains on both sides of the coastline, and many small islands are distributed in the harbor. The horizontal depth of the port of a certain place is about 35km. Most of the water depth in the bay is more than 10m. There is a deep trough with a depth of more than 20m in the channel near point A, and the maximum water depth is 45m; there is a vast intertidal zone of mudflats inside point A. The estuary of the port of a certain place is about 2km wide and faces east. There is an island B as an important barrier to the estuary to prevent natural disasters such as storm surges. The port of a certain place is a natural shelter. The tidal range in the bay is large, the tide is strong, the water exchange is sufficient, and there is a developed marine aquaculture industry. Due to the strong tidal effect, it is difficult for silt to accumulate in the harbor of a certain place. Therefore, the coast near the port of a certain place is mainly composed of bedrock. There is no large surface runoff near the port of a certain place, and no barrier sand is formed at the estuary. It is a tectonic harbor.

[0052] The climate of a certain port belongs to the subtropical marine monsoon climate. It is surrounded by mountains, with a suitable climate, four distinct seasons and moderate precipitation. The annual average temperature of a certain port is 18.5℃. The highest average temperature of the year occurs in July, which is 28.2℃, and the lowest average temperature occurs in January, which is 8.6℃. The record of extreme high temperature in previous years is 40.6℃, and the record of extreme low temperature is -5.2℃; the annual average precipitation is 1699.5mm; the precipitation in coastal areas is between 1300mm and 1700mm, of which the annual average precipitation on islands is less than 1200mm; the annual average evaporation is 1314.2mm, and the evaporation is at its peak from June to October, and the monthly evaporation can reach more than 120mm. In addition, southeast wind prevails in a certain port in summer and north wind prevails in winter. There is a strong seasonal difference in wind. The average wind speed for many years is 1.6m / s, and the number of days with an annual average wind speed greater than 17m / s is 5.8d.

[0053] The tide of a certain port belongs to the regular semi-diurnal tide. Since records began, the highest tide level in the history of a certain port is 11.26m (July 31, 1999, the assumed elevation of a certain tide station, the same below), the lowest tide level in history is 3.3m (December 10, 1964), the average high tide level is 9.23m, the average low tide level is 5.1m, the average sea level is 7.24m, the average tidal range is 4.12m, the largest tidal range in history is 6.82m (December 21, 1959), the average high tide lasts 6h13min, and the average low tide lasts 6h12min. The tide of a certain port belongs to the semi-diurnal tide, the rising and falling tides flow in a reciprocating manner, and the rising tide is weaker than the falling tide, and the surface current is stronger than the bottom current. The dominant factors affecting the tidal movement of a certain port are the shape of the coastline and the constraints of the distribution of water depth and terrain.

[0054] Under the combined effects of human factors (land reclamation) and changes in the natural environment, the coastline within the harbor will change due to near-shore projects, land reclamation, silt deposition, tidal erosion, etc., so the coastline is often in a state of continuous dynamic change. Figure 1 This is an overlay comparison of the positions of a certain port's shoreline in 1984, 2000 and 2020; Table 1 shows the length and enclosed area of ​​a certain port's shoreline in 1984, 2000 and 2020:

[0055] Table 1 Length and enclosed area of ​​a port coastline in different eras

[0056]

[0057] from Figure 1 It can be seen from Table 1 that the coastline of a certain port has changed significantly from 1984 to 2020.

[0058] 2. Configure the mathematical model and calculate the hydrodynamics:

[0059] According to the coastline data of different ages, all the coastline boundaries of different ages to be compared and analyzed are added to the mathematical model pre-processing program such as MIKE21 or SMS (Surface Water Model System), and then gridded in blocks. The common areas in the boundaries of different ages generate block 1, the unique areas of n1 age generate block 2, the unique areas of n2 age generate block 3..., and so on, to generate model boundary files of different ages; generate the boundary grid of n1 age, the block 1 generated by the common area and the block 2 generated by the unique area of ​​n1 age generate grids, and the remaining blocks do not generate grids; generate the grid of n2 age, the block 1 generated by the common area and the block 3 generated by the unique area of ​​n2 age generate grids, and the remaining blocks do not generate grids; and so on, to generate grid files of different ages n1, n2...;

[0060] Import the water depth data of different ages into the generated grid files of the corresponding ages, generate the corresponding terrain grid files, and set the model hydrological boundaries; according to the bay conditions and related data, verify and determine the values ​​of the bay bottom roughness and eddy viscosity coefficient through the latest measured hydrological data, and make relevant parameter files for the parameters whose values ​​change with time or space;

[0061] Import the terrain grid file, hydrological boundary conditions and parameter files into the MIKE21 hydrodynamic calculation mathematical model or a similar finite volume coastal ocean model (FVCOM) developed by the Marine Ecological Dynamics Model Laboratory of the University of Massachusetts, and start the calculation file to calculate the hydrodynamic characteristics of the bay in different eras.

[0062] Specifically, according to the coastline data of a certain port in 1984, 2000 and 2020, all the shoreline boundaries in 1984, 2000 and 2020 are added to the mathematical model preprocessor, and then the grids are divided into blocks and the corresponding grids are generated. The grids of a certain port in 1984, 2000 and 2020 are as follows:

[0063] In terms of horizontal grid allocation, the hydrodynamic model of a certain port in 1984 set the number of horizontal grids to 48925, with a horizontal resolution of 840m in the open ocean, which was encrypted near the coast and about 10m in the sea area of ​​model concern. The grid transitioned evenly from the encrypted area to the open boundary. Figure 2 The hydrodynamic model of a certain port in 2000 set the number of horizontal grids to 42978, with a horizontal resolution of 840m in the open ocean, and was encrypted near the coast. The grid was about 10m in the sea area of ​​interest of the model, and the grid transitioned evenly from the encrypted area to the open boundary. Figure 3 The hydrodynamic model of a certain port in 2020 sets the number of horizontal grids to 41457, with a horizontal resolution of 840m in the open ocean, encrypted near the coast, and about 10m in the sea area of ​​model focus. The grid transitions evenly from the encrypted area to the open boundary, as shown in the figure below. Figure 4 shown.

[0064] For the model water depth, the area at point A and the inner bay use the measured water depth data contained in the CAD drawing, and the bay area outside point A and the open sea area use the measured elevation data and the water depth data of the nautical chart, which are interpolated to the horizontal grid points of the model through the inverse distance weighted interpolation method. Figure 5-7 The water depth distribution of the 1984, 2000 and 2020 models were obtained by inverse distance weighted interpolation. Figure 8The figure shows the change of water depth of a certain port from 2000 to 2020. The red area in the figure indicates that the water depth becomes shallower or changes from water to land, and the blue area indicates that the water depth becomes deeper or changes from land to water. The figure shows that the overall trend of the water depth of a certain port from 2000 to 2020 is that the water depth along the coast becomes deeper and the water depth in the central axis of the river becomes shallower.

[0065] The model open boundary is located in the open sea outside a certain port, with a total of 97 open boundary points, an open boundary grid resolution of 800m, and the farthest distance from the land is 16.7km. The model open boundary forcing is set to tide drive, and the water level data comes from the TPXO7.2 tidal model. In order to suppress the high-frequency unstable oscillation of the model, a sponge layer is added to the model open boundary, the sponge layer influence radius is set to 3000m, and the action coefficient is set to 0.001.

[0066] 3. Model Validation

[0067] When conducting water level verification, the measured water level data is compared and verified with the water level simulation results of the model; when conducting tidal flow verification, the measured tidal flow data is compared and verified with the tidal flow simulation results of the model.

[0068] In order to verify the water level simulation results of the model, two water level verification sites were selected. Site 1 was located in the inner bay of a port, and Site 2 was located in the outer bay of the bay. The measured water level data at the water level verification sites were compared with the water level simulation results of the model for verification. Figure 9-10 The figures are the model results and the water level comparison verification results of the two water level verification stations. The figure shows that the model can simulate the time of spring tide and neap tide well, and the degree of fit with the observed water level data is good. Overall, the simulation results during spring tide are better than those during neap tide. The simulation error of station 1 is larger than that of station 2. The simulation results of station 2 are closer to the measured water level data. The main reason is that station 1 is located on the coast of the inner bay, and it is difficult for the model to fully simulate the complex and changeable actual terrain around the station, which causes a certain deviation.

[0069] In order to verify the tidal simulation results of the model, eight tidal verification sites were selected, among which tidal verification sites C1-C3 measured sites were distributed in the inner bay, tidal verification sites C6-C8 were distributed near the outer bay, and tidal verification sites C4 and C5 were distributed in the bay between tidal verification sites C1-C3 measured sites and tidal verification sites C6-C8.

[0070] See also Fig.11The results of the model and the measured tidal current data at the C1 station during spring tide and neap tide are shown as examples. The results show that the model and the measured data have a good fit. The model can simulate the turning time well, and the simulated flow velocity trend is consistent with the measured data. In general, the simulation results during spring tide are better than those during neap tide. The tidal current verification results show that the model can simulate the tidal current in the bay more accurately.

[0071] 4. Analysis of the evolution of bay hydrodynamics:

[0072] Analyze and compare the changes in water levels, tidal currents, and tidal volume in the bay in different eras, and conduct an analysis of the evolution of ocean hydrodynamics.

[0073] 1. Analysis of water level evolution:

[0074] 30 typical geographical locations in a certain port were selected to analyze the water level evolution in 1984, 2000 and 2020.

[0075] Tables 2 and 3 show the tidal ranges during high tides and low tides for 30 stations (only some stations are listed in the tables) in 1984, 2000 and 2020.

[0076] Table 2 Tidal range (cm) at 30 stations in a certain port during spring tides in different years (only some stations are shown)

[0077]

[0078] Table 3 Tidal range (cm) during neap tides at 30 stations in a certain port in different years (only some stations are shown)

[0079]

[0080] It can be seen from Table 2 and Table 3 that:

[0081] Stations T1-T30 gradually extend from the inside of a certain harbor to the outside of the bay. The tidal range of the stations generally shows a trend of gradually decreasing from T1 to T30, showing the characteristics of large tidal range inside the bay and small tidal range outside the bay.

[0082] The tidal range has generally shown a decreasing trend from 1984 to 2020;

[0083] The tidal range during the spring tide of a certain port did not change much from 1984 to 2000, but changed significantly from 2000 to 2020, which may indicate that the shoreline changes caused by human factors have a significant impact on the balance in a certain port;

[0084] During the spring tides from 1984 to 2000, the station with the largest tidal range change was T3, which was closely related to the reclamation activities in a port around T3. Between 2000 and 2020, the stations with large changes were T6, T11, and T30.

[0085] During the low tide from 1984 to 2000, the station with the largest tidal range change was T5, which has a lot to do with the significant shoreline changes caused by the Shangyuwei reclamation project; between 2000 and 2020, the stations with large tidal range changes were T6, T11 and T30.

[0086] Further analysis is conducted on areas with frequent reclamation activities, taking point T5 as an example, see Figure 12-13 , Figure 12-13 This is a comparison of the water levels at this point in different years. The figure shows that the high tide water levels in 1984, 2000 and 2020 are close, the low tide water level is the lowest in 1984, followed by 2000, and the low tide water level in 2020 is the highest. The results show that the tidal range was the largest in 1984, followed by 2000, and the smallest in 2020. There was a certain gap between the tidal range in 1984 and 2000, and the difference in the tidal range from 2000 to 2020 continued to increase. It can be considered that the shoreline changes from 1984 to 2000 had a greater impact on the water level near Shangyu, and this impact continued to extend to 2020, and the water level near T5 continued to decrease.

[0087] The water levels of 30 stations in a certain port in different eras were simulated by numerical model to analyze the impact of reclamation activities on the water level of a certain port. According to the simulation results of the numerical model and the overall analysis of 30 stations in a certain port, it can be concluded that the water level of a certain port has changed significantly after the reclamation activities. The water level changes in the middle and lower sections of a certain port are more significant; in areas where reclamation activities are more intense, the water level has changed dramatically; the water level changes in the coastal area are greater than in the center of the river; the impact of reclamation activities on the water level during high tide is more significant than during low tide.

[0088] 2. Trend evolution analysis:

[0089] The rapid flow and ebb flow fields of spring tides and neap tides in 1984, 2000 and 2020 were simulated. Table 4 shows the mean flow velocity of 30 stations in a certain port (the same as the stations in the water level evolution analysis) in different years. The flow velocity in the middle of the river in a certain port as a whole did not change much from 1984 to 2000, but increased from 2000 to 2020, while the flow velocity along the coast continued to increase from 1984 to 2020. At the same time, from a regional perspective, the flow velocity in the upper section of the harbor of a certain port continued to decrease from 1984 to 2020, while the flow velocity in the middle and lower sections of the harbor continued to increase from 1984 to 2020.

[0090] Table 4 Mean flow velocity (cm / s) of 30 stations in a certain port in different years (only some stations are shown)

[0091]

[0092]

[0093] Figure 14-17 The example shows the distribution of the rising and falling rapids in the entire computational domain in 2020. The results of the distribution of the rising and falling rapids in the entire computational domain in 1984, 2000 and 2020 show that from 1984 to 2020, due to the shoreline changes caused by the reclamation project in a certain port, the overall tidal current in a certain port has a tendency to strengthen, which is related to the narrowing of the river channel and the acceleration of the tidal current velocity caused by the migration of the shoreline to the sea. At the same time, this strengthening trend is more obvious in the middle section of a certain port.

[0094] Through the geographical locations of the three sections intercepted, the changes in flow velocity in the three sections at different ages are observed; Fig.18 The comparison of flow velocity in Section 2 in 1984, 2000 and 2020 is shown as an example. The flow velocity in Section 2 of a certain port has significantly weakened between 1984 and 2020. This weakening mainly occurred between 2000 and 2020, and there is a situation where the flow velocity at high tide and low tide are inconsistent. The change range of Section 2 during high tide from 1984 to 2000 is: -3% flow velocity during high tide, -2% flow velocity during low tide; the change range during low tide is: -23% flow velocity during high tide, -8% flow velocity during low tide. It can be seen that the change range of flow velocity at low tide in different eras is much greater than that of flow velocity at high tide, which is directly related to the different duration of high and low tide in a certain port.

[0095] Through the rapid rise and fall of high tides and low tides at the mouth of point A in 1984, 2000 and 2020, combined with the comparison of flow velocities in the section at the center of point A in different years, it can be observed that the tidal flow velocity at the mouth of point A is continuously weakening. The obvious changes in flow velocity between 1984 and 2020 indicate that the natural coastline changes caused by the reclamation project around point A of a certain port have had a significant impact on the tide at point A, and the tide has been weakened by about 14%.

[0096] By establishing three sets of nearshore ocean dynamic models of different ages to simulate the tidal movement in a certain port, the impact of reclamation activities on the tidal currents in a certain port was analyzed. The numerical simulation results show that due to the changes in the natural coastline caused by reclamation activities, the tidal currents in a certain port have been strengthened as a whole, among which the tidal currents along the coast have been significantly enhanced, and the tidal currents in the center of the river have also been enhanced to a certain extent. From a regional analysis, the tidal currents in the middle and lower sections of a certain port have been significantly enhanced, while the tidal currents in the middle and upper sections of a certain port have not changed significantly; from a temporal analysis, the period of time when the tidal currents in a certain port have undergone significant changes is between 2000 and 2020, while the tidal currents did not change much between 1984 and 2000.

[0097] 3. Analysis of tidal volume evolution:

[0098] Generally speaking, tidal capacity refers to the amount of tidal water that a bay can accept under the average tidal range conditions. The average tidal range tidal capacity P m The calculation formula is:

[0099] p m =h×S

[0100] Among them, h is the average tidal range and S is the average water area.

[0101] However, since the above formula has a large error when used for calculating the tidal volume from the model results, and deviates greatly from the actual situation, the following formula is used to calculate the tidal volume, and the situation of each unit grid is applied to it. The formula is:

[0102]

[0103] Where P is the tidal volume; n is the total number of model grids; S i , H 1i , H 2i are the area of ​​the ith grid and the high and low tide levels of the grid respectively.

[0104] Table 5 shows the tidal volumes in three different areas during high tides and low tides in 1984, 2000 and 2020.

[0105] Table 4.3-1 Tidal volume in different areas of a port during high tide and low tide (m 3 )

[0106]

[0107] Tidal volume is the volume of tidal water that a body of water can accommodate. Its size directly affects the exchange intensity between the bay and the open sea, thus restricting the self-purification capacity of the bay lagoon. Tidal volume is an important indicator of the viability of semi-enclosed bays, and seawater exchange is the main indicator of the self-purification capacity of the sea area. Both are crucial to maintaining a good ecological environment in the bay and conducting scientific coastal development and utilization.

[0108] Taking section 1 as an example, for the entire port area inside section 1, the tidal volume during the spring tide in 1984 was 3.758×10 8 m 3 , the tidal volume of a neap tide is 2.249×10 8 m 3 ; The tidal volume of the spring tide in the 2000s was 3.013×10 8 m 3 , the tidal volume of a neap tide is 1.814×10 8 m 3 ; The tidal volume of the spring tide in 2020 is 2.900×10 8 m 3 , the tidal volume of a neap tide is 1.723×10 8 m 3 . From the 1984s to the 2000s, the tidal volume during high tides in the entire port of a certain place decreased by about 20%, and the tidal volume during low tides decreased by about 19%; from the 2000s to the 2020s, the tidal volume during high tides in a certain port of a certain place decreased by about 3%, and the tidal volume during low tides decreased by about 5%.

[0109] The numerical model is used to simulate the tidal volume in a certain port in different eras to analyze the impact of the reclamation activities of a certain port on the tidal volume of a certain port. According to the numerical simulation results, the reclamation activities of a certain port have caused a decrease in the tidal volume of a certain port. The tidal volume during high tides decreased by 20% and the tidal volume during low tides decreased by 19% from 1984 to 2000. The tidal volume during high tides decreased by 3% and the tidal volume during low tides decreased by 5% from 2000 to 2020. From 1984 to 2020, the tidal volume of a certain port during high tides decreased by about 8.45×10 7 m 3 , the tidal volume during low tide is reduced by about 5.26×10 7 m 3 .

Claims

1. A method for comparative analysis of the hydrodynamic environment of bays in different ages, characterized in that: The following steps are involved: Step 1: Collect water depth data and coastline data of different ages for at least the bay and the offshore areas adjacent to the bay, as well as basic data on measured tide level data in the bay area; Step 2: Based on the coastline data of different ages, all the coastline boundaries of different ages to be compared and analyzed are added to the mathematical model pre-processing program, and then gridded into blocks. The common areas in the boundaries of different ages generate block 1, the unique areas of the n1 era generate block 2, the unique areas of the n2 era generate block 3..., and so on, to generate model boundary files containing different ages; Step 3: Generate a grid for the n1 era. Block 1 generated by the common area and block 2 generated by the n1 era-specific area generate grids, and no grids are generated for the other blocks; generate a grid for the n2 era. Block 1 generated by the common area and block 3 generated by the n2 era-specific area generate grids, and no grids are generated for the other blocks; and so on, generate grid files for different eras n1, n2, ...; Step 4: Import the water depth data of different ages into the generated grid files of corresponding ages, generate corresponding terrain grid files, and set the model hydrological boundaries; Step 5: According to the bay conditions and relevant data, the values ​​of the bay bottom roughness and eddy viscosity coefficient are verified and determined through the latest measured hydrological data, and parameter files are prepared for the coefficients whose values ​​change with time or space; Step 6: Import the terrain grid file, hydrological boundary conditions and parameter files into the hydrodynamic calculation mathematical model, and start the calculation file to calculate the hydrodynamic characteristics of the bay in different ages; Step 7: Analyze and compare the changes in water levels, tidal currents, and tidal volume in the bay in different eras, and conduct an analysis of the evolution of ocean hydrodynamics.

2. The method for comparative analysis of the bay hydrodynamic environment in different ages according to claim 1 is characterized by: The mathematical model pre-processing program adopts the MIKE21 software pre-processing program, the mathematical model adopts the MIKE21 hydrodynamic calculation model, and the grid attribute is set to a triangular grid.

3. The method for comparative analysis of the bay hydrodynamic environment in different ages according to claim 1 is characterized by: The water depth data include measured water depth data of the inner bay of the bay, measured elevation data of the outer bay of the bay and charted water depth data of the open sea adjacent to the bay. The water depth data are interpolated to the horizontal grid points of the model by using the inverse distance weighted interpolation method.

4. The method for comparative analysis of the bay hydrodynamic environment in different ages according to claim 1 is characterized by: The model open boundary is located in the open sea, and the model open boundary forcing is set to be tidal driven.

5. The method for comparative analysis of the bay hydrodynamic environment in different ages according to claim 1 is characterized by: The hydrological boundary conditions of different ages uniformly adopt the latest measured hydrological data.

6. The method for comparative analysis of the bay hydrodynamic environment in different ages according to claim 1 is characterized by: The water level evolution was analyzed by the changes in tidal range during spring tides and neap tides at multiple different stations in the bay in different years.

7. The method for comparative analysis of the bay hydrodynamic environment in different ages according to claim 1 is characterized by: The tidal evolution analysis is carried out by using the mean flow velocity of different stations in the bay in different years and the distribution of rising and falling rapids in the entire calculation domain.

8. The method for comparative analysis of the bay hydrodynamic environment in different ages according to claim 1 is characterized by: The tidal volume is calculated using the following formula: Where P is the tidal volume; n is the total number of model grids; S i , H 1i , H 2i are the area of ​​the ith grid and the high and low tide levels of the grid respectively.

9. The method for comparative analysis of the bay hydrodynamic environment in different ages according to claim 1 is characterized by: Add a verification step for the mathematical model of hydrodynamic calculation. When conducting water level verification, compare and verify the measured water level data with the water level simulation results of the model; when conducting tidal current verification, compare and verify the measured tidal current data with the tidal current simulation results of the model.

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