NL2032745B1 - Test method for simulating vegetation wave attenuation based on vegetation canopy porosity - Google Patents
Test method for simulating vegetation wave attenuation based on vegetation canopy porosity Download PDFInfo
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Abstract
U I T T R E K S E L The present disclosure belongs to a technical field of ecological simulation model, in particular to test method for simulating vegetation wave attenuation based on vegetation canopy porosity. The model tree of the present disclosure reveals the correlation 5 between the porosity and the wave attenuation rate, and proves that the porosity is a key parameter of vegetation simulation. The model tree significantly improves the simulation accuracy of the vegetation wave attenuation rate, improves the disaster prevention and mitigation evaluation effect of coastal vegetation wave 10 attenuation, and provides a technical foundation for the construction of disaster prevention seawalls. (+ Fig. l)
Description
P1492 /NL
TEST METHOD FOR SIMULATING VEGETATION WAVE ATTENUATION BASED ON
VEGETATION CANOPY POROSITY
The present disclosure belongs to a technical field of eco- logical simulation models, and in particular relates to a test method for simulating vegetation wave attenuation based on vegeta- tion canopy porosity.
Coastal erosion and seawall damage caused by waves are urgent problems to be solved in the coastal engineering field. Mangroves grow in coastal intertidal zones of tropical and subtropical or in estuaries of rivers that can be reached by tides, and are widely distributed in the south coasts and tidal estuaries of China. The resistance of coastal mangroves to wave water can effectively re- duce wave energy, slow down flow velocity, promote siltation and protect beaches. It can not only resist typhoons, storm surges and other marine disasters and play a protective role in coastal beaches and seawalls, but also has the function of enriching land- scape and ecological benefits. So the mangroves are also known as "wave attenuation pioneers and coast guards".
As a common way, physical model test can simulate the parame- ter characteristics of mangrove and the interaction between Man- grove and wave after mangrove generalization, and more accurately simulate the wave dissipation of mangrove. The method of making model tree is related to the accuracy of evaluating the wave at- tenuation and disaster reduction of mangrove vegetation.
At present, physical models are used to simulate vegetation wave attenuation in China, which basically generalize vegetation into rod-shaped structures or branches and leaves plus rod-shaped structures. Most of the model making methods generalize vegetation according to their tree height, without considering the important parameter vegetation porosity that affects the wave attenuation rate. Therefore, it is impossible to accurately simulate and eval-
uate the disaster prevention and mitigation effect of vegetation wave attenuation, and it is also difficult to accurately determine the design swath height parameters of seawall after vegetation wave attenuation.
The purpose of the present disclosure is to provide test method for simulating vegetation wave attenuation based on vegeta- tion canopy porosity. The model tree made based on canopy porosity can better reveal the correlation between canopy porosity and veg- etation wave attenuation rate, improve the simulation accuracy of vegetation wave attenuation rate, and assist in the construction of disaster prevention seawall.
Beneficial effects:
The model tree established by the present disclosure based on the vegetation canopy porosity reveals the correlation between the porosity and the wave attenuation rate in the test method of the present disclosure, and proves that the porosity is a key parame- ter of vegetation simulation. The model tree made based on the canopy porosity significantly improves the simulation accuracy of the vegetation wave attenuation rate, and realizes the refined simulation of the wave attenuation and slow flow effects and laws of coastal vegetation, improves the assessment results of disaster prevention and mitigation of coastal vegetation wave attenuation.
At the same time, when building the seawall behind the coastal vegetation, the test method can be used to simulate the vegetation wave attenuation, so as to determine the wave height in front of the seawall, calculate the swath height, precise the de- sign seawall top elevation, eliminate the hidden dangers of marine disasters caused by the too low seawall top, and avoid unnecessary waste caused by the too high seawall top elevation.
In order to more clearly explain the embodiments of the pre- sent disclosure or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below.
Fig. 1 is an example of a real mangrove field photo, 101 in the figure is a digital electronic photo of the mangrove field, 102 in the figure uses a gray channel to extract the mangrove en- tity formed by a vector layer, 103 in the figure represents a con- version of the vector layer into a vector line, 104 in the figure represents a cutting crown vector, and 105 in the figure repre- sents a gap vector of the crown;
Fig. 2 is a model tree production process;
Wherein, 201 is a rigid PVC pipe required for making a trunk of the model tree, 202 is a polyethylene material sheet required for the model branches and leaves, and 203 is a top view of the model tree, consisting of two 204 and two 205. 204 is an elevation projection of the branches of the simulated vegetation in horizon- tal and vertical directions in 203, 205 in the figure is an eleva- tion projection of oblique branches in 203, and 206 is the poly- ethylene material sheet in the inverted triangular crown of the model tree in the horizontal and vertical directions, 207 is a canopy gap in the inverted triangular crown of the model tree in the horizontal and vertical directions, 208 is a polyethylene ma- terial sheet of the inverted triangular crown of the model tree in the oblique direction, 209 is the canopy gap of the inverted tri- angular crown of the model tree in the oblique direction, and 210 is the model elevation, wherein, 2101, 2102 and 2103 constitute the vertical projection area of the model tree crown, and 211 is a cube space diagram explaining the relationship between 204 and 205;
Fig. 3-1 is a front sectional view of a mangrove wave attenu- ation simulation device;
Fig. 3-2 is a top view of the mangrove wave attenuation simu- lation device; wherein, 301 is a mangrove model test flume, 302 is a wave height meter before the mangrove model test planting belt, 303 is a wave height meter after the mangrove model test planting belt, 304 is a wave-making plate of the wave making flume, 305 is a fixed plate of a mangrove model tree, 306 is a mangrove model tree, 307 is a water surface line, and 308 is a fixed hole of the fixed model tree.
Fig. 4 is a schematic diagram of elevation photographing, 401 is the ground where the vegetation is located, 402 is a digital camera, 403 is a photographing range, and 404 is a photographed vegetation.
The present disclosure provides a model tree for simulating vegetation wave attenuation, including a crown and a trunk, and the crown includes a canopy gap part and branches and leaves; the canopy gap part of the crown is simulated by a porosity parameter a; the porosity parametero=S;/Ss, Sy is a canopy gap area, S, is a total crown elevation projected area: S,=5,+S;, Si is a crown branches and leaves area; the porosity parameter o is the same as a porosity parameter of a simulated vegetation
The crown of the present disclosure includes the canopy gap part and branches and leaves. The canopy gap part of the present disclosure is obtained by simulating the porosity parameter a.
In the present disclosure, preferably, an elevation of the simulated vegetation is imaged once every n degrees within a 360 ° range of a single plant, and a total of m elevation projection im- ages are obtained, nxm=360°. When m>1 in the present disclosure, the porosity parameter a of the present disclosure and a total el- evation projection area S, of the crown are preferably expressed in a form of an average value. In the present disclosure, the o=o,/m , m2l, Ou=Stn/Ssm | Ssm=Sim+Son. The m in the present disclosure is pref- erably 4-8, more preferably 4. Specifically, when m is 4, the pre- sent disclosure preferably uses a photographing device to image the elevation of a single plant every 90 degrees within a 360- degree range (elevation imaging refers to an image including the plant outline and boundary taken by a person or a fixed instrument directly in front of the plant and in a visual plant direction through a digital device, as shown in Fig. 4), a total of 4 images are taken, and the canopy gap areas Ss, Sg, Sos, See and the areas of the crown and branches and leaves Si, Siz, Si», Sus are calculat- ed respectively. According to the formula S~=5;+S;, a total projec- tion area S44 of the crown of the four images are obtained respec- tively. According to the calculation formula of the porosity pa-
rameter o=Su./ Sm, the porosity parameters ol, «2, «3, od of the four images are obtained, then the average value is calculated and denoted as a, and the average value of the total projected area of the crown of the four images Sea, Ss, Ss, Sse is denoted as Ss. The 5 single plant of the present disclosure is preferably from the beach where the model tree is used, that is, the model tree is used to simulate the wave attenuation rate of which place, and the single plant of which place is selected to determine relevant pa- rameters. The single plant is preferably a representative single plant, and the representativeness is not specially defined in the present disclosure, which can be defined by those skilled in the art according to professional experience. The photographing device is not specially limited in the present disclosure, and conven- tional photographing devices in the art can be used, such as digi- tal cameras. After the elevation imaging is completed, and before calculating the canopy gap area S; and the crown branches and leaves area S1, the present disclosure preferably also includes image processing for the image after the elevation imaging, and the image processing preferably includes correction and vector im- age processing. The software and process used for the image pro- cessing are not specially limited in the present disclosure, and conventional image processing software in the art can be used for conventional processing as required. After the image processing described in the present disclosure, the crown branches and leaves are displayed in gray (solid area), and the canopy gap is dis- played in white. As shown in Fig. 1, 104 shows the gray crown sol- id part, and 105 shows the white gap part.
After obtaining the average porosity parameter a and the av- erage total crown projected area S,, the present disclosure prefer- ably produces the model tree. A preparing method of the model tree of the present disclosure preferably includes: measuring a tree height, a crown width, a crown height and a trunk diameter at breast height representing a vegetation; determining a length scale A of a model and a time scale A; making the crown and trunk of the model tree respectively and combining to obtain the model tree.
The methods for measuring the tree height, crown width, crown height and trunk diameter of the representative vegetation are not particularly limited in the present disclosure, and conventional measurement methods in the art may be used. The length scale of the present disclosure is preferably confirmed according to vege- tation size parameters, hydrological conditions and test water tank conditions. The above-mentioned operations for confirming the length scale are all routine operations in the field, and there is no unique standard, and those skilled in the art can determine ac- cording to common sense. The time scale of the present disclosure is preferably confirmed according to the length scale, and the time scale is A=A%°.
After confirming the length scale A and the time scale Ag, the present disclosure makes the crown and trunk of the model tree respectively. The present disclosure preferably scales the meas- ured parameters of the representative vegetation according to the length scale A and the time scale A, to obtain parameter infor- mation of the model tree, wherein the parameter information in- cludes the tree height, a crown width, a crown height and a trunk diameter at breast height. After obtaining the parameter infor- mation of the model tree, the present disclosure preferably deter- mines a top horizontal span of the crown of the model tree accord- ing to the crown width, determines the lower position of the crown according to the crown height, and generalizes the crown into an inverted triangle or an inverted trapezoid to obtain an inverted triangular crown or an inverted trapezoid. The present disclosure is preferably described below with an inverted triangular crown, but it cannot only be regarded as the entire protection scope of the present disclosure. The top horizontal span in the present disclosure is preferably the average of the east-west and north- south widths of the crown, and the lower position of the crown is preferably the first branch on the upper part of the trunk.
After obtaining the inverted triangular crown, the present disclosure preferably generalizes and simulates the crown branches and leaves, and more preferably replaces the crown branches and leaves with branches, and the simulated branches are preferably symmetrically distributed on both sides of the trunk at angle of to 60 degrees, that is, the overall simulation of the inverted triangular crown is realized by branches at the angle of 45 to 60 degrees with the trunk. The material of the present disclosure for simulating the crown branches and leaves is preferably polyeth- ylene, more preferably strip polyethylene. The width of the strip polyethylene is preferably 0.b5cm~2cm, that is, the present disclo- sure preferably simulates the generalized tree crown branches and leaves with branches. After generalizing the simulated crown branches and leaves, the present disclosure preferably determines the number and length of the strip polyethylene according to the obtained average porosity parameter o and the average total crown projected area S..
The model tree of the present disclosure preferably includes ml number of inverted triangular crowns, and the ml number of in- verted triangular crowns constitutes the three-dimensional model tree of the present disclosure. The M1 of the present disclosure is consistent with the m value in m number of vertical projection images. Specifically, as shown in Fig. 2, when the m is 4, the 4 inverted triangular crowns in the model tree of the present dis- closure are in vertical cross contact, wherein the two inverted triangular crowns overlap and cross the trunk position vertically to form a cross-shaped crown, and the other two inverted triangu- lar crowns also overlap and vertically intersect the trunk posi- tion to form a cross-shaped crown. The two cross-shaped crowns overlap along a cross line, so that a vertical projection line of the adjacent crowns is at 45 degrees, and a top view of the formed three-dimensional model tree is shown as 203 in Fig. 2. In order to ensure that the projection of 205 to 204 coincides with the crown branches of 204 without affecting the porosity in 204 direc- tion, the relationship between the length of polyethylene plastic strips 208 and 206 of the 205 and 204 at the same position is 3/2, and the explanation of the relationship is shown in Fig. 211.
The information of tree height, crown width, tree crown height and tree trunk diameter at breast height preferably ob- tained in the present disclosure is used to make the trunk of the model tree. The material used for making the tree trunk in the present disclosure is preferably PVC, more preferably rigid PVC pipe. The canopy porosity produced by the present disclosure is consistent with the canopy porosity actually measured on site.
After obtaining the crown and trunk of the model tree, the present disclosure preferably combines the crown and trunk of the model tree to obtain the model tree. The material used in the pre- sent disclosure for assembling the model tree preferably includes glue and iron wire.
The present disclosure also provides a device for vegetation wave attenuation simulation, which includes the model tree, model tree fixing plate, wave height meter, wave making equipment and water tank described in the above technical solution. The model tree is fixed on the model tree fixing plate, and the model tree fixing plate is fixed on a bottom of the water tank. The wave height meter is located on the front side and the back side of the planting belt composed of several model trees. The wave making equipment is located on the right side of the inside of the water tank. As shown in Figs. 3-1 to 3-2 of the first embodiment of the present disclosure, from left to right are a water tank 301, a wave height meter 303 measured after the planting belt, a model tree 306, a model tree fixing plate 305, a wave height meter 302 measured before the planting belt, and a wave-making equipment 304. In the Fig. 3-1, a model placement area is the planting belt.
The present disclosure preferably adjusts the number of the model trees in the simulation device according to a planting den- sity, a width of the planting belt and a planting arrangement, and several model trees constitute the planting belt in the simulation device. In the present disclosure, the planting belt is fixed on the model tree fixing plate. The model tree fixing plate of the present disclosure is preferably a plastic plate, and the shape of the plastic plate is preferably a rectangle. The material is pref- erably PVC, the length is preferably 0.5-1 m, the width is prefer- ably 0.5-1 m and the thickness is preferably 10-20mm. The model tree fixing plate of the present disclosure preferably includes several fixing holes. The number of the fixing holes and the dis- tance between the fixing holes are not particularly limited in the present disclosure, and can be conventionally adjusted according to the planting density of the simulated vegetation. The plastic plate of the present disclosure preferably includes fixing holes for fixing the model tree, and the size of the fixing hole is preferably adjusted according to the size of the bottom of the model tree.
In the present disclosure, the fixing plate fixed with the model tree is fixed on the bottom of the water tank. The bottom of the water tank of the present disclosure preferably includes fix- ing holes for fixing the model tree fixing plate. In the present disclosure, screws are preferably used to fix the fixing plate with the model tree in the water tank.
In the present disclosure, the front side and the back side of the planting belt in the simulation device preferably further includes wave height meters respectively, that is, wave height me- ter at the front side is marked as the first wave height meter, and wave height meter at the rear side is marked as the second wave height meter. The side close to the wave making equipment is the front side of the planting belt, and the far side is the rear side. The first wave height meter and the second wave height meter of the present disclosure can be used to measure the wave heights before and after the planting belt, respectively.
The simulation device of the present disclosure also includes a wave making device, preferably a wave making machine. The wave making device of the present disclosure is preferably located on the right side of the inside of the water tank. The sources and models of the wave-making equipment and wave height meter are not particularly limited in the present disclosure, and conventional wave-making equipment and wave height meters in the field may be used.
The present disclosure also provides a test method for simu- lating vegetation wave attenuation based on vegetation canopy po- rosity, adopting the model tree or the simulation device described in the above technical solution for testing. A process of the test comprises: fixing the model tree on a model fixing plate to obtain a planting belt; fixing the planting belt, a wave height meter, and a wave-making device in a water tank; controlling the wave making device to generate waves towards the planting belt; count- ing a wave height H; before the planting belt and a wave height AH;
after the planting belt, and calculating a wave attenuation rate
K, and the wave attenuation rate K=(H;,-H;)/H;; designing parameters of a beach and seawall, after the wave attenuation rate K is ob- tained, according to the wave attenuation rate K.
The waves in the present disclosure are preferably regular waves or irregular waves, more preferably irregular waves. The present disclosure preferably adopts the JONSWAP spectrum or the
PM spectrum to simulate the irregular waves, and the expression of the JONSWAP spectrum is preferably:
SC) = al XT5* f° exp an pte duds 4 wherein: a= 006 [094 ~0.01915/my 0.230+0.0336y ~0.185(1.9 + 7) oo fos f<f, 009 f>f,
H, is an effective wave height, the unit is m, T, is a spec- trum peak period, the unit is s, f is a spectrum peak frequency, the unit is H,, and y is a spectrum peak parameter, which is 3.3.
The water level when the present disclosure performs the test is preferably the design high tide (water) level, more preferably the high tide (water) level once in 50 years, the high tide (wa- ter) level once in 20 years, the high tide (water) level once in 30 years , the high tide (water) level once in 100 years, the high tide (water) level once in 200 years or the high tide (water) lev- el once in 1000 years, more preferably the high tide (water) level once in 50 years.
The present disclosure also provides the application of the model tree, the simulation device or the test method described in the above technical solution in evaluating the wave attenuation effect of coastal vegetation and/or assisting the construction of seawalls.
The auxiliary seawall construction in the present disclosure preferably includes confirmation of seawall construction parame- ters, and more preferably includes the confirmation of the eleva- tion of the top of the seawall. The vegetation described in the present disclosure preferably includes mangrove, more preferably include one or more of avicennia marina, rhizophora stylosa griff, kandelia obovata and aegiceras corniculatum, more preferably avi- cennia marina, rhizophora stylosa griff, kandelia obovata or ae- giceras corniculatum. The present disclosure applies the tree can- opy gap parameter to the preparation of the model tree, and the simulation device including the model tree of the present disclo- sure can realize the refined simulation of the wave attenuation and slow flow effects and laws of coastal vegetation. The model tree reveals a correlation between porosity and wave attenuation, and proves that porosity is a key parameter in plant simulation.
At the same time, the present disclosure formulates the model tree of corresponding vegetation by measuring the relevant parameters of the coastal vegetation, and simulates the wave attenuation ef- fect of the corresponding coastal vegetation, which can be applied to the evaluation of the wave attenuation effect of the coastal vegetation and to assist the construction of the seawall corre- sponding to the coast.
In order to further illustrate the present disclosure, the technical solutions provided by the present disclosure are de- scribed in detail below with reference to the accompanying draw- ings and embodiments, but they should not be construed as limiting the protection scope of the present disclosure.
Embodiment 1
The avicennia marina grows in the seaside and salt marshes, and is usually one of the plant species that make up the coastal mangroves. The tree height is 1.5~6m, and it is widely distributed in the coastal areas of South China. The avicennia marina has wide adaptability to soil and is not demanding on soil fertility. It can appear on silt, semi-silky and sandy beaches. The avicennia marina is distributed in front of seawalls and can play a protec- tive role on seawalls. Now the avicennia marina selected as the representative tree species of mangrove to illustrate the specific implementation steps of the present disclosure: 1. Setting scales of the model test;
The length scale A is taken as 10, the time scale A.=A"", and
Ax is 3.16.
2. Selecting a representative tree species of mangroves on the site, avicennia marina, with a tree height of 2.8m, a crown height of 1.7m, a crown width plane size of 1.9mx1.9m, a trunk height of 1.1m, and a trunk diameter at breast height of 0.08m.
The selected avicennia marina is digitally photographed and imaged every 90 degrees of elevation within 360 degrees, and a total of 4 images are taken. The image size is corrected based on an image processing software, then the image of the crown part is processed to extract the vector layer from the gray channel, the solid area is displayed as gray, and the gap area is displayed as white, then vector segmentation is performed on the solid area and solid area of plant branches, leaves, etc., the gap area Sq and crown branch- es and leaves area Si, of the four images are counted respectively, and the total area S$.=5:+S5;, and the porosity O4=Som/ Sn are calcu- lated, wherein m=1, 2, 3, 4, the calculated average porosity a is 0.25 (as shown in Fig. 1).
Then, according to the size of each part and the porosity, the mangrove model tree is made by scaling the scale, and the po- rosity is kept consistent with the porosity of the measured tree.
The preparing method of the model tree is as follows: according to the trunk diameter at breast height, the PVC pipe with the corre- sponding diameter is selected after scaling, and after obtaining the crown information of the model tree; the top horizontal size of the model tree crown is determined firstly according to the crown width; and then according to the crown height, the lower po- sition of the crown is determined; the tree crown is generalized into an inverted triangle, and polyethylene plastic strips are used to generalize and simulate the branches and leaves of the tree crown; the simulated branches are symmetrically distributed on both sides of the trunk at an angle of 45 degrees; the width of the polyethylene strips is preferably 0.5cm; according to the ar- rangement rule, the number and length of the used polyethylene plastic strips are determined according to the average porosity parameter o and the average crown projected total area S,. Two hor- izontal and vertical crowns and two oblique crowns are made re- spectively, and the length of the oblique crowns at the same posi- tion is V3/V2 times the length of the horizontal crown.
The crown and trunk of the mangrove are made of polyethylene branches and leaves, rigid PVC pipes, polyethylene plastic strips, etc. The polyethylene plastic strip is drilled in the trunk of the
PVC pipe and fixed with glue, and if necessary, with iron wires (as shown in Fig. 2). 3. A fixed mangrove model tree plastic board is made, the mangrove model tree plastic board is a rectangular structure, the material is PVC board, the size of a single board is 1m (length) x lm (width) x 0.01m (thickness), and the spacing between the plas- tic plates is 0.1m, and the hole diameter is 8mm. There are 100 holes in a single plate, the front and rear ends of the plastic plates are fixed at the bottom of the test tank with expansion screws. 4. Three kinds of trees were selected for the simulation in the test. In order to simulate the influence of porosity on wave attenuation rate, except for the inconsistency of porosity parame- ters, the other tree height, crown width, crown height, and trunk diameter at breast height are kept the same. Three kinds of simu- lated porosities are selected, which are 0.15, 0.20, and 0.25, re- spectively. The width of mangroves is 1m, 2m, 4m, 6m, and the planting density is 60 plants/ m?. Then the mangrove model tree is installed on the plastic board, and then arranged in the wave tank {as shown in Fig. 3-1~3-2). 5. The test groups are determined according to the difference of mangrove porosity. The test is designed with 3 porosity and 4 mangrove widths, so there are 12 test groups in total. The water level is selected as the design high water level of 0.342m once in 50 years, the wave adopts irregular wave, the effective wave height H. is 0.06m, and the spectral peak period 7, is 1.93s. 6. The test wave elements are determined according to the wave conditions, and the JONSWAP spectrum is used to simulate the irregular wave.
According to wave elements and different porosity parameters of mangroves, the test results are shown in Table 1:
Table 1 Wave attenuation rate of mangroves with different po- rosity porosity water level oe ee
It can be seen from Table 1 that there is a positive correla- tion between porosity and wave attenuation rate. Under the condi- tions of mangrove widths of lm, 2m, 4m, and 6m, with the increase of porosity, the wave attenuation rate gradually decreases, so it can be concluded that, so whether the porosity of the vegetation model is accurate or not has an important impact on the wave at- tenuation, and also affects the evaluation of disaster prevention and mitigation effects.
After obtaining the wave attenuation rate, the seawall param- eters are confirmed according to the wave attenuation rate. The steps are as follows:
In the process of seawall design, the seawall top elevation is determined by three parameters: the high (tide) water level of the design frequency, the swath height value, and the safety heightening value. The swath height is a key parameter for deter- mining the seawall top elevation. For embodiment 1, after the veg- etation wave attenuation rate is determined by the experimental simulation method, the design high water level once in 50 years and the wave design once in 50 years are determined according to the wave attenuation rate, and when the mangrove planting width is 6m, the porosity is 0.15, the wave attenuation rate is 583, then after wave attenuation through mangroves, the effective wave height Hs is attenuated from 0.06m to 0.0252m. The attenuated ef- fective wave height Hs is used and converted into the prototype value according to the scale of 1:10. 0.252m. The design high wa- ter level once in 50 year is 3.42M after being converted into the prototype value according to the scale of 1:10. The empirical for- mula Rp = KAKyRgH{4 Ky in Appendix E.0.3 of "Code for Design of Sea- wall Engineering” (GBT 51015-2014) is used to calculate the swath height. Considering the first-class seawall, the slope gradient of the upstream slope is 1:0.4, the concrete protective surface, the water depth in dike drn=4.42m, and the design wind speed is taken as 28.7m/s. After calculation and look-up table, the roughness and permeability coefficient K4=0.9 related to the structure type of the protective surface, the empirical coefficient Ky =1.02 related to the wind speed and the water depth in dike drent; and the rela- tive climbing height of the impervious smooth wall Ry; = 1.32. The effective wave height Hs=0.252m is converted into the wave height value Hi, with a wave height accumulation rate F=1% is 0.378m. The climb height accumulation rate converts the cumulative frequency conversion factor Kp=0.77 based on accumulation rate F=13%. Ac- cording to the calculation, the swath height is 0.35m, and the al- lowable safe heightening value during overtopping is 0.5m. The seawall top elevation is calculated according to the formula in section 8.3.1 of the Code for Design of Seawall Engineering (GBT 51015-2014), and the seawall top elevation=3.42 m+0.35m+0.5m=4.27m.
It can be concluded from the above embodiments that the model tree, simulation device and test method based on the crown porosi- ty of the present disclosure can better simulate the wave attenua- tion rate of vegetation and guide the determination and construc- tion of the seawall top elevation behind the mangrove.
Although the above-mentioned embodiment has made a detailed description of the present disclosure, it is only a part of the embodiments of the present disclosure, not all of the embodiments.
People can also obtain other embodiments according to the present embodiment without creativity, and these embodiments all belong to the protection scope of the present disclosure.
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