Method for evaluating nitrogen and phosphorus reduction effect of coastal zone

Abstract

The invention discloses a coastal zone nitrogen and phosphorus reduction effect evaluation method, which comprises the following steps: acquiring multispectral image data and a digital surface model, and acquiring actual gradient, altitude and long-term hydrological dynamic data through ground actual measurement, sampling and investigation; extracting core parameters, correcting a digital surface model by utilizing ground actual measurement altitude data, constructing a target coastal zone precise digital elevation model, determining a gradient and dividing a gradient interval, and identifying a target coastal zone type and a planting / slope protection combined structure by combining multispectral image data, ground survey data and the digital surface model; obtaining a nitrogen and phosphorus reduction reference value according to the core parameters, extracting a rainfall intensity correction coefficient and a water level amplitude correction coefficient in combination with hydrological dynamic data, and calculating a final nitrogen and phosphorus reduction proportion; and spatial visualization is carried out, so that efficient, accurate and standardized evaluation of the nitrogen and phosphorus reduction effect of the coastal zone is realized, and a scientific basis is provided for design, optimization and effect inspection of ecological restoration engineering of the coastal zone.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of data processing and ecological environment assessment, and particularly relates to a method for evaluating nitrogen and phosphorus reduction effect of a riparian zone. BACKGROUND

[0002] As a transition area of water-land ecosystem, the nitrogen and phosphorus reduction capacity of the riparian zone directly affects the water environmental quality and is a core evaluation index of ecological restoration engineering. The existing methods for evaluating the nitrogen and phosphorus reduction effect of the riparian zone have obvious deficiencies: first, the slope data acquisition relies on manual measurement, which is low in efficiency and limited in accuracy, and it is difficult to reflect the spatial heterogeneity of the riparian zone slope; second, the identification of plant structure and riparian zone type relies on field reconnaissance, which is limited in coverage and cannot quickly obtain distribution information of a large area; third, the correction of hydrological factors such as rainfall intensity and water level amplitude in the evaluation process is not comprehensive, or the application of correction coefficients lacks systematicness, resulting in large deviation of the evaluation results; fourth, there is no standardized process of data acquisition-parameter extraction-correction calculation-effect evaluation, which cannot meet the efficient and accurate evaluation needs in engineering practice.

[0003] In the prior art, although some studies use remote sensing data to extract shorelines or classify land use, and some scholars obtain nitrogen and phosphorus reduction benchmark values of different plant-soil combinations through indoor experiments, low-altitude multispectral unmanned aerial vehicle data, ground measured data and nitrogen and phosphorus reduction benchmarks and hydrological correction coefficients have not been systematically fused, and the rapid, accurate and large-scale evaluation of the nitrogen and phosphorus reduction effect of the riparian zone cannot be realized, which restricts the optimization and popularization of the riparian zone ecological restoration engineering. SUMMARY

[0004] In view of the problems of low data acquisition efficiency, insufficient parameter extraction accuracy, non-systematic hydrological correction and non-standardized evaluation process in the existing methods for evaluating the nitrogen and phosphorus reduction effect of the riparian zone, the present application provides a method for evaluating the nitrogen and phosphorus reduction effect of the riparian zone, which is used to realize efficient, accurate and standardized evaluation of the nitrogen and phosphorus reduction effect of the riparian zone and provide a scientific basis for the design, optimization and effectiveness test of the riparian zone ecological restoration engineering.

[0005] The present application adopts the following technical scheme: a method for evaluating the nitrogen and phosphorus reduction effect of a riparian zone, comprising the following steps:

[0006] Step 1, data acquisition: obtaining multispectral image data and digital surface model (DSM) of the target riparian zone by using a low-altitude multispectral unmanned aerial vehicle; and obtaining actual slope, elevation and long-term hydrological dynamic data of the target riparian zone by ground measurement, sampling and investigation;

[0007] Step 2, core parameter extraction: establish a lookup table of nitrogen and phosphorus reduction ratio of riparian zone type-slope-planting combination and hydrological correction coefficient; correct the digital surface model using the ground elevation data, construct the target riparian zone accurate digital elevation model (DEM), determine the slope, divide the slope interval according to the lookup table, and identify the target riparian zone type and planting / slope protection combination structure combined with multispectral image data, ground survey data and digital surface model;

[0008] Step 3, nitrogen and phosphorus reduction ratio calculation: according to the lookup table in step 2, the nitrogen and phosphorus reduction reference value is obtained, combined with the rainfall intensity correction coefficient and water level amplitude correction coefficient extracted from the hydrodynamic data, the final nitrogen and phosphorus reduction ratio is calculated;

[0009] Step 4, output of evaluation results: spatial visualization of nitrogen and phosphorus reduction ratio, generation of nitrogen and phosphorus reduction effect spatial distribution map of target riparian zone, output of statistical report.

[0010] As a preferred, the data collection of step 1 comprises:

[0011] Low-altitude multispectral unmanned aerial vehicle data collection is performed on the target riparian zone to obtain image data and digital surface model containing green light, red light and near-infrared band, and the aerial survey accuracy meets the requirements of slope calculation and plant identification (the ground resolution recommended by the application is ≤5cm, and the slope calculation error is ensured to be ≤5%).

[0012] Typical sampling points are arranged in the target riparian zone, and ground field survey data collection is performed, soil samples are collected, plant species and structure are recorded, actual slope and elevation data of the sampling points are measured, and long-term rainfall intensity data (low ≤20mm / h, medium 20~50mm / h, high ≥50mm / h) and water level amplitude data (small ≤0.5m, medium 0.5~1.5m, large ≥1.5m) in the region are recorded synchronously.

[0013] Among them, the rainfall intensity data is recorded at least continuously for 1 hydrological year, and the water level amplitude data covers the wet, flat and dry seasons.

[0014] As a preferred, in the lookup table of nitrogen and phosphorus reduction ratio of riparian zone type-slope-planting combination and hydrological correction coefficient in step 2, according to the riparian zone type, the slope grade, the planting / slope protection combination type, the total nitrogen (TN) reduction ratio, the total phosphorus (TP) reduction ratio, the rainfall intensity correction coefficient and the water level amplitude correction coefficient are determined;

[0015] The riparian zone type comprises a bank slope type and a near-shore water type.

[0016] The slope grade comprises:

[0017] Gentle slope: the ratio between the vertical height of the slope surface and the horizontal width is ≤1:2.

[0018] Moderate slope: the ratio between the vertical height and the horizontal width of the slope surface is 1:1.5~1:2;

[0019] Steep slope: the ratio between the vertical height and the horizontal width of the slope surface is ≥1:1.5;

[0020] Flat water area: no obvious slope.

[0021] As a preferred, the core parameter extraction of step 2 comprises the following sub-steps:

[0022] Step 2.1, digital elevation model construction: using the ground measured elevation data to correct the digital surface model obtained by the unmanned aerial vehicle, eliminating the interference of the vegetation canopy, for the arbor-shrub-grass complex layer area, through the field measurement of vegetation height to assist the correction, obtaining the accurate target riparian zone digital elevation model;

[0023] Step 2.2, slope and slope interval determination: based on the digital elevation model, using geographic information software to obtain the slope distribution data of the target riparian zone, combining with the slope classification standard to divide the slope interval;

[0024] Step 2.3, riparian zone type and plant structure identification: combining the unmanned aerial vehicle multispectral image green light band reflecting the vegetation chlorophyll content, near-infrared band distinguishing vegetation vigor, ground survey photos and digital surface model, through the normalized difference vegetation index NDVI to assist the identification of plant covered area, combining with the field investigation record to determine the target riparian zone type (shore slope type, nearshore water type) and planting / slope protection combination structure (such as arbor-shrub-grass complex layer, stone cage slope protection, submerged plant community, etc.).

[0025] As a preferred, the normalized difference vegetation index NDVI of step 2.3 is calculated as follows:

[0026] NDVI=(near-infrared band-red light band) / (near-infrared band+red light band);

[0027] When NDVI≥0.3, it is determined as effective vegetation coverage;

[0028] As a preferred, the nitrogen and phosphorus reduction ratio calculation of step 3 comprises the following sub-steps:

[0029] Step 3.1, reference value lookup: according to the target riparian zone type, slope interval and planting / slope protection combination structure extracted in step 2, obtaining the total nitrogen reduction ratio and total phosphorus reduction ratio reference value from the lookup table;

[0030] For example: shore slope type-moderate slope-arbor-shrub-grass complex layer, corresponding TN reference value≥30%, TP reference value≥25%.

[0031] Step 3.2, hydrological correction: according to the rainfall intensity level and water level amplitude level of the target coastal zone, the corresponding rainfall intensity correction coefficient and water level amplitude correction coefficient are extracted from the lookup table, and the total nitrogen reduction ratio and the total phosphorus reduction ratio are multiplied by the rainfall intensity correction coefficient and the water level amplitude correction coefficient, respectively, to obtain the final nitrogen and phosphorus reduction ratio, which is expressed as: final reduction ratio = baseline value x rainfall intensity correction coefficient x water level amplitude correction coefficient.

[0032] As a preferred, in step 3.2, if there is a spatial difference in rainfall or water level in the target coastal zone, the correction coefficient is extracted according to the sub-region, and the hydrological correction is carried out, so as to avoid the error caused by the overall average.

[0033] As a preferred, the nitrogen and phosphorus reduction effect spatial distribution map in step 4 adopts a hierarchical color setting method, and the reduction effect is divided into four levels according to the reduction ratio: excellent (≥30%), good (20%-30%), medium (10%-20%) and poor (<10%); the statistical report clearly shows the difference in reduction effect and the key influencing factors.

[0034] The technical scheme of the present application also provides an electronic device, comprising:

[0035] One or more processors;

[0036] A storage device having one or more programs stored thereon;

[0037] When the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned coastal zone nitrogen and phosphorus reduction effect evaluation method.

[0038] The technical scheme of the present application also provides a computer readable storage medium having a computer program stored thereon, which is executed by a processor to implement the steps of the aforementioned coastal zone nitrogen and phosphorus reduction effect evaluation method.

[0039] Compared with the prior art, the technical scheme of the present application has the following technical effects:

[0040] 1. The method of the present application realizes rapid data acquisition of large-area coastal zone by low-altitude multispectral unmanned aerial vehicle, greatly reduces the workload of artificial field investigation, and significantly improves the evaluation efficiency. Precise DEM is obtained by correcting unmanned aerial vehicle DSM with ground data; combined with the plant structure recognition accuracy of multispectral image and field investigation, the hydrological correction coefficient is superimposed, so that the evaluation error of nitrogen and phosphorus reduction ratio is reduced, and the precision requirement of ecological restoration engineering is met.

[0041] 2. The method of the present application establishes a standardized process of data acquisition-parameter extraction-correction calculation-result output, clearly defines the technical requirements of each link, ensures the comparability of evaluation results of different regions and different batches, and avoids evaluation deviation caused by method difference.

[0042] 3、The evaluation result of the application can directly reflect the difference of nitrogen and phosphorus reduction ability of different coastal zones, and provide accurate guidance for optimizing planting structure (such as changing single herb to arbor-shrub-grass complex layer in the middle slope area), adjusting slope (such as reducing the steep slope to the middle slope to improve the reduction effect), hydrological regulation (such as increasing the water retaining facility in the high water level fluctuation area to control the fluctuation range of ≤0.5m), and the like, so as to improve the ecological restoration effect of the coastal zone. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The flow chart of the nitrogen and phosphorus reduction effect evaluation method of the application. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the application more clear, the technical scheme of the application will be further described in detail below with reference to the drawings, and the described embodiments are only a part of the embodiments involved in the application. All non-innovative embodiments of other researchers in the field on the basis of the embodiments belong to the protection scope of the application. Meanwhile, the step numbers in the embodiments are only set for the convenience of description and explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiments can be adaptively adjusted according to the understanding of the person skilled in the art.

[0045] In an embodiment of the application, the slope type coastal zone of Yiai Lake in Huanggang City is selected as the research area, the area of the research area is about 5km², it is located on the north bank of the middle reaches of the Yangtze River, belongs to subtropical monsoon climate, and the annual average rainfall is 1200-1400mm; the terrain in the region includes three slope intervals of gentle slope, middle slope and steep slope, and the planting structure covers arbor-shrub-grass complex layer (willow + amsonia + zoysia grass), single herb (bermuda grass) and ecological concrete slope protection (with zoysia grass) and the like; according to the data of the weather station and the hydrological station in the past three years, the annual average rainfall intensity in the region is mainly medium intensity (20-50mm / h), accounting for 65%, and the water level fluctuation is at a medium level (0.8m on average, and the fluctuation range is 0.5-1.2m).

[0046] The nitrogen and phosphorus reduction effect of the coastal zone is evaluated by the method of the application, as shown in the following table, including the following steps: Figure 1

[0047] Step 1, data acquisition

[0048] In this embodiment, the low-altitude multispectral unmanned aerial vehicle data acquisition: DJI P4 Multispectral unmanned aerial vehicle is selected, the flight height is set to 100m, the heading overlap is 85%, and the lateral overlap is 70%, and the green light, red light, near-infrared band image and DSM data of the research area are obtained.

[0049] ​Ground field survey data collection: multiple sampling points were evenly distributed in the study area according to the slope interval, meeting the 1 / km2 density requirement, and the sampling point coordinates were recorded using a handheld GPS; 3 0-20 cm soil samples were collected within a 10 m range around each sampling point (mixed into 1 sample for testing), the plant species at each sampling point, and the planting structure (e.g., sampling point 1 on a gentle slope: weeping willow (diameter 5-8 cm) + amsonia (height 1.2-1.5 m) + St. Augustine grass (coverage 80%)) were recorded; the rainfall data (Jiali Lake Weather Station, data interval 1 h) and water level data (Jiali Lake Hydrological Station, data interval 1 d) in the collection area in the past 3 years were collected, and the rainfall intensity grade was medium (35 mm / h, corresponding to the average intensity of medium rain in the past 3 years), and the water level amplitude grade was medium (0.8 m, corresponding to the average amplitude in the past 3 years).

[0050] Step 2, parameter extraction

[0051] First, a lookup table of nitrogen and phosphorus reduction ratios and hydrological correction coefficients for the type-slope-planting combination of the riparian zone was constructed.

[0052] In this embodiment, based on the WOS core collection and CNKI database from 2000 to 2024, the rules for nitrogen and phosphorus interception technology in the riparian zone were systematically sorted out through bibliometric analysis, as shown in Table 1 below.

[0053] Table 1: Lookup table of nitrogen and phosphorus reduction ratios and hydrological correction coefficients for the type-slope-planting combination of the riparian zone

[0054]

[0055] Specifically, the riparian zone types in the lookup table include shore slope type and nearshore water type.

[0056] In the shore slope type riparian zone, the gentle slope planting / slope protection combination types include: plant slope protection (arbor-shrub-grass complex: weeping willow + amsonia + St. Augustine grass), gabion slope protection (coal bottom ash filler + vegetation), ecological bag slope protection (ryegrass), and ecological concrete slope protection (with vegetation: St. Augustine grass); the medium slope planting / slope protection combination types include: plant slope protection (single herb: centipede grass) and geocell slope protection (ryegrass + fill); and the steep slope planting / slope protection combination types include: ecological concrete slope protection (with vegetation: centipede grass) and gabion slope protection (pebble filler + centipede grass).

[0057] In the nearshore water type riparian zone, the gentle water area planting / slope protection combination types include: submerged plants (single community of cattail, coverage 50%), submerged plants (mixed community: black algae + cattail + potamogeton, coverage 50%), ecological floating island (mixed plants: canna + cattail + acorus), and ecological floating island (enhanced biological membrane: glasswort + cattail + yellow cattail + biological carbon fiber).

[0058] According to the above planting / slope protection combination type, respectively corresponding to determine its total nitrogen (TN) reduction ratio, total phosphorus (TP) reduction ratio, rainfall intensity correction coefficient, water level amplitude correction coefficient, for subsequent lookup.

[0059] Then, construct DEM, use multiple sampling points of measured elevation data, through geographic information software of geographic registration tool to correct unmanned aerial vehicle DSM (adopting quadratic polynomial fitting, R²=0.98), remove the height interference of willow (crown height 3~5m), amsonia (crown height 1.2~1.5m) and other vegetation canopy, obtain DEM data; through 3 ground control points verification, DEM elevation error is ±0.08m, meet the accuracy requirements.

[0060] Next, carry out slope interval division, based on DEM, adopt geographic information software to calculate slope, combine the grading standard in step 2 constructed riparian zone type-slope-planting combination nitrogen and phosphorus reduction ratio and hydrological correction coefficient lookup table, divide into gentle slope area (≤1:2, corresponding to slope ≤50%, area 2.3km²), middle slope area (1:1.5~1:2, corresponding to slope 50%~66.7%, area 1.8km²), steep slope area (≥1:1.5, corresponding to slope ≥66.7%, area 0.9km²).

[0061] Finally, type and plant structure recognition, calculate NDVI through unmanned aerial vehicle image, formula: (B4-B3) / (B4+B3), wherein B4 is near infrared band, B3 is red light band), NDVI≥0.3 area is determined as effective vegetation coverage; combine field photos and investigation records, identify that the arbor and shrub grass layer area is 1.2km² (NDVI 0.6~0.8), single herb (dog tooth grass) area is 1.5km² (NDVI 0.3~0.5), ecological concrete slope protection area is 2.3km² (NDVI 0.2~0.3, centipede grass coverage 30%), riparian zone type is all bank slope type (no near shore water type area).

[0062] Step 3, nitrogen and phosphorus reduction ratio calculation

[0063] Step 3.1, reference value lookup: according to bank slope type + slope interval + planting structure combination, extract reference value from step 2 riparian zone type-slope-planting combination nitrogen and phosphorus reduction ratio and hydrological correction coefficient lookup table, as follows:

[0064] 1) gentle slope + arbor and shrub grass layer (willow + amsonia + centipede grass): corresponding to lookup table “bank slope type-gentle slope-plant protection (arbor and shrub grass layer) ” entry, TN reference value ≥30%, TP reference value ≥25%;

[0065] 2) Medium slope + single herb (dog tooth grass): TN reference value 15%~20%, TP reference value 12%~18%, corresponding to the lookup table entry "bank slope type-medium slope-plant slope protection (single herb)";

[0066] 3) Steep slope + ecological concrete slope protection (with zoysia grass): TN reference value 35%~40%, TP reference value 55%~60%, corresponding to the lookup table entry "bank slope type-steep slope-ecological concrete slope protection (with vegetation)" (in the lookup table, it is "with pachysandra", because zoysia grass and pachysandra are both herbaceous slope protection plants, and their reduction capacities are similar, so the reference values of this entry are used).

[0067] Step 3.2, hydrological correction: according to the regional rain (35mm / h) + medium water level amplitude (0.8m), the corresponding correction coefficient is extracted from the lookup table, as follows:

[0068] 1) Gentle slope + arbor-shrub-grass complex: rain correction coefficient 0.8 (rain coefficient in lookup table "bank slope type-gentle slope-plant slope protection"), water level correction coefficient 0.9 (water level coefficient in the same entry);

[0069] 2) Medium slope + single herb (dog tooth grass): rain correction coefficient 0.75 (rain coefficient in lookup table "bank slope type-medium slope-plant slope protection"), water level correction coefficient 0.85 (water level coefficient in the same entry);

[0070] 3) Steep slope + ecological concrete slope protection: rain correction coefficient 0.8 (rain coefficient in lookup table "bank slope type-steep slope-ecological concrete slope protection"), water level correction coefficient 0.8 (water level coefficient in the same entry).

[0071] Final reduction ratio calculation (calculated according to reference value x rainfall coefficient x water level coefficient):

[0072] 1) Gentle slope + arbor-shrub-grass complex: TN≥30%×0.8×0.9=21.6%, TP≥25%×0.8×0.9=18%;

[0073] 2) Medium slope + single herb (dog tooth grass): TN (15%×0.75×0.85)~(20%×0.75×0.85)=9.56%~12.75%, TP (12%×0.75×0.85)~(18%×0.75×0.85)=7.65%~11.48%;

[0074] 3) Steep slope + ecological concrete slope protection: TN (35%×0.8×0.8)~(40%×0.8×0.8)=22.4%~25.6%, TP (55%×0.8×0.8)~(60%×0.8×0.8)=35.2%~38.4%.

[0075] It should be noted that in this embodiment, the calculation logic for the regional average reduction ratio is as follows: a weighted average based on the area of ​​each region, and the specific calculation formula is as follows:

[0076] (Area of ​​gentle slopes × average reduction rate of gentle slopes + area of ​​medium slopes × average reduction rate of medium slopes + area of ​​steep slopes × average reduction rate of steep slopes) / total area;

[0077] The average reduction rate is taken as the median of the baseline value range for each region (e.g., the TN baseline value for medium slope is 15%~20%, and the median is 17.5%). The calculation process is as follows:

[0078] Average TN percentage: (2.3×21.6%+1.8×11.16%+0.9×24%) / 5≈18.9%;

[0079] Average TP percentage: (2.3×18%+1.8×9.57%+0.9×36.8%) / 5≈21.7%.

[0080] The summary table of modifications to this embodiment is shown in Table 2 below.

[0081] Table 2: Summary Table of Revision Notes

[0082]

[0083] The correction coefficient rules for this embodiment are as follows:

[0084] Rainfall intensity is classified as "low (≤20mm / h), medium (20~50mm / h), high (≥50mm / h)", with a smaller correction coefficient for higher intensity; water level fluctuation is classified as "small (≤0.5m), medium (0.5~1.5m), large (≥1.5m)", with a smaller correction coefficient for larger fluctuation.

[0085] Step 4: Output of Evaluation Results

[0086] Finally, the nitrogen and phosphorus reduction ratios were spatially visualized using geographic information software to generate a spatial distribution map of the nitrogen and phosphorus reduction effects in the target coastal zone.

[0087] In this embodiment, a graded coloring method is adopted, which divides the reduction into four levels according to the reduction ratio: excellent (≥30%), good (20%~30%), medium (10%~20%), and poor (<10%). Statistical reports are output simultaneously to clarify the differences in reduction effect and key influencing factors in different areas. For example, the reduction effect in single herbaceous areas on medium slopes is poor, mainly due to the large slope and weak herbaceous interception capacity.

[0088] In the embodiment of the present application, an electronic device is also provided, comprising: one or more processors; a storage device having one or more programs stored thereon; and when the one or more programs are executed by the one or more processors, the one or more processors implement the method for evaluating the nitrogen and phosphorus reduction effect of the coastal zone described in the above embodiment.

[0089] In the embodiment of the present application, a computer readable storage medium having a computer program stored thereon is also provided, and when the program is executed by a processor, the steps in the method for evaluating the nitrogen and phosphorus reduction effect of the coastal zone in the above embodiment are implemented.

[0090] The above description is only the preferred embodiment of the present application, and it should be pointed out that for those skilled in the art, without departing from the principle of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for evaluating nitrogen and phosphorus reduction effect in a coastal zone, characterized by, The method comprises the following steps: Step 1, data acquisition: obtaining multi-spectral image data and digital surface model of the target coastal zone by low-altitude multi-spectral unmanned aerial vehicle; ground survey, sampling and investigation are carried out to obtain the actual slope, elevation and long-term hydrological dynamic data of the target coastal zone; Step 2, core parameter extraction: establishing a lookup table of coastal zone type-slope-planting combination nitrogen and phosphorus reduction ratio and hydrological correction coefficient; correcting the digital surface model by using the ground measured elevation data to construct the accurate digital elevation model of the target coastal zone, determining the slope, dividing the slope interval according to the lookup table, and identifying the target coastal zone type and planting / slope protection combination structure in combination with the multi-spectral image data, ground survey data and digital surface model; Step 3, nitrogen and phosphorus reduction ratio calculation: obtaining the nitrogen and phosphorus reduction reference value according to the lookup table in step 2, and combining the rainfall intensity correction coefficient and water level amplitude correction coefficient extracted from the hydrological dynamic data to calculate the final nitrogen and phosphorus reduction ratio; Step 4, output of evaluation results: spatial visualization of the nitrogen and phosphorus reduction ratio is carried out to generate a spatial distribution map of the nitrogen and phosphorus reduction effect of the target coastal zone, and a statistical report is output.

2. The method for evaluating the nitrogen and phosphorus reduction effect of the coastal zone according to claim 1, characterized in that, The data acquisition in step 1 comprises: Carrying out low-altitude multi-spectral unmanned aerial vehicle data acquisition on the target coastal zone to obtain image data and digital surface model containing green light, red light and near-infrared wave band; Typical sampling points are arranged on the target coastal zone, ground survey data is collected, soil samples are collected, plant species and structure are recorded, actual slope and elevation data of the sampling points are measured; long-term rainfall intensity data and water level amplitude data in the region are recorded synchronously, wherein the rainfall intensity data is recorded for at least one hydrological year, and the water level amplitude data covers the high, medium and low water periods.

3. The method for evaluating the nitrogen and phosphorus reduction effect of the coastal zone according to claim 1, characterized in that, In step 2, the lookup table of coastal zone type-slope-planting combination nitrogen and phosphorus reduction ratio and hydrological correction coefficient is established based on the existing WOS core collection and CNKI database through bibliometric analysis, and the rules of coastal zone nitrogen and phosphorus interception technology are systematically sorted out, which is used to determine the corresponding slope level, planting / slope protection combination type, total nitrogen reduction ratio, total phosphorus reduction ratio, rainfall intensity correction coefficient and water level amplitude correction coefficient according to the type of coastal zone; The type of coastal zone includes: shore slope type and near-shore water area type; The slope level includes: Gentle slope: the ratio between the vertical height and the horizontal width of the slope surface is ≤1:2; Medium slope: the ratio between the vertical height and the horizontal width of the slope surface is 1:1.5~1:2; Steep slope: the ratio between the vertical height and the horizontal width of the slope surface is ≥1:1.5; Flat water area: no obvious slope.

4. The method for evaluating the nitrogen and phosphorus reduction effect of the coastal zone according to claim 1, characterized in that, The core parameter extraction in step 2 comprises the following sub-steps: Step 2.1, digital elevation model construction: correcting the digital surface model obtained by the unmanned aerial vehicle by using the ground measured elevation data, eliminating the interference of the vegetation canopy, and for the arbor, shrub and grass layer area, the accurate target coastal zone digital elevation model is obtained by auxiliary correction through field measurement of vegetation height; Step 2.2, slope and slope interval determination: based on the digital elevation model, the slope distribution data of the target coastal zone is obtained by using geographic information software, and the slope interval is divided in combination with the slope grading standard; Step 2.3: Identification of riparian zone type and plant structure: Based on the multi-spectral images of unmanned aerial vehicle, ground survey photos and digital surface model, the normalized difference vegetation index (NDVI) is used to assist in identifying the vegetation coverage area. In combination with field survey records, the target riparian zone type and planting / slope protection combination structure are determined.

5. The method for evaluating the nitrogen and phosphorus reduction effect of the coastal zone according to claim 4, characterized in that, The normalized difference vegetation index (NDVI) in step 2.3 is calculated as follows: NDVI = (near-infrared band - red band) / (near-infrared band + red band) When NDVI ≥ 0.3, it is determined as effective vegetation coverage.

6. The method for evaluating the nitrogen and phosphorus reduction effect of the coastal zone according to claim 4, characterized in that, The calculation of nitrogen and phosphorus reduction ratio in step 3 includes the following sub-steps: Step 3.1: Reference value lookup: According to the target riparian zone type, slope interval and planting / slope protection combination structure extracted in step 2, the total nitrogen reduction ratio and total phosphorus reduction ratio reference values are obtained from the lookup table; Step 3.2: Hydrological correction: According to the rainfall intensity grade and water level amplitude grade of the target riparian zone area, the corresponding rainfall intensity correction coefficient and water level amplitude correction coefficient are extracted from the lookup table, and the final nitrogen and phosphorus reduction ratio is calculated, as follows: Final reduction ratio = reference value × rainfall intensity correction coefficient × water level amplitude correction coefficient.

7. The method for evaluating the nitrogen and phosphorus reduction effect of the coastal zone according to claim 6, characterized in that, In step 3.2, if there are spatial differences in rainfall or water level within the target riparian zone area, the correction coefficients are extracted for each sub-area for hydrological correction.

8. The method for evaluating the nitrogen and phosphorus reduction effect of the coastal zone according to claim 6, characterized in that, The nitrogen and phosphorus reduction effect spatial distribution map in step 4 uses a grading color method to divide the reduction effect into four levels: excellent, good, medium and poor. The statistical report clearly shows the differences in reduction effect and the key influencing factors.

9. An electronic device, comprising: Comprise: One or more processors; Storage device having one or more programs stored thereon; When the one or more programs are executed by the one or more processors, the one or more processors implement the riparian zone nitrogen and phosphorus reduction effect evaluation method according to any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that, A computer program is stored thereon, which is executed by a processor to implement the steps of the riparian zone nitrogen and phosphorus reduction effect evaluation method according to any one of claims 1 to 8.

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