Quantification method for important hydrological connected region of estuary wetland

Abstract

The invention discloses a method for quantifying an important hydrological connected region of an estuary wetland, which comprises the following steps of: firstly, extracting a tidal creek surface grid image, defining a road-shaped water body in the tidal creek surface grid image as a road according to the tidal creek distribution condition of the estuary wetland, and creating vector data of a road center line by using a road center line method; processing the vector data to obtain a plurality of tidal creek line elements; determining a plurality of tidal creek plaques according to the tidal creek line elements, determining a distance threshold and a selection group score, calculating a possible connectivity index PC and an overall connectivity index IIC of each tidal creek plaque, and measuring the contribution degree of a certain tidal creek plaque to the overall hydrological connectivity of the region by using connectivity importance indexes CDiic and Cdpc. And finally obtaining a quantification result of the important hydrological connected region of the estuary wetland. According to the method, data are easy to obtain, the analysis method is universal, repeated manual processing work can be reduced to a certain extent, and a reliable analysis tool is provided for scientific research personnel.

Description

Technical Field

[0001] The invention belongs to the technical field of estuarine wetland monitoring, and in particular to a method for quantifying important hydrological connected areas of estuarine wetlands. Background Art

[0002] Estuarine wetlands connect river basins and sea areas, and are transitional areas between terrestrial river ecosystems and marine ecosystems. They play a significant role in carbon-nitrogen biogeochemical cycles, biodiversity maintenance, global climate change mitigation, and blue carbon sinks. Hydrology, soil, and plants are the three basic elements for maintaining the ecological functions of estuarine salt marsh wetlands, and changes in hydrological connectivity are the most critical factors in connecting and driving these elements, regulating the material cycle, energy transfer, and biological ecological processes of ecosystems with water as the medium. For a long time, under the influence of multiple factors such as sea reclamation, land reclamation, and reservoir dam interception, the natural hydrological connectivity and hydrological rhythm of estuarine wetlands have changed, leading to ecosystem degradation and a decline in ecological functions. Understanding the spatiotemporal changes in hydrological connectivity such as tidal channel morphology and water network structure in estuarine wetlands, especially quantifying important hydrological connectivity areas in estuarine wetlands, will help to deeply understand the coordinated evolution characteristics of wetland ecological functions and micro-topographic structures.

[0003] At present, the main methods used to quantify the hydrological connectivity of estuarine wetlands are graph theory, which is to digitize the water system network and analyze the hydrological connectivity of the basin based on the geometric topological relationship between points and lines. The main advantage of graph theory is that it can reflect the spatial heterogeneity of the horizontal hydrological connectivity of wetlands, which is more useful for the restoration of estuarine wetland vegetation, but lacks analysis of the morphological characteristics of tidal channels. Another method is to quantify hydrological connectivity based on the tidal channel morphological characteristic index. Specifically, it uses remote sensing images to extract tidal channel surface raster images, and establishes an evaluation model by calculating the parameters such as the tidal channel length, bifurcation rate, and curvature of the area. This method can reflect the wetland hydrological connectivity pattern to a certain extent, but lacks analysis on the spatial scale. Although the above two methods can quantify the overall hydrological connectivity of estuarine wetlands, it is difficult to evaluate the importance of a single patch without a unified measurement standard, that is, it is impossible to accurately quantify the important hydrological connectivity areas of estuarine wetlands. Summary of the invention

[0004] The present invention aims to solve the above-mentioned technical problems existing in the prior art and provides a method for quantifying important hydrological connected areas of estuarine wetlands.

[0005] The technical solution of the present invention is: a method for quantifying important hydrological connectivity areas of estuarine wetlands, which is carried out according to the following steps:

[0006] Step 1. Extract the tidal gully surface raster image;

[0007] Step 2. For the extracted tidal gully surface raster image, according to the distribution of tidal gullies in estuarine wetlands, the road-shaped water body is defined as a "road", and the road centerline method is used to create the vector data of the road centerline, that is, the line element of the road center axis;

[0008] Step 3. The actual length of the line element of the road center axis is obtained through geometric calculation in ArcGIS. The lengths of the path polylines connected in the same patch visible to the naked eye are added up, and the path polyline with the longest length is taken as a tidal ditch line element. All patches visible to the naked eye are traversed to obtain multiple tidal ditch line elements.

[0009] Step 4. Determine n tidal gully patches based on multiple tidal gully line features, determine the distance threshold and the number of selected components, and use the Conefor plug-in in ArcGIS 10.8 software to calculate the possible connectivity index PC and the overall connectivity index IIC of each tidal gully patch. The specific formula is as follows:

[0010]

[0011] Where n is the total number of tidal gully patches in the landscape, i = 1, 2, 3, ... n, j = 1, 2, 3, ... n, i ≠ j; a i and a j are the attributes of tidal gully patches i and j respectively; A L represents the maximum landscape attribute; nl ij is the number of links in the shortest path between i and j; is the maximum product probability of all paths between i and j;

[0012] Step 5. Calculate the connectivity importance index Cdiic and Cdpc. The specific formula is as follows:

[0013]

[0014] In the formula, C i diic and C i dpc represents the importance index of the overall connectivity and possible connectivity of tidal creek patch i, IIC i and PC i It represents the overall connectivity index and possible connectivity index calculated after removing the tidal gully patch i from the overall patch;

[0015] Step 6. Use the spatial interpolation method in ArcGIS 10.8 to calculate the possible connectivity index PC and the overall connectivity index IIC of the spatial area without tidal channels;

[0016] Step 7. In ArcGIS 10.8 software, all calculated values ​​in steps 5 and 6 were combined to obtain the evaluation results of the importance of tidal gully patches in spatial regional hydrological connectivity, that is, the quantitative results of important hydrological connectivity areas in estuarine wetlands.

[0017] The present invention first extracts the tidal ditch surface grid image, defines the road-shaped water body in the tidal ditch surface grid image as a "road" according to the distribution of tidal ditch in estuarine wetlands, and uses the road centerline method to create the vector data of the road centerline; then the vector data is processed and multiple tidal ditch line elements are obtained; then multiple tidal ditch patches are determined by the tidal ditch line elements, and the distance threshold and the number of selected components are determined at the same time, and the possible connectivity index PC and the overall connectivity index IIC of each tidal ditch patch are calculated, and the connectivity importance index Cdiic and Cdpc are used to measure the contribution of a certain tidal ditch patch to the overall hydrological connectivity of the region, and finally the quantitative results of the important hydrological connectivity area of ​​the estuarine wetland are obtained. The data of the present invention are easy to obtain, and the analysis method is versatile, which can reduce the repetitive manual processing work to a certain extent, and provide a reliable analysis tool for scientific researchers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of an embodiment of the present invention.

[0019] Figure 2 This is a distribution map of the importance of Liaohe River estuary patches obtained in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] A method for quantifying important hydrological connectivity areas of estuarine wetlands according to the present invention is as follows: Figure 1 As shown, follow these steps:

[0021] Step 1. Input the sentinel-2 multispectral image of the study area into the tidal creek extraction model to extract the tidal creek surface raster image;

[0022] The sentinel-2 multispectral image of the study area is an image that determines the geographical and temporal range of tidal gully extraction, collects high spatial resolution satellite remote sensing image data at high and low tides and performs preprocessing. The high spatial resolution satellite remote sensing image is a 10-meter spatial resolution remote sensing image of Sentinel-2;

[0023] The tidal creek extraction model is a model that uses a network structure based on deep learning to extract small rivers and is trained and tested using the sentinel-2 surface water quality dataset;

[0024] Step 2. For the extracted tidal ditch surface raster image, according to the distribution of tidal ditch in estuarine wetland, the road-shaped water body is defined as "road", and the road centerline method is used to create the vector data of the road centerline, that is, the line element of the road center axis. The non-road-shaped water body can be ignored to exclude the influence of non-tidal ditch water body;

[0025] Step 3. The actual length of the line element of the road center axis is obtained through geometric calculation in ArcGIS. The lengths of the path polylines connected in the same patch visible to the naked eye are added up, and the longest path polyline is taken as a tidal ditch line element. All patches visible to the naked eye are traversed to obtain multiple tidal ditch line elements, each of which represents a complete tidal ditch.

[0026] Step 4. Determine n tidal gully patches based on multiple tidal gully line features, determine the distance threshold and the number of selected components, and use the Conefor plug-in in ArcGIS 10.8 software to calculate the probability of connectivity index PC (PC) and the integral index of connectivity IIC (IIC) of each tidal gully patch. The specific formula is as follows:

[0027]

[0028] Where n is the total number of tidal gully patches in the landscape, i = 1, 2, 3, ... n, j = 1, 2, 3, ... n, i ≠ j; a i and a j are the attributes of tidal gully patches i and j respectively; A L represents the maximum landscape attribute; nl ij is the number of links in the shortest path between i and j; is the maximum product probability of all paths between i and j;

[0029] Step 5. Calculate the connectivity importance indexes Cdiic and Cdpc to measure the contribution of a tidal gully patch to the overall hydrological connectivity of the region. The specific formula is as follows:

[0030]

[0031] In the formula, C i diic and C i dpc represents the importance index of the overall connectivity and possible connectivity of tidal creek patch i, IIC i and PC i It represents the overall connectivity index and possible connectivity index calculated after removing the tidal gully patch i from the overall patch. This index can better reflect the changes of different tidal gully patches in the spatial area;

[0032] Step 6. In order to maintain the consistency of the data in the spatial area without tidal channels, the Inverse Distance Weighting (IDW) spatial interpolation method in ArcGIS 10.8 was used to calculate the possible connectivity index PC and the overall connectivity index IIC of the spatial area without tidal channels;

[0033] Step 7. Combine all the calculated values ​​in steps 5 and 6 in ArcGIS 10.8 software to obtain the evaluation results of the importance of tidal gully patches in spatial regional hydrological connectivity, that is, the quantitative results of important hydrological connectivity areas in estuarine wetlands.

[0034] According to the method of the embodiment of the present invention, the importance distribution diagram of Liaohe River estuary plaques at different periods is obtained as follows: Figure 2 shown. Figure 2 (a) and (b) show the Liaohe Estuary patch C in 2016 and 2023, respectively. i diic distribution map, (c) and (d) are the Liaohe River estuary patch C in 2016 and 2023 respectively i dpc distribution chart. Figure 2 The important hydrological connectivity areas of estuarine wetlands can be intuitively seen, which helps to deeply understand the coordinated evolution characteristics of wetland ecological functions and microtopographic structures.

Claims

1. A method for quantifying important hydrological connectivity areas in estuarine wetlands, characterized in that Follow these steps: Step 1. Extract the tidal gully surface raster image; Step 2. For the extracted tidal gully surface raster image, according to the distribution of tidal gullies in estuarine wetlands, the road-shaped water body is defined as "road", and the road centerline method is used to create the vector data of the road centerline, that is, the line element of the road center axis; Step 3. The actual length of the line element of the road center axis is obtained through geometric calculation in ArcGIS. The lengths of the path polylines connected in the same patch visible to the naked eye are added up, and the path polyline with the longest length is taken as a tidal ditch line element. All patches visible to the naked eye are traversed to obtain multiple tidal ditch line elements. Step 4. Determine n tidal gully patches based on multiple tidal gully line features, determine the distance threshold and the number of selected components, and use the Conefor plug-in in ArcGIS 10.8 software to calculate the possible connectivity index PC and the overall connectivity index IIC of each tidal gully patch. The specific formula is as follows: Where n is the total number of tidal gully patches in the landscape, i = 1, 2, 3, ... n, j = 1, 2, 3, ... n, i ≠ j; a i and a j are the attributes of tidal gully patches i and j respectively; A L represents the maximum landscape attribute; nl ij is the number of links in the shortest path between i and j; is the maximum product probability of all paths between i and j; Step 5. Calculate the connectivity importance index Cdiic and Cdpc. The specific formula is as follows: In the formula, C i diic and C i dpc represents the importance index of the overall connectivity and possible connectivity of tidal creek patch i, IIC i and PC i It represents the overall connectivity index and possible connectivity index calculated after removing the tidal gully patch i from the overall patch; Step 6. Use the spatial interpolation method in ArcGIS 10.8 to calculate the possible connectivity index PC and the overall connectivity index IIC of the spatial area without tidal channels; Step 7. In ArcGIS 10.8 software, all calculated values ​​in steps 5 and 6 were combined to obtain the evaluation results of the importance of tidal gully patches in spatial regional hydrological connectivity, that is, the quantitative results of important hydrological connectivity areas in estuarine wetlands.

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