| Urban lakes are an important part of urban water environment and have important ecological service functions.Unreasonable development activities will directly lead to dramatic changes in lake landscapes,resulting in the degradation and extinction of lakes,which will seriously affect the production and life of residents and the ecology of cities.Civilization construction.The rapid development of Earth observation technology has provided a large number of data sources and strong technical support for the study of lake landscape changes.This paper uses six Landsat remote sensing images covering the downtown area of Wuhan City from 1978 to 2017 as the data source:(1)Based on the comparison of multiple water extraction methods and threshold segmentation algorithms,the MNDWI combined with the improved OTSU algorithm is applied to the study area.The water body information was accurately and quickly extracted.(2)Using SVM classification algorithm to classify the remote sensing images in the study area,and on this basis,a detailed analysis of the land use changes in the study area.(3)Using the theory of landscape ecology,empirical methods and principal component analysis were used to select various types of landscape indices for the study of temporal and spatial dynamic characteristics of lake landscapes.(4)At the grid scale,combined with the changes of the Urbanization Intensity Index(UII)and landscape feature index,the relationship between urban expansion and lake landscape feature changes was explored using a geographically weighted regression model.With a view to enriching the analysis methods of lake landscape changes,it will provide scientific basis for the optimization of urban construction in Wuhan and the promotion of lake integrated management and protection planning.The experimental results show that the changes in the lake area in downtown Wuhan experienced slow-recovery-substantially-decrease-and slowly-decreasing(and slower rates)processes.Lake landscape features vary in different time periods.Among them,the policy expansion,urban expansion in the absence of legislation,and interest-driven real estate development are the main causes of lake landscape changes in downtown Wuhan.It is found that there is regional heterogeneity in the impact of urbanization on the landscape features of lakes.It is manifested in places where the intensity of urbanization is greater.The more dramatic lake landscape changes,the stronger the ability of urbanization to explain lake landscape changes.In most regions of the study area,the changes of urbanization and landscape index are negatively correlated,but the negative correlation shows different performance in different regions.In areas with proper protection and reasonable planning,the influence of urbanization on lake landscape will be significant.The decline indicates that targeted lake management protection can effectively reduce lake degradation rates.In terms of the techniques used in the study,it was found that modified NDWI and OTSU algorithm were able to provide rapid and accurate extraction of water information from Landsat multi-spectral images.In addition,post-classification change detection based on SVM algorithm produced high accurate results,which was benefit to detailed land cover change analysis.It can be stated that continuous change detection based on remote sensing techniques enable us to better understand the detailed spatial changes of urban lakes on one hand,and the trends of urban growth on the other hand. |
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