| As an important part of the coastal zone.gulf is the area where the ocean and the land meet each other.The area belongs to the transition zone between the marine system and the land system and is closely related to the survival and development of human beings.The gulf area is not only an important activity place for human survival and development,but also contains abundant coastal wetland resources,marine fishery resources,oil,natural gas and other mineral resources.It has unique geographical location advantages.Therefore,the gulf area has become the most intense area for human development in the world.However,the ecological environment of the gulf area is extremely fragile.The increasing degree of land use and development in the gulf area,global climate change and environmental pollution spread have all brought tremendous pressure to the natural environment of the gulf area.Great changes have taken place in the original natural form and land use pattern in the gulf area,which has broken the original balance of the area and led to further deterioration of the ecological environment.Therefore,it is necessary to strengthen the planning,management and protection of coastal land use in the gulf area.However,the existing research mainly focuses on coastal land use change,and less on land use pattern change in the gulf area.Therefore,it is of great significance to study the temporal and spatial change of land use in the gulf area.In view of the dramatic changes in land use patterns in the gulf,this paper selects the coastal zone of the typical bays of the Indochina Peninsula as the study area which includes Bangkok Bay,Haiphong Bay and Yafeng Bay respectively.The paper can be divided into two aspects.First,the paper studies the remote sensing image extraction method of the gulf land use,and proposes the object-oriented classification method or model of the gulf land cover,and a new extraction method aiming at the extraction of the typical land type of the gulf area,that is,the coastal aquaculture land which has achieved high classification accuracy after a lot of experiments.Second,the paper analyzes the spatial and temporal changes of land use in the typical gulf area of Bangkok Bay,Haiphong Bay and Yafeng Bay in recent 30 years.By using two Landsat satellite remote sensing images,the ASTER GDEM digital elevation data and the Indochina Peninsula basic map as data sources,and 3S and other technical means as support,the paper explains the 28-view remote sensing image according to the proposed object-oriented remote sensing image classification method,compares and analyzes the results,an finally reveals the land use change in typical bays and its driving forces.The main conclusions are as follows:First,the paper uses an object-oriented automatic land use type extraction method based on moderate resolution remote sensing images suitable of the gulf coastal zone in Indochina Peninsula and the combination of image segmentation,NDWI,NDVI and entropy feature methods to extract land types,which has high classification accuracy.Especially for the unique coastal aquaculture land extraction in the gulf area,this paper proposes to use the relationship between adjacent objects to acquire it,and constructs a relative width to eliminate the interference of objects with similar characteristics,which avoids the influence of the objects themselves and the space,texture and spectral characteristics of the objects,and overcomes the difficulties of automatic extraction of remote sensing interpretation.Compared with the previous classification accuracy,the accuracy of coastal aquaculture land can reach 91.13%.Second,the spatial and temporal changes of land use in Bangkok Bay from 1987 to 2015 show that the main types of land use have not changed.Aquaculture land covers the largest area,accounting for 26.29% of the total land area,but it is reduced to 903.69 square kilometers compared with 1987,and is concentrated in the top of the bay.The second is gardens,accounting for 25.92% of the total land area,with a sharp reduction of nearly 1/5 compared with 1987.The distribution area has not changed,but shows a trend of fragmentation.Urban land is growing rapidly,with its coverage area ranking third,accounting for 23.45% of the total land area.It is mainly distributed at the estuary of the bay top and the headland along the east coast of the bay,and scattered at the bottom on the west side of the bay.In 2015,the development intensity of gulf towns was relatively high,and the coverage area of urban land occupied nearly one fourth of the total land area.The area of mangrove and forest land in the region showed a decreasing trend,especially the forest land is shrinking sharply,with a reduction of nearly 34%,which requires strengthening protection.The spatial and temporal changes in land use in Haiphong Bay from 1988 to 2013 indicate that the net increase area of urban land is the largest,that is,83.05 square kilometers,and the increase area is concentrated in the western plain and the northern triangular coast.The development of regional towns has been further enhanced.The urban land has gradually expanded from small plaques to larger plaques,and the coverage area has gradually increased.The development of coastal towns has shown a trend of expansion towards the sea.Almost all mangrove forests at the top of the bay have been converted into farming land.The water area in the bay has the largest net decreasing in the bay area,reaching 61.7 square kilometers.The reduced areas are mainly distributed along the western and northern coasts of the gulf area.The western waters are mainly converted into farming land while the northern waters are mainly converted into urban land.Mangroves are concentrated at the top of the bay and on the northern triangular coast,which are mainly converted into farming land.The spatial and temporal changes of land use in Yafeng Bay from 1988 to 2013 indicate that forest land is the dominant land use type in the area,accounting for 69.94% of the total land area,and is distributed in the mountainous and hilly areas and islands of the gulf.The second is paddy field,which covers 18.76% of the total land area and is distributed in the coastal area of the bay and the relatively flat zone in the bay.Urban land accounts for 2.9% of the total land area,scattered in paddy fields.The artificial development of the regional coast is weak,the distribution of urban land is scattered,and the traffic land only accounts for 0.43%.Compared with 1985,forest land is still the dominant land use type in the area,with an area reduced by nearly 100 square kilometers,and the reduced area is mainly the inland area close to paddy field.The area of paddy field has been reduced by more than 50 square kilometers,which is mainly developed for garden plot and urban land.Urban land has more than doubled,and transportation and aquaculture lands have increased accordingly.Mangroves in the area have been fully developed into farming land;salt fields and beaches have been developed into urban land and farming land.The increase of sand area have indicated that ecological protection measures in Ninghe District are inappropriate in the process of urbanization.Third,studying the comparative analysis of typical bays in Indochina Peninsula and understanding the natural and anthropogenic driving forces of land use change in the coastal zone of Indochina Peninsula Bay contributes to the establishment of an empirical model for the region,and a deeper understanding of the important node cities of the National Belt and Road Maritime Silk Road in ASEAN.Through the analysis of remote sensing images,the spatial change process of land use in the area in the past 35 years can be understood,and the driving factors can be linked to establish the interpretation of land use spatial and temporal change and infer its development and change trend in the future. |
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