Spatial Distribution And Reason Analysis Of The Surface Vertical Deformation In The East Of Dongting Basin

The evolution of the Dongting Lake is influenced by the surface vertical deformation of the Dongting Basin, and the development of Dongting Lake District is affected by the expansion or contraction of Dongting Lake. The surface vertical deformation of the Dongting Basin is mainly affected by geological tectonic activities, sedimentation and human activities, of which tectonic activities and sedimentation play an important role. Based on topographic maps, remote DEM data and synthetic aperture radar (SAR) data, the surface vertical deformation and its reasons in the eastern Dongting Basin are studied by using the data processing and spatial analysis method of GIS in this paper. Firstly, based on the topographic maps of Nandashan, Xinhekou, Guozhenshi, Xinqiang and Taolinsi with a scale of1:50000, the surface vertical deformation and its reasons are studied in the typical regions of eastern Dongting Basin. Secondly, based on the remote sensing DEM data, the surface vertical deformation and its reasons in the eastern Dongting Basin are reseached. Finally, the feasibility of the D-inSAR technology used to measure the surface vertical deformation in the Dongting basin is analyzed by processing the synthetic aperture radar of the part of Dongting Basin with the technology of D-inSAR. The main conclusions are as follows:(1) Between1955and1983, subsidence areas were slightly larger than the uplift areas in the center area of the basin such as Nandashan and Xinhekou districts. The main reasons were that the whole region was influenced by tectonic subsidence, but sediment deposition in the region was more serious to lead to the thickness of the sediment deposition greater than the depth of surface subsidence caused by the tectonic subsidence so that some areas were keeping in a state of uplift. In the edge of the basin area such as Guozhenshi, Xinqiang and Taolinsi districts, the uplift areas were far greater than the subsidence areas. Analying the causes, it could be found that the edge of the basin was close to the uplift of Mufu-Jiuling which affected the uplit areas of the edge of the basin.(2) The eastern Dongting Basin was mostly keeping in the state of settlement during the period from2000to2009. The main reasons were that the policy of returning the grain plots to forestry was carried out, and several projects were implemented between1958and2003, which made the sediments decrease in the basin. And then the thickness of the sediment deposition was also decreased. So the depth of surface subsidence caused by the tectonic subsidence was greater than the thickness of the sediment deposition. It had to be admitted that the evolution trend of the basin plays a positive role in the surface environment evolution of Dongting Lake.(3) The result of experiment that measuring the surface vertical deformation by using D-inSAR technology showed that the quantity of deformation measured by the D-inSAR technology was closer to the quantity of deformation measured by leveling. But the quantity of deformation measured by the D-inSAR could not accurately reflect actual deformation in Dongting basin, because of the temporal noncorrelation and the tiny deformation of the basin.