[H-TT14] HIGH-DEFINITION TOPOGRAPHIC AND GEOGRAPHIC DATA FOR EARTH SURFACE CONNECTIVITY

[HTT14-P02] Topographic changes based on LiDAR data during 2008-2022: A case study of the South Kujukuri Plain, Chiba, Japan

★Invited Papers

*Yuka Ito¹, ChiSan Tsai², Tomochika Tokunaga² (1.Osaka Metropolitan University , 2.The University of Tokyo)

Keywords:LiDAR, DEM, DSM, Land subsidence

Periodic light detection and ranging (LiDAR) surveys can extract and accumulate ground surface change data, providing essential information for evaluating long-term impacts on regional surface and subsurface environments. LiDAR surveys were conducted in 2008, 2012, and 2022 to evaluate long-term ground deformation in the southern Kujukuri Plain in eastern Japan. This area has experienced ground deformation due to past major earthquakes, plate movements, and land subsidence associated with groundwater extraction, raising concerns about its impact on surface environments. The LiDAR elevation data were corrected for horizontal displacement due to crustal deformation and noise removal, and vertical ground deformation maps were generated for 2008-2012 and 2012-2022. During 2008-2012, localized subsidence was observed along coastal areas, likely due to the 2011 earthquake. In contrast, during 2012-2022, a localized uplift zone was identified along the rivers, while subsidence was observed in parts of the hills and back swamp areas. Surface changes along the rivers were likely influenced by levee improvements for flood control and embankments for new residential development. As for the minor localized changes in the hills, DSM (Digital Surface Model) and orthoimage analysis suggest the possibility of anthropogenic land modifications, such as embankment and cutting. In particular, embankment areas, primarily along the valleys, were identified, and volume changes were calculated using point clouds and 3D mesh data. Surface changes in the back swamp area are likely to be influenced by newly constructed infrastructure, such as flood controls within the watershed. Additionally, analysis of geological borehole data reveals a relatively high number of peat layers in this region. These suggests the need for further investigation of other possible factors such as geological conditions. Detailed analysis of high-resolution data has revealed topographic changes influenced by anthropogenic activities in some locations during the last decade. In areas of significant ground deformation, regular accumulation, comparison, and analysis of high-resolution data to spatially extract and visualize topographic changes is important for appropriate consideration of future impacts on the local environment.