Considering the contribution to disaster prevention of national land, I developed a unique method to estimate the surface velocity of flood and the flow direction of the Kuma River during the heavy rain of July 2020 using the oblique aerial photographs linked to the GSI maps. After confirming the motion vectors of the drifting objects using the stereo pair of aerial photographs, an ortho aerial photograph is created from them. The distance of movement of drifting objects and the flow direction are measured from the ortho photograph, and the surface velocity is calculated by the distance and the time interval of shooting. In the distribution map with the theme of surface velocity and flow direction, the spatial features of the flood flow can be estimated and the background of the flood damage can be discussed. The center line of stream with high surface velocity is approximately near the center of the river channel, and the velocity gradually slows down toward both shores. The flow directions coincide with the direction near the center line of stream and vary near the shore. In the velocity distribution in the longitudinal direction, areas with high surface velocity at the center line of the stream appear repeatedly at intervals of about 150 to 200 m. In the distribution map, the three features of the flood flow were understood. The first is that the location of the center line of stream and flow direction change due to river bend. The second is that the surface velocity and flow direction change due to river width. The third is that the surface velocities of the main stream and the tributary are very different. This method for flood flow seems to be practical for use because there are spatial correlations between the surface velocity and severity of the damage, and between the low surface velocity and the sediment accumulation. Therefore, the surface velocity and flow direction could be analyzed by the combination of SfM and GIS using oblique aerial photographs taken urgently in the event of the disaster. I believe that the method and the result will be an effective method for obtaining basic materials to reduce flood damage in applied geology.

At the construction site, the topography changes daily due to embankment and cut, and the amount of change is measured using surveying instruments to check the progress of construction. In the large-scale reconstruction work after the Great East Japan Earthquake, hundreds of thousands of cubic meters of earth and sand will be moved. In order to manage the process of such construction, we frequently and accurately grasp the progress with respect to the design soil volume. We used UAV photogrammetry to manage the progress of the construction site in order to accurately and easily measure the topographical changes at the construction site. In other words, by taking aerial photographs with the UAV and creating point cloud data by SfM / MVS processing, the accurate topography was grasped in a plane. By comparing the design data and the measurement data and finding the time-series change of the measurement data, it is possible to find the daily amount of earth and sand transported and the amount of work in the future. We confirmed the effectiveness of this method by applying it in the field. In addition, at such sites, the terrain will be rich in undulations as the construction of embankments and cuts progresses. Therefore, in order to keep the GSD of aerial photographs constant, we are also devising ways to control the flight altitude of the UAV. This method can be useful not only for construction work, but also for grasping changes in the ground surface after a landslide disaster and for subsequent restoration.

National Institute for Land and Infrastructure Management （NILIM） by Ministry of Land, Infrastructure, Transport and Tourism （MLIT） is planning to consider prioritization and priority evaluation of liquefaction measures for the network of infrastructure facilities and prepare liquefaction hazard maps for infrastructure facilities. for that purpose, we created a three-dimensional ground structure model for actual districts experimentally that the complexity of the distribution of ground and geological features and the ground property which cause liquefaction damage are reflected. On the basis of this model, we examined a method for highly accurate prediction of liquefaction damage.

It is important to predict the location and magnitude of landslides when planning for disaster prevention and mitigation. Locations where landslides may occur and flat sizes are organized by topographical interpretation. Furthermore, the depth measurements required to determine the scale of active landslides and the relationship between the plane shape and depth are established for use in estimating the depth of a landslide; this is mainly carried out by the Sabo project. To further develop the results that are currently being organized, it is necessary to collect information regarding landslides that are currently inactive. This study aimed to enable the estimate of the depth of a landslide by using the plane range, which can be determined without any fieldwork. The results of landslide studies conducted around reservoirs （23 dams, 214 blocks）at the time of dam construction were collected, organized, and analyzed. During the analysis, the relationship between the plane range and depth was determined without any fieldwork, and the distribution range of the minimum and maximum values was obtained. The results show that the maximum value representing the relationship between the width and maximum estimated depth （D）is D＝0.45×W, while that representing the relationship between the length and maximum estimated depth is D＝0.40×L.