Application of three-dimensional laser point cloud technology to river management

Abstract

Recently, rainfall volumes have been increasing owing to various factors such as global warming, causing large-scale disasters, such as levee breaches, throughout Japan every year. However, in current river management scenarios, only the results of visual inspections performed on foot every 200 m are used to make decisions. Therefore, recently, we considered the application of three-dimensional (3D) laser point clouds acquired by Information and Communication Technology (ICT) devices in river management. The 3D data obtained by laser point clouds can be used to visualize the topography as a continuous surface. Thus, the 3D data is expected to lead to more efficient and sophisticated river management. Therefore, the purpose of this study is to investigate the application of 3D laser point clouds to river management using a drone equipped with a green laser scanner that penetrates underwater. We examined the effect of river transparency on riverbed understanding, accuracy verification on land, and to develop a method to extract deformations using laser data at two periods. Therefore, the depth at which the drone equipped with the green laser scanner can be measured depends on the transparency, but it is effective for surveying underwater topography in areas shallower than approximately 2.0 m. Additionally, it was found that the survey can be conducted with an accuracy of 5 cm by using adjustment points, whereas the management of the river channel shape required an accuracy of approximately 30 cm. Furthermore, we demonstrated that it is possible to detect the location of deformation in real time by developing a method of superimposing laser point clouds at two periods.