Recent heavy rain events brought tremendous human damages and material damages. Speculation is that frequency of disastrous heavy rain events will increase as the climate change progresses, and the prevention from their damages requires various data concerning rivers, reservoirs, and coastal waters. Our study demonstrates analysis of topographic change in a water area, which is based on measurement data. A GPS receiver or a GNSS receiver, and an echo sounder unit mainly constitute a hard ware system to generate three-dimensional data. Those data are processed in a further analysis for investigation of change in the topography.

Masaji Watanabe, Emeritus Professor, Specially Appointed Professor (Research), Okayama University, is active in research fields of applied mathematics. Those include a study on topographic surfaces of water areas. His recent activities include joint studies on measurement and analysis of underwater topography with Mr. Satoshi Iwakami, Mr. Masahiko Tamega, Mr. Masahide Sanada, Mr. Michiaki Mohri, Mr. Yoshitaka Iwakami, Mr. Naoki Okamoto, Mr. Eishi Mitsui (Earth Rise Company, Inc., Okayama, Japan), Associate Professor Ryosuke Akoh (Faculty of Environmental, Life, Natural Science and Technology, Okayama University), and Dr. Shuji Jimbo (Visiting Researcher, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan).