In the field of earth system analysis,we study diverse research areas to protect earth's environment and protect humankind from various natural disasters. The spatial scale of research ranges from a small catchment scale to a global scale. Research areas we treat are landscape ecology, landscape planning, geophysical information system, hydraulic engineering, river engineering, hydrology, meteorology, and seismology. As research tools, we mainly use consideration of theory and computational analysis, but observation is often used.