If its a natural phenomenon taking place , we can only take precautions as its not in ours hands entirly. but if it is a manmade disaster the it surely can be prevented.few ways through which impact of disaster can be reduced:-
1) in case of disasters such as landslides, the area must be wel constructed , building houses should be avoided in low lying areas, as they're most threatened.
2) in cases of earthquakes, nevr take cover inside a place, always outside where there are no buildings or obstacles.
3) in case of flooding, its a global awareness now that we grow more trees, as they reduce the speedy flow.and so on