Dear Abdulatheem, thanks for your question. Actually you should try to avoid building in risk areas, because even using building materials which are more resistant to floods, when they are very serious, no matter what sort of material you use, they might be damaged by a heavy flood. Therefore, the best way is to avoid risky areas, where floods occur frequently. In Brazil, according to our environmental legislation one can not build close to a river and the minimum distance to the river bank is 30 metres.