Floods in the past brought humanity many positive effects as floods in the Nile, which helped ensure the livelihood of the population in ancient Egypt. Only when the floods began to threaten the lives, health and property of the population and economic activities of society, they became a serious problem for the mankind.

Not the nature can be held responsible for the fact that the floods are harmful to society, but the people because they take natural space from water and put themselves in her way. On the other hand, building of settlements in the watercourses was necessary because rivers provided enough water to cater for the necessities of life and the most fertile land due to floods is in riverside floodplains. Society is becoming more aware that floods can be controlled to a limited extent, and that absolute safety against floods is a myth.

The flood as a natural hazard has effect on the stability of society. If more people are to dwell in vulnerable areas and more and more businesses settle down in these areas the more intensive effect a flood event will have upon society (Seifert, 2012). It will be necessary to evacuate more buildings, provide emergency accommodation for more people, more workers will not be able to make money, because they will have to rescue and look after their property.

More and more companies will have to suddenly cease production, services will no longer be provided, unexpected shortfalls in tax receipts shall bring the municipal budgets out of balance and public services will no longer be funded.

The infrastructure to repair after a flood event will also be more extensive.

One single event may produce both benefits and losses to different parts of the riverine ecosystem.

These impacts are extremely difficult to quantify or monetize e.g. by quantifying ecosystem services before and after an event or accounting for the number of fish killed or trees damaged. Regular annual floods provide water resources for domestic supply, irrigation or industrial use. Some of the most important benefits of floods are linked to the maintenance of biological diversity in the flood plain ecology (Smith and Ward, 1998),

 Furthermore, many rivers carry minerals and nutrients which support agricultural production on the flood plains. Another aspect that makes it difficult to quantify the ecological consequences of floods is that some of the benefits from floods tend to become evident months or years after the event, or are often not apparent at all (e.g. recharging of groundwater stocks). This suggests that any immediate ecological accounting is prone to error (NRC, 1999). Flooding in river ecosystems should be regarded as a natural process and not as a disturbance.