Natural Hazards: Causes and Effects - Disaster Management Center ...

enter the waterways, flushing of nutrients in river systems, preserving of wetlands, recharging of
groundwater, and maintaining of river ecosystems by providing breeding, nesting, feeding and
nursery areas for fish, shell fish, migrating waterfowl, and others. 11
Impact on Development
Widespread floods can have a significant effect on the long-term economic growth of the
affected region. Indirect and secondary effects on the local and national economy may include
reduction in family income, decline in the production of business and industrial enterprises,
inflation, unemployment, increase in income disparities, and decline in national income. In
addition, relief and reconstruction efforts often compete with development programs for
available funds. In countries where flooding occurs frequently, floods can create an enormous
financial burden.
The loss of crops and the need to find alternate sources of income have often caused smallscale
migrations of farmers and skilled workers from rural areas to cities. Once established in a
city, few return to their homes or farms.
Small marginal farms usually cannot survive economically following a major flood. Farmers are
often forced to sell their land because they cannot afford to rehabilitate it. This may result in a
substantial increase in the number of people migrating to urban areas, and thus a related
housing shortage.
International Implications
In many of the great river basins, significant portions of their watersheds lie upstream within
another nation’s boundaries. The causes of the flooding may well be created outside of the
affected country in those upstream areas. This has occurred where deforestation, erosion,
overgrazing, desertification and other environmental degradations have increased the runoff
from previously normal rainfalls. The upstream country may be suffering environmental
degradation but may not experience the effects of the flood. The downstream country may have
little control over protecting itself from these recurrent floods.
Disaster Mitigation Strategies
The majority of the deaths and much of the destruction created by floods are largely
preventable. A great deal can be done to lessen the impact of a disaster. First, though, the
general public as well as engineers, planners, politicians and others need to understand the
nature of the hazard. Based on that understanding, a decision and a commitment needs to be
made to provide mitigation measures to reduce flood damage. Reducing the harmful effects of
a flood requires actions on three fronts: reducing the vulnerability of the physical settlements
and structures in which people live; reducing the vulnerability of the economy; and
strengthening the social structure of a community so that community coping mechanisms can
help absorb the impact of a disaster and promote rapid recovery.
The first step in vulnerability reduction for human settlements is to identify the high-risk areas.
This is done by relating a natural hazard, such as a flood, to the terrain and to the probability
that such an event will occur. This activity is known as risk mapping. Flood risk mapping, for
example, would indicate the areas likely to be covered by water during floods of given
magnitude.