Flood: Natural Hazard

water and street signFlooding hazards can be divided as primary, secondary and tertiary. Primary hazards are those that occur due to contact with flood water. Secondary effects are those that occur as direct effect of flooding such as disruption of services (such as power interruptions) and health impacts such as famine and disease. A sample of a tertiary effect, on the other hand, are changes in the position of river channels.

Flooding is considered to be one of the most devastating disasters in terms of cost as reflected to property damages and life casualties. Major floods in China had surfaced a number of casualties: 2 million people in 1887, 4 million in 1932 and about 1 million in 1938. Another destructive flood is that of the Upper Mississippi River, despite only 47 people were killed, an economic loss from 15 to 20 million dollars was estimated.

Direct contact with flood waters compromises the primary effects of floods. Floods with an increase of discharge increases velocity, and with higher velocities, streams could transport large particles such as rocks and sediments. Floods can cause erosion, wall, floor and furniture damages. Flooding in farmland can results in crop loss. Livestock, pets and other animals are often carried away and drown. Even humans can get carried away and drown. It could also concentrate on garbage, debris and toxic pollutants that can cause secondary effects.

Secondary effects are direct results of the primary effects. Basically, these are disruption of services. Pollution of drinking water is the greatest example and it can cause diseases especially in under developed countries. Gas and electrical service may also be disrupted, as well as transportation systems. Disruption of transportation systems can even lead to shortages of food and clean up supplies.

Tertiary effects are the long term changes that take place due to flooding. Location of river channels may change as the result of flooding, new channels develop, leaving the old channels dry. It can also lead to the destroy of farmlands due to sediment deposits. Jobs may be lost due to the disruption of services and destruction of business. Destruction of wildlife habitat is another effect.

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