FLOOD - A flood is an abnormal progressive rise in the water level of streams or rivers which may result in overflowing. Floods in the Caribbean can often be caused by heavy rainfall, dam or levee failures, tsunamis, storm surges or burst water mains.
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Flood Prevention and Mitigation

Mitigation refers to any structural or non-structural measures undertaken to limit the adverse impact of hazards.

Flood Mitigation Measures can be divided into three (3) main areas:

  • Control over the river;
     
  • Control over the land;
     
  • Other measures.

Control Over the River

In order to achieve control over the flow and height of the water carried by the river, the channel, flood plain or watershed must undergo some physical alterations.

These include:

  • Construction of dams, retention basins or reservoirs on mainstreams or tributaries to store excessive water and release it gradually after the threat has passed;
     
  • Levees or floodwalls can be constructed to confine flood waters to a floodway, thereby reducing flood damage;
     
  • Channel improvements, which include, straightening to remove undesirable bends, deepening and widening to increase size of waterways; clearing to remove brush, trees and other obstructions; lining with concrete to increase efficiency.
     
  • Watershed Treatment can also be employed to help the soil on slopes to become more absorbent of rainfall until flood heights have receded. Watershed Treatment involves, crop rotation, construction of terrace, contour strip cropping; selective planting and reforestation.

Control Over the Land

To protect against flooding, certain Land Use Policies were developed.

Below is a list outlining the measures undertaken within these policies.
 

Designated Floodways and encroachment lines

These are the lateral boundaries of the floodway where no construction or land filling should be permitted. This is done to ensure that the flow of water is not obstructed.
 

Zoning

This is a legal tool used by governments to control development in areas which are or are likely to become prone to flooding;
 

Subdivision Regulations

These specify the manner in which land may be divided. Typical provisions show the extent of the flood plain on maps. Floodway limits or encroachment lines prohibit filling in channels and floodways that restrict flow and require that each lot contain a building site with an elevation above the flood level.
 

Building Codes

These are standards for construction of buildings and other structures and, if enforced, can reduce damages to buildings in flood-prone areas. Some requirements include, the establishment of basement elevations and first flood elevations consistent with potential flood levels, ensuring that buildings have adequate structural strength which would likely withstand water pressure or the high velocity of flowing water, prohibiting the use of equipment that might be hazardous to life when submerged and installing proper anchorage to prevent the floatation of buildings.

Additional Mitigation Measures

These include flood proofing, flood forecasting, warning and evacuation systems.

Flood Proofing

This is a combination of structural changes and adjustment to properties which can be used in new or existing construction. Action includes seepage control, protective coverings, elevation or raising anchorage and under pinning.
 

Flood Forecasting

This is reliable, accurate and timely forecasting of floods, coupled with timely evacuation to save lives and reduce property losses.
 

Temporary Evacuation

This removes persons and property from the path of flood waters.
 

Permanent Evacuation

This removes an affected population from areas subject to inundation. This involves the acquisition of lands and the removal of developments. The acquired lands can be used for agriculture, parks or other purposes that would not interfere with flood flows or result in material damage.
 

Flood Insurance

This assists by compensating for flood damage. Insurance rates should realistically reflect the flood risk in order to avoid encouragement of improper development of flood plains.

 

 

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12 inches of water can cause you to lose control of your vehicle.
New land development can increase flood risk, especially if the construction changes natural runoff paths.
In cases of severe flooding, water can take weeks to subside.
Large volumes of water can cause roadbeds to collapse.
Deforestation can cause flooding.
Flooding is the most common natural hazard.
Flash-flooding can occur within minutes.
Dams and levees are built to prevent flooding.
Flooding can cause millions of dollars in damage.
6 inches of moving water can sweep you off your feet.
Oil, and other chemicals carried in floodwaters can ruin crops and be hazardous to your health
When soil gets saturated with water, landslides may occur
More people die from drowning in fresh water floods during a hurricane or storm, than from any other cause.