Flooding is responsible for extreme damage and destruction to property, public areas, and the environment which incurs enormous costs for government. In addition to damage costs, flooding results in lost productivity, reduced hours worked and losses in GDP due to the need for resources to be put towards recovery efforts and away from daily activities. Direct Impact Insurable Losses The amount of money spent on insurable losses varies depending on the extent of flooding, property type impacted, individual insurance policy and political circumstances.
Deluge myths are mythical stories of a great flood sent by a deity or deities to destroy civilization as an act of divine retributionand they are featured in the mythology of many cultures. Principal types Areal Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can either infiltrate or run off.
The excess accumulates in place, sometimes to hazardous depths. Surface soil can become saturated, which effectively stops infiltration, where the water table is shallow, such as a floodplainor from intense rain from one or a series of storms.
Infiltration also is slow to negligible through frozen ground, rock, concretepaving, or roofs. Areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope.
Endorheic basins may experience areal flooding during periods when precipitation exceeds evaporation. When overland flow occurs on tilled fields, it can result in a muddy flood where sediments are picked up by run off and carried as suspended matter or bed load.
Localized flooding may be caused or exacerbated by drainage obstructions such as landslidesicedebrisor beaver dams. Slow-rising floods most commonly occur in large rivers with large catchment areas.
The increase in flow may be the result of sustained rainfall, rapid snow melt, monsoonsor tropical cyclones. However, large rivers may have rapid flooding events in areas with dry climate, since they may have large basins but small river channels and rainfall can be very intense in smaller areas of those basins.
Rapid flooding events, including flash floodsmore often occur on smaller rivers, rivers with steep valleys, rivers that flow for much of their length over impermeable terrain, or normally-dry channels.
The cause may be localized convective precipitation intense thunderstorms or sudden release from an upstream impoundment created behind a damlandslide, or glacier. In one instance, a flash flood killed eight people enjoying the water on a Sunday afternoon at a popular waterfall in a narrow canyon.
Without any observed rainfall, the flow rate increased from about 50 to 1, cubic feet per second 1. The deadly flood resulted from a thunderstorm over part of the drainage basin, where steep, bare rock slopes are common and the thin soil was already saturated.
Flash floods are the most common flood type in normally-dry channels in arid zones, known as arroyos in the southwest United States and many other names elsewhere. In that setting, the first flood water to arrive is depleted as it wets the sandy stream bed.
The leading edge of the flood thus advances more slowly than later and higher flows.
As a result, the rising limb of the hydrograph becomes ever quicker as the flood moves downstream, until the flow rate is so great that the depletion by wetting soil becomes insignificant. Estuarine and coastal Flooding in estuaries is commonly caused by a combination of sea tidal surges caused by winds and low barometric pressureand they may be exacerbated by high upstream river flow.
Coastal areas may be flooded by storm events at sea, resulting in waves over-topping defenses or in severe cases by tsunami or tropical cyclones. A storm surgefrom either a tropical cyclone or an extratropical cyclonefalls within this category.
Storm surge should not be confused with storm tide, which is defined as the water level rise due to the combination of storm surge and the astronomical tide.
This rise in water level can cause extreme flooding in coastal areas particularly when storm surge coincides with normal high tide, resulting in storm tides reaching up to 20 feet or more in some cases. Although sometimes triggered by events such as flash flooding or snowmelturban flooding is a condition, characterized by its repetitive and systemic impacts on communities, that can happen regardless of whether or not affected communities are located within designated floodplains or near any body of water.
In urban areas, flood effects can be exacerbated by existing paved streets and roads, which increase the speed of flowing water. The flood flow in urbanized areas constitutes a hazard to both the population and infrastructure.
Flood flows in urban environments have been studied relatively recently despite many centuries of flood events. Examples include outburst floods and lahars.
Tsunamis can cause catastrophic coastal flooding, most commonly resulting from undersea earthquakes. Causes Flood due to Cyclone Hudhud in Visakhapatnam Upslope factors The amount, location, and timing of water reaching a drainage channel from natural precipitation and controlled or uncontrolled reservoir releases determines the flow at downstream locations.
Some precipitation evaporates, some slowly percolates through soil, some may be temporarily sequestered as snow or ice, and some may produce rapid runoff from surfaces including rock, pavement, roofs, and saturated or frozen ground.
The fraction of incident precipitation promptly reaching a drainage channel has been observed from nil for light rain on dry, level ground to as high as percent for warm rain on accumulated snow.
Frequency of a precipitation threshold of interest may be determined from the number of measurements exceeding that threshold value within the total time period for which observations are available. Individual data points are converted to intensity by dividing each measured depth by the period of time between observations.
This intensity will be less than the actual peak intensity if the duration of the rainfall event was less than the fixed time interval for which measurements are reported.Economic Impact of Flooding. Economic Impact on Food Costs due to the Recent Flooding in eastern Australia.
In response to the effects of these floods, the Victorian Government established recovery support to help the communities that were most affected to rebuild and resettle. Immediate impacts of flooding include loss of human life, damage to property, destruction of crops, loss of livestock, non-functioning of infrastructure facilities and deterioration of health condition owing to waterborne diseases.
Flash floods, with little or no warning time, cause more deaths than slow-rising riverine floods. Effects of Urban Development on Floods. By C. P. Konrad. Over the past century, the United States has become an increasingly urban society.
The changes in land use associated with urban development affect flooding in many ways. Removing vegetation and soil, grading the land surface, and constructing drainage networks increase runoff to streams. Major land–use changes have occurred in the United States during the past 25 years.
The total area of cropland, pastureland and rangeland decreased by 76 million acres in the lower 48 states from to , while the total area of developed land increased by 36 million acres or 48%. Effects of flooding Floods can have devastating consequences and can have effects on the economy, environment and people.
Economic During floods (especially flash floods), roads, bridges, farms, houses and automobiles are destroyed. This article has been optimized for offline reading on Washington Post apps.
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