What causes a flash flood?

Answer 1

Flash FloodA flash flood is caused by excess water, usually from a storm. This usually happens downstream from the storm as heavy rains produce more water than the area can handle with nothing to impede its buildup or soak it into the ground.

As a weatherman in Oklahoma recently put it: "It is when a large rain and storm system hovers an area and does 'not leave' or 'move on' (as generally seen with systems) but instead stays, dumping supernatural amounts of water in a "flash," overwhelming even the more extraordinary and multi-competant drainage and levy systems."

Answer 2

Flash floods have a number of causes, but the primary one is when a very large amount of water is dumped suddenly in one region. This is usually the result of a storm cell. Flash floods are common in parts of Australia where the drainage systems are not used to handling sudden deluges.

Continuous rain in a river catchment can lead to that catchment becoming waterlogged, over-saturated with water to the point where it cannot take any more. In this instance, it takes only another 50mm (2 inches) or so of rainfall to trigger a flash flood.

Answer 3

Flash floods can be caused by:

• a heavyrain in a area with high runoff (no absorbtion)
• a prolonged heavy rain feeding into area watercourses
• a suden snow mealt
• a rain on frozen soil which melts the snow in addition to the rain volume which cannot be absorbed into frozen ground
• a breakage in a dam or containment system
• high tides
• storm surges
• tsunamis

• downsteam blockage of the river channel

These all lead to the same effects

• destruction of roads and bridges
• faster erossion of river banks
• disruption of water supplies and waste treatment
• danger to the public.

Answer 4

The main factors that result in flash floods in deserts and semi deserts are;

- sudden, intense rain. Total rainfall amounts (measurements) do not have to be high, even storms of less than .5 inches can cause flash floods, if the rainfall is intense .

- topography. Areas that have high, barren mountains protruding from gently sloped, depositional plains provide conditions where a very high percentage of the rain that falls on the mountains and areas of higher elevation will take the easiest path possible (arroyos and washes) downhill, and without the topographical features of wetter climates (such as lakes, vegetation, topsoil, developed stream-beds) this flood water can arrive with little or no warning in places where there has been little or no rain.

-soil conditions. For a number of reasons, (primarily lack of vegetation and geology), desert soils have a very low capacity to hold water, so a very low percentage of the water that lands on them (rain) and runs across them (runoff) soaks into them. It is also the nature of many desert soils to be hydrophobic (water repellent). This is due to visible features (such as "desert pavement"), and microscopic features related to alkalinity and mineral (and in some cases organic) composition of the soil.

Answer 5

1.heavyrainfall

2.cutting of trees

3.clogged canals

that's all thanks

Answer 6

Flash floods occur in low lying areas. They happen after heavy rains cause water accumulation, or cause rivers and streams to swell.suck coc

Answer 7

The flashflood is causeb by Heavy rain,Hurricane etc.Thanks I'm Dianne Nicole

Answer 8

Heavy rains.