What cause flood in America- Tan Shang Jien

Causes of floods in America:

1.Spring Thaw

Spring Thaw

  • During the spring, frozen land prevents melting snow or rainfall from seeping into the ground.
  • Add spring storms to that and the result is often serious, spring flooding.

2.Heavy rain

  • Several areas of the country are at heightened risk for flooding due to heavy rains.
  • This excessive amount of rainfall can happen throughout the year, putting your property at risk.
  • Storms over the Pacific Ocean bring heavy rains to the western United States between the months of November and April.
  • Cresting rivers, backed-up storm drains or saturated ground can cause significant floods across the region during this time.

3. Flood After Fire

  • Many areas in the western states are at an increased flood risk due to wildfires in recent years.
  • After a wildfire, the charred ground where vegetation has burned away cannot easily absorb rainwater, increasing the risk of flooding and mudflows over a number of years.
  • Wildfire-affected areas include states such as Arizona, California, Idaho, Nevada, Oregon and Washington. 

4.Mudflows

Mudflow

  • Mudflows are rivers of liquid and flowing mud on the surface of normally dry land, often caused by a combination of brush loss and subsequent heavy rains.
  • Mudflows can develop when water saturates the ground, such as from rapid snowmelt or heavy or long periods of rainfall.
  • Mudflows are different from other earth movements, such as landslides, slope failures, and even moving saturated soil masses in which masses of earth, rock, or debris move down a slope where there is not a flowing characteristic. 


5.Snowmelt

Snow melt

  • A midwinter or early spring thaw can produce large amounts of runoff in a short period of time.
  • Because the ground is hard and frozen, water cannot penetrate and be reabsorbed.
  • The water then runs off the surface and flows into lakes, streams and rivers, causing excess water to spill over their banks.
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