Flooding Flashcards
What are floods?
The overflowing of the normal
confines of a stream or other body of
water, or the accumulation of water over
areas that are not normally submerged
What causes floods?
- Heavy rainfall
- Tropical cyclones and very strong midlatitude
cyclones, via their storm surge - Snowmelt and ice jams in rivers during winter
- Saturation of soil from previous rainfall +
additional rainfall
What factors can influence their occurence?
- intensity, duration, and amount of rainfall
- Saturation levels of soil
- Presence of snow/ice
What interactions exist between meteorology and another geography that cause floods to occur?
Topography of the land
Proximity to dams/ levees
Land use
What are flash floods?
floods that occur rapidly and with little warning
How do they differ from widespread floods?
They develop faster, but they are shorter
What causes flash floods and when do they appear most?
Caused by slow moving thunderstorms and high rainfall rates over a short time. Occur usually in the summer months, in the late afternoons.
Why can flash floods be more dangerous than widespread floods?
There is little warning, so less time to prepare and evacuate if needed
What are widespread floods?
Floods that occur when a large amount of rainfall falls over a watershed for many days
What causes widespread floods?
training storms (storms that fall over one area for an extended period of time)
What types of weather patterns (i.e. frontal boundaries) usually contribute to
widespread floods?
They are usually associated with a stationary front, which causes parcels to continuously form over the same spot, creating more and more precipitation.
What are coastal floods?
caused by a rise in the ocean surface due to storm surge
What causes them? How do they form?
storm surge- rise in the sea level due to two factors
1. the low pressure in the center of the storm
2. The winds blowing forward ahead of the storm
Where do coastal floods happen?
Most extreme along the East and Gulf coasts
X-year flood terminology
An “X-Year Flood” means that in any
given year, there is a 1/X chance of a
flood of that magnitude happening
EX: A 500 year flood means there is a 1/500, or 0.2% chance of that flood happening
