Floods

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Floods
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Floods

• Most common natural disaster to strike the US
• A flood is typically associated with a defined
  body of water (river flood, ice jam, storm surge
  flooding etc.)
• An overflow or accumulation of a body of water
  that submerges land
• Floods occur when
• The soil cannot fully absorb the rainfall
• Bodies of water do not have the capacity to hold
  the amount of rainfall

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Flash floods

• According to the National Weather Service, a
  flash flood is a life-threatening flood that
  begins within 6 hours and often within 3 hours
• Heavy rainfall
• Rapid run-off

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Atmospheric Conditions

• Heavy rainfall
• moisture in the lower to mid levels of the
  atmosphere
• instability
• a source of lifting

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Soil Conditions

• Dry soil leads to greater water absorption
  leading to greater risk of flooding
• Although ground saturation increases the runoff
  risk, many flash floods occur when the ground is
  not saturated
• The texture of the soil also effects the
  absorption levels

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Where floods occur

• The type of land that is prone to flooding are
  broad and flat usually situated on the banks of a
  river or main waterway
• River Deltas
• Mississippi, Nile, Amazon, Yangtze, etc.
• Canyons (gulley washers)
• Creeks, streams and rivers
• Levees breaching

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Human influences

• Certain farming techniques, such as clear-cutting
  land, doesnt allow water to return to the
  atmosphere.
• Construction of concrete and stone buildings-
  these man made structures do not absorb water
  well, which can lead to a sufficient amount of
  water build up. (urbanization)

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Energy of Moving Water

• Water possesses kinetic energy since it is moving
• It is falling through a gravitational field
  (potential energy), and as it falls energy is
  released and is used to move (kinetic energy) the
  water
• Energy is transferred to plants and the soil on
  the banks of the creek
• It is pushing on the soil and forcing it
  downstream
• Uprooting, some of the smaller trees and washing
  them downstream
• Only takes about 18-24 of moving water to lift
  an SUV
• Just six inches of fast-moving flood water can
  sweep a person off his or her feet.

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Ecological benefits

• Refill lakes and reservoirs
• Flooding waters transport silt/soil onto areas
  (makes areas more fertile)
• Floods was debris into waterways which can
  provide habitats of organisms

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Surviving a Flood

• Dont wait for bad weather. Make sure you have
  everything you need in advance
• Create a Disaster Pack
• Keep at home, or take along if you evacuate
• Include enough food and bottled water for three
  days

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Flood Terms

• Flood Watch Flooding is possible.
• Flash Flood Watch Flash flooding is possible. Be
  prepared to move to higher ground.
• Flood Warning Flooding is occurring or will
  occur soon if advised to evacuate, do so
  immediately.
• Flash Flood Warning A flash flood is occurring
  seek higher ground on foot immediately.

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Surviving Floods Dos Donts

• Do leave if the local authorities recommend
  evacuation
• Do not walk through flowing water
• Do not drive through a flooded area (Turn
  Around-Dont Drown)
• Do not drink floodwater
• Stay away from power lines and electrical wires
• Look before you step

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The Georgia Flood of 2009

• Atlanta metropolitan area
• Damage estimated cost to 500 million with the
  potential for it to rise
• 17 Georgia counties received Federal Disaster
  Declarations
• Hundreds of people were rescued by boat from
  their homes
• At least 10 people died
• Most in cars

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The Economy

• Economic hardships due to
• Temporary decline in tourism (depending on
  location)
• Rebuilding costs
• Food shortage leading to price increase