Basic Terminology:
  • Stream Valley - The entire area from the top of a slope on one side of the river to the top of the slope on the other side of the river
  • Channel - The bottom part of the valley through which water flows
  • Flood plain - Surrounding area of a channel, level with the top of the channel, into which the water overflows when the stream floods
  • Meanders - A term that describes the bending and curving of a channel
  • Oxbow lake - A crescent-shaped loop, formed from an abandoned path of a meander, that  usually forms after a flood, causing this area to become a segregated lake
  • Braided Streams - Describes numerous streams that are split apart and rejoin into one stream downstream
  • Discharge - A measurement used to describe the volume of water that passes a given point in a channel with a given width and depth in a given time period (width of channel x depth of channel x velocity of water (in seconds))
What Causes a Normal Flood?
  • Discharge
    • The greater the discharge, the faster the velocity of the water
      • Causes the channel to increase in volume of water
      • If the volume of water exceeds that which the channel can hold, it overflows it's banks and floods
Other Types of Floods:
  1. Flash Flood
    • Caused by the release of an extreme amount of water into a channel
      • More water than the channel can hold, hence flooding
    • Duration can vary depending on the saturation of the ground, discharge rate, evaporation rate, etc.
  2. Riverine Floods
    • Caused by the melting of winter precipitation (ice & snow)
    • Take place in river systems for large geographic regions
      • It takes longer for the waters to recede
    • Different from flash floods in their extent and duration
  1. Tidal Floods
    • Caused by tides, waves, tsunamis, surges, hurricanes, or a combination of these
    • Occur on coastlines
    • Short duration
Reoccurrence:
  • The greater the frequency, the lower the intensity
  • The lower the intensity, the greater the frequency
To check water and flood conditions nearest you, click here
  • Based on Grade
    • Grade includes:
      • Climate
      • Resistance of rock to weathering
      • Topography
      • Discharge and velocity of a stream
    • If all these are in equilibrium for the given area, then the frequency of flood is reduced
    • Flooding can affect how a stream flows and erodes
      • If these are not in equilibrium for the given area, then flooding can be frequent
Problems/Risks:
  • Increases rate of physical weathering
  • Aids in erosion which causes the ground to be unstable
  • Expands and can change the direction of the channel which can affect nearby areas of population
  • Causes damage to property
  • Can trigger land movements
  • Can cause drowning and loss of life
  • Can backwash sewage - leads to disease
  • Rapidness of flash flooding can leave no time to get to safety
What You Should Know and Safety Tips to Follow:
  • Pay attention to warnings issued concerning flooding & flash flooding and take heed to what is being said
  • Do not build on a floodplain or a low-lying area that has a potential to flood (ex: in a valley next to a river)
  • If you're going to build by a river, stream, etc., check with the county about flooding precautions first and make sure steps have been taken to ensure your property will not be damaged
    • For example:  If you want to build next to a river, see if it drains into or is fed by a reservoir.  Check to make sure they will let the reservoir flood before the river will flood
  • If it is an absolute must that you have to build by a river, stream, etc., build on high ground and make sure the ground below is stable and will not erode out from below you
  • Be smart when driving.  If a road is covered with water, do not drive over it because the current may sweep you away
  • Do not swim or boat in flooded water
    • Too strong of a current - too powerful
    • Good chance of getting sick if sewage has been backwashed into the water
  • Most important:  Use common sense concerning flooding
Areas of Notable Concern:
 


*U. S. Department of Commerce & National Oceanic and Atmospheric Administration & National Weather Service (1992).  Flash Floods and Floods.  City and Publisher Unknown.
 
 


* The Council of State Governments. (1979). The States and Natural Hazards.  Lexington KY:  Author.


External Links:


References:

  • Hays, W. W. (Edr.) (1981).  Facing Geologic & Hydrologic Hazards.  Washington DC:  U. S. Government Printing Office.
  • U. S. Department of Commerce & National Oceanic and Atmospheric Administration & National Weather Service (1992).  Flash Floods and Floods.  City and Publisher Unknown.
  • Press, Frank & Siever, Raymond (2000).  Understanding Earth.  New York:  W. H. Freeman and Company.
  • The Council of State Governments. (1979). The States and Natural Hazards.  Lexington KY:  Author.