Flood Hazards and Terms

Flood Hazards

  Primary Hazards

    The primary hazards are the effects of floods due to direct contact with the flood waters.

• With higher velocities, streams are able to transport larger particles as suspended load. These large particles can include not only rocks and sediment, but, during a flood, could include such large objects as automobiles, houses and bridges. 

• Flood waters can produce massive amounts of erosion. Such erosion can weaken and undermine bridges, levees/dykes, and buildings causing their collapse.

• Water entering human built structures cause water damage. Even with minor flooding of homes, furniture is ruined, floors and walls are damaged, and anything that comes in contact with the water is likely to be damaged or lost.   Flooding of automobiles usually results in damage that cannot easily be repaired.

• Flooding of farmland can result in crop loss.  Livestock, pets, and other animals are often carried away and drown.

• Humans can get caught in the high velocity flood waters and can drown in the water.

• Floodwaters can concentrate garbage, debris, and toxic pollutants that can cause the secondary effects of health hazards.
  
    

    Secondary Hazards

    Secondary hazards are those that occur because of primary hazards.

        1)  Drinking water supplies may be polluted, especially if sewage treatment plants are within the flooded area.  This contamination can result in disease

              and other health complications.

        2)  Gas and electrical services can be interrupted. 

        3)   Transportation systems can be disrupted as a result food supplies and aid can be delayed.  This has resulted in starvation in lesser developed countries.

    Long Term Hazards

    Long term changes

      1)  Location of river channel my change.

        2)  Sediment deposited during flooding may leave farm land in poor condition (all though silt deposits can increase productivity).

        3)  Destruction of wildlife habitat.

                    The previous modified form Nelson, S.A., 2004

Terms

   Floodplain - a low area of land, adjacent to streams or rivers, in which flood water moves into during a flood.

Source:  www.ohioline.osu.edu/ aex-fact/0442.html

  Flood - High water flow or an overflow of rivers or streams from their natural or artificial banks, inundating adjacent low lying areas.

 Source: http://www.math.montana.edu/~nmp/materials/ess/hydrosphere/expert/rrf/flood/flood2.html

  Flood Crest - the highest peak elevation of the water level during a flood in a stream or river.

  Stream Channel - An open conveyance of surface having a bottom and sides in a linear configuration. Channels can be natural or man-made. Channels have levees or dikes along their sides to build up their depth.
 

  Stream Discharge - The amount of water that passes a specific point on a watercourse over a given period of time. Rates of discharge are usually measured in cubic feet per second.

  Dyke / Levee - A man-made structure, usually an earthen embankment often reinforced with soil cement, that is designed to contain or divert the flow of water.
 

  Peak Flow - The maximum rate of flow through a watercourse for a given storm.