Floods

1
Floods

• School Abdallah Al-Alayly
• Teacher Ms. Abeer Abdallah
• Prepared by Grade 9 students

2
What Is A Flood?

• Floods are the most common and widespread of all
  natural disasters except fire. A flood as defined
  by the National Flood Insurance Program is a
  general and temporary condition of partial or
  complete inundation of two or more acres of
  normally dry land area or of two or more
  properties from overflow of inland or tidal
  waters, unusual and rapid accumulation or runoff
  of surface waters from any source or a mudflow.

3
Kinds of Floods

• River Flood Some floods occur seasonally when
  winter or spring rains, coupled with melting
  snows, fill river basins with too much water too
  quickly. Torrential rains from decaying
  hurricanes or tropical systems can also produce
  river flooding.
• Coastal Flood Winds generated from tropical
  storms and hurricanes or intense offshore low
  pressure systems can drive ocean water inland and
  cause significant flooding. Coastal flooding can
  also be produced by sea waves called tsunamis.
• Urban Flood As land is converted from fields or
  woodlands to roads and parking lots, it loses its
  ability to absorb rainfall. During periods of
  urban flooding, streets can become swift moving
  rivers, while basements can become death traps as
  they fill with water.
• Flash Flood Dams are designed to hold a rivers
  water in reserve for when people may need it. If
  a dam were to break then all the trapped water
  would rush down the river at the same time and
  cause a flash flood.
• Ice Jam Floating ice can accumulate at a natural
  or manmade obstruction and stop the flow of water.

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Causes of Floods

• Numerous factors contribute in causing floods.
  When it rains or snows, some of the water is
  retained by the soil, some is absorbed by
  vegetation, some evaporates and the remainder,
  which reaches stream channels, is called runoff.
  Floods occur when soil and vegetation cannot
  absorb all the water water then runs off the
  land in quantities that cannot be carried in
  stream channels or retained in natural ponds and
  constructed reservoirs. About 30 percent of all
  precipitation is runoff and this amount may be
  increased by melting snow masses. Moreover, heavy
  rain combined with melting snow causes the rivers
  to overflow their banks and flood. In addition,
  intense rainfall over a relatively small area may
  lead to a flood. Furthermore, high tides induced
  by severe winds over ocean surfaces result in
  floods. Thus, floods occur due to prolonged
  rainfall lasting several days, intense rainfall
  over a short period of time, an ice or debris jam
  that causes a river or stream to overflow and
  flood the surrounding area, snow-melt combined
  with rain in winter, severe thunderstorms, or
  tropical cyclones that bring intense rainfall to
  the coastal and inland areas in the summer and
  fall.

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Effects of Floods

• There are two kinds of flood effects Domestic
  and national
• Domestic effects are the erosion of people which
  continues in several places of the effected
  place, city drainage systems that fail to serve
  their purpose and the drains that carry the
  polluted waste water which should have actually
  gone to a sewerage system for treatment.
• National effects are the soil erosion which is
  one of the main effects of heavy floods the flow
  of rivers above the danger level insufficient
  stock of food and medicine to cope with the
  situation the fact that the affective places
  remain cut off with the rest of the country the
  damage occurred to several hutments, granaries,
  fisheries and standing crops the submersion of
  many roads and relief camps by flood water
  catastrophic debris slides can be triggered by
  flood producing rain and a great heap of
  destruction for floods can roll boulders, tear
  out trees, destroy buildings and bridges and
  scour out new channels.

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What To Do?

• There are some steps that should be taken before
  or during a flood.
• one should head for higher ground and stay away
  from flood water .
• If one lives in a flood-prone area or think he is
  at risk, he should evacuate immediately. It is
  important to move to a safe area before access is
  cut off by floodwaters. The most dangerous thing
  one can do is to try walking, swimming or driving
  through flood waters.
• one should follow the instructions and advice of
  local authorities.
• If one is driving, he should avoid already
  flooded areas.
• If ones vehicle becomes surrounded by water or
  the engine stalls, and if he can safely get out,
  he should abandon his vehicle immediately and
  climb to higher ground.

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Places Hit By Floods

• BangladeshAn exceptionally heavy flood affected
  3.5 million people in half of the country's 64
  districts.
• India the east and north-east of India
  witnessed floods which killed at least 43 people
  in landslides yesterday.