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About
Floods
What
are floods and flashfloods?
The distinction
between a flood and "flash-flood" is usually determined
by the amount of warning (less than six hours for a flash-flood)
that affected areas might receive prior to the flood conditions.
Flash
floods may trigger hazardous events such as
mud and landslides, structural bridge failures, and other
threatening conditions. Rainfall intensity and duration
are the primary source of flash floods. Intensity is the
rate of rainfall, and duration is how long the rain lasts.
Other factors include topography, soil conditions, and
ground cover.
Floods
are a long-term event and may last several days, or even
weeks. Hurricanes and earthquakes directly cause flood
conditions such as "storm surge" or tsunami respectively.
There are also floods that have characteristics associated
with the geographic areas they are in, such as river,
coastal and urban flooding.
River
Floods in Hawaii are usually triggered by hurricane
or tropical storm rains.
Coastal
Floods
are caused by winds generated from tropical storms and
hurricanes or intense offshore low pressure systems that
can drive ocean water inland and cause significant flooding.
Urban
Floods
are triggered because the paved streets cannot absorb
the rainfall. Therefore, the streets becomes a rivers
and people can lose a lot of their property and some times
their lives.
What
is the difference between “watch,” “warning,” and “advisory?”
The National
Weather Services uses specific words when they issue alerts
to the public about dangerous flood-related conditions.
Flash
flood watch: A flash flood is possible in the
area, stay alert.
Flash
flood warning: A flash flood is imminent or
occurring; take immediate action.
Urban
and small stream advisory: Flooding of small
streams, streets, urban storm drains, and low lying areas.
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