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:
-
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.
-
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
-
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.
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