Geoscience Reference
In-Depth Information
catastrophic damage—estimated at $75 billion in the New Orleans area and
along the Mississippi coast. The death toll is estimated at 1200, including
about 1000 in Louisiana and 200 in Mississippi. Seven additional deaths
occurred in southern Florida.
5
Debris Flooding
—hese types of floods are caused by an accumulation of
debris, such as rocks, sediment, logs, or other debris in a stream or creek
channel. The accumulated debris causes a temporary dam, and as water
builds up behind the temporary dam, the dam gives way and the release of
water becomes a flash flood.
Mudflow Flooding
—Also known as lahars, these occur when volcanic
activity melts snow and glaciers on the mountain. The result is a large amount
of water mixed with debris and mud that rapidly moves down the mountain
slope.
This type of flooding occurred on May 18, 1980, with the eruption of
Mount St. Helens. The eruption melted snow and ice atop Mount St. Helens,
which in turn caused large amounts of mud to stream down the side of the
mountain. This contributed to the 57 lives that were lost.
Consequences of Flooding
Mass amounts of water from flood events can cause extensive damage throughout
a community (Figure 5.2). Like many disasters, flooding can cause many different
types of secondary disasters that must be considered and planned for. These include
power outages from destroyed electrical grid infrastructure, road washouts, sewer
infiltration, septic system destruction, erosion, mass evacuations of people and ani-
mals (leading to temporary housing issues), crop damage, contamination of water
supplies, public and private property damage, large amounts of debris, contamina-
tion of homes due to mold and other contaminants, and mass casualties.
Figure 5.2 Flooding from the Tar River in Greenville, North Carolina (1999).
(Dave Gately, Federal Emergency Management Agency.)
