Public Information Statement
Issued by NWS La Crosse, WI
NOUS43 KARX 151306
Public Information Statement
National Weather Service La Crosse WI
800 AM CDT Wed Mar 15 2017
The National Weather Service (NWS) has declared March 13 through
March 17 as Flood Safety Awareness week. The National Weather
Service in La Crosse is providing information about a different
flood topic each day during the awareness week.
Today`s topic: Flood Hazards
A flood is defined as any high flow...overflow...or inundation of
water that causes or threatens damage. Flooding can occur with
prolonged rainfall over several days...intense rainfall over a short
period of time...or when water from an existing source moves too
quickly (i.e. snowmelt...dam break...etc.). Brief descriptions of
the various types of flooding you may experience are found below.
More information about these flood hazards can be found on the
NWS Flood Safety website at www.floodsafety.noaa.gov.
Flash flooding is a rapid and extreme flow of high
water into a normally dry area...or a rapid water level rise in a
stream or creek above a predetermined flood level...beginning within
six hours of the causative event (i.e. intense rainfall...dam
River flooding occurs when rivers rise and overflow
their banks...inundating areas that are normally dry.
Flooding due to snowmelt most often occurs in the spring when
warming temperatures quickly melt the snow. The water runs off the
still partially frozen or already saturated ground into nearby
streams and rivers...causing them to rapidly rise and sometimes
overflow their banks.
Ice and Debris Jams:
A backup of water into surrounding areas can
occur when a river or stream is blocked by a build-up of ice or
Dam Break and Levee Failure:
A break or failure can occur with
little to no warning. Most often they are caused by water
overtopping the structure...excessive seepage through the
surrounding ground...or a structural failure.
When heavy rain falls over dry land...the water rushes
towards low-lying areas...which may include dried up stream beds.
This can quickly turn a dry channel into a raging river.
Burn Scars/Debris Flows:
Wildfires burn away the vegetation of an area...leaving behind bare
ground that tends to repel water. When rain falls...it runs off a
burn scar towards a low lying area...sometimes carrying branches...
soil and other debris along with it. Without vegetation to hold the
soil in place...flooding can produce mud and debris flows.
Tropical Systems and Coastal Flooding:
At any time of year...a storm from over the ocean can bring heavy
precipitation to the U.S. coasts. Whether such a storm is tropical
or not...prolonged periods of heavy precipitation can cause
freshwater flooding in coastal areas...as well as further inland as
the storm moves on shore. In addition to the freshwater flood
threat...tropical systems and nor`easters can bring the threat of
storm surge related coastal flooding.
Understanding the different flood hazards and knowing the actions to
take before...during...and afterwards can help you protect your
life...the lives of your loved ones...and your property. Prepare
now by visiting www.floodsafety.noaa.gov.
Join us tomorrow for information on flood related services provided
by the National Weather Service.