Public Information Statement
Issued by NWS Des Moines, IA

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PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
900 AM CDT WED MAR 19 2014

...FLOOD SAFETY AWARENESS WEEK DAY 3...FLOOD HAZARDS...

THE NATIONAL WEATHER SERVICE /NWS/ HAS DECLARED MARCH 16 THROUGH
MARCH 22 AS FLOOD SAFETY AWARENESS WEEK. THE NWS IN DES MOINES
WILL FEATURE 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. NOTE THAT WHILE NOT ALL OF THE BELOW
TYPES OF FLOODING MAY BE FOUND IN IOWA THEY ARE STILL INCLUDED
HERE FOR YOUR REFERENCE. MORE INFORMATION ABOUT THESE FLOOD
HAZARDS CAN BE FOUND ON THE NWS FLOOD SAFETY WEB SITE AT
HTTP://WWW.FLOODSAFETY.NOAA.GOV/.

.FLASH FLOODING...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 FAILURE OR ICE JAM/.

.RIVER FLOODING...RIVER FLOODING OCCURS WHEN RIVERS RISE AND
OVERFLOW THEIR BANKS INUNDATING AREAS THAT ARE NORMALLY DRY.

.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 FLOODING IN COASTAL AREAS
AS WELL AS FURTHER INLAND AS THE STORM MOVES ON SHORE.

.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.

.SNOWMELT...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 OTHER DEBRIS.

.DRY WASH...WHEN HEAVY RAIN FALLS OVER DRY LAND THE WATER RUSHES
TOWARDS LOW-LYING AREAS...WHICH MAY INCLUDE DRIED UP CANYON OR
STREAM BEDS. THIS CAN QUICKLY TURN A DRY CHANNEL INTO A RAGING
RIVER.

.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.


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 HTTP://WWW.FLOODSAFETY.NOAA.GOV/.


JOIN US TOMORROW FOR INFORMATION ON FLOOD-RELATED SERVICES
PROVIDED BY THE NWS.

$$

ZOGG



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