WFO Denver/Boulder


TODAYS TOPIC DURING THIS FLOOD SAFETY AND WILDFIRE AWARENESS WEEK IS FLASH 
FLOODS.    

FLASH FLOODS ARE NO STRANGERS TO COLORADO. SINCE THE YEAR 1900...NEARLY 300 
PEOPLE HAVE BEEN KILLED IN FLASH FLOODS ACROSS THE CENTENNIAL STATE.  

IN TERMS OF LIVES LOST...THE WORST FLASH FLOOD OCCURRED ON JULY 31 1976 IN 
THE BIG THOMPSON CANYON BETWEEN ESTES PARK AND LOVELAND. A NEARLY STATIONARY 
STORM PRODUCED AROUND 12 INCHES OF RAIN IN 4 HOURS...CLAIMING 144 LIVES.

THREE OTHER NOTABLE FLASH FLOODS IN COLORADO WERE...

IN 1904...JUST NORTH OF PUEBLO...A BRIDGE FAILED AND AROUND 100 PEOPLE 
DROWNED WHEN A PASSENGER TRAIN PLUNGED INTO FOUNTAIN CREEK.

LAST YEAR...9 PEOPLE DROWNED DURING THE HISTORIC SEPTEMBER RAIN 
EPISODE...WHICH WAS A COMBINATION OF FLASH FLOODS AND RIVER FLOODS. THESE 
FLOODS WERE MUCH MORE EXTENSIVE THAN THE BIG THOMPSON CANYON FLOOD OF 
1976...BUT BECAUSE OF TIMELY AND ACCURATE WARNINGS...MANY LIVES WERE SAVED.

THE 1997 FORT COLLINS EPISODE KILLED 5 PEOPLE AND CAUSED 200 MILLION DOLLARS 
OF PROPERTY DAMAGE.

A FLASH FLOOD IS DEFINED AS A RAPID RISE IN WATER LEVELS...GENERALLY 
OCCURRING IN LESS THAN 6 HOURS...ALONG LARGE CREEKS...NORMALLY DRY 
WASHES...ARROYOS...OR OVER NORMALLY DRY LAND AREA...AND CAN OCCUR WITH LITTLE 
ADVANCED NOTICE.  

FLASH FLOODS FREQUENTLY RESULT FROM HIGH RAINFALL RATES...AND INFREQUENTLY  
RESULT FROM DAM FAILURES...LEVEE FAILURES...OR SUDDEN BREAKS IN RIVER ICE 
JAMS.  FLASH FLOODS ARE VERY DESTRUCTIVE...DUE TO THE FORCE OF THE MOVING 
WATER...AND THE ACCOMPANYING DEBRIS. THIS TREMENDOUS FORCE CAN EASILY DAMAGE 
OR DESTROY ROADWAYS...BRIDGES...AND BUILDINGS. 

IN RECENT YEARS...COLORADO HAS SEEN MAJOR FLOODING AND DAMAGE WHEN HEAVY 
RAINS HAVE OCCURRED ON WILDFIRE BURN SCAR AREAS.  IF YOU ARE IN OR NEAR A 
BURN SCAR AREA...YOU NEED TO PLAN AHEAD.  BE AWARE OF GENERAL FLASH FLOOD 
PLANS AND PROCEDURES THAT HAVE BEEN DEVELOPED AND IMPLEMENTED BY YOUR LOCAL 
EMERGENCY MANAGEMENT OFFICIALS. YOU SHOULD KNOW YOUR FLASH FLOOD RISKS...AND 
MAKE YOUR PLANS TO SAVE YOUR LIFE AND THOSE AROUND YOU.

THE NATIONAL WEATHER SERVICE FORECAST OFFICES WILL DISCUSS FLASH FLOOD 
POTENTIAL IN DAILY HAZARDOUS WEATHER OUTLOOKS...AND IN GRAPHICAL WEATHER 
STORIES ON NATIONAL WEATHER SERVICE FORECAST OFFICE WEB SITES. 

DURING DAYS WHEN FLASH FLOODING IS POSSIBLE A FLASH FLOOD WATCH WILL BE 
ISSUED.  

DURING DAYS WHEN FLASH FLOODING IS LIKELY OR OCCURRING A FLASH FLOOD WARNING 
WILL BE ISSUED. 

WHEN A FLASH FLOOD WARNING IS ISSUED FOR YOUR AREA...YOU NEED TO ACT QUICKLY 
IF YOU ARE IN A DRAINAGE AREA OR IN OTHER LOW SPOTS.  KNOW YOUR ESCAPE ROUTES 
TO HIGHER GROUND AND ACT AS QUICKLY AS POSSIBLE. IT MAY BE JUST A SHORT WALK 
OR CLIMB TO THAT HIGHER GROUND.

MANY FLASH FLOOD DEATHS OCCUR IN VEHICLES.  DO NOT DRIVE THROUGH A FLOODED 
ROADWAY.  THE WATER MAY BE MUCH DEEPER THAN YOU THINK...BECAUSE THE ROADWAY 
MAY BE DAMAGED OR WASHED AWAY. ONE TO TWO FEET OF WATER WILL CARRY AWAY MOST 
VEHICLES. INSTEAD TURN AROUND...DONT DROWN.   

FOR MORE INFORMATION ON FLOOD SAFETY GO TO...

HTTP://WWW.FLOODSAFETY.NOAA.GOV

FLOOD SAFETY AND WILDFIRE AWARENESS WEEK CONTINUES THROUGH THIS SATURDAY.  

TOM MAGNUSON
WARNING COORDINATION METEOROLOGIST
NATIONAL WEATHER SERVICE PUEBLO

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