NOUS42 KCHS 220918
PNSCHS
GAZ087-088-099>101-114>119-137>141-SCZ040-042>045-047>051-230900-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
418 AM EST WED MAR 22 2006

THE NATIONAL WEATHER SERVICE HAS DECLARED MARCH 20 THROUGH 24 AS 
FLOOD SAFETY AWARENESS WEEK. THE NATIONAL WEATHER SERVICE IN 
CHARLESTON WILL FEATURE A DIFFERENT EDUCATIONAL TOPIC EACH DAY 
DURING THE AWARENESS WEEK. TODAY/S TOPIC IS...FLOODING ASSOCIATED 
WITH TROPICAL CYCLONES.

WHEN IT COMES TO TROPICAL CYCLONES (A GENERIC TERM FOR A HURRICANE 
OR TROPICAL STORM)...WIND SPEEDS DO NOT TELL THE WHOLE STORY. 
INTENSE RAINFALL...NOT DIRECTLY RELATED TO THE WIND SPEED OF A 
TROPICAL CYCLONE...OFTEN CAUSES MORE DAMAGE. SINCE THE 1970S... 
INLAND FLOODING HAS BEEN RESPONSIBLE FOR MORE THAN HALF OF THE 
DEATHS ASSOCIATED WITH TROPICAL CYCLONES IN THE UNITED STATES. 
TYPICALLY... GREATER RAINFALL AMOUNTS AND FLOODING ARE ASSOCIATED 
WITH TROPICAL CYCLONES THAT HAVE A SLOW FORWARD SPEED OR STALL OVER 
AN AREA.


WHAT DO I NEED TO KNOW ABOUT INLAND FLOODING FROM TROPICAL CYCLONES?

INLAND FRESHWATER FLOODS ACCOUNTED FOR MORE THAN HALF OF U.S. 
TROPICAL CYCLONE DEATHS OVER THE PAST 30 YEARS. RAINFALL IS 
TYPICALLY HEAVIER WITH SLOWER MOVING STORMS AS THEY ALLOW HEAVY RAIN 
TO PERSIST OVER A LOCATION FOR LONGER. THEREFORE...PEOPLE LIVING IN 
AREAS WELL AWAY FROM THE COASTLINE STILL NEED TO BE ALERT IF A 
TROPICAL CYCLONE MAKES LANDFALL NEARBY. 


WHAT TYPES OF INLAND FLOODING ARE CAUSED BY TROPICAL CYCLONES?

FLASH FLOODING OCCURS IN CREEKS...STREAMS...AND URBAN AREAS WITHIN A 
FEW MINUTES TO A FEW HOURS OF EXCESSIVE RAINFALL. STREETS CAN BECOME 
SWIFTLY-FLOWING RIVERS AND UNDERPASSES CAN BECOME DEATH TRAPS.

RIVER FLOODING OCCURS FROM HEAVY RAINS ASSOCIATED WITH DECAYING 
HURRICANES OR TROPICAL STORMS. FLOODING ASSOCIATED WITH TROPICAL 
SYSTEMS CAN LAST FOR SEVERAL WEEKS TO MORE THAN A MONTH. 


HOW DO I KNOW HOW SEVERE A FLOOD WILL BE?

THE NWS IN CHARLESTON ISSUES TWO AREAL FLOOD PRODUCTS FOR NON-RIVER 
FLOODING: FLOOD STATEMENTS AND FLASH FLOOD WARNINGS. A FLOOD 
STATEMENT IS ISSUED WHEN MINOR FLOODING IS EXPECTED...BUT IS NOT 
EXPECTED TO POSE A SIGNIFICANT RISK TO LIFE OR PROPERTY. THIS CAN 
INCLUDE AREAS THAT FREQUENTLY FLOOD DURING HEAVY RAIN...SUCH AS 
DOWNTOWN CHARLESTON. A FLASH FLOOD WARNING IS RESERVED FOR FLOODING 
EVENTS THAT POSE A SIGNIFICANT THREAT TO LIFE AND/OR PROPERTY.   

FOR RIVER FLOODING...THE NWS IN CHARLESTON CONVEYS THE MAGNITUDE OF 
OBSERVED OR FORECAST FLOODING USING FLOOD SEVERITY CATEGORIES. THESE 
CATEGORIES INCLUDE MINOR FLOODING...MODERATE FLOODING...AND 
MAJOR FLOODING. EACH CATEGORY HAS A DEFINITION BASED ON PROPERTY 
DAMAGE AND PUBLIC THREAT.

MINOR FLOODING: MINIMAL OR NO PROPERTY DAMAGE BUT POSSIBLY SOME 
PUBLIC THREAT OR INCONVENIENCE. SOME SECONDARY ROADS ADJACENT TO THE 
RIVER MAY BECOME IMPASSABLE. 

MODERATE FLOODING: SOME INUNDATION OF STRUCTURES AND PRIMARY ROADS 
NEAR THE RIVER. SOME EVACUATIONS OF PEOPLE AND/OR TRANSFER OF 
PROPERTY TO HIGHER ELEVATIONS ARE NECESSARY.

MAJOR FLOODING: EXTENSIVE INUNDATION OF STRUCTURES AND ROADS. 
SIGNIFICANT EVACUATIONS OF PEOPLE AND/OR TRANSFER OF PROPERTY TO 
HIGHER ELEVATIONS.

THE IMPACTS OF A FLOODS VARY LOCALLY. FOR EACH NWS RIVER FORECAST 
LOCATION...FLOOD STAGE AND THE STAGE ASSOCIATED WITH EACH OF THE NWS 
FLOOD SEVERITY CATEGORIES ARE ESTABLISHED IN COOPERATION WITH LOCAL 
PUBLIC OFFICIALS. INCREASING RIVER LEVELS ABOVE FLOOD STAGE 
CONSTITUTE MINOR...MODERATE...AND MAJOR FLOODING. IMPACTS VARY FROM 
ONE RIVER LOCATION TO ANOTHER BECAUSE A CERTAIN RIVER STAGE (HEIGHT) 
IN ONE LOCATION MAY HAVE AN ENTIRELY DIFFERENT IMPACT THAN THE SAME 
LEVEL ABOVE FLOOD STAGE AT ANOTHER LOCATION.

$$