Flooding A Deadly Inland Danger

U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration March 2005 What You Need to Know about Inland Flooding

When it comes to tropical cyclones (a generic term for a hurricane, typhoon, or tropical storm), speeds do not tell the whole story. Intense rainfall, not directly related to the wind speed of a tropical cyclone, often causes more damage. Just ask the citizens of Richmond, Virginia.Virginia. Storm surgesurge fromfrom Hurricane Isabel at Rock Hall, Md, Sept. 2003 IInn latelate AAugustugust 22004,004, ddecayingecaying TTropicalropical SStormtorm GGastonaston ttraversedraversed tthroughhrough tthehe CCarolinasarolinas aandnd iintonto ssouthernouthern thethe PPresident.resident. VVirginia.irginia. AAlthoughlthough iitsts ccirculationirculation hhadad llostost mmuchuch ooff iitsts sstrength,trength, GGastonaston rremainedemained a ddangerousangerous sstormtorm aass Factors Affecting Inland mmoreore tthanhan a ffootoot ooff rrainain ffellell ooverver RRichmondichmond iinn a ffewew hhours,ours, causingcausing mmajorajor fl oooding.oding. FFiveive ppeopleeople ddied,ied, mmanyany Flooding hhousesouses andand businessesbusinesses werewere destroyed,destroyed, ppowerower wwasas llost,ost, ForwardForward SSpeedpeed – SlowerSlower movingmoving ttropicalropical ccyclonesyclones aandnd IInterstatenterstate 9955 wwasas fl ooodedoded fforor mmoreore tthanhan 2244 hhours,ours, allowallow hheavyeavy rrainain ttoo ppersistersist ooverver a llocation.ocation. pprohibitingrohibiting ggroundround ttransportationransportation oonn a mmajorajor EEastast CCoastoast hhighway.ighway. TThehe eeventvent wwasas ddeclaredeclared a nnaturalatural ddisasterisaster bbyy OrographyOrography – WWhenhen wwarm,arm, mmoistoist ttropicalropical aairir iiss fforcedorced upup hillshills aandnd mmountains,ountains, tthehe rrainain iiss iintensifintensifi eed.d. Deaths caused by the effects of tropical IntersectionIntersection wwithith otherother wweathereather ffeatureseatures – TThehe cyclones in the U.S. since 1970 remainsremains ooff hhurricaneurricane AAgnesgnes ((1972)1972) mmergederged wwithith �������� anotheranother mmid-latitudeid-latitude sstorm,torm, pproducingroducing mmajorajor fl ooodsods iinn ��� thethe nnortheastortheast UU.S..S. ���������������������� AntecedentAntecedent conditionsconditions – TThehe wwetteretter tthehe ssoiloil aandnd tthehe ���������������� ��� �������� hhigherigher tthehe wwaterater llevelevel iinn sstreams,treams, rrivers,ivers, pponds,onds, llakes,akes, ��� aandnd rreservoirs,eservoirs, tthehe ggreaterreater tthehe sseverityeverity ooff fl oooding.oding. TropicalTropical ccyclonesyclones usuallyusually ccauseause bbothoth fl aashsh aandnd rriveriver fl oooding.oding. ���������� ���������� ���������������� FlashFlash FFloodinglooding occursoccurs iinn ccreeks,reeks, sstreams,treams, aandnd uurbanrban �� �� �������������� ��� �� areasareas wwithinithin a ffewew mminutesinutes oorr hhoursours ooff eexcessivexcessive rainfall.rainfall. RRapidlyapidly rrisingising wwaterater ccanan rreacheach hheightseights ooff 3300 Since the 1970s inland fl ooding has been responsible for feetfeet oorr mmore.ore. SStreetstreets ccanan bbecomeecome sswiftwift mmovingoving rriversivers more than half of all deaths associated with tropical cyclones in the United States. andand uunderpassesnderpasses ccanan bbecomeecome ddeatheath ttraps.raps. RiverRiver FFloodinglooding occursoccurs ffromrom ttorrentialorrential rrainsains “During“During thethe 20th20th century,century, fl ooodsods wwereere tthehe nnumber-umber- oonene naturalnatural disasterdisaster inin thethe UUnitednited SStatestates iinn ttermserms aassociatedssociated wwithith ddecayingecaying hhurricanesurricanes oorr ttropicalropical sstorms.torms. ooff thethe nnumberumber ooff llivesives llostost aandnd ppropertyroperty ddamage.”amage.” RRiveriver fl ooodsods ccanan llastast a wweekeek oorr mmore.ore. MMarcharch 22000,000, UU.S..S. GeologicalGeological SSurveyurvey

Inland fresh water fl ooding disasters due to tropical cyclones are all too common. 20022002 TropicalTropical SStormtorm FFayay 20012001 TropicalTropical SStormtorm AAllisonllison 19991999 HurricaneHurricane FloydFloyd bbroughtrought producedproduced hheavyeavy rrainfallainfall aandnd causedcaused moremore damagedamage thanthan anyany iintensentense rrainsains aandnd rrecordecord fl oodingooding inlandinland fl oodingooding aacrosscross tthehe uupperpper tropicaltropical sstormtorm iinn UU.S..S. hhistoryistory wwithith ttoo tthehe EEasternastern UUnitednited SStates.tates. OOff TexasTexas coastalcoastal area.area. RainfallRainfall ttotalsotals estimatesestimates inin excessexcess ofof $5B.$5B. ThreeThree tthehe 5566 ddeaths,eaths, 5500 wwereere drowningsdrownings ofof nnearlyearly 2 ffeeteet ddestroyedestroyed homes,homes, ffeeteet ofof rrainain wwasas rreportedeported iinn TTexas.exas. ffromrom iinlandnland fl oooding.oding. DDamagesamages businesses,businesses, aandnd ppublicublic ffacilities.acilities. OOff tthehe 2233 ddeathseaths iinn TTexas,exas, 2200 wwereere rreachedeached moremore thanthan $$6B.6B. ffromrom ddrowning.rowning. Understanding Potential Impacts

Within fl ood warnng products, the NWS conveys the magnitude of observed and forecast fl ooding using fl ood severity categories. Each category has a defi nition based on property damage and public threat.

 Minor Flooding – minimal or no property damage, but possibly some public threat or inconvenience.

 Moderate Flooding – some inundation of structures and roads near streams. Some evacuations of people and/or transfer of property to higher elevations are necessary.necessary. Graphical depiction of NWS severity categories  Major Flooding – extensive inundation of structures and roads. Signifi cant evacuations of people and/or transfer of property to higher elevations. TheThe iimpactsmpacts ooff fl ooodsods vvaryary llocally.ocally. FForor eeachach NNWSWS rriveriver fforecastorecast llocation,ocation, fl ooodod sstagetage aandnd tthehe sstagetage aassociatedssociated wwithith eacheach ooff tthehe NNWSWS fl ooodod sseverityeverity ccategoriesategories aarere eestablishedstablished iinn ccooperationooperation wwithith llocalocal ppublicublic ooffiffi ccials.ials. IIncreasingncreasing rriveriver levelslevels aabovebove fl ooodod sstagetage cconstituteonstitute mminor,inor, mmoderate,oderate, aandnd mmajorajor fl oooding.oding. IImpactsmpacts vvaryary ffromrom oonene rriveriver llocationocation ttoo anotheranother bbecauseecause a ccertainertain rriveriver sstagetage ((height)height) aabovebove fl ooodod sstagetage iinn oonene llocationocation mmayay hhaveave aann eentirelyntirely ddifferentifferent iimpactmpact thanthan tthehe ssameame llevelevel aabovebove fl ooodod sstagetage aatt aanothernother llocation.ocation.

a nearby NWS Offi ce (For more information: http:// What Can YYouou Do? wwwwww.nws.noaa.gov/nwr/.nws.noaa.gov/nwr/). Determine whether you live in a potential fl ood zone (For more information: wwwwww.fl.fl oodsmart.gov). Keep abreast of road conditions (For more information: wwwwww.. Assemble a disaster supply kit (For more information: fhwa.dot.gov/traffi cinfo/index. www.redcross.orgwww.redcross.org). htm). Protect your home and family before a fl ood by When you hear hurricane or purchasing fl ood insurance (For more information: www.fema.gov/nfiwww.fema.gov/nfi p) oror callcall 11-800-427-4661.-800-427-4661. tropical storm, think inland fl ooding. Develop a fl ood emeremergencygency action plan with your community leaders (For more information: wwwwww.. DO NOT attempt to cross fema.gov). fl owing water.water. TURN AROUNDAROUND DON’TDON’T DROWNDROWN. Learn how you can prepare for fl ooding and reduce As little as 6 inches of fl ood loss (For more information: water may cause you wwwwww.fema.gov/library/prepandprev.shtm.fema.gov/library/prepandprev.shtm). to lose control of your vehicle, and 2 feet of Monitor wwwwww.weather.gov.weather.gov for the latest watches, water will carry most warnings, and current conditions in your area. vehicles away (For more Monitor NOAAs WWeathereather Radio All Hazards to receive continuous weather information directly from information: hhttp://tadd.weather.govttp://tadd.weather.gov). What to Look and Listen For

Hydrologic Outlook is used to indicate that a hazardous fl ood event may develop. It is intended to provide information to those who need considerable lead time to prepare for it. “Get Ready” Flood Watch is used when the expectation of a fl ood event has increased, but its occurrence, location, and/or timing is still uncertain. It is intended to provide enough lead time so those who need to set their mitigation plans in motion can do so. “Get Set” Flash Flood Warning, fl ood warnings, and various advisories under the fl ood statement are issued whenever a fl ood event is occurring, imminent, or has a high probability of occurrence. “Go, Take Action” Current listing of all hydrologic forecasts, watches, and warnings for your local area can be viewed at www.weather.gov Take Action

When a FLOOD WARNING is issued • Evacuate immediately, if advised to do so! • Move to a safe area before access is cut off by rising water. • Monitor NOAA Weather Radio All Hazards, television, emergency broadcast stations or go to www.weather.gov.

Get to high ground – Climb to safety! • Get out of areas subject to fl ooding, including dips, low spots, canyons, washes, etc. • Avoid already-fl ooded areas and do not attempt to cross fl owing water. • Be especially cautious at night, when it is harder to recognize fl ood dangers.

During the Flood • Avoid areas subject to sudden fl ooding. • NEVER drive through fl ooded roadways! STOP! Turn Around Don’t Drown. Do not attempt to drive over a fl ooded roadbed. Be aware that the roadbed may be washed out. • NEVER allow children to play around high water, storm drains, creeks, or rivers.

After the Flood • Throw out fresh water that has come into contact with fl oodwater. • Boil drinking water before using it. Wells should be pumped out and tested for quality before drinking. If in doubt, call your local public health authority. • Seek necessary medical care at the nearest hospital. Food, clothing, shelter, and fi rst aid are available from the American Red Cross. • Check and dry out electrical equipment before being returned to service. • Use fl ashlights, not lanterns, torches, or matches, to examine buildings. Flammables may be inside. • Report broken utility lines to appropriate authorities.

Water Predictions This is an Advanced Hydrologic Prediction Service for Safety Message Life Decisions NOAA/PA 200465