Intio Flooding in Washington, DC A fist look at wh it occus in th Distict of Columbia DC Silv Jackts Intio Flooding Task Goup August 25, 2017 Figu 1: A potion of th map poducd by th DC Silv Jackts that is th subjct of this pap. Th full map is at th nd of th documnt.
Contnts List of Figus... 2 About th DC Silv Jackts... 2 Intoduction... 3 What is Intio Flooding?... 3 Why Study Intio Flooding?... 3 Rpot Pupos... 3 Backgound... 5 Rcnt Intio Flood Evnts... 5 How Futu Intio Flood Risks May Chang... 5 Data fo Intio Flooding... 6 About th Map... 7 About th Data... 7 About th Mapping Pocss... 8 Nots Whn Using th Map... 8 Nxt Stps and Rcommndations... 9 Full Pag Intio Flooding Map... 10 List of Figus Figu 1: A potion of th map poducd by th DC Silv Jackts that is th subjct of this pap. Th full map is at th nd of th documnt....1 Figu 2: Typs of flooding in Washington, DC..... 4 Figu 3: How flood locations a summd in ach 300m x 300m gid...8 About th DC Silv Jackts Th DC Silv Jackts is an intagncy tam compisd of mmbs fom fdal, Distict of Columbia, and gional agncis, as wll as acadmia. Th tam lvags soucs to idntify and implmnt comphnsiv, silint, and sustainabl solutions to duc flood isk aound Washington, DC and to assist local communitis in thi flood isk mitigation ffots. Flood isk managmnt is citical in th Distict of Columbia, as it is hom to numous sidnts and businsss, cultual and histoic tasus, and fdal assts that if floodd would hav both local and national consquncs. Th DC Silv Jackts has stablishd multipl task goups to hlp implmnt th tam s mission and goals. Cuntly, thy includ: Dvlopmnt of Flood Inundation Mapping/Stam Gaugs; Flood Emgncy Planning; Intio Flooding; Lv Ctification and Accditation; and Flood Risk Communication. Th Intio Flooding Task Goup ppad this pot. Pag 2 of 10
Intoduction What is Intio Flooding? Intio floods, also known as flash floods, stomwat floods, o uban dainag floods, a causd by havy ainfall that accumulats too quickly to b absobd by th gound, o daind by th stom sw systm. Intio flooding can occu whn iv lvations a nomal. Factos that contibut to intio floods includ topogaphy, sufac pmability, localizd wath, buid stams, high wat tabls, and th capacity of th stom sw systm. Why Study Intio Flooding? Washington, DC is vulnabl to th typs of flooding: ivin, coastal, and intio (s Figu 2). Rivin and coastal flooding a th subjct of many maps and oth sach in th gion, including fdally fundd mapping ffots such as th Stom Sug Inundation Maps and th Flood Insuanc Rat Maps. Intio flooding and wh it occus in th gion, howv, is not wll undstood. Rcnt studis in th Unitd Stats and aboad indicat that flood losss fom intio flooding a on th is. 1 In Washington, DC th w numous cnt and wll publicizd intio flood vnts that ancdotally suppot ths findings. Futhmo, intio flooding is xpctd to scalat as a sult of th incasd intnsity and fquncy of sv stoms du to climat chang. Th lack of data, as wll as th gowing intio flooding isk in Washington, DC, a two pimay asons why th DC Silv Jackts flt futh study on intio flooding was ncssay. Rpot Pupos This pot, and th associatd map (locatd at th nd of th documnt), summaiz th cunt stat of knowldg about intio flooding in Washington, DC and psnts th fist Distict-wid map of wh intio flooding occus. This pot is dividd into two sctions. Th fist sction, Backgound, povids infomation on intio flooding and pvious attmpts to map it. Th scond sction, About th Map, dscibs th data and mthodology bhind th map poducd by th DC Silv Jackts Intio Flooding Task Goup. Th map agggatd th bst availabl intio flooding data at th tim, which still only povids a limitd pictu of th intio flooding poblm. As th scond sction dscibs, uss must b caful not to daw conclusions that th data dos not suppot. 1 Th Cnt fo Txas Bachs and Shos, Uban Flooding Study, 2017, Apil 2017 Nwsltt. http://www.tamug.du/ctbs/nwsltt/ctbs_nwsltt_apil_2017.pdf Pag 3 of 10
Figu 2: Typs of flooding in Washington, DC. Pag 4 of 10
Backgound Rcnt Intio Flood Evnts Intio floods can hav a significant impact on facilitis and opations in th gion. Th 2006 Fdal Tiangl flood, fo xampl, dstoyd citical pats of th Intnal Rvnu Svic hadquats lctical and mchanical quipmnt and submgd th basmnt lvl und fiv ft of wat. This sultd in millions of dollas of damag and quid th building s 2,000 plus mploys to b locatd fo almost six months. 2 Th 2006 flood also had significant impacts to oth buildings including th Dpatmnt of Commc, th Dpatmnt of Justic, th National Achivs, and sval Smithsonian musums. In addition, th Washington Mtopolitan Aa Tansit Authoity (WMATA) shut down its Fdal Tiangl Mtoail Station fo fou days, and spnt millions of dollas to clan and plac citical tain contol and communication quipmnt. Th 2012 floods in th Bloomingdal nighbohood a xampls of intio flooding and th dvastation it can caus sidntial communitis. Ov th span of six wks, th nighbohood xpincd fou intio floods. 3 An inadquat combind stom sw systm could not handl th amount of ain. This, combind with th lack of backflow pvntion dvics in many homs, ld to stomwat and aw swag backups into basmnts. Rsidnts w displacd and homowns and landlods still had to pay thi motgags without compnsation fom th local govnmnts in addition to paying fo pais that w ncssay bfo sidnts could com back into thi homs. This localizd flooding vnt lft a significant stain on th nighbohood. Sinc thn, DC Wat has mad significant impovmnts to th nighbohood to mitigat intio flooding, 4 including th compltion of th Fist Stt Tunnl that can sto 8 million gallons of stomwat and wastwat duing intns ainstoms. In 2017, isolatd havy ains in Nothwst Washington, DC sultd in a cascad of wat into th Clvland Pak Mto Station, causing th station to clos fo a fw hous duing th vning commut. 5 WMATA, in patnship with DC Wat and th Distict Dpatmnt of Tanspotation, has sinc bgun th pocss of constucting pmannt flood potction fo this station, as wll as oth Mto locations that fquntly xpinc intio flooding. How Futu Intio Flood Risks May Chang Futu intio flood isk is xpctd to incas pimaily as a sult of changs in pcipitation. Ths changs includ both an incas in avag annual ainfall and an incas in th intnsity and fquncy of sv stoms. Th 2015 Distict of Columbia pot, Climat Pojctions and Scnaio Dvlopmnt, outlins ths pcipitation pojctions. Th pot includs data on xpctd annual ainfall changs, and how th fquncy and svity of stoms will chang ov tim. Fo xampl, today s 100-ya stom is pojctd to b quivalnt to a 15-ya stom by th 2080s. 6 Sa lvl is is also xpctd to mak intio flooding mo fqunt and sv. As sa lvls is, th fsh wat tabl also iss, 7 dcasing th capacity of th soil to absob stomwat unoff. With high sa lvls and mo fqunt nuisanc flooding vnts, th will also b mo days whn th stom sw outlts a blow th wat sufac lvation of th Potomac and Anacostia Rivs. Whn this occus, stomwat that 2 Govnmnt Accountability Offic (GAO), IRS Emgncy Planning (2007), 4-5. http://www.gao.gov/nw.itms/d07579.pdf 3 Floods occud on July 10, 18, 19, and Sptmb 2, 2012 accoding to th Flood Pvntion Task Foc. 4 DC Wat, Th Nothast Bounday Nighbohood Potction Pojct. https://www.dcwat.com/pojcts/nothast-boundaynighbohood-potction-pojct 5 Hnsly, Saah Bth, Clvland Pak Mto station opns aft flooding (photos) (2016). http://wtop.com/spawl-cawl/2016/06/floodingcloss-clvland-pak-mto-station-photos/slid/1/ 6 Dpatmnt of Engy and Envionmnt (DOEE), Climat Pojctions and Scnaio Dvlopmnt (2015). http://do.dc.gov/sits/dfault/fils/dc/sits/ddo/publication/attachmnts/150828_area_rsach_rpot_small.pdf 7 USGS, Coastal Goundwat Systms (2014). http://wh..usgs.gov/sl/coastalgoundwat.html Pag 5 of 10
nomally dains though pips connctd dictly to th ivs (in MS4 aas) 8 will b tappd. If havy ains happn at th sam tim as lvatd wat sufac lvls, intio flooding may occu in aas of th City that a connctd to ths pips bcaus of thi inability to dain into th ivs. Intio flooding is havily influncd by th built nvionmnt, which includs changs in land us. Changs in th amount of pvious sufac in a stom sw dainag aa can significantly impact th quantity and timing of wat nting th stom sw systm. Th addition of gn infastuctu fatus, such as gn oofs and sidwalk stomwat infastuctu, o impovmnts to xisting infastuctu (i.. nlaging pips to incas capacity) will hlp duc intio flood isk, but will not compltly liminat it. Altnativly, adding mo impvious sufacs such as pavmnt and conct will likly incas intio flood isk bcaus of th duction of pmability. Data fo Intio Flooding Th is a scacity of maps that show wh intio flooding occus in Washington, DC. Th pimay asons a that modling and mapping intio flooding is complx, souc intnsiv, and no comphnsiv o unifom collction of lvant Distict-wid data xists. Without modls o comphnsiv data, poxy data to appoximat th locations of intio flooding must b usd. Th Complxity of Modling Intio Flooding Cuntly, th is an infomation gap that hinds th ability to fully valuat intio flood isk in Washington, DC. Asid fom spcific mapping don in th Fdal Tiangl as a sult of th 2006 flood, 9 studis of intio flooding in Washington, DC a scac. Intio flooding is oftn difficult to map bcaus it quis hydologic modlling and a hydaulic modl of th stom sw infastuctu. This is ncssay bcaus intio flooding is impactd by th flow of wat ov th sufac, and its intaction with th stom sw systm. In many cass, intio flooding occus as a sult of ainfall ovwhlming th stom sw systm. A hydaulic modl to pdict intio flooding should contain infomation on th location and siz of stom sw inlts and pips, as wll as how th pips a connctd to oth aas of th city. Sinc data on public utilitis and infastuctu can b snsitiv, it is gnally not publicly availabl. Th lack of data on intio flooding should not b mistakn fo a lack of isk. In Fdal Tiangl, th on aa in Washington, DC that was modld, th liklihood of intio flooding is gat than that of ivin o coastal flooding, bcaus of th 17 th Stt Lv Closu. 10 Many oth aas of Washington, DC, including th Bloomingdal nighbohood, a known aas of intio flooding but hav not bn officially mappd. Collcting Intio Flooding Data Without th availabl data and soucs to modl th nti Distict of Columbia and idntify all th aas wh intio floods may occu, w must us poxy data in od to map intio flooding. Poxy data fs to data that dos not dictly masu th dsid data points (locations of intio flooding), but masus data points that a closly latd. In th cas of intio flooding, on xampl of poxy data is DC Wat s data on calls fo svic du to standing wat. Ths data points can sv as a poxy fo intio flooding locations. Whn th locations of th svic calls a plottd on a map it can b a usful, though unscintific, poxy fo wh intio flooding occus in th gion. Lik all poxy data, uss must b caful not to mak conclusions that th data dos not suppot. 8 MS4 aas, o Municipal Spaat Stom Sw Systms, a aas of th city wh stomwat dains though pips connctd dictly to th ivs. In oth aas of th city, stomwat flows into a combind sw systm that snds both stomwat and swag though undgound tunnls to th Blu Plains Wastwat Tatmnt Plant. 9 This mapping ffot is dscibd h (PDF) and was also incopoatd into th 2010 FEMA Flood Insuanc Rat Maps (FIRMs). 10 This can b sn in th visd FIRMs. With th 17th Stt Lv closu now accditd, facilitis lik th National Achivs a potctd fom th 1 pcnt annual chanc iv o coastal flood, but a still vulnabl to th 1 pcnt annual chanc intio flood. Pag 6 of 10
About th Map This sction of th pot fs spcifically to th map at th nd of th documnt. Th map, poducd by th DC Silv Jackts Intio Flooding Task Goup, is th fist Distict-wid map of wh intio flooding occus. 11 Bcaus this map lis on poxy data, th a limits on th typs of conclusions uss can daw. Th following txt dscibs th data inputs and pocss of cating th map. About th Data Fou spaat agncis povidd th task goup with data that can hlp appoximat locations of intio flooding. An xplanation of th data that ach agncy povidd is blow. DC Wat As it spcifically lats to intio flooding, DC Wat tacks data on all calls about issus latd to high standing wat, blockd stom wat catch basins, and blockags in th sw systm. Data points on th map psnt spcific locations (ith intsctions o addsss) wh th o mo flooding complaints w codd btwn 2009 and 2015. Th complaints usd fo this map a only thos fom a wok od databas that focusd on DC Wat catch basin complaints and oth stt flooding issus. This datast contains an attibut that indicats th numb of flood calls fo svic that hav occud at ach location, though this attibut is only usd to filt out locations with lss than 3 complaints. Fo xampl, if intsction A civd two complaints about standing wat at that intsction, no data point was codd. If intsction B civd six complaints about standing wat, on data point was codd. If intsction C civd 60 complaints about standing wat, on data point was codd. Distict Dpatmnt of Tanspotation (DDOT) Th DDOT data coms fom a list of aas that a pon to flooding. Th locations a idntifid by stt intsctions, sttchs of oad btwn two intsctions as wll as lag gogaphical aas lik Hains Point. In cass wh a DDOT data point fd to a sttch of oad that xtndd acoss multipl intsctions, a point was placd in ach intsction along that sction of oad. Fo xampl, if th on itm on DDOT s list ad Constitution Avnu, btwn 4 th and 17 th Stts, NW, a point was placd at 4 th and Constitution, 5 th and Constitution, 6 th and Constitution, tc. Fo th lag aas that w simply dscibd, lik Hains Point, on point was placd in ach 300 mt by 300 mt cll on th gid lay wh all th point data is joind. National Flood Insuanc Pogam Th Distict of Columbia s Dpatmnt of Engy and Envionmnt (DOEE), as th National Flood Insuanc Pogam (NFIP) coodinato fo th Distict of Columbia, obtaind flood claim data as of Novmb 30, 2015 fom NFIP BuauNt. Individual infomation of policy holds has bn movd fom th NFIP flood claim data usd fo this pupos. Th NFIP flood claim data is a tabl of locations containing addsss that w all gocodd using DC GIS s MAR Gocod. Th data includ all NFIP flood insuanc claims in Washington, DC fom 1977 until Novmb 30, 2015. This datast only captus poptis that had an activ NFIP flood insuanc policy at th tim of flooding and mad a claim that was paid o unpaid. Washington Mtopolitan Aa Tansit Authoity (WMATA) WMATA data points psnt locations wh wat ntd WMATA facilitis. Each point psntd fiv to 10 flood incidnts at th sam location that a shown as on data point. To duc flood isk, th a a total of 18 Mtoail stations that a bing analyzd fo dsign solutions to duc o liminat flooding to th intio ail systm. Som of th stations a within th 100 and 500-ya flood plain. Oth stations a subjct to localizd flooding du to th suounding gads and an undsizd stom sw systm. 11 A vsion of this map was catd fo th 2016 Flood Summit on Sptmb 8, 2016. Pag 7 of 10
About th Mapping Pocss Data points fo all fou agncis w agggatd in 300 by 300 mt gid clls, so that xact locations of data points would not b shown fo scuity asons. Each cll was assignd a valu fom last flooding to most flooding basd on how many data points w in ach gid. Th pocss fo counting data points within ach gid is dscibd in th diagam blow. With th xcption of DC Wat s data, data points fom th agncis diffnt data sts w givn qual wight. Fo DC Wat data, th goup dcidd that only locations that civd th o mo calls would b shown as a data point. All fou of ths point datasts w mgd into on datast using ESRI s AcMap. That mgd datast was thn spatially joind to a 300 mt by 300 mt gid that covs th nti city, using AcMap. As pat of that pocss, all of th points that intsctd a gid cll w summd togth as a count and addd to th gid cll. Th gid clls w goupd into fiv diffnt data classs on th map using th Jnks Natual Baks, which is a mthod of data classification availabl in AcMap that is dsignd to minimiz th data vaianc within ach data class. Figu 3: How flood locations a summd in ach 300m x 300m gid. Nots Whn Using th Map Plas b caful whn using this map. Do not daw conclusions that a not suppotd by th data. Blow a a fw nots on th data which may b hlpful in undstanding th data s limitations. 1. Datasts usd in th map a at diffnt tim scals. Thy hav not bn standadizd; on data st may flct a majo flood vnt that occud bfo anoth datast bgan coding. Old data may not b as lvant as cnt data. 2. Datasts hav diffnt dfinitions of flooding, and data points fom ach datast psnt diffnt impacts of flooding. DC Wat data, fo xampl, psnt calls fo svic, whil NFIP data psnt flood insuanc claims. 3. Sinc DC Wat s data is divn by complaint calls, if th is an aa of th city that is lativly unpopulatd, it would stand to ason that th would b lss svic calls, vn though flooding may actually occu mo oftn. Pag 8 of 10
Nxt Stps and Rcommndations Th Intio Flooding Task Goup of th DC Silv Jackts dvlopd th following commndations on how to impov th accuacy of futu maps and btt undstand th intio flooding poblm. Th pimay commndation of this goup is to cat a citywid intgatd flood modl. Th modl will combin coastal, ivin, and intio flooding modls and incopoat comphnsiv data, including climat chang pojctions fo sa lvl is and pcipitations. Spcifically, this modl would includ locations and connctions of stom-sw inlts and pips, as wll as dtaild topogaphy data that allow accuat pdiction of wh intio flooding would occu givn a ctain amount of ainfall. This modl would not only allow fo idntification of flood-pon aas, but would also b usd to idntify th fficacy of poposd flood mitigation solutions. In liu of a city-wid intio flood modl, th Intio Flooding Task Goup commnds th following to impov upon th initial mapping ffot outlind in this pot. 1. Find additional xisting data soucs to includ on th map Distict of Columbia agncis, fdal agncis and oth ntitis may hav additional flood data that has not yt bn accssd. 2. Locat data on flood damags at locations of intio flooding to btt quantify consquncs. 3. Conduct small scal hydaulic modling studis on aas with suspctd intio flooding, as idntifid in this and futu maps. 4. Futh standadiz th data that is alady bing collctd by vaious agncis. 5. Dvlop impovd systms to collct intio flooding data so that a simila map catd 10 yas fom now would b mo accuat. This might involv a conctd agncy ffot to stat collcting nw data, such as adding a nw intio flooding catgoy fo complaint calls, o publishing pots on lvant data at gula monthly o quatly intvals. 6. Cat additional mapping ovlays (such as poposd dvlopmnt zons, citical infastuctu locations, o population dnsity). 7. Utiliz dpth-damag cuvs (an analysis that stimats damag to facilitis basd on th dpth of flood wat) to stimat impacts of flooding fom modld sults. Combining pobability with consquncs will giv btt pictu of intio flood isk. 8. Impov coodination amongst stakholds on data collction and shaing that will hlp nhanc intio flooding modling and mapping. Pag 9 of 10
Intio Flooding in Washington, DC ThDCS il v J ac k ts p oduc dthis mapf om anac c umul ationofdataf om f ousou c s: DCWat, thdist ic t D pa tm nt oft anspo tation( DDOT), thwashingtonm t opol itana at ansit Autho ity ( WMATA), andth National Fl oodi nsu anc P og am ( NFI P). Thmapd pic ts a as w h int iof l oodingoc c u s w ithin Washington, DC s bounda i s, anddo s not f nc th100y ao500y af l oodpl ains.this is not a gul ato y map.pl ass thassoc iat d po tf omo inf o mationonthdatasou c s andhow this mapw as c at d. Takoma Findship Hights Fot Tottn Tnlytown Van Nss Gogia Av Clvland Pak Ptwoth Bookland Woodly Pak Rhod Island Av Columbia Hights U St/Cadozo Shaw Dupont Cicl Mt Vnon Sq Faagut Noth Danwood NoMa Minnsota Av McPhson Sq Gally Pl Union Station Foggy Faagut Wst Mto Cnt Bottom Judiciay Sq Achivs Fdal Tiangl Capitol Eastn South Smithsonian Makt L'Enfant Fdal Plaza Cnt SW Watfont Stadium Amoy Bnning Road Potomac Av Navy Yad Anacostia Congss Hights ² WMATA, DDOT, NFIP and DC Wat Documntd Flood Locations Summd by a 300 Mt by 300 Mt Gid Mto Station Last Flooding Lss Flooding Flooding Mo Flooding Most Flooding 0 1 2 3 Mils Svic Lay Cdits: Soucs: Esi, HERE, DLom, USGS, Intmap, INCREMENT P, NRCan, Esi Japan, METI, Esi China (Hong Kong), Esi Koa, Esi (Thailand), MapmyIndia, NGCC, OpnSttMap contibutos, and th GIS Us Community