Linearized G102 Watershed Flood NOS Week PDF

1. R eading s M ustdo: V ideosin m odulesand som e sortof interaction ( w it h A I ortake not es) T hisreading on the Concord L absw e w illbe doing , uncert aint...

1. R eading s M ustdo: V ideosin m odulesand som e sortof interaction ( w it h A I ortake not es) T hisreading on the Concord L absw e w illbe doing , uncert aint y and risk S hould do: ions 153-. S ect (Erosion/weathering) , 1 1.5 Surface water from An Introduction to Geology N ice t o do: Sections 1. , 1.2, 1.5, and1.6 inAn Introduction toGeology FloodingandR ecurrence Intervals St ream G aug es A ct ivit ies: L ab: F lood R isks& Im pact sM odule from Concord Consort ium e: https:learn. W ebsit / concord.org/geo-flood Thisweek, you’ll dive intoanonline labontheConcord Consortium website: Flood Risks& Impacts. WithEarth’ sclimate changing,extreme weather events arebecoming morefrequent around theglobe.In someareas, this meansmoreintense rainanda higherriskof flooding—one of themostdangerous natural hazards humansface. In this module,you’ll workwith theFloodExplorermodelandstudy real-worldcasesto examinethefactors thataffectflood riskandimpact.You’ll explore scientific factorslike precipitation, topography , permeability , andthewatertable, aswellassocial factors, including population density andinfrastructure. Throughthese investigations, you’ll gain insight into how flooding varies onbothlocalandregional scales. Finally , you’ll look at theeffectof rising global temperatures onfuture floodrisks. By the endof thismodule,you’ll beable toanswertheguiding question: How will flood risks andimpacts changeover the next 10 years? D iscussion: Yourow n Illusion of E x planat ory D ept h E x perim ent In ourweeklydiscussion, you’ll doyourown Illusion of Explanatory DepthExperiment. How willyourfriends andfamilydo? In L ive Zoom Class In ourlive Zoom class, I w illint roduce m y self and y ou’llhave a few act ivit iest o g etto know y our classm ates. W e w illw orkon a m apping act ivit y thatinvit esy ou t o ex plore and ident ify t he w atershed y ou live in, asw ellasw hich nat ive tribestradit ionally lived and used t he land y ou now live on. O urindividualt askw illbe t o screenshota m ap show ing t he t ribesthatt radit ionally used t he land asw ellasident ify ing y ourw atershed ( and producing a screenshot ). V ideos Transcript : W eat hering , E rosion, and D eposit ion [P art1 ]- YouTube ht tps: / / w w w. y out ube. com / w at ch? v= ew j 6 2 9 B4 O e8 ht t ps: / / docs. g oog le. com / docum ent / d/ 1 W cO Zt Q rm G H k2 1 t u5 A y U T IR A K g bA 4 O 8 CiH BeCy TO S t 1 A / edit ? usp= sharing Transcript : ( 0 0 : 0 0 ) in t hisvideo w e' re g oing t ot alkaboutw eat hering erosion and deposit ion let ' sbeg in w it h som e sim ple definit ionsof t hese t hree term sso w eat hering in t hissense ist he breaking dow n and chang ing of rocksasa resultof ex posure t ot he environm entso if I have a larg e slab of g ranit e in nat ure and overhundredsand t housandsof y earst he w avesof t he ocean are crashing ont ot hatrockinevit ably t he rockisg oing t o breakdow n int o sm allerpiecesitm ig htg et rounded outit ' sessentially g oing t o chang e asa resultof ex posure t o it s ( 0 0 : 3 3 ) environm entand t hat' sjustone ex am ple of w hatw eat hering can be t here are lot sof differentt y pesand w e' re g onna lookatt hose in t hisvideo aft errocksare w eat hered t hey are oft en eroded and t hatprocesserosion ist he transport ation of the sedim ent st hathave been broken dow n by w eat hering so if y ou im ag ine little bitsof g ranite being pounded off of t hatslab because it ' sbeing hitby w ave aft erw ave and t hen being carried aw ay in t he ocean currentt oa differentlocat ion w ellthe actof carry ing t hose lit tle chunksof ( 0 1 : 0 8 ) g ranit et hose w eat hered sedim ent sfrom pointA t o pointB t hatiserosion erosion isall aboutm ovem entand t ransport ation the finalpartof t he processiscalled deposit ion so deposit ion ist he dropping off of t he sedim ent st hathave been w eat hered and eroded so t o cont inue m y ex am ple if t hose lit t le tiny bitsof g ranit e broken off and w eat hered by t he w aves and t hen eroded ort ransport ed by t he ocean current sevent ually g etdeposit ed on a coast line m any hundredsof m ilesaw ay t hatisdeposit ion t he dropping off and ( 0 1 : 4 3 ) so t o kind of sum m ariz e t hisand som e of t he ot herkey ideasw e' re g oing t o use t his surface processflow chartw hich isavailable on t he w ebsit e and w e' llbeg in by filling in t he t hree box eson t he t op t o kind of sum m ariz e t hese t hree m ain processesst arting w it h w eat hering w hich w e know isbreaking a partof rockand t hen erosion w hich ist he transport at ion of t he sedim ent sand finally deposit ion ort he dropping off of t hose sedim ent sso anot herw ay t ot hink aboutt hist hisisj ustkind of a quickanalog y t hat ( 0 2 : 1 4 ) and ithelpsm e rem em bert he differencesbet w een t hem ist hatw eat hering islike kind of like nat ure' sham m errig htit sm ot hernat ure' sw ay of t aking big bit sof rockand sm ashing t hem int o sm allerbit sorchang ing t hem int o som et hing new and t hen erosion in t hisex am ple w ould be som et hing like a dum p t ruckora pickup t ruckcarry ing allt he little bitsand piecesbroken apartby w eat hering from one locat ion t o anot herand t hen deposit ion ist hatdum p t ruckkind of opening it st ailg at e and dum ping every t hing outint o a big pile on t he ( 0 2 : 4 5 ) g round - t hat ' sdeposit ion so t hat ' sjustkind of a helpfullit tle w ay t o rem em bert he difference isbet w een t hese t hree part sof t hislarg erw eat hering erosion deposit ion processnow fort he restof t hisvideo w e' re really g oing t o focuson w eat hering specifically and w e' re g oing t o st artby looking att he t w o m ain t y pesof w eat hering and t he firstex am ple w e' re g onna lookatis called phy sicalw eat hering now I j ustw antt o pointoutt hatphy sicalw eat hering isalso oft en know n asm echanicalw eat hering okay so phy sical ( 0 3 : 1 7 ) and m echanicalare t he sam e t hing and t hisw ould be t he breakdow n of rocksint o sedim ent sand t he key ist hatit ' sw it houtchang ing t heircom posit ion so t hisislit erally chang ing siz e and shape of Iraq so t he w avescrashing ag ainsta boulderand breaking itint o sm all pebblest hatm ig htbe rounded outt hat ' sphy sicalorm echanicalw eat hering butit ' sst illg rant ed it ' snotchang ing t he rockorw hatit ' sm ade of butt hatdoesalso happen in nat ure and w e have a differentnam e fort hatt hat' scalled chem icalw eat hering and so t hisisw hen (0 3 :4 8 ) t he rocksare chang ed chem ically because of som e react ion w it h usually som et hing like w hen airorw at erin nat ure so t he alt ering of rocksasa resultof ex posure t o different subst ancesso let ' sadd t hisinform at ion t o ourflow chartso w e' re breaking dow n w eat hering int ot w o sm allert y pest he firstisphy sicalorm echanicalw eat hering w hich isbreaking cracking and g rinding t hing slike t hatand w e' llsee ex am plesof t hose short ly and t hen chem ical w eat hering w hich involve som e sortof react ion thatchang escom posit ion so (0 4 :2 4 ) t hat ' sa really key difference bet w een t he two t y pesof w hatso let ' sdive a lit tle deeper int o ourphy sicalorm echanicalw eat hering and lookatsom e differentex am plesforour purposesw e' re g onna breakt hisint o fourspecific t y pesfrostact ion ex foliat ion abrasion and rootw edg ing so w e w illst artw it h frostact ion w hich by t he w ay isalso know n asice w edg ing t here are a lotof differentnam esforitand asy ou m ig htim ag ine t hisinvolvesice and so w hat happensist ake an area t hatm ay be it ' sa lit tle bit ( 0 5 : 0 0 ) above freez ing t em perat ure during t he day and y ou g etsom e rain orm ay be som e m elt ing snow and y ou have som e w at ert hatseepsint ot he cracksw it hin a rockrig htand t hen t he S un set sand inevit ably the t em perat ure dropsand t hatw at erfreez esint o solid ice now y ou m ay know already w hen w at erfreez esitex pandsslig ht ly and itg et sa lit t le bitbig g erand so as itex pandsit ' sg oing t o be pushing out w ardson t he rockt hatithasseeped int o and t hatforce believe itornotisact ually strong enoug h t o very slow ly and g radually ( 0 5 : 3 6 ) breakapartrocksand t hisprocessisknow n asfrostact ion orice sw eat ing and so w e see ex am plesof t hisin allsort sof areasw here t he t em perat ure isa lit tle bitabove freez ing during t he day and t hen below freez ing atnig htand in facta g ood ex am ple of t hisisw hatw e calla pot hole w hich y ou see allovert he st reet spart icularly in t he nort heast ern U nit ed S tat esin t he spring t im e w hen y ou have t hese big fluct uat ionsin t em perat ure t he w at eract ually g etsint o cracksin t he road and t hen freez esand ex pands ( 0 6 : 0 8 ) and t hen y ou drive overitt he nex tday and itj ustbreaksapartand y ou end up w it h t hese big nast y holesin t he g round t hat' sa g ood ex am ple of frostact ion orice sw eat ing second w ould be ex foliat ion and t hisisin a w ay kind of sim ilart hisinvolvest em perat ure chang esas w ellso t hisoccursin areasw here y ou have really dram at ic tem perat ure chang esw here itg et s very hotduring t he day and t hen very cold atnig htt he the rockit self w illact ually ex pand slig ht ly in t he heatand t hen cont ractin t he cold ( 0 6 : 3 9 ) and if t hishappensday aft erday nig htaft ernig htitw eakenst he out erlay ersof t he rock unt ilt hey event ually beg in t o crackand peelapartlike t hisorlike t hisrig hthere it ' salm ostlike t he rockisshedding it sout erlay ersand phy sically orm echanically breaking apartlarg ely asa resultof t hese t em perat ure chang esa t hird ex am ple w hich ist he m ostcom m on and w e see it allovert he w orld iscalled abrasion so abrasion isbasically w heneverR ockg rindsag ainstot her rockand itcom esin m any form slike here in t he desertw e ( 0 7 : 1 3 ) see a lotof w ind abrasion w here g ust sof w ind w illblow g rainsof sand t hatcrash int o ot herrockand very very slow ly overt housandsand t housandsof y earsw illact ually eataw ay at t he rockand so w ind w ind abrasion isact ually responsible fora lotof t he interest ing kind of rock form at ionst hatw e see in t he A m erican S out hw estw e also can have w at erorst ream abrasion aslit tle pebblesand sedim ent sare bounced along t he bot tom of a st ream ast he w at erflow s and t hat ' sg oing t o eataw ay att he rockt hatt hey ' re bouncing overw e ( 0 7 : 4 4 ) also see t hison coast linesasI m ent ioned before w it h w avescrashing int o rockand g rinding itdow n by carry ing lit t le bitsof sand and sedim entand eat ing aw ay att he rockand t hen finally w it h g laciersg lacialabrasion isvery com m on g laciersg lide dow nhillpulled by g ravit y and t hey scrape along t he rockand carve itaw ay overm any hundredsof y earsfinally t he last t y pe of phy sicalorm echanicalw eat hering w e' re g onna lookatiscalled rootw edg ing and it 's pret t y self- ex planat ory thisisw hen plantroot sact ually g row w it hin the ( 0 8 : 1 8 ) cracksof rockand ast he plant sg row larg erand larg ert hey breakapartt he rockast hey g row int o itso w e see ex am plesof t hisallovert he w orld and it ' sam az ing how pow erfult ree root sand plantroot scan act ually be so m uch so t hatt hey w illphy sically breakapartrocksas t he plant sg row so t hose are fourm ain ex am plesof phy sicalw eat hering and w e w antt o add t hem t o ourflow charthere so underourphy sicalw eat hering area w e' re g onna add frostact ion w hich isfreez ing and t haw ing of ice isg oing t o crackapartrocks ( 0 8 : 5 1 ) w e have ex foliat ion w hich ist he alt ernat ing hotand cold old isg oing t o crackrocksw e have abrasion w hich isg rinding of one rockag ainstanot herorsand ag ainstrockand t hen finally rootw edg ing w hich w ould be ourplantroot sg row ing int ot he rocksand so t hose are four m ain t y pesof phy sicalw eat hering now let ' sshiftg earsand lookatt he second t y pe of w eat hering chem icalw eat hering so rem em bert hisist he alt ering ort he chang ing of rockasa resultof ex posure t o differentsubst ancesand w e' re g oing (0 9 :2 2 ) t o lookatt w o m ain ex am plesof t hisox idat ion and carbonat ion w e' llbeg in w it h ox idat ion w hich isa t erm y ou m ay have heard before it ' st he form at ion of rustand t hisisg oing t o occur w henevert he elem entiron isex posed t o ox y g en and t hatcan happen in t he airorin t he w at er and so w hatw e find are t hatt here are a lotof rocksaround t he w orld t hatcont ain larg e am ount s of iron and ast hatiron react sw itht he ox y g en in airorw at erit ' sg oing to phy sically rustand t he resultist hatw e see rockst hat ( 0 9 : 5 4 ) looklike t hey ' ve been rust ed t hey have t hisorang e e colort ot hem and t hatisact ually a form of chem icalw eat hering t hisrockisbreaking dow n t he rustisvery crum bly t hisiron ox ide t hatform sand itbreaksapartt he rockovert im e it ' san act ualchem icalreact ion w it h ox y g en in t he airort he w at erand t hen finally w e have carbonat ion carbonat ion isreally int erest ing t hisis responsible fort he form at ion of t hese fascinat ing beaut ifullim est one cavest hatw e see around t he w orld and it ' sbasically w hen w at erflow st hroug h t he ( 1 0 : 2 8 ) g round itreact sw it ht he differentm at erialsin t he soilt o creat e a very m ild acid t his carbonic acid and carbonic acid isst rong enoug h t hatif itencount erscert ain m ineralsorrocks like calcit e orlim est one itw illeataw ay ordissolve t hatlim est one and so w hatw e end up g et t ing are t hese underg round cavernsw here t here once w asa w hole larg e ex panse of lim est one but t hathasallbeen kind of eat en aw ay slow ly by t he dissolving of t hiscarbonic acid so w e see som e of t hese am az ing am az ing landscapesaround t he ( 1 1 : 0 3 ) w orld form ed asa resultof t hist y pe of chem icalw eat hering anot hert hing t hathappens w it ht hiscarbonat ion ist hatsom et im est he g round w illact ually g ive w ay because allt he rock beneat h ithasbeen eat en aw ay and t hat ' sw hen w e g etsom et hing like t hisw hich iscalled a sinkhole w hich isw hen t he rockisg one beneat h and t he g round collapsesabove and so t hose are t wo t y pesof chem icalw eat hering and ag ain w e' llsum m ariz e t hem on ourflow chartso t he firstt y pe w asox idat ion iron and ox y g en g ivesy ou iron ox ide orrustand (1 1 :3 5 ) t hen carbonat ion w hich isw hen w e have t hisacidic rain and acidic w at erdissolving lim est one and g iving uscavesokay now t here are t w o m ain t y pesof w eat hering w it h som e ex am plesof each w e have t hem nicely sum m ariz ed on ourflow chartand t he lastquest ion w e w antt o askhere isso w hat ' sg oing t o affectw eat hering like w hatdict atest he t y pe of w eat hering w e have in a reg ion how fastitw illhappen et c and so w e have t hree m ain t hing st hatw e' re g onna lookatand t he firstisclim at et he second w ould be hardnesshow hard ist he rock ( 1 2 : 1 0 ) orhow resist antisitbeing w eat hered and t hen t he t hird w ould be t he surface area of t he rockhow m uch of t he rockisex posed t ot he elem ent sallrig htso let ' sst artw it h clim at e and t o underst and t hisw e lookatt hischartt hisisa very com m only used chartin g eolog y and so w hatt hisshow sist he effectof t he t em perat ure and m oist ure on w hatt y pe of w eat hering w ill t ake place so forex am ple in an area t hatism ore hotso t hispartof ourg raph rig hthere w hich is a hig hert em perat ure okay butnota lotof m oist ure because ( 1 2 : 4 7 ) rem em berif w e g o up on t he chartt hat ' sa w et terarea so t hisisan area rig hthere t hat 's hotand dry hotand dry w e don' treally see a lotof w eat hering w e m ig htg etsom e w ind abrasion like in t he desertbutnot hing t oo severe if w e t hen sw it ch up t o an area t hatishig heron t he chartt hatishot terand w et t ert hat' sw here w e' re g onna st artt o see m ore of t hischem ical w eat hering t hiscarbonat ion occursa lotand a lotfast erin areast hatare hotand w etw e see a lotof lim est one cavesand sinkholesin a place like F lorida for ( 1 3 : 1 9 ) ex am ple w here it ' svery w arm and on t he ot herhand if w e g o t ot he leftside w here it 's colderlow ert em perat urest hisisw here w e' re g onna st artt o see frostact ion happening because thisisw here w e have a lotof chang e in t em perat ure it ' scoldercold enoug h t o g etice and enoug h w at ert o have t he ice form ing and m elt ing and form ing and m elt ing day aft erday any t hing up in t hist op area up here t hese are clim at e condit ionst hatw e don' treally see on eart h so t hey ' re notreally relevantt o w hatw e' re t alking ( 1 3 : 5 1 ) aboutany w ay t hist hisg raphic g ivesy ou a really g ood sense of t he im pactt hatclim at e hason t he t y pe and t he severit y of w eathering t hathappensin a part iculararea in addit ion t o clim at e w e also have t o lookathardnessso of course w e know t hatallrocksare differentall m ineralsare differentsom e are very hard som e are very softand t hat' sg oing t o have an im pact on how quickly t hey ' re g oing t o w eatherso if w e lookata diag ram like t hisw hich show sa cross- sect ion of a w at erfallw hatw e' llnot ice ist hatsom e of t he ( 1 4 : 2 2 ) rocklay erslike rig htin here rig htin here rig hthere have been w orn aw ay m ore t han ot herrocklay erslike t hisone isnotw orn aw ay asm uch t hese onesdow n here t hisa lit tle bit rig hthere isnotreally w orn aw ay and t hatt ellsm e t hatt hese are differentt y pesof rockand so I can conclude t hatt hislay erof rockrig hthere w hich believe islike a shale isa soft erR ockso w hen allof t hisw at ersplashesup on itit ' sg onna st artto w earaw ay fast ert hen a harderR ock like say a sandst one so t he hardnessof (1 4 :5 7 ) t he R ockhasa big im pacton how quickly it ' sg oing t o be w eat hered and so finally t he lastt hing w e w antt o lookatissurface area so surface area referst o how m uch of t he rockis act ually ex posed so if I have t w o rockslike y ou see here t hey ' re g oing t o be ex posed t ot he elem ent sata differentclip rig htso t he only partof t hisrockforex am ple t hat ' sg oing to be ex posed ist he out side of t he rockso t he surface ist hatI' m hig hlig ht ing rig hthere t hat' st he only partt hatcan g ethitby rain and ice and snow and ox y g en ( 1 5 : 2 9 ) et ct hat ' sthe only partt hatcan be w eat hered t he cent erof t hisrockisnotex posed it s prot ect ed and t herefore it ' snotg oing t o be w eat hered w hereasin t he rig hthand side I have t he out sidesof t hese rocksbutI also have t hese inside areasrig htbecause t he rockisbroken dow n w e have ex posed addit ionalsurfacest hatcan be hitby rain snow and ice and ox y g en and ot her chem icalreact ionsand so because t hishasm ore surface area t he purple it ' sg oing t o break dow n ata fast errat e okay so w e can sum m ariz e (1 6 :0 6 ) t hese t hree t hing sin ourlarg e box att he bot tom of t he flow chartw e can sum m ariz e t he fact orst hatare g oing t o affectw eat hering okay so w eat hering ism ostaffect ed by t hese t hing s t he clim at et he hardnessof t he rockand t he am ountof ex posed surface area t hat ' sw hat ' sreally g oing t o dict ate how quickly a rockisg oing t o breakapartso in t hisvideo w e t ooka lookatt he differentt y pesof w eat hering along w it h som e basic definit ionsof w eat hering erosion and deposit ion and t hen finally atw hateffect sw eat hering short ly I' m ( 1 6 : 3 8 ) g oing t o release anot hervideo t hat ' sg oing t o g o int o det ailsaboutt he processesof erosion t ransport ation and deposit ion are dropping off of sedim ent sso keep y ourey e outfor those t hanksforw at ching R iverE rosion and D eposit ion - YouTube ht tps: / / w w w. y out ube. com / w at ch? v= 3 Y dE keg vJ CQ https: / / docs. g oog le. com / docum ent / d/ 1 5 vr_CD D R O g P c- l5 s9 N hT H Q g ZbO fH t h5 ux 6 ct nM R t g x E / ed it ? usp= sharing Transcript : ( 0 0 : 0 0 ) in t hisvideo w e' re g onna cont inue ourlookatw eat hering in t hisvideo w e' re g onna cont inue ourlookatw eat hering erosion and deposit ion pay ing part icularat t ent ion t o riversand how t hey erode and depositsedim entacrosst he eart h asalw ay sw e have a quickhandoutt o g o along w it hthisvideo w hich y ou can g o and g rab att he w ebsit e so let ' sbeg in by review ing t hese key t erm sso w eat hering ist he breaking dow n and chang ing of rocksasa resultof ex posure t ot he environm entso w hen rockand nat ure isex posed t ot he airand ( 0 0 : 3 7 ) w ind in w at erand ice t hose forcesw illevent ually breakrocksdow n from larg erpieces int o sm allerpiecesknow n assedim ent sin som e casest hose rocksm ig htact ually chang e com posit ion asa resultof t hese w eat hering int eract ionst hen w e have erosion erosion is t ransport at ion so once m y sedim ent shave been broken dow n by w eat hering erosion isg onna m ove t hem from pointA t o pointB so t hinkaboutt o g ive y ou an ex am ple from t oday ' slesson sedim ent sbeing t ransport ed by t he m ovem entof w at erw it hin a rivert hat ' serosion finally at ( 0 1 : 1 4 ) som e pointdeposit ion isg onna occurand t hisist he dropping off of sedim ent st hathave already been w eat hered and eroded so once t hey ' ve been broken dow n once t hey ' ve been m oved t hen t hey g etdum ped som ew here and t hatprocessisknow n asdeposit ion so ag ain t oday w e' re g onna focuson one part icularag entof erosion and t hat ' sriversorflow ing w at eron t he surface of t he eart ht hese have a hug e im pacton shaping ourplanetand so w e' re g onna lookatallt he det ailsaboutw hatt hey do t ot he surface and how t hey affectt he rock (0 1 :4 4 ) t hatt hey flow overso w e' llbeg in w it h a sim ple quest ion w hich isw hatisa riverso if w e had t o act ually define t hist erm it ' spret ty sim ple it' ssim ply w at erflow ing dow nhillt hroug h a channelorsom e sortof defined pat hw ay by t he w ay y ou' llsee I used t he w ord st ream in creeks and Brookw e can use t hese essent ially int erchang eably oft ent im escreeksand brookand st ream ' are used forsm allerriversw hereast he t erm riversused fora larg ervolum e of w at erbut forallpurposest hose can be sy nony m sso let 's ( 0 2 : 2 0 ) lookatt he anat om y of a riverororw hatsom e of t he part sof riversare and w e' llbeg in w it ht hislittle diag ram rig hthere of lit tle sect ion of a st ream ora riverand t he firstt hing and t his isg oing t o becom e very im port antisisw hen w e see t hese curvesorbendsin riversand w e have a nam e fort hatt hose are called m eandersand t hat ' svery im port antbecause ata m eanderw e see a lotof erosion and deposit ion happening in specific w ay sw hich w e w illlookat along t he edg esof t heirst ream ort he riverw e callt hose t he banksso t he ( 0 2 : 5 3 ) st ream banksare t he riverbanksand t hen along t he bot tom w e callt hatt he bed so t he st ream bed ort he riverbed so w hen w e have a sm allerst ream t hatflow sint o and m erg esw it ha larg erst ream w e callt hata t ribut ary and allt og etherw it h allt he t ribut ariesand a m ain riverw e have a riversy st em oft ent im esa riversy st em ispartof w hat ' scalled a w at ershed and so a w at ershed isan ent ire reg ion of land itm ay be hundredsand hundredsof m ilesbutit ' san entire reg ion of land w here allof t he t ribut ariest he st ream sand (0 3 :2 8 ) t he riversand allt he g roundw at erin t hatreg ion m erg ed t og et herand flow int o one cent ralw at erbody w het herit ' sa riverlake ort he ocean so t hatw hole area of land iscalled a w at ershed ora drainag e basin so let ' st alkaboutt he speed atw hich a riverflow sorvelocit y of a riverso t he velocit y of a rivert endst o depend on t hree m ain t hing st he firstbeing t he am ountof w at erw it hin t he st ream and t hat ' scalled discharg e so t y pically speaking t he m ore discharg e t he m ore volum e of w at erw it hin a st ream ( 0 4 : 0 6 ) orrivert he fast ert hatst ream orriverisg oing t o flow nex tisslope so ist hisa st eep st ream bed ora fairly flatone so log ic t ellsust hata st eeperslope isg oing t o m ake t he river flow and a fast ervelocit y and t hat ' sbecause g ravit y isg oing t o pullt hatw at erhellfast erfinally t he shape of t he st ream channelact ually play sa pret ty m aj orim pactso if y ou t hinkaboutt wo st ream sso t othinkabouta narrow kind of v- shaped st ream channelw hich isy ou know pret ty st eep m ay be a lotof w at erbutbutt he channelit self ispret ty ( 0 4 : 4 6 ) narrow and v- shaped oralm osteven like a u- shape w ellt hatw at er' sg oing t o be able t o flow fast ert hen a st ream t hat ' sg onna have a very w ide and flatbot tom t o bed and t he reason t hatisisbecause t he m ore area w here t he w at erisflow ing overt he rocky st ream bed t he slow erit ' sg oing t o g o because of allof t hatsurface area so t hatw at erhast o flow overallof t hose rocksand in and alloutof allt hose nooksand cranniesasopposed t o if w e have a V shape t hatw at erisg oing t o have lessfrict ion w it ht he g round t hen it ' sg oing t o be ( 0 5 : 2 0 ) able t o g o fast erso t y pically a rounderdeepera m ore curved orv- shaped channelt he fast ert he st ream w illflow versusa w ide flatchannelso if w e lookata riverchannelw hich oft en doeshave t hiskind of V shape w it hin the riverit self t he fast estvelocit y isg oing t o be w here w e see t hisX rig hthere so notalong t he bedsw here t he w at eriskind of g rinding ag ainstt he g round butup aw ay from t he bedsg enerally in t he m iddle of t he st ream t hisdoeschang e if w e' re g oing around a m eanderin a st ream a st raig htflow ing st ream w illt end t o ( 0 5 : 5 6 ) see itw here t hisX isso fast estin t he cent erup aw ay from t he st ream bed so now let 's t alkaboutt he ag e of a riverand y esriversdo have ag esy ou can t ellby looking ata river w het herit ' sa y oung new ly form ed riverora m ore ancientriverand so w e' llst artw it h looking at t he charact eristicsof a y oung riversy st em and so t hese are g oing t o be g enerally speaking kind of m ore int ense so t hey ' re g oing t o be st eepert hey ' re g onna have deeperm ore narrow channelsw it h a fast erflow of w at ert hey ' re g onna have few ercurvesor ( 0 6 : 2 8 ) m eandersand asa resultof allt hatt hey ' re g oing t o g o fasterand t hatm eansm ore sedim entisg oing t o be eroded and lessw illbe deposit ed so allt he rocksand t he sand and t he siltand clay are g oing t o be rig htaw ay notbeing dropped off and t hat ' sdue t o allof t hese charact erist icst og et herso if y ou see a riverlike t he one in t hispict ure rig hthere y ou can conclude t hatt hisisa fairly new ly form ed R ivert hishasnotbeen around fort housandsand t housandsof y earson t he ot herhand an olderR iverisg oing t o be ex act ly the ( 0 6 : 5 9 ) opposit e it' sg onna have a g radualslope so m ore flatasfarast he bed g oesshallow w ide channelsw hich allresultin a slow erflow velocit y w illoft en see t hese big w ide curving m eandersand t he resultist hatw e had a lotof deposit ion so sedim entisconst ant ly being dropped off and y ou can act ually see t hatin t hisex am ple rig hthere w it h allof t hese sandbars w it hin t he t he riverflow t hat ' salldeposit ed sedim entbecause t he w at erisconst ant ly slow ing dow n and dropping off w hat everit ' scarry ing so now w e' ve t alked a lit t le ( 0 7 : 3 6 ) bitaboutvelocit y it' sim port antt o pointsom et hing outt houg h itispret t y log icaland t hat ist he fast erriverisflow ing t he big g ert he sedim ent st hatitcan erode ort ransportw hich m akes sense if I have a very fastflow ing riverit ' sg oing t o be capable of t ransport ing long larg ersiz ed sedim ent sso sand and siltand clay butalso in som e casesitcan even bounce along pebbles and in t he fast estriverspossibly even cobble siz ed rockst hisisvery log icalit ' sallsum m ariz ed in t hischartrig hthere so if w e lookatt hisw hatw e see along (0 8 :1 0 ) t he bot tom here ist he velocit y of t he st ream so asI g o from leftt o rig htt he st ream is g oing fast erand t hen on t he vert icalax isI see siz e of sedim entbeing t ransport ed so w hatI' ll not ice here ist hatlet ' ssay I have a velocit y of a st ream t hatisaboutone cent im et erpersecond so if I com e up and I hitt he curve here and I g o overt he sedim entt hatst ream isg oing t o be able t ot ransportisg oing t o be classified assand rig htso it ' sg oing t o be som ew here bet w een pointz ero z ero six and pointt w o cent im et ersin ( 0 8 : 4 5 ) siz e so t hat ' sfairly sm allsedim entt hat ' sw hata riverg oing t hatfastisable t ot ransport butif I speed up t o let ' ssay 5 0 cent im et erpersecond riverso a m uch fast erflow ing rivert hat 's g oing t o be able t o carry pebblesand t hatislog icalrig htbecause t he fast ert he riverisflow ing t he big g ert he sedim ent sitcan carry only t he fast estriverson eart h are able t o carry big sedim ent sso if I looky ou know m ay be ata hundred ora lit tle m ore t han a hundred cent im eters persecond t hatkind of riverisable t o act ually t ransport ( 0 9 : 2 4 ) rockst hatare six seven eig htcent im etersin diam et erso t hose w ould be classified as cobblesso t hischartshow sust hatt he fast ert he st ream velocit y the larg ert he sedim ent sitcan carry so if w e lookatt hose sedim ent st hisisw hatt hey w ould looklike ast hey ' re being eroded w it hin a riverso obviously t he sm allersedim ent sare g oing t o be suspended so t he siltand t he clay t hat ' sg oing t o be carried along up in t he body of t he w at eritself and t hat ' sg oing t o be subj ectt othe current sand t he velocit y of t he flow ( 0 9 : 5 7 ) sand m ig htbe hopping orbouncing along t he bot tom and t hen t he big g ersedim ent st hat g ravelt he pebblesand possibly cobblesare g onna slide and rolland bounce along t he st ream bed so t hisisw hatitlookslike and y ou can see m assive am ount sof sedim entare eroded by riversespecially fastflow ing y oung erriversso w hen st ream sflow fastt hey ' re g oing t otend t o erode sedim ent st o pickitup and carry itaw ay and w hen t hey flow slow ly t hey ' re g onna deposit itt hey ' re g oing t o drop itoff so t he log icalquest ion becom esokay w ellw hy ( 1 0 : 3 5 ) do st ream sspeed up w hy doesst ream slow dow n because if y ou can ident ify thatt hen y ou can predictw here m ore erosion w illhappen and w e' re m ore deposit ion w illhappen so if w e lookatourm eanderag ain w hatw e' re g onna know ist haton t he inside partof curvesw at eris g oing t o be forced t o slow dow n and t he reason t hatisisbecause w hen w at erist raveling around a sharp curve like t hison t he inside partitcan' tg o asfastit ' sa sharpert urn and phy sics t ellsust hatt hatw at erg onna be forced t o slow dow n asopposed ( 1 1 : 1 0 ) on t he out side of a curve it ' sg ott hisbig sw eeping area t o g o and it ' slesssharp and t herefore itcan g o fast erI oft en thinkof t hist he sam e w ay I t hinkof a racecarg oing around a curve on a racet racky ou have a choice w hen y ou approach t he curve do y ou slow dow n and hug t he inside of t he curve y ou have t o slow dow n orelse y ou' llflip ordo y ou keep y ourspeed and g o on t he out side of t he curve w here y ou can keep y ourspeed up a lit t le bithig herw ellit 's t he sam e in t he riveron t he inside of a curve t he w at erslow sand on t he out side ( 1 1 : 4 1 ) of t he curve t he w at erspeedsup and so of course t here' sa consequence of t hatand t hatist haton t he inside w here itslow sdow n t he depositsedim entt hatt hey ' re carry ing and y ou can act ually see t hisin t he pict ure by looking att hisw hole area rig hthere allof t hissand and sedim entt hatw asdeposit ed t here because t he riverslow ed dow n and w hen t he riverslow s dow n itdropsoff w hat everit ' scarry ing w hereason t he out side w here itspeedsup it sg oing t o erode addit ionalsedim entand y ou can t ellbecause allt he sedim enthasbeen ( 1 2 : 1 1 ) w orn aw ay and y ou can see t hatw it ht hisst eep riverbankso y ou can t elljustby looking ata m eanderw here t he erosion and w here t he deposit ion hast aken place sim ilarly w e have anot herdiag ram here show ing m eanderson t hisex am ple one of t he t hing st o pointoutist hat depending on t he direct ion of t he m eandert he shape of t he channelisact ually g oing t o vary so if I lookatt hislet ' slookatP ointa here and pointB here so a ist he out side of a curve so t hat's erosion and B ist he inside of t he curve so t hat ' sdeposit ion ( 1 2 : 4 5 ) so w here t here z ero j ' en the rockand t he sedim ent sbeing w orn aw ay so w e' re g onna have a st eep m ore j ag g ed kind of slope so t hatm eanst hatt hatw ould looksom et hing like t his so t hisw ould be pointa here and t hen w here B ist hat ' sw here t he stuff isbeing dropped off so w e w ould have a m ore w ide flatdeposit ion driven area of t he riverso a and B m at ch up like t hat and w e should be able t o do t hatif I lookdow n here atC and D so C ison t he inside of t his m eanderso C isg oing t o have t he flatslope and D ison t he out side w here it 's ( 1 3 : 2 0 ) g oing fast estw here w e see erosion so t hat ' sg oing t o be t he st eeperslope so let ' slook atsom e real- w orld ex am pleshere so here' sa m eanderand a riverand j ustby looking t hisrig ht off t he batw e can t ellw here t here' sdeposit ion and w here t here' serosion so w e should be able t o labelitw it ht hese t erm srig htso inside of a curve isslow out side of a curve isfastso t hose w ordsg o t here inside of a curve w here itslow sdow n w e' re g oing t o g etdeposit ion and y ou can act ually see t he sedim entdeposit ed and t he out side isg oing t o be erosion ( 1 3 : 5 4 ) so y ou can see pret ty clearly w hat ' sg oing on let ' slookatanot herex am ple t hisis anot herg reatex am ple so I' m g oing t o bring m y t erm sin so inside isslow out side isfastokay inside isdeposit ion out side iserosion and ag ain y ou can act ually see itif y ou lookatt he diag ram here t hisst eep slope rig hthere it ' sallst eep slope t hat ' sbecause allof t hatsedim entis being carried aw ay asopposed t ot hisw hole reg ion rig hthere w here allt hissand and sedim ent ist hat ' sy ourdeposit ion because t he w at erhasslow ed dow n so w e ( 1 4 : 3 1 ) see t hisallovert he place and itbecom esvery very clearw hen w e see st uff like t his sedim entrig hthere t hisist he inside of a curve and t hat ' st here because t he w at erhasslow ed and deposit ed w hatitw ascarry ing and y ou can see t hism ostriverson eart h itbecom esvery obviousw hat ' shappening here t hisisa g reatex am ple because y ou can act ually see w it hin t he w at ert hatallof t hissedim enty ou see how t hisw at eriscloudy t he sedim entison t he inside of t he curve because t hat ' sw here t he deposit ion ist aking place so if (1 5 :0 4 ) t haterosion and deposit ion cont inueslong enoug h t hen t hose m eandersm ig htg etso w ide t hatitact ually alt erst he shape of t he riverand itm ay even cutoff a port ion of t he rivert o form som et hing called an ox bow lake so overhere t hisisourox bow lake okay so t hatused t o be partof t he riverbutdue t o ex t ensive erosion and deposit ion t hatpartof t he riveract ually g ot cutoff and t hatshape of t he channelhaschang ed leaving t hatlake behind w it ht hist ellt ale kind of horse t o shape so if y ou lookatt hist hisis ( 1 5 : 3 7 ) how t hathappenst he erosion and deposit ion cont inue t he m eandersg etw iderand w iderunt ilthe riveract ually m eet sit self in a locat ion and t hen deposit ion takesoverand cut soff t hatm eandercreat ing an ox bow lake so here' san ex am ple of an ox bow lake t here are act ually severalin t hispict ure and here' ssom e m ore y ou can see t hem overhere' san ox bow lake here' san ox bow lake here isan ox bow lake so t hose w ere allact ually partof t he m eandersat som e pointin overt im e t hey ' ve been cutoff so let ' sfinally shiftourat tention t o ( 1 6 : 1 2 ) focusspecifically on t he deposit ion t hatoccursw it hin a riverso st ream sslow dow n not only w hen t hey ' re on t he inside of a curve butalso w hen t hey ent era larg erbody of w at erlike forex am ple if a riverorst ream flow sint o a lake a larg erR iverororeven in som e casest he ocean t hatw at er' sg onna slow dow n and w e know from ourpreviousconversat ion here t hat w hen w at erslow sdow n itcan' tcarry asm uch so itdeposit sitso w heneverw at erslow sdow n deposit ion occursso here w e have a cross- sect ion of a riverflow ing dow n (1 6 :4 5 ) t he side of a hillslope rig htfastfastfastfastfastbutt hen ithit st he lake and itslow s dow n and because itslow sdow n rig htt here can' tcarry t he sedim entany m ore so rig htin here w e' re g onna see lot sof deposit ion I like t ot hinkaboutt hist he sam e w ay asI t hinkabouta w at erslide so if y ou' ve everbeen on a w at erslide y ou know t hatasy ou' re g oing dow n t he slide y ou' re g oing fast erfast erfast erand t hen allof a sudden y ou hitt he poolatt he end and y our body st opsessent ially and t hat ' sbecause y ou' ve ent ered t hislarg erbody ( 1 7 : 1 6 ) of w at erand t he velocit y slow sdow n and t he sam e t hing happensin a riverand w hen t hatoccurst he sedim entt hatt he riveriscarry ing isdropped off and so t he sedim entt hatis deposit ed creat est hiskind of w eird accum ulat ion of sand and siltand clay and t hat accum ulat ion iscalled t he D elt a in som e casest hatD elt a can becom e a new landm assso here' san ex am ple of a delt a so allof t hiskind of g ray ish m uddy sedim enthasbeen deposit ed ast hislit t le stream ent erst hislarg erbody of w at erallof t hese D elt a' s ( 1 7 : 4 9 ) can act ually t hey ' re m assive y ou can see t hem from space on t he A m az on R iverD elt a it ' shug e am ount sof sedim entt hathave been deposit ed overt im e so t he sedim ent st hatare deposit ed w ithin a D elt a are g enerally sort ed outby siz e w it ht he larg estonesdropped off first and t hen sm allerand sm allersedim ent sasy ou g etfurt herand furt heroutint ot he lake ort he ocean so here' sa diag ram t hatkind of show st hatbecause w hen t he st ream ent erst he body of w at eritslow soff itslow sdow n it ' sg onna drop t he big g erst uff firstand t hen as ( 1 8 : 2 8 ) itslow sm ore sm allerst uff and t hen asitslow sm ore sm allerst uff and t hen event ually sm allerand sm allerunt ilithasdeposit ed every t hing t hatit ' scarry ing so t hatsedim entt hat sort ing iscalled horiz ont alsort ing because t he siz e of the sedim ent sissort ed outfrom big t o sm allfrom side t o side okay som et im est houg h w e' llhave sedim ent st hatdeposit ed very quickly and t hatm ig htresultnotin horiz ont alsort ing butin vert icalsort ing so rapid deposit ion y ou know forex am ple if I have a rockslide on a cliff w here a ( 1 9 : 0 6 ) bunch of sedim entisdum ped int o a lake allatonce t hen m y big g estsedim entisg oing t o accum ulat e on t he bot t om and t he sm allerst uff isg onna set tle a lit tle bitslow erand end up being on t op and so w e end up w it ht hisvert icalsort ing and w e have a nam e forvert icalsort ing it ' scalled g raded bedding so t hat ' sw hen w e have t op t o bot t om sm allt o larg e and t hisisn' tw hat t hatact ually lookslike y ou can see on t he bot t om ourlarg ersiz e sedim ent sand asy ou g o up t hey ' re sm allerand t hatw ould g ive usg reet ed bedding so horiz ont al ( 1 9 : 3 8 ) sort ing occursw hen t he sedim enthappensg radually w hereasvert icalsort ing happens w hen itoccursquickly t hat ' skey now finalt hing isbecause of t hisabrasion so t hisisa w ord w e' ve used in ot hervideosabrasion isa t y pe of w eat hering w hen R ockkind of g rindsag ainst rocksnow in riverssand isconst ant ly bouncing ag ainstpebble and rockand it ' sw earing itdow n and so t he rockst hathave been w eat hered and eroded and deposit ed by st ream sand rivers t end t o be g enerally rounded and sm oot hed outsom et hing like w e see in (2 0 :1 5 ) t hispict ure rig hthere so if I w ere t oj usthand y ou one of t hese rockseven t houg h y ou don' tnecessarily know w here itcam e from y ou could int erprety ou could conclude t hatit ' sspent t im e in running w at erand t hat ' show itg ott he sm oot h rounded shape t haty ou see and so t hat 's ourlookatriversfort oday j ustt o kind of sum up som e of t he key ideasm eanderscurvesand riverst ellusaboutt he ag e of t he riverand w e can ident ify w here erosion and deposit ion occurs w e see sort ing w het herit ' shoriz ont alor ( 2 0 : 4 7 ) vert icaland w e see rounding in t hese sedim ent sand so t hose are som e of ourkey ideasforR ivererosion and deposit ion riversare an incredibly pow erfulforce t hathasbeen shaping t he eart h forbillionsof y earsand riversallhave a st ory t ot ellby looking att hem and ex am ining t heircharact erist icsand t he charact eristicsof t he sedim ent sw ithin t hem w e can act ually learn a lotaboutt heirag e and how t hey have im pact ed the eart h in t he pastand how t hey ' re chang ing t he surface in t he fut ure t hey ' re an am az ing force t hat ( 2 1 : 2 0 ) really leavesitsim printon ourplanett hanksforw at ching R ivers- YouTube ht tps: / / w w w. y out ube. com / w at ch? v= 6 w E N 6 8 3 X X iM Transcript : ( 0 0 : 0 0 ) [m usic]9 7 % of allt he w ateron E art h’s surface isin t he ocean. T he rem aining roug hly 3 % isfresh and found on land. O f t hatfreshw at er, 6 9 % ist rapped in g laciersand ice caps, and 3 0 % can be found in poresand cracks, soaked int ot he g round ( know n asg roundw at er). ( 0 0 : 2 6 ) T he rem aining 1 % of freshw at ersuppliesincludes w at erin the at m osphere orin plant s ort he biosphere, and w at erpooling orrunning across t he surface. T he w at erin lakesm akes up 0. 2 6 % of allfreshw at ersupplies; and rivers, st ream s, and creeksm ake up only 0. 0 0 6 % of freshw at eron t he planet. H ow doesw at erm ove around bet w een allt he differentreservoirsin w hich it ’sfound? H eatfrom t he sun evaporat esw at er( t urnsitint o w at ervapor) , m oving itup int ot he at m osphere. ( 0 0 : 5 8 ) T hisat m ospheric w at erw illg etm oved around t he planetby w inds. W hen t hatairlat er cools, w at ervaporw illcondense backint o liquid w at er and drop dow nw ard asrain, ot herw ise know n as precipit ation. S om e of t hatrain landsdirect ly in the oceans. S om e landsin g lacialor ice sheet areas. S om e dropsdirect ly intot he g round and soaksint o it. ( 0 1 : 2 4 ) W here g roundsare sat urated w it h w at erand can hold no m ore, any rain t hatfalls t here w illrun along t he surface int o rivers, st ream s, and lakes. E vent ually m ostof t his running w at erw illm ake it sw ay backt othe ocean. W hataboutocean w at ert hatsoaksint o t he sedim entand crackson t he seafloor? W hen t hiscrustevent ually sinksint othe m ant le at subduct ion z ones, t hatw at erissqueez ed out and because it ’slessdense, risesupw ards. ( 0 1 : 5 2 ) S ince t he addit ion of w at ert ot he ast henosphere drops it sm elt ing point , m ag m as form. T he m ag m as produced are rich in w at erand rise upw ards t o produce volcanoest hat release t he w at er backint ot he atm osphere asa g as. T hroug h cont inued evaporat ion and precipit at ion, running w at er, subduct ion, and volcanism , E art h’sw atercont inually cy clesin and outof t he variousreservoirs, processescollect ively know n ast he hy drolog ic orw at ercy cle. N ow let ’sfocuson t he 0. ( 0 2 : 2 4 ) 0 0 6 % of freshw at er found in rivers. D espit e being such a m inorcom ponentof w at er st orag e, running w at erist he m ostpow erfulerosionalag entatw orkon P lanetE art h. R unning w at erw eat hers, erodes, and deposit sm at erialacrossE art h’s surface and producesa m ult itude of unique and varied landform s. ( 0 2 : 4 9 ) E ven in desert s, w here w at er runson t he surface foronly a few w eeksa y ear, t hat running w at erisstillthe m ostpow erfulof t he forcesatw orksculpt ing thatlandscape. H ow doesw at erg etint o a river? A river’sdrainag e basin orw at ershed is t he area of land in w hich allt he rain t hatfalls w illult im at ely m akesit sw ay int ot hatriver. T he line bet w een t w o drainag e basinsorw at ersheds iscalled a divide. ( 0 3 : 1 2 ) T he cont inent aldivide in t he U nited S tat es, forex am ple, isa divide t hatrunsalong t he t op of t he R ocky M ount ains. W at er t hatfallson one side of t hisdivide w illt raveleastand sout h int ot he M ississippiR iverBasin; and w at ert hatrunson t he ot herside w illt ravelw est int o differentbasins, such ast he basin of t he Colorado R iver. ( 0 3 : 3 8 ) W e callt he w at ersatt he hig hestelevat ion of a drainag e basin t he headw at ers. A s w at erm oves dow nhillitw illbe j oined by m ore w at erfrom t he g round orfrom ot herst ream s. E ach of t he sm allst ream sand rivulet st hatj oin t og et herare called t ribut aries. T he low est pointof a river, w here itent ersa lake ort he ocean, iscalled t he m out h. ( 0 3 : 5 9 ) Tect onicsand isost at ic upliftpush t he land up – erosionalag ent ssuch asrunning w at er carve itdow n. A sw at erm ovesdow nhill, itw illcarve outrockfrom t he hig h count ry and carry it t o t he low count ry. It sw orkisdone w hen t he river hascarved t he land flat. Base levelist he low est levelt o w hich a riverw illerode – U lt im at e base levelform ostriversin t he w orld ist he ocean, unlessa riverisdraining int o an interiorbasin low ert han sea leveland w it h no out lett o t he ocean. A n ex am ple of t hiscan be found in D eat h Valley , California, w here t he low estpoint is ( 0 4 : 3 7 ) 2 8 2 feetbelow sea level. A lake m ig htbe a localorint erm ediary base level. In t hatlocal area, t he riverst hatfeed int ot hatlake w illerode dow n only t othe levelof lake. T hen t heir w ork isdone unt ilt he lake drainsdow nw ard and t he riversare backatw orkag ain. W hy is running w at ersuch a pow erfuleroderorsculpt orof t he land? F irstlet ’sreview a few t erm s. W eat hering ist he processof phy sicalorchem icalbreakdow n of rock. ( 0 5 : 0 8 ) E rosion ist he transportof w eat hered debrisor sedim entfrom one locat ion t o anot her. D eposit ion ist he dropping of t he sedim entint o piles. R iversphy sically w eat herorbreakdow n rock t hroug h t w o prim ary m et hods: hy draulic pressure and abrasion. A sw at erm ovesdow nhill, t he w eig ht and velocit y of t he w at erput spressure on t he rocksoverw hich itflow s. ( 0 5 : 3 4 ) W hen cracksex istin t hose rocks, t hispressure can g radually ex pand t he crack. A lso, t he sedim entcarried along t he base of a river, pushed dow nhillby t he force of t he w eig htof t he running w at er( also know n asbed load) w illm ove acrossrocksurfacesand scrape and abrade t hose surfaces. Chem icalw eat hering asdiscussed in t he W eat hering video t utorialis aided by w at er, so w hen riversputw at erin cont inualcont actw ith solid rock, t hey increase t he rat e atw hich t hatrockw illchem ically break dow n, prim ary m et hodsbeing t hatm inerals w ill dissolve, ox idiz e, ort urn int o clay s. ( 0 6 : 0 7 ) O nce rockshave broken dow n t hroug h any act ivit y, the riverit self, g ravity , g laciers, w ind, hum ans, w aves, et c. , the riverw illpickup t hose w eat hered piecesand t ransportt hem t o a new locat ion. D ischarg e ist he t erm w e use t o describe t he volum e of w at era river t ransport s pasta g iven pointevery second. It ’sm easured in cubic m et erspersecond ( cm 3 / s). ( 0 6 : 3 3 ) T he hig her t he discharg e, t he m ore sedim entload a river can carry. T he m ax im um sedim entload a river can carry iscalled it scapacit y. A sdischarg e increases, so t oo does capacit y. N ew sedim ent can be carried by a riveronly if ithasn’ty etreached it scapacit y. R iverst hatare atcapacit y w illrun acrosssedim entbutnothave room t o pickitup. ( 0 6 : 5 7 ) S im ilarly , w hen a river’sdischarg e decreases, like in t he day saft era st orm , it s capacit y w illshrink, and ithast o drop sedim entitcan no long ercarry. A ddit ionally , t he abilit y to pickup and carry a sedim entg rain of a part icularw eig htorsiz e dependson t he river’s velocit y. T he g reat er t he velocit y, t he g reat ert he pow erand hence t he larg ert he g rain siz e it can carry. ( 0 7 : 2 0 ) W e call t he m ax im um g rain siz e t hata rivercan carry , it scom pet ence. Com pet ence g oesup asvelocit y g oesup. S im ilarly , asvelocit y g oesdow n, com pet ence g oesdow n. R esult ? W hen velocit y drops, allt he larg estg rainsare dropped att he sam e place in a pile, creat ing a pile of w ell- sort ed g rainsw hich m eanssim ilarly siz ed. ( 0 7 : 4 6 ) P ilesof sedim entdropped by riversare called alluvium , and t hey are easily recog niz able by t heirex cellentsort ing and also by t he rounding produced by t he cont inual knocking aboutw it h ot herg rainsast hey w ere t ransport ed by t he riverand ast he river cont inuest o m ove overt hem once t hey w ere deposit ed. N ow t hatw e know underw hat condit ionsriverspick up sedim entand underw hatcondit ionst hey drop it , w here are w e m ost likely t o see bot h happening in a river? L et ’sst artby looking closerat velocit y. W here along a riverdoesvelocit y increase? O rdecrease? T he slope org radient ( 0 8 : 2 3 ) of a riverist he rat io of vert icalt o horiz ontaldist ance thata riverm ovesdow n a hill. H ow does g radientim pactt he velocit y ? W e w ould ex pectriverst o m ove fast erdow n st eeper slopes and slow eron g ent lerones. W here riversm ove from t he st eep m ount ainsont ot he flat plains, g radientflat t ensoutconsiderably , slow ing t he river. ( 0 8 : 4 9 ) T he slow er- m oving riverhasa low er com pet ence and hast o drop sedim entg rainst oo big t o carry. T he alluvialdeposit st hatform in t hese circum st ancesare referred t o asan alluvialfan. W hy flat terslopesatt he base of t he m ount ains? T hat ’sw here allt he sedim ent from erosion of t hose m ount ainspilesup. ( 0 9 : 1 0 ) T he rem aining w at ert hat runsdow n m ustnow m ake it sw ay acrosst hispile of sedim entand t huscan splitint o m any different rivulet sorbraidsasitw eavesitw ay t hroug h t he pile. W e callt he pat t ern of such a river a braided river. In cont rast , rivershig h in t he m ount ainst y pically have st raig htchannelsw it h a V - shape cross- sect ion, asriverserode dow nw ard asdirect ly aspossible, and g ravit y carries t he slope m at erialon eit herside dow nhill. ( 0 9 : 4 0 ) W here riversg o from flat terslopest o steeper slopes, like w hen t hey spillover w at erfalls, t he velocit y speedsup and t he rivercan pick up larg erpart icles. H ow do w at erfalls form ? W hen y ou have a resist antlay erof rockt hat isdifficultforriverst o erode, t hey w illfind cracksand erode dow nw ard t hroug h t hose crackst o lessresist antrocksbelow. ( 1 0 : 0 4 ) A st he river erodest he lessresist antrockunderneat h, itw ill undercutt he top lay er. O vert im e t he cont inued undercut ting w illm ake t he t op lay erunst able, and t he overly ing cliff w illcrackand fall. A not herfact ort hatim pact svelocit y is friction – t he st ickinessof t he river bed t hatdrag son t he w at erw it hin. F rict ion and drag are affect ed by t he shape of t he channel asw ellas t he m at erialoverw hich t he riverruns. ( 1 0 : 2 8 ) S hallow channelsordeep narrow channelshave increased surface area so increased drag. A deep and broad channel, like a perfectsem icircle, hast he leastam ountof surface area t o volum e of w at erand t he leastdrag. L arg e boulderslike w hat ’sfound in t he m ount ains in shallow st ream sproduce hig h drag. S m oot h rocksurface orfine m udscause very lit tle drag. L essfrict ion ordrag , fast erriver. ( 1 0 : 5 6 ) W hataboutt he w idt h of the river? J ustlike w it h y ourfing eron t he end of a hose, w hen the channel of t he riverflow isconst ricted ornarrow s, velocit y speedsup. E rosion increases, and t he narrow scan be eroded quit e deep. W here channels w iden, velocit y drops, and deposit ionsoccurs. T he discharg e of a riveralso affect s speed – t he hig hert he discharg e, t he hig hert he velocit y. ( 1 1 : 3 1 ) S o w hatm akesdischarg e increase ordecrease? A salready m ent ioned, discharg e in a riverisa funct ion of how m uch w at errainsdow n in t he drainag e basin. E vent ually allt he t iny st ream sin t he basin w illj oin tot he m ain river. S o discharg e should be hig hestt he closerw e g ett ot he m out h of the river. D ischarg e w illalso chang e t hroug hout t he seasonsast he am ountof rain and snow m eltvaries. ( 1 1 : 5 3 ) If w e can erode t hroug h a drainag e divide and increase t he area of a drainag e basin, t hatshould also lead t o g reat erdischarg e. W hathappensatdam s? D am sacrossa river w ill st op t he flow of t he river. T hatst op in velocit y m eanssedim entisdropped att he m out h of t he riverasitent erst he lake. ( 1 2 : 1 3 ) W e callsedim entdropped att he m out h of a riverw here itent ersanot herbody of w at er, a delt a. T hatdelt a sedim entovert im e w illcause t he lake levelt o rise, so in sum m ert he lake m ig htneed t o be drained, and t he sedim entrem oved. M eanw hile, dow nriver, t he w at ert hat spillsovert he dam hasno sedim entw it hin and isdropping from g reatheig htw it h g reat velocit y. Itw illpickup and erode sedim entfrom t he areasim m ediat ely below t he dam. ( 1 2 : 3 7 ) H ow ism at erialt ransport ed by a river? In addit ion tot he bed load already discussed (t he sedim entpushed along t he bot tom of t he river due t ot he pressure of t he w at erm oving dow nhill) , riversalso carry part iclesin suspension, buoy ed up by t he energ y of t he w at er. T his suspended load m ake t he riverlookcloudy oropaque. ( 1 3 : 0 0 ) W e can rem ove suspended load by let ting a j arorbucketof riverw at ersitfor a few day sst ill. T he lackof energ y g ivest he part iclest im e to set tle outand depositin a lay eron t he bot t om of t he bucket. T he finest m udsm ig htt ake m ore t han a day t o fully set tle out. A lso carried by a riverare t he dissolved ionsproduced t hroug h chem icalw eat hering of t he rocks up river. ( 1 3 : 2 4 ) T hisdissolved load can be rem oved only if t he w at erisevaporat ed, allow ing t he ions t o find each ot herag ain and cry st alliz e. L et ’slookm ore closely atw hathappensw hen rivers flood. M eandering riversno long erhave any dow nw ard- eroding w orkt o do, ast hey m ove acrossflatplainsclose t o sea level. H ow ever, t hey are now eroding horiz ont ally , ast hey m eander acrosst he landscape, bending around obst ruct ions, avoiding resist antrocks, and carving outnew channelsduring floods. ( 1 3 : 5 4 ) M ostof t he y ear, t he riversit sin it schannel. Butw hen t he discharg e increasesand t he river’slevel risesduring heavy rains, t hey can overt op their banksand spilloutint ot he surrounding land. T hatm eansa fast - m oving riverchuck- fullof sedim entw illovert op it sbanks and im m ediat ely slow dow n asitspreadsacrosst he flatplain on eit herside of t he channel. ( 1 4 : 1 6 ) T hese plainsare know n ast he flood plains. T he drop in velocit y m eansdeposit ion – t he larg estg ravelsdeposit ing along t he banksof t he rivercreat ing st ruct ures called levees. T he finersandsand m udsdeposit behind t he leveesacrosst he flood plain. R iversuse t heir flood plainsevery t im e t hey flood, w hich isan annualprocess. ( 1 4 : 4 1 ) S om e floods are heavierorm ore int ense t han ot hers, and t he heaviert he flood, t he m ore sedim entisdeposit ed in t he flood plains. A lso, t he heaviert he flood, t he m ore w at erin the river, and t he fast er t he riverruns. T hatm akesitm ore erosive and m ore likely t o carve out a new channelorpat h. F orex am ple, in m eandering rivers, t he out side of t he m eandersor bendsex perience t he fast estm osterosive w at er, t he inside t he calm est. ( 1 5 : 0 4 ) T herefore, sedim entpilesup on t he inside of t hese bends, and erosion increaseson t he out side. O vert im e, t he bendsg etm ore and m ore ex t rem e unt ilduring a flood, t he pressure of t he w at ercan cuta new pat h rig htacrossa bend. T he cut - off bend now becom es a lake, know n asan ox bow lake, w hile t he riverhasst raig ht ened it self outa bit. ( 1 5 : 2 9 ) A ft ert he flood, the w at ert hatrem ainsin t he channelalso slow sdow n and deposit s any sedim entt hatitcan no long ercarry on t he bot t om of it sbed. T hatcausest he riverbed t o rise, w hich also m akest he riverlevelrise, so t he nat uralleveesw illalso rise during t he nex t flood, asw illt he flood plains. O vert im e, the ent ire reg ion g et sa t hickerand t hickerpile of sedim entast he m ount ainscont inue t o erode, and t he sedim entcont inuest o pile up att he coast. ( 1 6 : 0 0 ) W hathappensw hen w e build hom eson t he flood plainsand build leveest o keep t he w at eroutof t hose flood plainsduring floods? W hen t he rivert riest o overt op itslevees, itcan’t. T his put sex t ra pressure on ot herareasof t he river, and if itcan’tfind any w here t o overt op, t hen aft ert he flood, t he sedim entt hatitcarried w illbe deposit ed on t he bot tom of t he riverbed only. ( 1 6 : 2 3 ) Sot he riverit self w illcont inue t o rise, and t he leveeshave t o cont inually be builtup t o keep t he riverback, and t hatm akest he flood plain levelconsiderably low ert han t he river bed so w hen t he riverdoesevent ually break t hroug h overt op t he leveesorbreakt hroug h t he leveess, t he w at ert hatm akesitint ot he flood plainsw illhave t o be pum ped out , ast he area is now low ert han t he riverlevel. ( 1 6 : 4 5 ) T hisis t rue in the N ew O rleansarea on t he M ississippi R iver. T he area of hom esbuilt on t he flood plain are now sit t ing undert he levelof t he river, and pum psare w orking 2 4 - 7 in som e locat ionst o ensure t hatw at erdoesn’tm ig rat e underg round and t urn these areasint o lakes. A ft era flood breakst hroug h t he levees, itcan t ake w eeksor m ont hsbefore allt he w at erispum ped backout. ( 1 7 : 0 8 ) R iversflood w hen t here’sm ore w at erent ering the rivert han t he channelcan cont ain. T hishappens during heavy rainsoverlong periodsof t im e once t he g round hasbeen sat urat ed and can hold no m ore w at er. W hathappensw hen w e covernat uralforest ed land w it h ag ricult ure? T he runoff is fast erbecause t here are no t ree lim bsand root st o soakup t he w at er. ( 1 7 : 3 2 ) W hataboutw hen w e cover ag ricult uralland w it h urban land, especially concret e? T he rain runoff w illg o direct ly int o t he riverw it h none soaking int othe g round, so t he riverscan reach flood st ag e m uch fast er. T he riverchanneland floodplain are partof t he sam e sy st em , t og et herrepresent ing the pat ht hat t he riverw illt ake atvariousst ag esin it s seasonsand j ourney. ( 1 7 : 5 8 ) D et ailed m apping of t he flood plain around m eandering riversshow s t hatt hroug hout t he hist ory of t he river, it spat h hasm ig rat ed backand fort h across t he plainsassedim ent s cont inue t o deposit and build overt im e. Building com m unit ieson t he flood plainsof riversisa challeng ing featt hat requiresart ificialleveest o keep t he river in it spat h and const ant m aint enance t o ensure t he riverst ay sin itschannel. ( 1 8 : 2 4 ) Itrequires dredg ing t he bot tom of t he rivert o keep t he bed from rising and itrequires sig nificantflood plainst o be accessible elsew here t o release t he pressure of t he rising river. A llnat uralriverssy st em sflood every y earor t w o on averag e. T he int ensit y of flooding varies, and oft en floodsare described as1 0 0 - y earevent s, 5 0 - y earevent s, 1 0 - y earevent s, and so on. ( 1 8 : 5 1 ) T he g oalof these term sist o considert he building requirem entsand risksforvarious levels of flooding. T he hig hert he y earprovided, t he m ore int ense the flood w illbe. F or ex am ple, 1 0 0 - y earfloodsare so int ense t hey happen on averag e only once every 1 0 0 y ears. W hatt hatm eansfort hose w ho choose t o live in t he flood plainsof a riverist hatw e need t o be prepared t o handle the consequencesof any of t hese event s. ( 1 9 : 1 4 ) P ause now. [m usic][m usic] F loodsare increasing W AY fast ert han w e ex pect ed - YouTube ht tps: / / w w w. y out ube. com / w at ch? v= pD IpbX j Ctyg htt ps: / / docs. g oog le. com / docum ent / d/ 1 D O x y U 5 H P p8 rT K soK hpF N a6 z bW o7 ivP 5 A uBlX - 0 2 fn4 w / e dit ? usp= sharing Transcript : ( 0 0 : 0 0 ) - E xt rem e rain event sare increasing atan alarm ing rat e in t he U S and allovert he w orld, butt he problem isn' tt he am ountof rain t hatfallsin any one place, it ' show long itt akes t he rain t o fall. A nd fascinat ing new research shedslig hton ex act ly how t hat ' schang ing. O ver t he lastcent ury , g lobalprecipit ation hasonly increased by 0. 0 4 inchesperdecade. ( 0 0 : 2 4 ) Butlooking atindividualreg ionsin t he U S , w e can see t hatsom e placeshave ex perienced 3 0 % m ore rain overt he sam e period. H ow ever, m ore rain isn' tt he w hole story. T hat ' sw hy t he org aniz at ion F irstS t reetcreat ed a g roundbreaking riskm ap t hatshow sa big chang e in w hatN O A A calls1 0 0 y earfloods. T hese are event sso ex t rem e t hatt he oddsof t hem happening in any g iven y earare aboutone in 1 0 0. ( 0 0 : 5 1 ) - 1 0 0 y earprecipit at ion eventisoccurring m ore oft en aboutonce every seven t o eig ht y earsin t he m ostex t rem e cases. - A nd t hatm at tersbecause infrast ruct ure like sew ersy st em s are builtw it ht hism et ric in m ind. Butw hy t he chang e? It ' sbecause a w arm erat m osphere isa t hirst ierat m osphere, m eaning itcan hold m ore m oist ure - F oreach addit ionalincrease in t em perat ure. ( 0 1 : 1 4 ) By one deg ree Celsius. T he aircan hold 7 % m ore w at er- Vapor. A nd t hat 's fundam ent ally chang ing t he hy drolog ic cy cle. D ry tim esg etdrierand w ett im esg etw et t eratan ex ponent ialrat e, and notonly j uston a y early scale, butdow n t ot he hourand t he m inut e. S o F irstS t reetreanaly z ed rainfalldat a acrosst he U S dow n t othe m inut et heiranaly sisuncovered an im port antt rend and led t o a new flood riskm ap of t he U nited S t ates. ( 0 1 : 4 2 ) Itt urnsoutt hatsom e placescurrent ly seeing lessannualprecipit at ion and m ore droug ht should also ex pectm ore flooding. In t hisepisode w e' re g onna lookatt hism ap t o see w hat reg ionsare m ostatriskand how w e can adaptw it h allthisaddit ionalw at er. - T hisisnot som et hing t hatany one should g o t hroug h w hen itcom est o a disast er, especially a hurricane. ( 0 2 : 0 6 ) - W e can learn a lotfrom N ew YorkCit y w hen itcom est o ex trem e rain because t hey ' re g et t ing so m uch of it. J ustlastS ept em ber, the cit y saw nearly eig htinchesof rain in a sing le day. - A place like N ew YorkCit y used t o be very , very g reen, and itw ascovered in lakesand st ream s. A nd overt im e it ' sbeen filled in. ( 0 2 : 2 3 ) T he - S am e ist rue in nearly every cit y. W e' ve replaced nat uralperm eable surfacesw it h concret e and asphalt. N early 7 2 % of N ew YorkCit y isnow covered in im perm eable surfaces. S o inst ead of a nat uralw at ersy st em , runoff hast o be m anag ed by a sew ersy st em desig ned fora clim at et hatno long erex ist s. - T he orig inaldesig nerst hatbuiltoursew ersy st em did notknow t hatw e w ere g onna have 3 , 4 , 5 , 8 inchesof rain. ( 0 2 : 4 9 ) - O ne in a hundred y eareventin N ew YorkCit y act ually occursaboutonce every 3 5 y ears. - T hisisa new problem , so t hey can only m anag e aboutone t ot w o inchesof rain per hour. - O urinfrast ruct ure j ustcan' tkeep up w it h allt he rain t hatw e' re g et t ing. A nd the N O A A m aps, w hich are referred t o asA t las1 4 and A t las2 t hatw e use t o proj ectflood riskand fig ure outw here t o upg rade ourinfrast ruct ure forflooding , event saren' tkeeping up w it ht he rain eit her. ( 0 3 : 1 6 ) - T hey use t radit ionalhist oric m et hodsform easuring precipit ation risk. A nd fora long t im e, t hatw asperfect ly fine. T he problem isif y ou have an increasing precipit ation trend, then allof a sudden now t he averag e doesn' tact ually capt ure w hatt he currentevent sare. Itact ually peg st hem backt o a clim at et hatcould be asfaras2 0 or3 0 y earsag o. ( 0 3 : 3 5 ) - In ot herw ords, t he N O A A m apslookbackw ardsand notforw ards. S o F irstS t reet decided t ot ake a differentapproach t o N O A A ' sdat a. - O urreportw asreally focused on t he ex t rem e precipit ation event sasopposed t ot he averag e precipit ation levelsacrosst he count ry. A nd it ' snotnecessarily t hatw e' re seeing m ore of t hese event s, butw hen w e seen t hem , they ' re m ore severe, w e' re seeing m ore severit y in the int ensit y of t he rainfallevent sovershort er durat ions, w hich iscausing m ore - F looding. ( 0 4 : 0 1 ) A m itS hivprasad livesin H ollis, Q ueens. H isneig hborhood hasbeen im pact ed by flooding event sfora long t im e, butrecent ly it' sg ot ten w orse. L ooking around t he area hasvery few g reen spacest o absorb R ainw at erand A m itlearned t hatt hisarea used t o be an act ual lake. - S o t hisisact ually ourhouse w here y ou g uy sare rig htnow. ( 0 4 : 2 1 ) S o if if y ou look, it ' sact ually sitting in t he m iddle of a pond rig htnow, and t hisisw hatt he pond looked like backin 1 9 2 8. If y ou - L ookatan old m ap of N ew YorkCit y and see w here all t he creeksand t he lakesused t o be, and t hen y ou lookatt oday ' sflood m ap, y ou can act ually see t hatit ' spret ty m uch ident ical. ( 0 4 : 3 7 ) - F E M A ' s1 0 0 y earfloodplain m ap derived from N O A A ' sA t las1 4 direct ly im pactst he costof and accesst o flood insurance. Butsince t he m ap doesn' tinclude flooding from rainst orm s, m any com m unit iesare leftout. A nd asa result , overex posed - F lood insurance w as neversold t o any one in t hiscom m unit y because w e don' tlive in a flood z one ora F E M A hundred y earm ap. ( 0 5 : 0 0 ) But- F looding hasdevast at ed thiscom m unit y. In 2 0 2 1 , afterH urricane Ida m ade landfall asa cat eg ory four, itt raveled up t he E ast ern U S dum ping record breaking rainfallin it spat h in N ew YorkCit y alone. Itdropped overseven inches, peaking att hree inchesof rain perhour. A m it ' sneig hborhood w asnotprepared. ( 0 5 : 1 9 ) - Itst art ed off asa norm alday , had dinnerw it h m y folksand allt he w arning sst artt ogo off. R an dow nst airs, g rabbed m y poncho, w it h m e and m y dad t ookourshovelsand rake w ent outt o clean t he basinslike w e do every sing le t im e itrains. But- T he sew erbasinson A m it 's st reetw eren' tfunct ioning t hatday. ( 0 5 : 3 5 ) - Cit y w asdoing const ruct ion and t hey pret ty m uch had allt he basin coverscovered. N ot ice ast he rain w ascom ing in hig her. S o I ran up and g rabbed m y key s, m oved t he t ruckup t he blockbefore I g otbackdow n t he end of t he block, t he ent ire st reetw asflooded. - T he flooding killed 1 3 people in N ew York. ( 0 5 : 5 7 ) - 1 1 of t hose people died in flooded basem entapart m ent s, m ostof t hem here in Q ueens, 4 3 - y ear- old P ham at ee R am skrietand her2 2 - y ear- old son, K rishah, also know n as Tara, and N icholascould notsurvive lastnig ht ' srushing flood w at erscrashing t hroug h t he w all and pouring int ot heirbasem entapart m ent. - Tara and N icholasw ere t enant sin A m it ' sfam ily ' s basem ent. ( 0 6 : 2 0 ) Before Ida he lift ed t he doorst o hishom e, t hree t o fourfeett o prepare forflooding , but t he st orm broug htt oo m uch w at er. H e no long errent southisbasem entand now usest he space forcom m unit y event s. - U nfort unately , the w allcollapsed and t hat ' sthe reason w hy allt he dest ruct ion happened. S o I' ve done m y partw here itcom est o repair. (0 6 :4 1 ) Ij ustpray and askG od t hatitneverfloodsag ain. T hat ' sall. - Ida result ed in $ 7 5 billion in dam ag esacrosst he U. S. O ver3 3 , 5 0 0 building sin N ew YorkCit y w ere dest roy ed, and A m it 's rem odelalone costover$ 3 4 4 , 0 0 0. Butnotallareasw ere equally affect ed acrosst he H udson H oboken, N ew J ersey didn' tsuffert he sam e flooding , and t hisispart ly because of t heireffort s t o adaptt ot hisnew clim at e realit y. ( 0 7 : 1 0 ) - F looding hasalw ay sbeen a problem in t he cit y of H oboken. W e w ere orig inally a t idal m arsh, act ually. T he area w here w e w ere st anding , itw asm arshland. A llof t hese low - ly ing areast hatw ere m arsh t hatw ere filled in forindust rializ ation in t he early 1 9 hundredsare very subj ectt o flooding t oday. W e also have a com bined sew ersy st em w here ourst orm w at erand oursew ag e flow int ot he sam e pipes. ( 0 7 : 3 2 ) N ow w it h clim at e chang e, w e' re seeing m ore frequentst orm s, m ore severe st orm s. - To addresst he flooding issues, H oboken hasbeen building resiliencit y parksaround t he cit y. W e w enton a t ourof t he larg estparkt o underst and how t hese g reen spacesoperat e. - T hisisone of t he 1 9 rain g ardenst hatisin resiliencit y park. ( 0 7 : 4 9 ) A nd t hese rain g ardensw illm anag e w at erduring a rain event. You' llsee t hatitalm ost lookslike a pond. W at erisslow ly being delay ed from ent ering ourst orm w at ersy st em. It 's filt ered t hroug h t he rain g arden t hroug h allt he plant sand t he soil. T hen t hatw at erslow ly drains int ot he underg round t ankt hat ' sbelow t he parkand t hen g oesoutt o oursew ersy st em. ( 0 8 : 0 9 ) A nd t hat ' sallw at ert hatt hen isnoton ourst reet s. D uring a rain event , ourm illion g allon det ent ion t ankt hatisundert hislaw n can det ain st orm w at ert hatcom esfrom t he parksit e itself, asw ellasfrom allof N ort hern H oboken - A nd it ' sw orking. H oboken hasseen an 8 8 % decrease in flooding event ssince inst alling t hese m it ig at ion m easures. ( 0 8 : 2 9 ) A nd only t im e w illt ellif t hese m easureshold up ag ainstfut ure clim at e chang es. Butit 's st rong proof of concept. T he com parison of H oboken and H ollisalso follow sanot hert rend. R ecentst udiesfind t hatrace and w ealt h play a big role in w here nat uraldisast errecovery effort shappen, and t hisim pact ssafet y and econom ic out com esforresident s. ( 0 8 : 5 2 ) A st udy from 2 0 1 8 found t hatin areasw it h atleast$ 1 0 billion in dam ag esfrom a nat ural disast er, w hit e fam iliesact ually saw a w ealt h increase of about$ 1 2 6 , 0 0 0 postrecovery w hile blackfam iliessaw a w ealt h decrease of $ 2 7 , 0 0 0. T hism ap show st he ex t entof t hisw ealt h g ap in som e m aj orcit iesacrosst he U. S. ( 0 9 : 1 8 ) H oboken is6 4 % w hit e w hile A m it ' sn