river largest river entirely southern_california united_states drainage basin spans counties rises flows past cities cutting northern tip flowing southwest past drain pacific_ocean miles long drains watershed square miles km2 size drainage basin diverse ranges high peaks inland mountains north east hot dry interior semi desert basin flat coastal plains west climates range dry alpine desert watershed arid relatively little water actually flows river tributaries largest tributaries rarely reaches extremely wet years relative lack vegetation makes river prone flash flooding wide variety animal plant life dependent river people lived river years distinct indigenous groups area depended heavily river river crossed europeans received members spanish expedition largest water sources county region large developed alongside river major tributaries period growth culminated establishment large cities river including riverside anaheim derived names river early 20th century devastating floods poured leading river recent times course rises canyon southern confluence tiny streams elevation feet highest sources dollar lake feet feet northern flank small left tributary river initially flows west broad deep gorge miles receives major tributary right flowing southwest known river turns south passing seven oaks dam flowing canyon arid interior basin receives left winds westwards city passes urban area receives city creek right enters flood control channel flanked sides long confluence city creek enters right largest tributaries river rising flowing southeast main stem flows southwest passing city riverside normally dry flood control reservoir formed major tributaries river join reservoir area right left creek drains largest area tributaries provides outflow flows longest miles length years contains little water lake high overflow flowing cuts second water gap northern crossing river roughly county flows southwest ocean river entirely diverted spreading grounds north providing half entire county municipal water downstream river serves flood control waste drainage purposes typically water passing cities orange anaheim receives east enters city river entirely confined concrete flood control channel crossing interstate time concrete past freeway flows mouth river small flowing sea northern end watershed largest river basins southern_california largest watershed covers square miles km2 parts california counties main stem river flows counties tributaries drain parts watershed characterized flat arid basin coastal plain north central run nearly perpendicular river northwest southeast major tributaries free flowing perennial river valley constitutes major portion feature watershed area drained constitute watershed extend boundaries far south area million people lived river basin population concentrated close river urban centers riverside people live thin ribbon land river rest land agriculture nearly land urban result watershed thought having distinct parts separated major bodies water watershed include lake naturally formed rest formed dams constructed county state water agencies example major southern_california drainage basins border northwest major river mouth southwest watershed forms boundary rivers streams drain area southwestern boundary watershed pacific_ocean east drainage basins flowing north flows basin area river drains downstream extremely narrow diversion drainage area flood control channels pacific near mouth functions carry runoff upstream areas directly pacific drains little area downstream confluence square miles km2 land originally drained river drained flood control channels colloquially called watershed river originally different outlets pacific extended far north far south fact original mouth river drained eventually pacific_ocean located today entrance based coastal survey predominantly river estuary open channels river flowed bay bringing heavy making boating difficult eventually create sand deposited kept bay built divert river away bay current course ocean stone built form new river mouth islands product man forming sands deposited time geology ancient rock form base strata flat valleys basins watershed thousands feet sediment deposited seas climate changes erosion mountains basin consist granite million years old rock highlands elevations feet ancient rock billion years old rock originally formed ancient pacific_ocean highest peaks mountains ice ages glaciers rarely occurred southern_california mountains rock remained tens millions years significant erosion diverse complex instability shaped watershed runs northern section watershed responsible causing fault zone crosses downstream near line fault caused rising mountain ranges ridges run northwest southeast lower section watershed comprising coastal ranges larger allowed transverse ranges rise feet places ranges half height glacial period climate change caused rivers southern_california increase greatly volume able cut ranges creating gap range period changed course multiple times creating wind gaps range occasionally channel ancestral river later returned old course abandoned channel leaving wind gap ecology hundreds species animals plants characterize river diversity climates vegetation zones vegetation zones watershed including sparsely alpine zones mountains mid elevation forests pine oak coastal sage increasingly rare forest marshes river bed lined trees rushes coastal areas virtually flush sea level watershed supports bird species species species species fish species including trout largest portion watershed inland empire portion dominated hot dry desert climate supports sparse wildlife climate vegetation watershed similar southern downstream desert coastal sage dry grassland community coastal plain region entirely lost arid portions watershed zones consisting thick low bushes small trees generally found elevations feet feet occurs mainly closer coast oak common plants regions forming dense makes difficult humans large animals mountain lions traverse growth determined depends semi arid climate region perennial seasonal streams lined live oak transition zones main stem inland marshes upstream line degraded pollution left natural state system river degraded largest places occurs enormous marsh area closed development functions flood control basin similar dam small dwelling fish found zones rarely seen river drainage near mouth river abundant salt marshes stretched miles river near upper newport bay served alternate mouth river alpine zones despite high elevation feet meters significant rainfall inches year drought years sparsely terrain alpine zone primarily small brush trees small occur shielded depressions zone inland elevations feet support forest pine pine black oak pine willow constitute forested lands mountain habitats watershed support animals typical mountain regions including black bears deer species migratory birds river abundant rainbow trout lined willow river large upper tributaries mountain inland empire basin surrounded zone mix desert upper vegetation main stem zone begins base ends confluence historically named best stream southern_california trout habitat fish similar salmon rivers streams spawn unlike salmon usually reproduce reproduce multiple times longer life span found entire main stem main tributaries san_antonio present tributaries stocked 1930s inhabited disconnected river system 1950s significant numbers trout migrated ocean pollution modifications river use river population wild stream resident coastal rainbow trout upstream upper reaches tributaries despite rarity recent years fin samples trout collected tributary genetic analysis shown native stocks invasive species native region caused problems watershed years troublesome invasive species giant reed coastal southern_california waterways giant reed similar tall grass thin bamboo grows quickly native stands vegetation block hurts habitat native animals increases hazard largest effect giant reed usage water support fast growth rate giant reed population watershed consume acre feet water year invasive species affected prominent brown headed feeds parasites insects identified cattle brought southern_california spanish period brown headed brood parasite bird lays eggs bird nest afflicted birds bell population suffers loss habitat bell considered endangered species southwestern willow habitat shared bird invasive large like giant reed uses large amounts water unlike giant reed deeper roots making difficult remove allowing access use deep similar provides little usable habitat native animals history peoples human dates years ago close early stages period native americans live area nomadic tribes traveled place place grazing animals fertile gathering fruits seeds food ancestors early people originated people northwestern united_states eventually human population watershed reached peak years ago climate experienced change arid originally nomadic tribes began stay individual places longer semi nomadic establish agriculture raise animals live villages like native american tribes california staple food inland valley people people closer ocean hunted small animals tide pools coastal stream areas food major native american groups eventually gained control lands river people upper basin southeastern basin desert areas watershed people lower basin generally lived mountain tributaries present day basin present day foothills lived flat coastal plains present day south larger groups controlling coastal lands north south including spanish period spanish explorer sailed southern_california coast voyage passed mouth noting subsequent spanish sea borne explorers leave written notice river mouth led overland expedition northwards coastal southern_california largely california province gave river july party camped leagues exits canyon northern near present day olive members expedition wrote diary called spot jesus los referring earthquake struck camped alongside noted soldiers calling river rio probably recently celebrated remains today second oldest place mountain range city derived river missions actually located river watershed river basin nearly depleted native people spanish forced work nearby missions including mission san affected tribes usually renamed missions resulting tribal names difficult working living conditions european diseases smallpox killed native population roughly year long mission period act passed newly independent country mexico eventually brought end mission period post mission period native population entirely devastated population little native religions nearly lost land taken spanish settlers mexican government original intention act provide native americans land property provisions act actually happened spanish settlers continued press remaining tribal lands eventually tribes forced surrounding desert lands high mountains following mission period came period occurred enormous land holdings missions subdivided owned individuals new private merely converted mission private river acre km2 left bank lower acquired early river followed including ones inland areas exploited beginning missions established tradition raising cattle coastal southern_california custom upheld late 19th century agriculture established major industry flood caused river course change temporarily outlet newport bay sediment partially created spread towns military outposts trading posts river valley prosperous regions southern_california decades american settlement late 1840s california fought independence mexico mexican american war river played important victory americans mexican army year mexican military force set northwards attack smaller american force los_angeles area flooded preventing crossing river attack americans river flow finally subsided american forces reinforced drive region united_states american settlers began river region great numbers mexican divided smaller individual properties agriculture began large scale city original location founded period settled upper area started city gaining prosperity water river crops cattle industry began decline farms began replace soon white settlers region numerous time responsible attracting people state remained southern_california closer gold rush occurred discovered significant deposits northern drainage divide discovery exploded scale gold mining operation days served miners traveling region forests upper basin experienced result high resource demands boom gold discovered year following gold rush cultivation citrus economy lower area late 19th century citrus fields covered coastal plain led naming floods legacy notwithstanding increased prosperity 1860s decade scene series natural disasters great flood heavy rains dropped series winter storms caused burst banks flooding thousands acres land killing people greatest flood experienced recorded history river burst places flooding inland empire continuous body water miles wide stretching mouth river cuts downstream river overwhelmed nearly existing transformed coastal plain inland sea flow calculated year flood peaked roughly cubic meters second half average flow mississippi_river flood detrimental conditions continued region years following flood intense drought caused deaths tens thousands head livestock despite hardships experienced years conditions finally returned normal watershed agricultural region cities riverside established respectively saw pair devastating floods brought end area citrus industry burst banks flooded anaheim orange feet water stripping away thousands acres rich destroying citrus people killed disaster acres km2 land flooded despite fact flow river flood extreme damage floods decision dam concrete river beginning 1940s declared greatest flood hazard west mississippi_river built designed capture inland empire miles upstream river mouth dam designed handle year flood increased flood protection afforded major industrial development migrating south southern_california housing boom 1950s 1960s watershed began final transition agricultural urban population river basin increased dramatically brought threat greater damage floods somewhat protection afforded housing urban areas river historic area occupied farms river confined narrow channel flood similar ones surrounding turn 20th century cause damage construction roads buildings heightened runoff flow river rainfall process known urban runoff fact river flooded runoff captured probably saving greater flood large tributary flowing eroded banks swept away portions residential communities cities orange santa river project involved lower miles river proposed construction work began today river channel essentially enormous box second dam completed dam captures flood runoff canyon enter dam designed withstand year flood today river lies mainly concrete channels especially lower course functions flood drainage channel present day activities pollution restoration southern_california rivers heavily main stem free flowing upper tributaries river enters inland empire basin flow diverted municipal agricultural water use flow river city consists treatment plants dry season urban runoff collected flow makes downstream diverted pair dams approximately acres km2 basins providing approximately acre feet municipal water county year water supply downstream dam river urban runoff finally making pacific included list toxic hot spots list impaired waterways number organizations formed try gain public interest restoring river prominent santa watershed project authority formed municipal water districts river area second santa river association conducted studies beneficial uses aside water supply flood control removal sections lower river set studies known use analysis submitted state congress approved submission rejected result little work repair ecological damage caused river projects include santa watershed planning advisory committee river watershed alliance recreation recreational opportunities watershed includes parts mount san state wilderness area lake state recreation area lake lake popular recreational lakes watershed river actually flows lakes drainage river tributaries bicycle path complete run river mouth near currently extends miles river proposed distance trail miles miles recreational paths entities opting encompass strip land river entire course city like develop riverside green space near historic downtown district river lakes located near anaheim popular recreational fish farm fed water river ultimately trail link network river parks stretch river flanked north south miles vegetation convinced possibilities improving public access recreational opportunities crossings significant crossings bridges dams list places mouth source archival collections guide santa river report special collections archives california watershed association river watershed alliance
Santa Ana River