called mile stream california consists basin encompassing square miles km2 rises ranger district runs parallel winds west south joined numerous small tributaries joined main branch passes flows pacific_ocean foothills flows city flow direction generally northeast southwest basin san juan reach considered good recent efforts stream conservation planning stage including habitat conservation plan work historically san juan creek watershed inhabited received current spanish built mission san juan near giving spanish settlement development watershed continued grow pollution creek increased construction point harbor increased pollution mouth posing increasing danger visitors late 1990s early 21st century floods destroyed river control structures san_juan watershed risk floods continues grow san_juan watershed rich biodiversity sixteen major plant communities hundreds species birds invertebrates mammals watershed projected percent developed year reaches open land san_juan watershed heavily developed urban runoff coming residential communities taking increased toll creek tributaries major water dams tributaries heavily affected notably course begins high southwest head steep narrow roughly feet elevation draining western southernmost confluence flows downhill paralleling known winds rocky gorge drops foot cascade crosses arch bridge carries highway joined right bank meets left mountains proceeds broad shallow farming valley thick deposits creek swings west receive right residential communities border left enters left enter right creek crosses interstate enters flood control channel turning south receiving right receives largest tributary right bank continues south east pacific_ocean reaches sea enters northern end occasionally tributaries direct tributaries mouth source listed list includes streams join major tributaries geology rocks topography geology san juan creek watershed complex described having seismic fault zones streams tending follow fault zones formed having extremely soils tends deep concentrations lower reaches said poorly drained soil types san_juan watershed divided associations order level bedrock san_juan watershed poses landslide danger earthquakes severe erosion events cause failure stability seismic faults watershed include fault line running northeast southwest passing offshore miles south mouth fault zone mission parallels ends far south summary san_juan watershed considered faults running approximate center recorded earthquake area partially destroyed followed small coastal mountain range generally following pacific_coast created physical barrier streams flowing enormous climate change helped solve problem period time lasted years ago glaciers ice sheets moved south canada northern united_states radically altering climate entire continent arid southern_california climate supplanted temperate climate receive rainfall excess inches year streams powerful rivers cut way condition reverted end period wet periods occur ice age largest san juan creek basin referred san juan creek basin total volume roughly acre feet natural san_juan basin estimated roughly acre feet year historically precipitation reduced extensive development lower segment watershed continuing reduce open ground potentially serve artificially sourced water irrigation uses responsible roughly acre feet annually watershed essentially split half fault zones result division upper lower basins lies ranges depth feet lower watershed upper reaches watershed historically total surface outflow san_juan basin pacific calculated acre feet annually increasing urban development resulting increased runoff irrigation sources brought annual outflow acre feet maximum annual yield acre feet water tributaries basin increasingly limited agricultural municipal purposes annual yield watershed continually increasing rate watershed relatively high safe assume levels recover quickly human use human induced pollution lower san_juan watershed compared county year flood risk significantly lower nearby calculated year flood watershed affect roughly wide area lower reaches inside wide area affected mainly severe fact note failure miles upstream actually create slightly larger year flood race mouth san_juan area suited year flood regardless extent watershed occupy north east south parts approximately square mile km2 watershed small border watershed southwest east northwest major tributaries san_juan originate main river valleys watershed drained san_juan valley occupies south portion watershed running roughly south spreading wider near coast running northeast turns sharply southeast meet pacific_ocean city valley runs west portion watershed gradually wider section called joins smaller valley runs primarily south combined valley runs southward merge valley valley narrower beginning miles south california running perfectly straight southward course point shortly reach watershed major creeks watershed including creek drain parts foothills considered square mile km2 san juan unit coastal region running central south north extent borders south unit covers order north south elevation sea level ranges feet precipitation unit ranges inches annually streams unit relatively developed watershed receives extra runoff agriculture urban activities commercial irrigation human induced sources creates extra unnatural flow consisting urban runoff agricultural return flows runoff trash heavy metals oil received running pavement draining farmland specific point concern watershed southern_california said diving retrieve motor spent days diving retrieve motor skin broke suffered later operations year period wildlife originally rich zones habitats upper lower watershed wetlands totaling acres km2 historically lower reaches rapid population explosion began major vegetation zones watershed currently total wetland watershed acres km2 percent historic total bird species confirmed watershed fish benthic invertebrates certain insects confirmed observations insufficient site coverage trout recently observed creek tributary reason decline creek habitat wildlife mainly invasive plant animal species including giant reed sport fishes striped bass notable aspect creek water sample taken creek mouth january temperature degrees creeks coast higher temperatures operated stream city second gauge highest recorded peak flow period cubic feet second second february gauge height feet second highest peak flow period cubic feet second march presumably peak recent stream gauge highest recorded flow cubic feet second march gauge height feet second highest flow cubic feet second february gauge height feet highest flow recorded time stream gauge flow cubic feet second recorded january history indigenous peoples 18th century tributary indigenous names far unknown land san_juan watershed indian territory extended north south distance roughly miles north south population centered large perennial streams area san_juan inhabitants numbered roughly thousand overall hunter living small semi permanent villages near perennial streams villages main stem confluence parts watershed diet usually consisted fruits grains meat practiced little agriculture shell indicate harvested coast natural disasters floods drought occurred time today affect environment area negative positive way permanent structures built san_juan watershed arrival spanish spanish arrival european land exploration spanish expedition passed way way north camping creek july missionary noted diary came pleasant green valley live oaks trees known large point crossed carried good stream fresh good water running little way formed pools large patches return journey san_diego party january father founded mission san juan site probably close creek result creek takes mission site abandoned lack water creek known historical accounts perennial mission moved second site stands dubbed spanish mission spanish create changes san_juan watershed included irrigation channels water streams changing course streams grazing animals including cows sheep livestock began prevalence period destroying native grasses leaving ecosystem prone erosion origin spanish literally stems expedition soldier lost associated creek point origin spanish bear creek known creeks watershed names spanish origin likely named spanish long time area annexed united_states heavy earthquake severely damaged structures built spanish built years collapsed people reported killed urban development partially devastated lands caused spanish period potentially capable natural state urban percentage increased percent 1990s watershed percent urban projected growth percent areas watershed chance revert natural state long human continues 20th century present late 1960s construction point harbor began near mouth harbor prevented occurrence large surf break phenomenon colloquially known killer bay disappearance water circulation bay decreased pollution continued flow freely bay stayed longer period time comparison harbor built pollution problems ongoing posing problems annual visitors threatened continuing pollution floods 1990s sheer foot rapidly steep slope downstream railroad bridge upstream creek confluence drop required quick reinforcement exists average gradient percent stream pool poses major barrier migrating fish organisms lower miles relatively natural upper course severe floods caused heavy san_juan watershed caused san_juan creeks overflow destroying long sections concrete lining near confluence damage chiefly caused severe basal erosion led subsequent failure concrete walls concrete breached bare earth underlying exposed erosion threatening nearby residential community floods harm failed sections repaired seen today early severe floods caused flooding area streams impacted san_juan watershed time highest flow cubic feet second recorded january floods exceed channel capacity cubic feet second west channel inside nearly failed pumps installed tributaries flows remove urban runoff stemming acre km2 residential community nearby ridge pumps remove excess flow divert storage basins later use reclaimed irrigation water announced repairs close popular years repairs finished later spurred protests area residents common users path river modifications streams san_juan watershed developed neighboring san_juan undergone extensive series modifications designed control floods reduce excessive erosion provide reclaimed water irrigation growing urban runoff flows creek tributaries adding excessive perennial flow referred flow dry season flow historically san_juan creeks known perennial tributaries spring fed ones currently flow excess cubic feet second percent year finally long series human modifications creek resulted mouth placing tenth beaches california approximately miles immediately upstream interstate bridge mouth yards confluence larger stream sharp contrast nearly entire length free flowing large lake mission built total storage capacity roughly acre feet lake mission primarily recreation acre km2 collects water irrigation use low flow occurs dam collected small downstream dam feeds pipe pumps reservoir way considered pumped storage operation produce notable aspect reservoir vital providing water large october dam feet long feet high check dams exist small upper tributaries inside small abandoned structure lower structure small dam operation roughly foot drop poses problem migrating trout water diversion exist san_juan tributary streams divert water irrigation limited municipal uses limited flows water structures limited number drop structures small dams control water velocity exist streams san_juan watershed primarily creeks drop structures built largest foot cascade immediately downstream bridge concrete drop structure terminus crosses underneath interstate seven drop structures built notable drop structures dams water found lower san_juan watershed bounded upstream interstate near mouth upstream continuation highway downstream mouth raised banks certain smaller tributaries creek san juan said fairly high level protection currently failure scenarios san_juan watershed extensively studied determined possibly fail variety reasons demonstrated floods response danger flood work begun new west bank replacement finish stream crossings list major crossings proceeding upstream mouth
San Juan Creek