Y T C O U N E G RIVERSIDE COUNTY N A R Rainbow O Pendleton-De Luz Fallbrook Palomar Mountain P Pala-Pauma A Valley COUNTY IMPERIAL C I F Bonsall North Mountain I Borrego Springs C Valley Center O Hidden C Meadows E Twin A Oaks Valley N North County Metro Desert Julian LEGEND San Dieguito Landslide Susceptibility Ramona High Moderate Cuyamaca Incorporated Area Community/Subregional Planning Area Boundary Lakeside Central Mountain Subregional Group Descanso Boundary Tribal/State/Federal Lands Alpine Pine Valley Lakes Crest-Dehesa- Harbison Canyon- Rivers Granite Hills Valle De Oro Mountain Empire Spring Valley Sweetwater Jamul-Dulzura Boulevard Lake Morena / Campo Jacumba Potrero Otay Tecate O C Map Date: May 2009 I 1 X Source: County of San Diego, USGS, HAZUS E M Miles LANDSLIDE SUSCEPTIBILITY 0246810 San Diego County General Plan Figure S-3 Y T C O U N E G RIVERSIDE COUNTY N A R Rainbow O Pendleton-De Luz Fallbrook Palomar Mountain P Pala-Pauma A Valley COUNTY IMPERIAL C I F Bonsall North Mountain I Borrego Springs C Valley Center O Hidden C Meadows E Twin A Oaks Valley N North County Metro Desert Julian LEGEND San Dieguito Expansive Clays Ramona Incorporated Area Community/Subregional Planning Area Boundary Cuyamaca Subregional Group Boundary Lakeside Tribal/State/Federal Lands Central Mountain Descanso Lakes Rivers Alpine Pine Valley Crest-Dehesa- Harbison Canyon- Granite Hills Valle De Oro Mountain Empire Spring Valley Sweetwater Jamul-Dulzura Boulevard Lake Morena / Campo Jacumba Potrero Otay Tecate O C Map Date: May 2009 I 1 X Source: SanGIS E M Miles EXPANSIVE CLAYS 0246810 San Diego County General Plan Figure S-4 GOALS AND POLICIES development in hazardous areas or require engineering solutions that mitigate dangers to proposed structuresandtooffͲsitelands. GOALSANDPOLICIES GOALSͲ7 ReducedSeismicHazards.Minimizedpersonalinjuryandpropertydamageresultingfromseismic hazards. Policies SͲ7.1 Development Location. Locate development in areas where the risk to people or resources is minimized.InaccordancewiththeCaliforniaDepartmentofConservationSpecialPublication42, require development be located a minimum of 50feet from active or potentially active faults, unless an alternative setback distance is approved based on geologic analysis and feasible engineering design measures adequate to demonstrate that the fault rupture hazard would be avoided. SͲ7.2 EngineeringMeasurestoReduceRisk.Requirealldevelopmenttoincludeengineeringmeasures toreduceriskinaccordancewiththeCaliforniaBuildingCode,UniformBuildingCode,andother seismic and geologic hazard safety standards, including design and construction standards that regulate land use in areas known to have or potentially have significant seismic and/or other geologichazards. SͲ7.3 LandUseLocation.Prohibithighoccupancyuses,essentialpublicfacilities,andusesthatpermit significantamountsofhazardousmaterialswithinAlquistͲPrioloandCountyspecialstudieszones. SͲ7.4 UnreinforcedMasonryStructures.Requiretheretrofittingofunreinforcedmasonrystructuresto minimizedamageintheeventofseismicorgeologichazards. SͲ7.5 Retrofitting ofEssential Facilities. Seismicretrofit essentialfacilitiestominimizedamageinthe eventofseismicorgeologichazards. GOALSͲ8 Reduced Landslide, Mudslide, and Rock Fall Hazards. Minimized personal injury and property damagecausedbymudslides,landslides,orrockfalls. Policies SͲ8.1 LandslideRisks.Directdevelopmentawayfromareaswithhighlandslide,mudslide,orrockfall potentialwhenengineeringsolutionshavebeendeterminedbytheCountytobeinfeasible. SͲ8.2 RiskofSlopeInstability.Prohibitdevelopmentfromcausingorcontributingtoslopeinstability. COUNTY OF SAN DIEGO 7Ͳ15 GENERAL PLAN CHAPTER 7 SAFETY ELEMENT FloodHazards CONTEXT Floodingisapersistentortemporaryconditionofpartialorcompleteinundationofnormallydrylandareas. Flooding is commonly associated with the overflow of natural rivers or streams, but can also occur near stormwaterdiversionfacilities,orinlowͲlyingareasnotdesignedtotransportorinfiltratewateratanytime. ThepotentialforfloodinginSanDiegoCountyishigh.Stormeventsarethemostcommoncauseofflooding, andareasmostpronetofloodingaremappedbytheState,federalagencies,andtheCounty. Nearlyeverycommunityplanningarea(CPA)orsubregionintheunincorporatedCountyhasstudiedareas subjecttofloodinundation,(althoughtherearealsoknownfloodhazardareasintheCountythathavenot beenstudied).TheCountyofSanDiegopublishesmapsshowingstudied100Ͳyearfloodplainandfloodway boundaries,and100Ͳyearfloodwatersurfaceelevations(whereavailable),orfloodplainhazardareas.These areasaremappedas100ͲyearfloodplainsinFigureSͲ5(Floodplains).1Floodplainsarerelativelyflatareasof lowlandsadjoiningandincludingthechannelofariver,stream,watercourse,bay,orotherbodyofwater whichissubjecttoinundationbythefloodwatersofthe100Ͳyearfrequencyflood.Watercoursessubjectto floodcontrolrequirementsbytheCountyareaffectedbylargedrainageareas(typicallyonesquaremileand greater for FEMA mapped floodplains and 100 acres or greater tributary area for CountyͲdefined watercourses)andareshownontheCountyfloodplainmaps.Afloodwayisthechannelofariverorother watercourseandtheadjacentlandareasthatmustbereservedinordertodischargethebaseflood(100 year flood) without increasing the water surface elevation more than the designated height, but not to exceedmorethanonefoot.Encroachmentintothefloodwaybystructuresisgenerallyprohibited. Most community planning areas have between 100 to 4,700acres of land identified as a floodplain. The exception is Borrego Springs (within the Desert Subregion), which has nearly 30,350acres of land in its alluvialfloodplain.Thishighnumbercanbeattributedtoflashfloodingthatoccursindeserts.TheCountyof SanDiegoFloodHazardMapforBorregoValleydelineatesboundariesofknownspecialfloodhazardareas on alluvial fans and lines of equal probability of flood depths and velocities. Alluvial fans are generally a desert phenomenon where streams emerge from canyons and deposit sand and rock in a coneͲshaped formationfanningoutfromthecanyonmouth.Thepotentialforhighvelocityflowandheavysedimentload coupled with the complex nature of alluvial fan flooding means that virtually all parts of the fan can be threatened by catastrophic flooding. The Borrego Valley Flood Management Report (October 17, 1989), however,providesmethodsforreducingrisktostructuresbuiltonthealluvialfan. 1Communitylevelmapsshowingthe100ͲyearfloodplainareascanbeaccessedonlinebycontactingSANGISat http://www.sangis.org/maplibrary. COUNTY OF SAN DIEGO 7Ͳ16 GENERAL PLAN Y T C O U N E G RIVERSIDE COUNTY N A R Rainbow O Pendleton-De Luz Fallbrook Palomar Mountain P Pala-Pauma A Valley COUNTY IMPERIAL C I F Bonsall North Mountain I Borrego Springs C Valley Center O Hidden C Meadows E Twin A Oaks Valley N North County Metro Desert Julian LEGEND San Dieguito 100 year Floodway Ramona 100 year Floodplain Incorporated Area Cuyamaca Community/Subregional Planning Area Boundary Subregional Group Lakeside Boundary Central Mountain Descanso Tribal/State/Federal Lands Lakes Alpine Pine Valley Rivers Crest-Dehesa- Harbison Canyon- Granite Hills Valle De Oro Mountain Empire Spring Valley Sweetwater Jamul-Dulzura Boulevard Lake Morena / Campo Jacumba Potrero Otay Tecate O C Map Date: May 2009 I 1 X Source: FEMA, County of San Diego E M Miles FLOOD PLAINS 0246810 San Diego County General Plan Figure S-5 CHAPTER 7 SAFETY ELEMENT Floodingmayalsooccurastheresultofdamfailure.Thefailureofadamoccursmostcommonlyasaresult of poor design/construction, lack of maintenance, or structural damage caused by an earthquake. Areas subject to inundation due to a dam failure are shown in FigureSͲ6 (Dam Inundation Areas). This event is extremelyhazardous,asitwilltypicallyoccurquicklyandwithoutwarning.Areasdirectlybelowthedamare at the greatest risk, and, as the water moves further downstream, reduces in velocity, and becomes shallowerindepth,themagnitudeofthedamageandpotentialrisktolifeandpropertydecreases. Themosteffectivewaystoreducetheriskofflooding is to ensure development is located outside flood prone areas. However, it is also possible to reduce flooding by constructing drainage facilities or using other design measures to mitigate hazards. Urbanization affects flooding by reducing the permeabilityoflandsurfaces,whichalsoincreasesthe amount of stormwater runoff and the required capacityofchannels.InVillageandRuralVillagesand inareascontainingVillagedensities,theGeneralPlan policiesdiscouragefuturedevelopmentfromlocating within a floodplain, but recognize that there may be instanceswhereencroachmentiswarranted.Because lowerdensitydevelopmentprovidesgreaterflexibility DaminunincorporatedCounty when siting structures, future development in Semi RuralandRuralLandsdesignationsshouldbelocatedoutsidemappedfloodplainsandnaturalfloodcontrol systems. GOALSANDPOLICIES GOALSͲ9 ProtectionofLifeandProperty.Minimizedpersonalinjuryandpropertydamagelossesresulting fromfloodevents. Policies SͲ9.1 FloodplainMaps.Managedevelopmentbasedonfederalfloodplainmaps.Countymapsshallalso be referred to and in case of conflict(s) between the County floodplain maps and the federal floodplainmaps,themorestringentofrestrictionsshallapply. SͲ9.2 Development in Floodplains. Limit development in designated floodplains to decrease the potentialforpropertydamageandlossoflifefromfloodingandtoavoidtheneedforengineered channels, channel improvements, and other flood control facilities. Require development to conformtofederalfloodproofingstandardsandsitingcriteriatopreventflowobstruction. SͲ9.3 DevelopmentinFloodHazardAreas.Requiredevelopmentwithinmappedfloodhazardareasbe sited