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Table of Contents

County of Riverside General Plan - Hearing Draft
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[Table of Contents]
APPENDIX H
Section     County of Riverside General Plan - Hearing Draft Page No.
CHAPTER 1: SEISMIC HAZARD
         
1.1 Introduction 1-1
  1.1.1 Faults 1-2
  1.1.2 Causes of Earthquake Damage 1-5
  1.1.3 General Tectonic Setting 1-7
  1.1.4 Common Designations of Earthquake Hazard Potential 1-10
  1.1.5 Laws to Mitigate Earthquake Hazard 1-15
       
1.2 Major Earthquake Sources in Riverside County 1-17
  1.2.1 San Andreas Fault Zone 1-17
  1.2.2 San Jacinto Fault Zone 1-21
  1.2.3 Elsinore Fault Zone 1-21
  1.2.4 Cucamonga Fault Zone 1-22
       
1.3 Riverside County Seismicity 1-23
  1.3.1 Past Damaging Earthquakes 1-25
  1.3.2 Seismicity of Riverside County 1-28
  1.3.3 Earthquake Geographic Information System Coverage for Riverside County 1-31
       
1.4 Fault Rupture 1-34
  1.4.1 Geographic Information System Coverage of Faults 1-34
  1.4.2 Geographic Information System Coverage of Fault Special Studies Zones 1-37
       
1.5 Expected Earthquake Analyses 1-40
  1.5.1 Design Earthquakes 1-40
  1.5.2 Probabilistic Earthquake Hazard Assessment 1-42
  1.5.3 Foreshocks on Strike-Slip Faults 1-46
  1.5.4 Uses and Limitations of Seismic Hazard Mapping 1-48
       
1.6 Secondary Earthquake Hazards 1-50
  1.6.1 Liquefaction 1-50
  1.6.2 Guidelines for Delineating Liquefaction Hazard Zones 1-51
    1.6.2.1 Geographic Information System Coverage of Shallow Ground Water 1-55
  1.6.3 Liquefaction Hazard Zones in Riverside County 1-56
    1.6.3.1 Geographic Information System Coverage of Liquefaction Hazards in Riverside County 1-60
  1.6.4 Seismically Induced Settlement 1-60
  1.6.5 Seismically Induced Slope Instability 1-61
  1.6.6 Seiches 1-63
       
1.7 Vulnerability of the Built Environment to Earthquake Hazards 1-65
  1.7.1 Potentially Hazardous Buildings and Structures 1-65
  1.7.2 Essential Facilities 1-72
  1.7.3 Lifelines 1-82
       
1.8 HAZUS Earthquake Scenario Loss Estimations 1-86
  1.8.1 Methodology and Terminology Used in Earthquake Loss Estimation 1-87
  1.8.2 HAZUS Scenario Earthquakes 1-94
  1.8.3 Inventory Data used in the HAZUS Loss Estimations 1-96
  1.8.4 Estimated Losses Associated with Scenario Earthquakes 1-98
  1.8.5 Estimated Losses Associated with a Mw 6.9 San Jacinto Fault Earthquake (MPE) 1-103
  1.8.6 Estimated Losses Associated with a Mw 7.9 Southern San Andreas Earthquake 1-107
       
1.9 Reducing Earthquake Hazards in the County of Riverside 1-113
  1.9.1 1997 Uniform Building Code Impacts on the County of Riverside 1-114
  1.9.2 Retrofit and Strengthening of Existing Structures 1-120
       
1.10 Earthquake Safety 1-124
  1.10.1 Anatomy of a Safe Building 1-124
  1.10.2 Protecting the Contents of Your Home 1-125
  1.10.3 Personal Safety During an Earthquake 1-127
    1.10.3.1 Prepare a Plan 1-127
    1.10.3.2 Duck, Cover, and Hold 1-128
  1.10.4 After the Earthquake 1-129
    1.10.4.1 Fire Prevention 1-127
    1.10.4.2 What You Will Need 1-128
  1.10.5 Recommended Resources 1-131
       
1.11 Summary of Findings and Recommended Programs 1-133
       
CHAPTER 2: SLOPE AND SOIL INSTABILITY HAZARDS
       
2.1 Physiographic and Geologic Setting 2-1
       
2.2 Geology and Engineering Geology Hazards 2-5
  2.2.1 Development of GIS Engineering Geology Map 2-6
       
2.3 Mass Wasting-Slope Instability Map 2-7
  2.3.1 Introduction 2-7
  2.3.2 Rock Fall 2-11
  2.3.3 Debris Flows 2-11
  2.3.4 development of a GIS Landslide and Slope Instability Map 2-13
       
2.4 Expansive Soils 2-15
       
2.5 Collapsible Soils 2-16
       
2.6 Ground Subsidence 2-17
  2.6.1 Elsinore Trough 2-18
  2.6.2 San Jacinto Valley 2-23
  2.6.3 Coachella Valley 2-23
  2.6.4 Development of a GIS Subsidence Hazard Map for Riverside County 2-26
       
2.7 Wind Erosion 2-27
  2.7.1 Coachella Valley 2-27
  2.7.2 Development of a GIS Wind Erosion Susceptibility Map 2-31
       
2.8 Recommendations for Mitigation of Soil Instability Hazards 2-32
  2.8.1 Regulation and Governance 2-32
  2.8.2 Mitigation of Slope Instability 2-32
  2.8.3 Mitigation of Expansive Soils 2-35
  2.8.4 Mitigation of Collapsible Soils 2-35
  2.8.5 Ground Subsidence 2-35
    2.8.5.1 Recommended Minimum Requirements to Address Subsidence Potential 2-38
  2.8.6 Mitigation of Wind Erosion 2-40
       
2.9 Summary 2-41
       
CHAPTER 3: FLOOD HAZARDS
       
3.1 Overview 3-1
       
3.2 Previous Flood Disasters Affecting Riverside County 3-5
  3.2.1 Floods Meriting Disaster Proclamations 3-5
  3.2.2 Historic Flood Flows 3-7
  3.2.3 Winter Floods of 1980 3-11
       
3.3 Flood Problem Areas 3-14
  3.3.1 Earthquake Hazard to Local Water Tanks/Reservoirs 3-18
  3.3.2 Bridge Scour 3-18
       
3.4 Geographic Information Systems Flood Mapping 3-20
  3.4.1 Benefits of Flood mapping Using Geographic Information Systems 3-22
  3.4.2 Essential Facility Inventory Exposed to Flood Hazards 3-23
       
3.5 County Flood Control Reservoir Projects 3-24
  3.5.1 Seven Oaks Dam 3-24
  3.5.2 Prado Dam 3-24
  3.5.3 Lake Elsinore 3-25
  3.5.4 East Side Reservoir Project 3-25
  3.5.5 Inland Feeder Project 3-26
  3.5.6 Murrieta Creek-Flood Control Master Plan 3-26
  3.5.7 Lake Mathews 3-26
  3.5.8 Whitewater River 3-27
  3.5.9 Salton Sea 3-27
  3.5.10 Riverside County Flood Control and Water Conservation District Projets 3-29
       
3.6 Dam Failure 3-32
  3.6.1 Dam Inventory Data for Riverside County 3-32
  3.6.2 Dam Inundation Potential Along the Colorado River 3-35
  3.6.3 GIS Dam Inundation Mapping for Riverside County 3-37
  3.6.4 Performance of Dams in Earthquakes 3-41
  3.6.5 Seismic Retrofit Projects 3-42
  3.6.6 Mitigation Alternatives-Storage Restrictions 3-43
       
3.7 Flood Hazard Reduction in Riverside County 3-44
  3.7.1 National Flood Insurance Program 3-45
  3.7.2 Riverside County Flood Control District 3-46
  3.7.3 Flood Protection Measures 3-47
  3.7.4 Flood Safety 3-50
       
3.8 The Future of Flood Hazard Mitigation 3-52
  3.8.1 Wetlands 3-52
  3.8.2 Conflicts with Environmental Legislation 3-53
  3.8.3 National Pollutant Discharge Elimination System (NPDES) 3-56
       
3.9 Summary 3-58
       
CHAPTER 4: WILDLAND FIRE HAZARDS
       
4.1 Overview 4-1
  4.1.1 Previous Fire Disasters 4-3
       
4.2 Fire Safety Regulations 4-7
  4.2.1 Real Estate Disclosure and Maintenance Requirements 4-9
       
4.3 Development of a GIS Wildland Fire Susceptibility Map 4-12
  4.3.1 HUD Study Program 4-17
  4.3.2 Bates Bill Process 4-19
    4.3.2.1 Classification Points for Basic Factors 4-20
    4.3.2.2 Additional Weighting Factors 4-21
       
4.4 Previous Fire Hazard Maps for Riverside County 4-23
  4.4.1 Environmental Hazards Map for Riverside County 4-23
  4.4.2 California Department of Forestry and Fire Protection, Fire Hazard Mapping 4-23
       
4.5 Prefire Management 4-24
  4.5.1 Fire Prevention 4-24
  4.5.2 Vegetation Management 4-25
  4.5.3 Fire Safe Construction and Land Use Planning 4-26
  4.5.4 Greenness Mapping 4-26
  4.5.5 Fire Potential Index 4-27
  4.5.6 Riverside Fire Laboratory 4-27
  4.5.7 Prescribed Fire 4-29
  4.5.8 Hazardous Fire Area Designation 4-30
  4.5.9 Hazard Abatement Notices 4-31
  4.5.10 Fire Flow 4-31
  4.5.11 Model Fire hazard Reduction Ordinance 4-32
       
4.6 Earthquake-Induced Fires 4-35
  4.6.1 Natural Gas Fires - Northridge Earthquake 4-35
  4.6.2 Earthquake-Induced Fire Scenarios for the Riverside County Area using HAZUS 4-36
       
4.7 Postfire Effects 4-43
       
4.8 Fire Response Resources 4-44
  4.8.1 California Department of Forestry 4-44
  4.8.2 Riverside County Fire Department 4-45
       
4.9 Fire Safety 4-47
  4.9.1 Homeowners Checklist to Reduce Fire Risk 4-47
       
4.10 Summary 4-49
       
4.11 Recommended Programs 4-54
       
CHAPTER 5: POLICIES
       
5.1 State Laws and Administrative Guidelines 5-2
  5.1.1 Basic General Plan Law 5-2
  5.1.2 Legislative Background 5-3
  5.1.3 State Safety Element Review 5-3
  5.1.4 Safety Element Guidelines 5-4
  5.1.5 Related Federal Laws 5-4
  5.1.6 Related State Laws and Guidelines 5-6
       
5.2 Insurance Programs 5-8
  5.2.1 Challenges Faced by Private Insurers 5-9
  5.2.2 Need for Government-Assisted Earthquake Insurance 5-12
  5.2.3 Federal Earthquake Insurance Proposals 5-12
  5.2.4 State Earthquake Insurance 5-13
  5.2.5 Improvements Still Needed 5-14
       
5.3 Disincentives to Unsafe Development 5-15
  5.3.1 Seismic Design Codes 5-15
  5.3.2 Geological Hazards Mapping 5-18
  5.3.3 Density Restrictions 5-18
  5.3.4 Impact Fees 5-19
  5.3.5 Proposition 218 5-20
       
5.4 Incentives for Safer Development 5-21
  5.4.1 Project Impact: Building Disaster Resistant Communities 5-21
  5.4.2 Retrofit financing Incentives 5-21
  5.4.3 Assessment District Formation 5-22
  5.4.4 Historic Preservation Incentives 5-22
  5.4.5 Extended Nonconforming Rights 5-22
  5.4.6 On-site Density Transfer Incentives 5-23
  5.4.7 Transfer of Development Rights 5-23
  5.4.8 Severe Development Restrictions 5-24
  5.4.9 Property Acquisition 5-25
       
5.5 Hazard Information Management Systems 5-26
  5.5.1 Geographic Information Systems 5-26
  5.5.2 Riverside County's Land-Based Data Systems 5-27
  5.5.3 Implementing an Emergency Management GIS 5-28
  5.5.4 User Responsive System Development 5-29
       
5.6 Hazards Overlay Zones 5-31
  5.6.1 Overlay Zones as a Planning Tool 5-32
  5.6.2 Hazards Management Zoning 5-33
  5.6.3 State Seismic Overlay Zones 5-34
  5.6.4 Disadvantages of Local Safety Overlay Zoning 5-34
       
5.7 Recovery and Reconstruction 5-36
  5.7.1 The Safety Element and Recovery Planning 5-36
  5.7.2 Status of Recovery Planning in Riverside County 5-37
  5.7.3 Recovery Planning Issues 5-37
  5.7.4 Recovery Ordinance as a First Step 5-38
       
5.8 Summary 5-40
       
LIST OF FIGURES
       
Figure 1-1 Geologic Provinces of the Riverside County Area 1-9
Figure 1-2 Regional Faulting of the Riverside County Area 1-13
Figure 1-3 Fault Segments and Earthquake Probabilities in Riverside County 1-20
Figure 1-4 Notable Historic Earthquakes in the Riverside County Region 1-24
Figure 1-5 Seismicity of Riverside County (1890 to 1999) 1-33
Figure 1-6 Mapped Faulting in Riverside County 1-35
Figure 1-7 Earthquake Fault Studies Zones in Riverside County 1-36
Figure 1-8 Index of Official Earthquake Fault Zone Maps for Riverside County 1-39
Figure 1-9 Probabilistic Acceleration Contour Mapping for Riverside County 1-44
Figure 1-10 Liquefaction Hazard Rating Criteria 1-58
Figure 1-11 Generalized Liquefaction Susceptibility Map 1-59
Figure 1-12 Earthquake-Induced Slope Instability Map 1-62
Figure 1-13 Unreinforced Masonry Building (URM) 1-67
Figure 1-14 Precast Concrete-Frame Construction 1-70
Figure 1-15 Inventory of Hospital Locations in Relation to Ground Shaking Risk 1-74
Figure 1-16 Inventory of Emergency Response Facilities in Relation to Ground Shaking Risk 1-75
Figure 1-17 Inventory of School Locations in Relation to Ground Shaking Risk 1-76
Figure 1-18 Inventory of Communication Facilities in Relation to Ground Shaking Risk 1-77
Figure 1-19 Inventory of Dam Locations in Relation to Ground Shaking Risk 1-78
Figure 1-20 Inventory of Highway Bridges in Relation to Ground Shaking Risk 1-79
Figure 1-21 Inventory of Hazardous Materials in Relation to Ground Shaking Risk 1-80
Figure 1-22 Inventory of Airport Locations in Relation to Ground Shaking Risk 1-83
Figure 1-23 Inventory of Highways in Relation to Ground Shaking Risk 1-84
Figure 1-24 Inventory of Rail Facilities, and Water, Oil, and Natural Gas Pipelines in Relation to Ground Shaking Risk 1-85
Figure 1-25 Flow Chart Illustrating HAZUS Methodology 1-88
Figure 1-26 Census Tract Boundaries HAZUS '99 Loss Estimation General Stock Inventory Aggregation 1-90
Figure 1-27 County of Riverside Building Inventory by Occupancy Type 1-96
Figure 1-28 Relative Projected Loss Estimations for Scenario Earthquakes 1-99
Figure 1-29 Near Source Zone Regions Impacting Riverside County and UBC Zone Boundary 1-115
Figure 1-30 General Uniform Building Code Soil Types 1-117
     
Figure 2-1 Map of Geologic Provinces of the Riverside County Area 2-3
Figure 2-2 Engineering Geologic Materials Map Riverside County 2-4
Figure 2-3 Regions Underlian by Steep Slopes 2-8
Figure 2-4 Slope Failure Types 2-10
Figure 2-5 Slope Failure and Landslide Susceptibility Rating Criteria 2-14
Figure 2-6 Documented Subsidence Areas in Riverside County 2-19
Figure 2-7 General Map of Temecula-Murrieta Area Showing Graben-Bounding Faults, and Major Fissure Areas 2-20
Figure 2-8 Schematic Cross-Sections Illustrating Collapsible Alluvium and Fissure Formation for the Murrieta Area 2-22
Figure 2-9 Groundwater Table Profile of the Upper Coachella Valley 2-25
Figure 2-10 Wind-Induced Soil Movement 2-28
Figure 2-11 Wind Erosion Susceptibility Map Riverside County 2-30
     
Figure 3-1 100- and 500-Year Flood Hazard Zones of Riverside County 3-4
Figure 3-2 Drainage Systems of Riverside County 3-15
Figure 3-3 Dam Failure Inundation Zones of Riverside County 3-40
Figure 3-4 Adding Waterproof Veneer to Exterior Wall 3-47
Figure 3-5 Raising Electrical Systems 3-48
Figure 3-6 Sewer Backflow Valve Installation 3-49
     
Figure 4-1 Historical Wildland Fires in Riverside County 4-4
Figure 4-2 Wildfire Hazard Rating Criteria 4-14
Figure 4-3 Wildfire Susceptibility Riverside County 4-15
Figure 4-4 Emergency Response Facility Damage Based on Mw 7.9 San Andreas Scenario Earthquake 4-38
Figure 4-5 Emergency Response Facility Damage Based on Mw 6.9 San Jacinto Scenario Earthquake 4-39
     
Figure 5-1 Insured Catastrophe Losses in the United States from 1949-1997 in 1997 Dollars 5-11
Figure 5-2 Insurance Claims versus Age of Structure as a Result of the 1994 Northridge Earthquake 5-16
     
LIST OF TABLES
     
Table 1-1 Abridged Modified Mercalli Intensity Scale 1-14
Table 1-2 Fault Source Parameters for Riverside County 1-19
Table 1-3 Historical Earthquakes Impacting Riverside County 1-23
Table 1-4 Alquist-Priolo Earthquake Fault Zone Maps Available for Riverside County 1-38
Table 1-5 Probable Earthquake Scenarios for Riverside County 1-41
Table 1-6 Probabilistic Earthquake Accelerations for Riverside County 1-45
Table 1-7 Magnitude of possible foreshock required to reach a specified probability level for four microseismic regions of the southern San Andreas fault (Working Group, 1991) 1-47
Table 1-8 Alert levels and response for anomalous earthquake activity along the southern San Andreas fault (working Group, 1991) 1-47
Table 1-9 General Liquefaction Potential Zones for Riverside County 1-57
Table 1-10 HAZUS Injury Classification Scale 1-93
Table 1-11 HAZUS Scenario Earthquakes for Riverside County 1-95
Table 1-12 Transportation System Lifeline Inventory 1-97
Table 1-13 Utility System Lifeline Inventory 1-98
Table 1-14 Number of Buildings Damaged 1-100
Table 1-15 Estimated Casualties 1-101
Table 1-16 Estimated Shelter Requirements 1-102
Table 1-17 Estimated Economic Losses 1-102
Table 1-18 Expected Building Damage by Occupancy Mw 6.9 San Jacinto Fault Earthquake 1-103
Table 1-19 Expected Building Damage by Building Type (all design levels) Mw 6.9 San Jacinto Fault Earthquake 1-104
Table 1-20 Expected Damage to Essential Facilities as a Result of a Mw 6.9 Earthquake on the San Jacinto Fault 1-104
Table 1-21 Expected Damage to the Transportation Systems as a Result of a Mw 6.9 Earthquake on the San Jacinto Fault 1-105
Table 1-22 Expected Electric Power System Performance as a Result of a Mw 6.9 Earthquake on the San Jacinto Fault 1-105
Table 1-23 Casualty Estimates as a Result of a Mw 6.9 Earthquake on the San Jacinto Fault 1-106
Table 1-24 Building-Related Economic Loss Estimates (millions of dollars) as a Result of a Mw 6.9 Earthquake on the San Jacinto Fault 1-107
Table 1-25 Expected Building Damage by Occupancy Mw 7.9 San Andreas Fault Earthquake 1-108
Table 1-26 Expected Building Damage by Building Type (all design levels) Mw 6.9 San Andreas Fault Earthquake 1-108
Table 1-27 Expected Damage to Essential Facilities as a Result of a Mw 6.9 Earthquake on the San Andreas Fault 1-109
Table 1-28 Expected Damage to the Transportation Systems as a Result of a Mw 6.9 Earthquake on the San Andreas Fault 1-109
Table 1-29 Expected Electric Power System Performance as a Result of a Mw 6.9 Earthquake on the San Andreas Fault 1-110
Table 1-30 Casualty Estimates as a Result of a Mw 6.9 Earthquake on the San Andreas Fault 1-111
Table 1-31 Building-Related Economic Loss Estimates (millions of dollars) as a Result of a Mw 6.9 Earthquake on the San Andreas Fault 1-112
Table 1-32 1997 Uniform Building Code Soil Profile Type 1-116
Table 1-33 1997 Uniform Building Code Seismic Source Types 1-118
Table 1-34 1997 Uniform Building Code Near-Source Zones and Classifications of Faults in Riverside County 1-119
     
Table 2-1 Sources Digitized for Geologic Map Coverage Riverside County 2-5
     
Table 3-1 Historical Stream Gage Data for Riverside County 3-10
Table 3-2 Peak Elevation Levels of Lake Elsinore 3-11
Table 3-3 U.S. Geological Survey Flood Prone Area Maps 3-21
Table 3-4 Facilities in Riverside County Exposed to Flood Hazards 3-23
Table 3-5 Flood Control Project Request FY 2000 Riverside County Flood Control District 3-29
Table 3-6 National Inventory of Dam (NATDAM) Data for Riverside County 3-33
Table 3-7 Inundation Modeling of Colorado River Dams 3-37
Table 3-8 Dam Failure Inundation Map Sources 3-39
Table 3-9 Local Agencies with Flood Control Responsibilities 3-45
     
Table 4-1 20 Largest California Wildland Fires (Ranked by Structures Lost) 4-5
Table 4-2 Disaster Declarations Impacting Riverside County 4-6
Table 4-3 Rating Systems Used for Development of GIS Map 4-16
Table 4-4 Sample Form for Bates Bill Process Determination of Very High Fire Hazard Severity Zone 4-22
Table 4-5 Unifirm Fire Code Minimum Fire Protection Flows 4-31
Table 4-6 Road Standards for Fire Equipment Access 4-33
Table 4-7 Structural Standards 4-34
Table 4-8 Model Ordinance Checklist, Fuel Modification Standards 4-34
Table 4-9 Scenario Earthquakes for Riverside County 4-37
Table 4-10 Earthquake Induced Fire Losses in Riverside County HAZUS Scenario Earthquakes 4-40
Table 4-11 Estimated Functionality (in percent) of County Fire Response Facilities Based on Scenario Earthquakes at One Day After Event 4-41
     
LIST OF APPENDICES
     
Appendix A References  
Appendix B Glossary  
Appendix C Fault Data  
Appendix D GIS Metadata  
     
LIST OF PLATES
     
Plate 1-1 Riverside County Seismicity (1890 to 1999) (1:250,000, in-pocket)  
Plate 1-2 Faults of Riverside County (1:250,000, in-pocket)  
Plate 1-3 Fault Study Zones (1:250,000, in-pocket)  
Plate 1-4 Depth to Groundwater in Riverside County (1:250,000, in-pocket)  
Plate 1-5 Liquefaction Susceptibility Map (1:250,000, in-pocket)  
     
Plate 2-1 Engineering Geologic Materials Map (1:250,000, in-pocket)  
Plate 2-2 Digital Elevation Model for Riverside County (1:250,000, in-pocket)  
Plate 2-3 Landslide and Slope Instability Map (1:250,000, in-pocket)  
Plate 2-4 Subsidence Hazard Map (1:250,000, in-pocket)  
Plate 2-5 Wind Erosion Susceptibility (1:250,000, in-pocket)  
     
Plate 3-1 Major Drainages of Riverside County (1:250,000, in-pocket)  
Plate 3-2 Flood and Inundation Susceptibility (1:250,000, in-pocket)  
Plate 3-3 Potential Dam failure Inundation Zones (1:250,000, in-pocket)  
     
Plate 4-1 Wildfire Susceptibility Map (1:250,000, in-pocket)  
 
 
 

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