Table of Contents Section Page D.4 Coastal Flooding Analyses and Mapping: Pacific Coast D.4.1-1 D.4.1 Pacific Coast Guidelines Overview D.4.1-2 D.4.1.1 Pacific Coast Setting and Characteristics D.4.1-4 D.4.1.2 Pacific Coast Flood Insurance Studies D.4.1-7 D.4.1.2.1 Study Scoping D.4.1-7 D.4.1.2.2 Regional vs. Local Studies D.4.1-9 D.4.1.2.3 Sheltered Waters D.4.1-10 D.4.1.2.4 Tsunami Hazards D.4.1-12 D.4.1.2.5 Debris D.4.1-12 D.4.1.2.6 Beach Nourishment and Constructed Dunes D.4.1-13 D.4.1.2.7 Hazard Zone Definitions and Use by FEMA D.4.1-13 D.4.1.2.8 Reporting Requirements D.4.1-15 D.4.2 Study Methodology D.4.2-1 D.4.2.1 Overview D.4.2-1 D.4.2.2 Setting D.4.2-2 D.4.2.2.1 Open Coast and Sheltered Water D.4.2-3 D.4.2.2.2 Shoreline Profile Settings D.4.2-3 D.4.2.3 Coastal Zones D.4.2-5 D.4.2.4 Event and Response Analysis Considerations D.4.2-8 D.4.2.5 Selection of Events D.4.2-10 D.4.2.5.1 Open Coast D.4.2-10 D.4.2.5.2 Sheltered Waters D.4.2-10 D.4.2.5.3 1% Annual Chance Conditions D.4.2-10 D.4.2.5.4 0.2% Annual Chance Conditions D.4.2-16 D.4.2.6 Summary of Methods D.4.2-16 D.4.2.7 Examples D.4.2-18 D.4.2.7.1 Open Coast, Dune Backed Beach Scenario Using Parametric DIM Model for Setup/Runup D.4.2-20 D.4.2.7.2 Open Coast, Dune Backed Beach Scenario Using Numerical DIM Model for Setup/Runup D.4.2-24 D.4.2.7.3 Sheltered Water, Seawall Backed Beach Scenario Using Parametric DIM for Setup/Runup D.4.2-27 D.4.3 Flood Frequency Analysis Methods D.4.3-1 D.4.3.1 The 1% Annual Chance Flood D.4.3-1 D.4.3.2 Event vs. Response Statistics D.4.3-2 D.4.3.2.1 Event-Selection Method D.4.3-2 D.4.3.2.2 Response-based Approach D.4.3-3 D.4.3.2.3 Hybrid Method D.4.3-4 D.4.3.3 General Statistical Methods D.4.3-4 D.4.3.3.1 Overview D.4.3-4 D.4.3.3.2 Elementary Probability Theory D.4.3-5 D.4.3.3.3 Distributions of Continuous Random Variables D.4.3-6 D.4.3.3.4 Stationarity D.4.3-8 D.4.3.3.5 Correlation Between Series D.4.3-9 D.4.3.3.6 Convolution of Two Distributions D.4.3-9 D.4.3.3.7 Important Distributions D.4.3-9 D.4.3.4 Data Sample and Estimation of Parameters D.4.3-12 D.4.3.4.1 Plotting Positions D.4.3-13 D.4.3.4.2 Method of Moments: Conventional Moments D.4.3-14 D.4.3.4.3 Method of Moments: Probability-weighted Moments and Linear Moments D.4.3-14 D.4.3.4.4 Maximum Likelihood Method D.4.3-14 D.4.3.5 Extreme Value Analysis in an FIS D.4.3-15 D.4.3.6 Simulation Methods D.4.3-17 D.4.3.6.1 JPM D.4.3-17 D.4.3.6.2 EST D.4.3-18 D.4.3.6.3 Monte Carlo Method D.4.3-18 D.4.3.7 Additional Resources D.4.3-19 D.4.4 Waves and Water Levels D.4.4-1 D.4.4.1 Waves D.4.4-1 D.4.4.1.1 Wave Spectra D.4.4-2 D.4.4.1.2 Measured Deepwater Wave Data D.4.4-4 D.4.4.1.3 Hindcast Wave Data D.4.4-6 D.4.4.1.4 Wave Transformations D.4.4-11 D.4.4.1.5 Waves in Sheltered Waters D.4.4-22 D.4.4.1.6 Data Requirements D.4.4-25 D.4.4.1.7 Documentation D.4.4-25 D.4.4.2 Water Levels D.4.4-26 D.4.4.2.1 Overview D.4.4-26 D.4.4.2.2 Astronomic Tide D.4.4-26 D.4.4.2.3 Surge D.4-4-31 D.4.4.2.4 Water Levels in Sheltered Waters D.4.4-34 D.4.4.2.5 Water Levels During El Niños D.4.4-38 D.4.4.2.6 1% Annual Chance Still Water Levels D.4.4-39 D.4.4.2.7 Non-Stationary Processes D.4.4-44 D.4.5 Wave Setup, Runup, and Overtopping D.4.5-1 D.4.5.1 Wave Setup and Runup D.4.5-1 D.4.5.1.1 Introduction D.4.5-1 D.4.5.1.2 Background, Definitions, and Approaches D.4.5-1 D.4.5.1.3 General Input Requirements D.4.5-6 D.4.5.1.4 Setup and Runup on Beaches: Descriptions and Recommendations D.4.5-7 D.4.5.1.5 Runup on Barriers D.4.5-10 D.4.5.1.6 Example Computations of Total Runup D.4.5-18 D.4.5.1.7 Documentation D.4.5-20 D.4.5.2 Overtopping D.4.5-20 D.4.5.2.1 Overview D.4.5-20 D.4.5.2.2 Background D.4.5-23 D.4.5.2.3 Data Requirements D.4.5-27 D.4.5.2.4 Mean Overtopping Rate at the Crest D.4.5-27 D.4.5.2.5 Limits of Overtopping and Hazard Zones Landward of the Barrier Crest D.4.5-28 D.4.5.2.6 Documentation D.4.5-32 D.4.5.3 Wave Dissipation and Overland Wave Propagation D.4.5-32 D.4.5.3.1 Assessment of Enhanced Wave Dissipation D.4.5-33 D.4.5.3.2 Wave Attenuation by Bottom and Vegetation Interactions D.4.5-34 D.4.5.3.3 Overland Wave Propagation (WHAFIS) D.4.5-38 D.4.5.3.4 Documentation D.4.5-39 D.4.6 Coastal Erosion D.4.6-1 D.4.6.1 Overview D.4.6-1 D.4.6.2 Pacific Coast Characteristics Related to Storm-induced Erosion D.4.6-1 D.4.6.3 Background and Definitions D.4.6-2 D.4.6.3.1 Coastal Exposure D.4.6-2 D.4.6.3.2 Beach Setting D.4.6-3 D.4.6.3.3 Data Sources D.4.6-9 D.4.6.4 Estimating Eroded Beach Profiles D.4.6-12 D.4.6.4.1 The Concept of the Most Likely Winter Profile D.4.6-12 D.4.6.4.2 General Approach for Estimating Eroded Beach Profiles from Single Storms D.4.6-12 D.4.6.5 Estimating Profile Changes for Sand Beaches Backed by Low Sand Berms or High Dunes (Beach Setting No. 1) D.4.6-14 D.4.6.5.1 General K&D and MK&A Model Characteristics and Applicability D.4.6-16 D.4.6.5.2 MK&A and Its Application to Beach Setting No. 1 D.4.6-17 D.4.6.5.3 Time Dependency of Profile Response (Within the MK&A and K&D Models) D.4.6-23 D.4.6.5.4 Summary of the MK&A Geometric Modeling Approach for Sand Beaches Backed by Sand Berms and Dunes (Beach Setting No. 1) D.4.6-26 D.4.6.5.5 K&D Geometric Modeling Approach for Sand Beaches Backed by Sand Berms and Dunes (Beach Setting No. 1) D.4.6-28 D.4.6.5.6 Potential Future Use of Process-based Models D.4.6-33 D.4.6.6 Estimating Profile Changes for Sandy Beaches Backed by Protective Structures (Beach Setting No. 2) D.4.6-34 D.4.6.7 Estimating Profile Changes for Gravel and Cobble Beaches (Beach Setting No. 3) D.4.6-36 D.4.6.8 Estimating Profiles for Beaches Backed by Erodible Bluffs or Cliffs (Beach Setting No. 4) D.4.6-40 D.4.6.8.1 General Approach for Beach Setting No. 4 D.4.6-42 D.4.6.8.2 Detailed Bluff Erosion Analyses D.4.6-44 D.4.6.9 Estimating Beach Profiles for Beaches Backed by Erosion- Resistant Bluffs or Cliffs (Beach Setting No. 5) D.4.6-48 D.4.6.10 Profiles in Tidal Flats and Wetlands (Beach Setting No. 6) D.4.6-48 D.4.7 Coastal Structures D.4.7-1 D.4.7.1 Purpose and Overview D.4.7-1 D.4.7.2 Evaluation Criteria D.4.7-2 D.4.7.2.1 Detailed Engineering Evaluation of Coastal Armoring Structures D.4.7-2 D.4.7.2.2 Coastal Armoring Structure Evaluation Based on Limited Data and Engineering Judgment D.4.7-3 D.4.7.2.3 Evaluation of Beach Stabilization Structures D.4.7-3 D.4.7.3 FIS Treatment of Coastal Armoring Structures D.4.7-4 D.4.7.3.1 Failure and Removal of Coastal Armoring Structures D.4.7-4 D.4.7.3.2 Partial Failure of Coastal Armoring Structures D.4.7-4 D.4.7.3.3 Buried Coastal Structures D.4.7-9 D.4.7.3.4 Coastal Levees D.4.7-9 D.4.7.3.5 Operation and Maintenance D.4.7-16 D.4.7.4 FIS Treatment of Beach Stabilization Structures D.4.7-16 D.4.7.5 FIS Treatment of Miscellaneous Structures D.4.7-17 D.4.7.5.1 Piers, Navigation Structures, and Port Facilities D.4.7-17 D.4.7.5.2 Bridges, Culverts, and Tide Gates D.4.7-18 D.4.7.6 Data Requirements D.4.7-18 D.4.7.7 Study Documentation D.4.7-19 D.4.8 Tsunamis (Future Section) D.4.8-1 D.4.9 Mapping of Flood Hazard Zones and Base Flood Elevations D.4.9-1 D.4.9.1 Review and Evaluation of Basic Results D.4.9-1 D.4.9.2 Identification of Flood Insurance Risk Zones D.4.9-2 D.4.9.2.1 VE Zone D.4.9-2 D.4.9.2.2 AE Zone D.4.9-5 D.4.9.2.3 AH Zone D.4.9-5 D.4.9.2.4 AO Zone D.4.9-5 D.4.9.2.5 X Zone D.4.9-5 D.4.9.3 Wave Envelope D.4.9-5 D.4.9.4 Criteria for Flood Boundary and Hazard Zone Mapping D.4.9-6 D.4.9.5 Transect Examples D.4.9-8 D.4.9.6 Mapping Procedures D.4.9-18 D.4.10 Study Documentation D.4.10-1 D.4.10.1 General Documentation D.4.10-1 D.4.10.2 Engineering Analyses D.4.10-1 D.4.11 References D.4.11-1 D.4.12 Notation D.4.12-1 D.4.13 Acronyms D.4.13-1 D.4.14 Glossary D.4.14-1 D.4.1-1 Applicable Area – Pacific Coast Guidelines D.4.1-1 D.4.1-2 Pacific Coast Guidelines Overview D.4.1-3 D.4.2-1 Study Methodology Development Considerations D.4.2-2 D.4.2-2a Shoreline Profile Setting Nos. 1 to 3 D.4.2-4 D.4.2-2b Shoreline Profile Setting Nos. 4 to 6 D.4.2-4 D.4.2-3 Coastal Zones D.4.2-6 D.4.2-4 Coastal Zones and Processes D.4.2-7 D.4.2-5 Transition from Multiple to Single Events D.4.2-9 D.4.2-6 Determination of 1% Conditions D.4.2-13 D.4.2-7 Methodology Examples D.4.2-18 D.4.3-1 Cumulative and Density Distributions for the La Jolla Tide Residual D.4.3-16 D.4.4-1a Example of a One-Dimensional Continuous Spectrum D.4.4-2 D.4.4-1b Example of a Two-Dimensional Continuous Energy Spectrum D.4.4-2 D.4.4-2a Example of a One-Dimensional Discrete Spectrum D.4.4-3 D.4.4-2b Example of a Two-Dimensional Discrete Spectrum D.4.4-3 D.4.4-3 NDBC Buoy Locations near Southern California D.4.4-5 D.4.4-4 NDBC Buoy Locations in the North Pacific D.4.4-5 D.4.4-5 WIS Stations in Central California D.4.4-8 D.4.4-6 WIS Stations in Southern California D.4.4-9 D.4.4-7 Example of GROW Station Locations Along the Pacific Coast D.4.4-10 D.4.4-8 Flow Chart for Wave Transformation Analysis D.4.4-14 D.4.4-9 Example Placement of Nearshore Point and Location of Cross-Shore Transects D.4.4-15 D.4.4-10 Conceptual Diagram of Spectral Transformation D.4.4-15 D.4.4-11 Flow Chart of Tasks to Derive Nearshore Wave Hindcast Information for a FEMA Study Area D.4.4-21 D.4.4-12 Predicted and Observed Tides at Crescent City, California D.4.4-30 D.4.4-13 Definition Sketch for the BST Formulation D.4.4-32 D.4.4-14 El Niño Fluctuations since 1970 D.4.4-39 D.4.4-15 Schematic Illustration of Riverine and Surge Rate Combination D.4.4-43 D.4.5-1 Schematic of Energy and Momentum Transfer from Winds to Waves within the Wave-generating Area, and to the Surf Zone and Related Processes D.4.5-2 D.4.5-2 Wave Setup Due to Transfer of Momentum D.4.5-3 D.4.5-3 Static Wave Setup Definitions at Still Water Level and Maximum Setup D.4.5-3 D.4.5-4 Definitions of Static and Dynamic Wave Setup and Incident Wave Runup D.4.5-4 D.4.5-5 Spectral Width Parameter Versus Gamma for JONSWAP Spectra D.4.5-7 D.4.5-6 Runup on Coastal Structures, Definition Sketch D.4.5-11 D.4.5-7 Non-dimensional Total Runup vs. Iribarren Number D.4.5-12 D.4.5-8 Berm Parameters for Wave Runup Calculations D.4.5-14 D.4.5-9 Structure Porosity Definition D.4.5-14 D.4.5-10 Example Plot Showing the Variation of Surf Zone Parameters D.4.5-17 D.4.5-11 Offshore Profile for Example Problem D.4.5-19 D.4.5-12 Definition Sketch for Two Types of Overtopping D.4.5-22 D.4.5-13 Parameters Available for Mapping BFEs and Flood Hazard Zones D.4.5-23 D.4.5-14 Definition Sketch for Wave Overtopping by Splash D.4.5-29 D.4.5-15 Solution of Trajectory Equations for Splashdown Distances D.4.5-30 D.4.5-16 Overtopping Resulting in Bore Propagation D.4.5-31 D.4.5-17 Schematic of Wave Attenuation Processes D.4.5-33 D.4.5-18 Native Pacific Cordgrass Meadow at Blackie’s Pasture, Marin County D.4.5-37 D.4.5-19 Tall Stand of Atlantic Smooth Cordgrass Hybrids Invading a Native Patch of Pacific Cordgrass Meadow near Tiburon, California D.4.5-37 D.4.6-1 Typical Pacific Coast Summer and Winter Beach Profiles D.4.6-2 D.4.6-2a Sand Beach Backed by High Sand Dune (Beach Setting No. 1) D.4.6-4 D.4.6-2b Sand Beach Backed by Low Sand Berm (Beach Setting No. 1) D.4.6-4 D.4.6-3 Sand Beach Backed by Shore Protection Structures (Beach Setting No. 2) D.4.6-5 D.4.6-4 Cobble, Gravel, Shingle, or Mixed Grain Sized Beach and Berms (Beach Setting No. 3) D.4.6-5 D.4.6-5 Erodible Coastal Bluffs (Beach Setting No. 4) D.4.6-6 D.4.6-6 Non-Erodible Coastal Bluffs and Cliffs (Beach Setting No. 5) D.4.6-6 D.4.6-7 Tidal Flats and Wetlands (Beach Setting No. 6) D.4.6-7 D.4.6-8 Evolution of the Initial Beach Profile Before Occurrence of Large Storm Event D.4.6-13 D.4.6-9 Definition Sketch of MLWP for Sand Beach Backed by Sand Dunes (Beach Setting No. 1) D.4.6-14 D.4.6-10 Sandy Beach Backed by Low Berm, Newport Beach, CA D.4.6-15 D.4.6-11 Sandy Beach Backed by Low Berm, Huntington Beach, CA D.4.6-15 D.4.6-12 Photograph of Netarts Bay, Oregon D.4.6-17 D.4.6-13 Definition Sketches for Terms and Dimensions Required by the Modified Komar & Allan Geometric Model D.4.6-19 D.4.6-14 Relationships Between Beach Slope and Median Diameter of Beach Sands D.4.6-20 D.4.6-15 Schematics of Dune Overtopping with the MK&A Model D.4.6-22 D.4.6-16 Storm Duration Recession Reduction Factor D.4.6-26 D.4.6-17 Key Activities to Determine Beach Profile Changes for Beach Setting No. 1 D.4.6-26 D.4.6-18 Definition Sketch for K&D Geometric Model D.4.6-29 D.4.6-19 Sketch for K&D Geometric Model for Case Where Historical Beach Profile Data Are Available to Prepare the MLWP D.4.6-29 D.4.6-20 Sand Beach Backed by Shore Protection Structures, Crystal Cove, California D.4.6-35 D.4.6-21 Key Activities to Determine Beach Profile Changes for Beach Setting No. 2 D.4.6-35 D.4.6-22 Sand Beach Backed by Cobble Berm and Bluffs, South Carlsbad, California D.4.6-37 D.4.6-23 Sand Beach Backed by Cobble and Shingle Berm and Sandy Terrace, Batiquitos Lagoon, California D.4.6-37 D.4.6-24 Measured Beach Profile Change Due to January 1988 Storm, Batiquitos Lagoon, California D.4.6-38 D.4.6-25 Measured Beach Profile Change Before and After January 1988 Storm, Batiquitos Lagoon, California D.4.6-38 D.4.6-26 Key Activities to Determine Beach Profile Changes for Beach Setting No. 3 D.4.6-39 D.4.6-27 Wave Cut Coastal Bluff, Encinitas, California D.4.6-41 D.4.6-28 Bluff Failure and Retreat During 1998 El Niño Storms, Pacifica, California D.4.6-41 D.4.6-29 Bluff Failure and Retreat, Encinitas, California D.4.6-42 D.4.6-30 Key Activities to Determine Beach Profile Changes for Bluffs Beach Setting No. 4 D.4.6-43 D.4.6-31 Typical Erodible Bluff Profile Fronted by Narrow Sand-capped Beach D.4.6-46 D.4.6-32 Photo of Erosion-resistant Cliff D.4.6-48 D.4.6-33 Key Activities to Determine Beach Profile Changes for Beach Setting No. 5 D.4.6-49 D.4.6-34 Photograph of Tidal Flats and Wetlands Complex D.4.6-50 D.4.6-35 Key Activities to Determine Beach Profile Changes for Beach Setting No. 6 D.4.6-50 D.4.7-1a General Classification of Coastal Armoring Structures D.4.7-5 D.4.7-1b General Classification of Coastal Armoring Structures D.4.7-6 D.4.7-2 Partial Failure of Vertical Coastal Structure D.4.7-7 D.4.7-3 Partial Failure of a Sloping Revetment D.4.7-8 D.4.7-4 Example of a Buried Coastal Structure that Could Affect Flood Hazard Zones and BFEs D.4.7-10 D.4.7-5 Methodology for Evaluating Buried Coastal Structures D.4.7-11 D.4.7-6 Buried Structure Remains Buried During 1% Annual Chance Flood D.4.7-12 D.4.7-7 Buried Structure Exposed During 1% Annual Chance Flood D.4.7-13 D.4.7-8 Levee Removal, Multiple Levee Situation D.4.7-15 D.4.9-1 Example Designation of High-velocity Flow VE Zones Based on Flood Depth and Velocity D.4.9-3 D.4.9-2 Simplified Mapping Procedure for Overtopped Barrier D.4.9-4 D.4.9-3 Seaward Portion of Wave Envelope based on Total Water Level and Wave Crest Elevation D.4.9-6 D.4.9-4a Non-erodible High Coastal Bluff with VE Zone Controlled by Wave Runup (No Overtopping) D.4.9-9 D.4.9-4b Plan View of Flood Hazard Zones and BFEs, Non-erodible High Coastal Bluff with VE Zone Controlled by Wave Runup (No Overtopping) D.4.9-9 D.4.9-5a Erodible Low Coastal Bluff with VE Zone Controlled by Wave Runup, Overtopping Splash, and High-velocity Flow D.4.9-10 D.4.9-5b Erodible Low Coastal Bluff with VE Zone Controlled by Wave Runup, Overtopping Splash, and High-velocity Flow D.4.9-10 D.4.9-6a Sandy Beach Backed by High Sand Dune with PFD Controlling the VE Zone D.4.9-11 D.4.9-6b Sandy Beach Backed by High Sand Dune with PFD Controlling the VE Zone D.4.9-12 D.4.9-7a Sandy Beach Backed by Low Sand Dune with Overtopping Splash Controlling VE Zone D.4.9-13 D.4.9-7b Sandy Beach Backed by Low Sand Dune with Overtopping Splash Controlling VE Zone D.4.9-13 D.4.9-8a Sandy Beach Backed by Shore Protection Structure with VE Zone Controlled by the Splash Zone and High-velocity Flow from Wave Overtopping D.4.9-14 D.4.9-8b Sandy Beach Backed by Shore Protection Structure with VE Zone Controlled by the Splash Zone and High-velocity Flow from Wave Overtopping D.4.9-15 D.4.9-9a Cobble, Gravel, Shingle, or Mixed Grain Sized Beach with VE Zone Controlled by Wave Runup, Overtopping, and High-velocity Flow D.4.9-16 D.4.9-9b Cobble, Gravel, Shingle or Mixed Grain Sized Beach with VE Zone Controlled By Wave Runup, Overtopping and High Velocity Flow D.4.9-17 D.4.2-1 Summary of Methods Presented in Section D.4 D.4.2-16 D.4.2-2 Open Coast, Dune Backed Beach Example using Parametric DIM Model for Setup/Runup D.4.2-22 D.4.2-3 Open Coast, Dune Backed Beach using Numerical DIM Model for Setup/Runup D.4.2-25 D.4.2-4 Sheltered Water, Seawall Backed Beach using Parametric DIM Model for Setup/Runup D.4.2-28 D.4.5-1 Summary of Factors to Be Applied with DIM D.4.5-9 D.4.5-2 Recommended Procedure to Avoid Double Inclusion of Wave Setup Components D.4.5-10 D.4.5-3 Summary of Runup Reduction Factors D.4.5-13 D.4.5-4 Example Characteristics D.4.5-18 D.4.5-5 Comparison of Results from Various Methods of Calculating 2% Total Runup for Examples D.4.5-19 D.4.5-6 Overtopping Parameters Used in Hazard Zone Mapping D.4.5-23 D.4.5-7 Equations for Wave Overtopping D.4.5-26 D.4.5-8 Summary of Equations for Overland Propagation (Over Uniform Depth) D.4.5-35 D.4.5-9 Common Vegetation Types on Atlantic, Gulf, and Pacific Coasts D.4.5-39 D.4.6-1 Common Beach Settings Found Along the California, Oregon, and Washington Coastlines D.4.6-7 D.4.6-2 Equilibrium Beach Profile Coefficients D.4.6-24 D.4.6-3 Estimates of the Beach Profile Time Response D.4.6-24 Guidelines and Specifications for Flood Hazard Mapping Partners [November 2004] D.4-i Appendix D.4 Table of Contents Guidelines and Specifications for Flood Hazard Mapping Partners [November 2004] Table of Contents (cont.) Section Page Guidelines and Specifications for Flood Hazard Mapping Partners [November 2004] Table of Contents (cont.) Figure Page Guidelines and Specifications for Flood Hazard Mapping Partners [November 2004] Table of Contents (cont.) Table Page