Mapping of Future Coastal Hazards for Southern California January 7th, 2014 David Revell, Ph.D. drevell@esassoc.com E. Vandebroek, 2012
Outline Coastal erosion hazard zones Flood hazard zones: Coastal flood hazards (extreme tides and wave impact areas) Fluvial flood hazard zones (Santa Clara River and Ventura River) Spatial Aggregation of Hazards Initial habitat modeling (SLAMM) findings E. Vandebroek, 2012
Model Applications Model analysis scale designed to support local decision making Pacific Institute 2009 (Revell et al 2011) General Plan - City of Santa Barbara City of Capitola General Plan FEMA Discovery Maps for Pacific Coast Flood Studies Coastal Resilience Ventura (TNC) LCPs City of Oxnard, Ventura County General Plan Ventura County Monterey Bay (Coastal Conservancy, Natural Capital) Model results included in publications Economics of Sea Level Rise Impacts (King and MacGregor) USFWS/UCSB SLR Impacts on Endangered Plants
Model Inputs Physical Forcings Offshore wave/ climate scenarios Transformed nearshore waves Tides Total Water Levels Backshore Characterization Geology Geomorphology (slopes, heights) Backshore type (cliff, dune, inlet, armored) Historic erosion rates (short term, long term) Coastal Armoring Topography Scale of Analysis 500m
FLOOD HAZARDS ANALYSIS Mapping Coastal Hazard Zones Example for Low SLR, 2060 Merge & dissolve 4 hazard layers
Model Outputs 1. Erosion hazard zones (integrated with coastal flooding) Future erosion increases hydraulic connection and risk of flooding 2. Coastal wave run-up hazard zone - momentum impact 3. Coastal Flooding inundation during extreme coastal events 4. Coastal Inundation - inundation during monthly extremes 5. River Flooding - Ballona Creek only 6. Beach response model (Dr. Flick Terra Costa Consulting)
Coastal Erosion Hazards Analysis Photos by D. Revell
COASTAL EROSION HAZARDS ANALYSIS Coastal Erosion Hazards Concepts Total Water Levels Sea Level Rise Exceeds Elevation of the dune toe Causes Erosion Response based on: Backshore Type Tides Geology Wave Run-up Shoreline Change Storm Surge Geomorphology El Niños Results Climate Change Accelerated Erosion Sea Level Rise Inland Migration of Shore Wave Climate Loss of Upland
COASTAL EROSION HAZARDS ANALYSIS Analysis Scale 74 Blocks 500 meters
COASTAL EROSION HAZARDS ANALYSIS Dune Erosion Model Dune Erosion Model 3 components 1. Changes in TWL from SLR combined with shoreface slope 2. Historic shoreline trends (USGS, updated with 2005, 2009, 2010) 3. Impact of a 100 year storm event
High SLR, Arkstorm & Double El Niño Frequency COASTAL EROSION HAZARDS ANALYSIS Coastal Erosion Hazard Zones
COASTAL EROSION HAZARDS ANALYSIS Erosion Distances (by Component) 2100, High SLR, Double El Nino + Arkstorm
Cliff Erosion Model Acceleration of historic erosion rates (Rh) Prorated based on % increase in TWL exceeding the elevation of the toe of the beach/cliff junction Include geologic unit standard deviation x planning horizon to account for alongshore variability
Flood Hazard Analysis Coastal and Fluvial E. Vandebroek, 2012
COASTAL HAZARDS ANALYSIS 2. Wave Run-up Hazard Zone Analysis Wave run-up analysis using full-length representative profiles Iterative program used to estimate dynamic water level and inland extent of flooding Developed GIS tool to erode and flood the coast Photos by D. Revell
3. Tidal Extent COASTAL HAZARDS ANALYSIS Much of coastal Ventura is low-lying Other parts of Ventura county are steeper (not shown here)
3. Tidal Extent COASTAL HAZARDS ANALYSIS and is very vulnerable to sea level rise
FLUVIAL HAZARDS ANALYSIS 4. Fluvial Flood Analysis Purpose: Evaluate changes to flooding extent for coastal confluences
FLOOD HAZARDS ANALYSIS 4. Fluvial Flood Analysis Purpose: Evaluate changes to flooding extent and sediment yield from the various watersheds Fluvial Climate Scenarios: Existing conditions A2 Climate Scenario* B1 Climate Scenario* Sea Level Rise 3 scenarios to drive changes in tail water Adjusted bed elevation from SLR changes * From Cayan et al 2009
Fluvial Analysis Hec -RAS models: Ventura River Santa Clara River Inputs Analysis/Model Ouptut Climate data 1 Runoff Baseflow Variable Infiltration Capacity Routing Model Daily streamflow data Annual peak streamflow Annual Peak Streamflow Flood Frequency Analysis Q 100 Q 100 Sea-level rise HEC-RAS Hydraulic Model Flood inundation patterns 1 Data produced by California Climate Change Center (Cayan 2009)
FLOOD HAZARDS ANALYSIS 100-yr Flood Profiles: Ventura River Elevation (ft NAVD) 60 50 40 30 20 A2 2030 - Q100 (117,000cfs) A2 2060 - Q100 (112,000cfs) A2 2100 - Q100 (107,000cfs) B1 2030 - Q100 (96,000cfs) B1 2060 - Q100 (89,500cfs) B1 2100 - Q100 (85,000cfs) 10 Pacific Ocean UPRR Highway 101 Main Street 0 0 1000 2000 3000 4000 5000 6000 Station (ft upstream of mouth)
Mapping Flood Hazard Zones Combine hazards for 9 scenarios for each time horizon 1. Erosion hazard zones Surfer s Point to Point Mugu Future erosion increases hydraulic connection and risk of flooding 2. Coastal wave impact hazard zone - momentum impact 3. Tidal extent - duration 4. River floodplains Ventura and Santa Clara Rivers only FLOOD HAZARDS ANALYSIS Clean resulting layers - Erode based on wave climate scenario (Existing) - Require connectivity with the ocean - Flood small gaps (15 m x 15 m)
FLOOD HAZARDS ANALYSIS City of Ventura Emma Wood to Surfer s Point
FLOOD HAZARDS ANALYSIS City of Ventura Pierpont Bay
COASTAL EROSION HAZARDS ANALYSIS Comparison: Pacific Institute 2009
COASTAL EROSION HAZARDS ANALYSIS Comparison: Pacific Institute 2009
COASTAL EROSION HAZARDS ANALYSIS NOAA Sea Level Rise Viewer
COASTAL EROSION HAZARDS ANALYSIS 2100 High Sea level Rise with Existing Waves
Model Uncertainties Input data sets: Topographic Scenarios Address uncertainty: Sensitivity analysis of inputs Spatial aggregation
City of Ventura Emma Wood to Surfer s Point FLOOD HAZARDS ANALYSIS
City of Ventura Pierpont Bay FLOOD HAZARDS ANALYSIS
Thank you! Questions? drevell@esassoc.com E. Vandebroek, 2012