Climate Change, Coastal Hazards Mapping and Shore Response

Modeling in California

Bob Battalio, PEChief Engineer, ESA

September 11, 2015

Flood Management Association (FMA)State Conference 2015, Rancho Mirage, CA

Acknowledgements

Clients / Funding:• California State Coastal Conservancy• California Ocean Protection Council • The Nature Conservancy• The Monterey Bay Sanctuary

Foundation• The Packard Foundation• Natural Capital • The Pacific Institute• Multiple Counties and Cities.

Collaborators:• US Geological Survey• University of California (Santa Cruz,

San Diego-Scripps, Santa Barbara)• California State University System

(Monterey Bay)• California State Geologic Survey• Naval Post Graduate School, Monterey• California Coastal Commission• Sea Engineering, Inc.• Revell Coastal• Argos Analytics• Pacific Institute

Environmental Science Associates (ESA), Environmental Hydrology Practice, Coastal Zone Engineering and Management Group, has developed methodologies and methods to produce coastal hazard maps that support planning within reasonable cost and time frames. Hazard maps are required to assess asset vulnerabilities and inform land use and adaptation planning.

Outline

1. Total Water Level, Erosion and Sea Level Rise2. Future Conditions Hazard Mapping

– Erosion– Geomorphic response to sea level rise – Example Hazard Maps

3. Fluvial hazards in coastal zone

1. Total Water Level, Erosion and Sea Level Rise

Modeling of wave propagation and runup: Time Series Simulation

Modeling of wave propagation and runup: Envelope of Wave Crest and Runup limits

Coastal Erosion is a major hazard not mapped

Effective FEMA DFIRM published 2008

Estimated – PWA, potential erosion by 2100, published 2009

Buildings uninhabitable2010

Example: Pacifica Ca – buildings not in flood hazard zone but damaged due to erosion

Climate Scenarios –

Sea Level RiseNational Research Council, 2012. Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, andFuture.National Academy Press: Washington, D. C.

Example for Central CAESA (2014)

2. Future Conditions Hazard Mapping

• Erosion

• Geomorphic response to sea level rise

• Example Hazard Maps

Coastal Hazard Mapping by ESA-PWA-PI

• Science-based shore response modeling funded by the State and called the ESA-PWA-PI Future Coastal Hazard Mapping is available for much of the California coast.

• 2008-2009: The original work provides flood estimates for the entire CA coast and erosion from Santa Barbara north to the Oregon border. Maps area available on-line via internet (1) (2) (3).

• 2010-2015: Refined studies developed for planning at higher resolution using updated methods are available for Ventura County (4), Monterey Bay (5) and Santa Barbara County (6) on the Coastal Resilience website of The Nature Conservancy (TNC) (7).

• Coastal flooding and erosion are mapped for a range of future sea level rise amounts through the year 2100, including erosion of sandy and rocky shores with accelerated sea level rise, and back-barrier flooding.

• Riverine flooding is also included for six major streams, using future precipitation changes from downscaled climate model output.

Coastal Hazard Mapping by ESA-PWA-PI - references1) ESA-PWA-PI Coastal Hazard Mapping was initially developed by Philip Williams and Associates (PWA) and the Pacific Institute with assistance from the Coastal

Data Information Program and Scripps Institution of Oceanography (CEC, 2009; PWA, 2009; Heberger et al, 2011; Revell et al, 2011).

CEC, 2009; THE IMPACTS OF SEA-LEVEL RISE ON THE CALIFORNIA COAST A Paper From: California Climate Change Center. Prepared By: Matthew Heberger, Heather Cooley, Pablo Herrera, Peter H. Gleick, and Eli Moore of the Pacific Institute http://www.energy.ca.gov/publications/displayOneReport.php?pubNum=CEC-500-2009-024-F

Heberger et al, 2011; J Climatic Change, V 109, N 1, R 10.1007/s10584-011-0308-1, The Potential impacts of increased coastal flooding in California due to sea-level rise , Springer Netherlands, 2011-12-01, Heberger, Matthew; Cooley, Heather; Herrera, Pablo; Gleick, Peter H.; Moore, Eli; 229-249, http://dx.doi.org/10.1007/s10584-011-0308-1http://link.springer.com/article/10.1007/s10584-011-0308-1

PWA, 2009; California Coastal Erosion Response to Sea Level Rise and Mapping, Prepared for the Pacific Institute, Prepared by Philip Williams & Associates, Ltd., March 11,2009, PWA Project 1939.http://www.esassoc.com/sites/default/files/PWA_OPC_Methods_final.pdf

Revell et al, 2011. Revell, D.L., Battalio, B., Spear, B., Ruggiero, P, and Vandever, J. A Methodology for Predicting Future Coastal Hazards due to Sea level Rise on the California Coast. Journal of Climatic Change (2011) B.V. 2011 109 (Suppl 1):S251–S276, DOI 10.1007/s10584-011-0315-2, 10 December 2011 # Springer Science+BusinessMedia http://dx.doi.org/10.1007/s10584-011-0315-2http://link.springer.com/article/10.1007%2Fs10584-011-0315-2

2) http://pacinst.org/the-impacts-of-sea-level-rise-on-the-california-coast-gis-data-downloads/

3) http://pacinst.org/publication/the-impacts-of-sea-level-rise-on-the-california-coast-sea-level-rise-maps/

4) ESA PWA (2013) COASTAL RESILIENCE VENTURA, Technical Report for Coastal Hazards Mapping, Prepared for The Nature Conservancy, July 31, 2013, ESA PWA project number D211452.00. http://maps.coastalresilience.org/california/# - select Ventura, and Flood and Sea Level Rise, and Technical Methods

5) ESA PWA (2014), MONTEREY BAY SEA LEVEL RISE VULNERABILITY ASSESSMENT, Technical Methods Report, Prepared for The Monterey Bay Sanctuary Foundation, June 16, 2014. ESA PWA project number D211906.00. http://maps.coastalresilience.org/california/#- select Monterey Bay, and Flood and Sea Level Rise, and Technical Methods

6) ESA (2015), SANTA BARBARA COUNTY COASTAL HAZARD MODELING AND VULNERABILITY ASSESSMENT, Technical Report for Coastal Hazards Mapping, Prepared for the County of Santa Barbara, August 3, 2015, ESA project number D130526. http://maps.coastalresilience.org/california/#- select Santa Barbara, and Flood and Sea Level Rise, and Technical Methods

7) Hazard Maps produced by ESA for Ventura County, Monterey Bay and Santa Barbara County http://maps.coastalresilience.org/california/#

Initial Assessment of Statewide SLR Hazard

PWA is now ESA Environmental Hydrology

Coastal Hazard Maps, PWA (2009), Pac. Inst. (2008)

Coastal Erosion Hazards Quantified Conceptual Model

MethodologyTotal Water Levels

• Sea Level Rise

• Tides

• Wave Run-up

• Storm Surge

• El Niños

Results

• Accelerated Erosion

• Inland Migration of Shore

• Loss of Upland

Erosion Response based on:

• Backshore Type

• Geology

• Shoreline Change

• Geomorphology

Climate Change

• Sea Level Rise

• Wave Climate

Elevation of the dune

toe

Exceeds Causes

Inputs

• Physical Forces– 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

Original Figure Source: FEMA, 2005. Guidelines for Pacific Coast Flood Studies

Methodology is an extension of the FEMA Guidelines, with erosion and future conditions, in a GIS environment for a range of scenarios

Climate Change affects water levels, waves, etc.

ADD: Long-term and sea level rise response

In Geographical Information System (GIS) environment, multiple time horizons and multiple climate change scenarios. Also add fluvial and estuarine flood sources.

ADD: Backshore classification and and response models

Time series, response based analysis:• Start with coincident long time series of water levels and waves– joint probability implicit • Compute wave runup, total water level and overtopping response time series• Conduct statistical analysis on response time series

Wave Transformations from deep to shallow water to account for along shore variability

Back refraction wave ray

Phase averaged, grid-based (SWAN)

Wave Transformation are important!

Southern Santa Barbara County

West side, Whidbey Island

Sea-Level Rise - Shoreline Response

+=

BhLSR

S = sea level riseR = recessionh = depth of active profileL = length of active profileB = berm height

source: estuary-guide.net

B

Applied geomorphology is required to predict shore response.Sea level rise induces shore transgression, with the water-shaped shore migrating up and inland. The result is dependent on:• shore geometry, • sediment type and supply, • back shore conditions, • rate of sea level rise, and • hydraulic power.

The beach is a sediment reservoir:Width changes with volume.

The shoreface is shaped by waves and water levels and is dynamic.

Elevation ofcliff or dune junction with the beach

Shore Face Morphology

Elevation ofcliff or dune junction with the beach (aka “toe elevation”)

Tide

Run up

Total Water Level = Tide + Set-up + Runup

Breaking wave momentumcauses wave setup and runup

Bluff erosion increases with the extent and duration of total water level above toe elevation

Bluff Recedes

Conceptual Model of Bluff Erosion

Soft Bluff = Bluff recedes rapidly, little change in potential beach width and toe elevation (relative to water levels)Hard Bluff = Erosion slow but potential increases, beach width decreases, toe elevation decreases, (relative to water levels)

Profile Analysis using LiDAR

crest

toe

beach slope

Example Coastal Hazard Zones

2100 + storm

2100

2060 + storm

2060

Existing storm HZ

2030

2030 + storm

• Existing + storm• Future with High SLR erosion + storm

Example Cliff Hazard Zone

2100 + stdev2100

2060 + stdev2060

Existing (5m)

Example Flood Hazard Zones

Mapping Coastal Hazard Zones

Example for Low SLR, 2060Merge & dissolve 4 hazard layers

http://www2.pacinst.org/reports/sea_level_rise/hazmaps.html

Pacific Institute – California Ocean Protection Council – PWA Maps circa 2009

These are first generation, and more accurate maps have been produced for Ventura County and the Monterey Bay area, as shown on the following slides.

In addition, updated erosion and wave hazard maps have been generated for the San Francisco – Daly City – Pacifica area but these are not yet published in final form pending review by State and Federal clients.

http://maps.coastalresilience.org/california/#

Ventura CountyFor TNC and locals

Monterey Bay Area, CACompleted 2014

on TNC coastal resilience websitehttp://maps.coastalresilience.org/california/#

Primary funding – California State Coastal Conservancy in cooperation with the

Monterey Bay Marine Sanctuary Foundation

http://maps.coastalresilience.org/california/#

3. Fluvial Hazards in Coastal Zone

Variable Infiltration

Capacity Routing Model

Climate data1

•Runoff•Baseflow

Daily streamflow data

Annual peak streamflow

Annual Peak Streamflow

Flood Frequency Analysis

Q100

Q100 HEC-RAS Hydraulic Model

Flood inundation patterns

Sea-level rise

Inputs Analysis/Model Ouptut

1Data produced by California Climate Change Center

Fluvial Analysis•Ventura River•Santa Clara River•Carpinteria Creek•Reclamation Ditch(Salinas River)•Soquel Creek

Precipitation Extremes – Santa Clara River

-5.0%

-4.0%

-3.0%

-2.0%

-1.0%

0.0%

1.0%

2.0%

3.0%

4.0%

5.0%

1940 1960 1980 2000 2020 2040 2060 2080 2100

% C

hang

e

Annual Average

10-yr Moving Average - Historic

10-year Moving Average - Projected

Percent change in number of days exceeding 95th percentile historic rainfall averaged from 1970-1999 (max of 6 GCMs for A2 emissions)

FLOOD HAZARDS ANALYSIS

Peak Precipitation ~2030

Flood Profiles for 2 climate scenarios and 3 future times,including sediment deposition in lower reaches with sea level rise

Ventura County, CASanta Clara River lower reaches

Considering uncertainty in future precipitation

Evaluating Uncertainty: Spatial Aggregation

End slide

Photographs copyright Colin Brown

Speaker: Bob BattalioProfessional Civil Engineer (CA,WA,LA,OR)Coastal Processes training from UC Berkeley, 1985Chief Engineer, Vice President @ ESA, San FranciscoEngineering Criteria Review Board, BCDC

Practices Coastal Zone Engineering and Management

Vice President, California Shore and Beach Preservation Association (Non profit)

Surfer