Demonstration Study to Evaluate Coastal Flood Hazards on Lake ErieASFPM, San Antonio, TXMay 22, 2012

Great Lakes Coastal Flood Study

Great Lakes Coastal Flood Study Overview

Current FIRMs are outdated due to the age of data and methodologies – many date to 1970s

Changes in NFIP policies and methodologies have since occurred, creating the need for an update

New methods have been developed• GLCFS is first implementation• Methods will be incorporated into official FEMA

guidance

Study includes entire U.S. Great Lakes coastline

Great Lakes Guides & Standards

Great Lakes Guidelines & Standards issued for Public Review and Comment on May 8th.

As part of the technical community, your review and comments are welcome.

60 day Comment period ends July 7th

Check website for link to document: http://www.greatlakescoast.org/ or www.FEMA.gov

First implementation of new methods Expansive project reach:

• Covers five lakes over eight States and many counties• Coordination of the efforts of many stakeholders and partners

Great Lakes are unlike other coastlines:• Local lake levels vary• Some Lakes have man made influences and controls to lake

levels• Ice cover impacts flood hazards

Great Lakes Coastal Flood Study Challenges

Great Lakes Water Levels Water levels have

fluctuated throughout history

Winds and storms create dramatic, localized changes in levels in a very short period

Climate causes changes in water supply gradually

Human regulation activity also influences water levels

Source: US Army Corps of Engineers

Great Lakes Water Levels

Seasonal Lake Levels Water Levels

vary 1-3 ft annually

• Western basin, comprising about one-fifth of lake, is very shallow with an average depth of 24 feet. Western basin is about 40 miles long.

• Central basin is both wider and deeper than the western basin and has maximum depth of approximately 90 feet and length of about 130 miles.

• Eastern basin is about 220 feet deep and 80 miles long.

Lake Depths

Lake Erie Seiche

Ice Cover Erie has history of

completely icing over in winter months

Oblique Aerials

Topographic LiDAR NOAA NGDC Bathymetry Combined Topo/bathy for a seamless DEM

Data Sources

Storm Surge Model ADCIRC/UNSWAN 789,750 nodes Maximum mesh resolution at 60 meters (200 ft)

Storm Selection 20 water level gages/ 8 used for storm selection 20 storms per station based on max surge 51 WIS stations used to select top 20 storms based on wave

heights. Storms are filtered out by:

• removing duplicate storms• maximizing individual storm effects over the entire lake• ensuring various long term lake levels are accounted for

Resulted in a total of 157 storms for simulation for Lake Erie

Top 20 Historical Storm Surges for Stations WIS Stations data (1956-1987)

Wave and Surge Modeling

Wind & Pressure Fields Storm identified using extreme value analysis of water

level data for each gauge Storm duration selected based on wave & wind fields of

a given storm Grid size 0.02 degree selected Wind and pressure data files associated with storm

date pulled out from CFSR data files or generated using Natural Neighborhood method

Wind and pressure files generated for given storm using FORTRAN routine by ERDC

Ice Field Generation

NOAA Ice Atlas use as data source• Ice coverage files (.NIC/.CIS) during storm pulled out from Ice archive (GLERL)

Ice field generation routines provided by ERDC data from 1960-2010

Simulation of Storm 12/12/2000

Wave Height (Hs)

Surge

Current

Ice Concentration

Coupled Wave and Surge Modeling

Data storage

Erie County, PADemonstration Project

RAMPP is conducting an early demonstration project for 20 miles of Erie County, PA shoreline

One of the first implementations of the new study methods ; precedes the remainder of the Great Lakes coastal counties

Test and refine the methodology and develop best practices, to inform the remainder of the GLCFS

Erie Area

Transect Overland Modeling Transects laid out along coast – typically ½

to 1 mile apart, denser where needed. Erosion – sandy and unconsolidated

shorelines. Runup – Response Method – Every identified

historic storm is used Overtopping Overland Wave Propagation - Event Method

– only single storm representing 1% storm.

Overland Wave Demonstration Project Comparisons:

• Event based vs. response based at selected transects WHAFIS and Wave Runup

• CSHORE model Wave runup Erosion Wave setup Overland waves.

Overland Wave Demonstration Project

Overland Wave Demonstration Project

Erosion USACE CSHORE

model• Applies real physics• Near-shore wave

processes• Cross-shore and

along shore sediment transport

• Requires sediment grain size Available data or

estimated

Run-Up Modeling USACE CSHORE model

Figure D.3.5-5. Wave Runup Sketch

Barrier Slope Breaker Depth

Limit of Wave Runup

Storm Still

Water Level

Source: FEMA, 2003

GeoCoastal Tools

Transect

Water level and Wave time series

Demo Transect

Water level and Wave time series

Response based Runup

Transect Model Results

Coastal Flood Hazard Mapping

Coastal Hazard Workmaps

Overland Wave Demonstration Project Demonstration project results:

• Will be presented to stakeholders for input• Will inform level of effort required to

complete analysis for each county• Will identify any data gap needs• Will inform the methodology for

effectiveness• May inform guidance needed in the G&S

Study used to update FEMA FIRMs and FIS to reflect current flood risk

Develop Risk MAP tools for enhanced floodplain and risk management

Early stakeholder engagement allows a better understanding of FEMA goals in hazard risk management

Two-way communication between the Study Team and communities affected by the Study results is essential

Great Lakes Coastal Flood StudyReview

3D Visualization

Outreach Telling others gives your organization a voice! Visit greatlakescoast.org for information and updates Contact us to become involved

Spread the word in your organization and community by:• Link study info to your org’s

website or social media• Discuss study at your org’s

next meeting• Attend future events

Questions?