Adaptation to Sea Level

Rise – A Regional Approach

in Saco Bay, MEPeter Slovinsky, Marine Geologist

Maine Geological Survey, Department of

ConservationProject Funding from:

Project Partners:

Saco Bay – Hazards and Habitats

Saco River

Scarborough

River

Goosefare

Brook

Data Development, Outreach, Education, and Partnership Development

Coastal Hazard Resiliency Tools (CHRT) Project

State Agencies – Regional Planning Commission - Municipalities

Year 3 Rounding Up!

Framing the Problem

Sea Level is RISING, right?

By how much? What will the potential impacts

be? What can be done?

Portland Tide gauge = global ocean over last century 1.8 mm/yr (IPCC, 2007).

In Maine, this is the fastest in past 3000 years

Sea Level, Portland, Maine1912-2009

y = 0.0058x - 11.581

R2 = 0.7358

-0.600

-0.500

-0.400

-0.300

-0.200

-0.100

0.000

0.100

0.200

0.300

1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Time (years)

Ele

va

tio

n (

ft,

MS

L)

P.A. Slovinsky, Maine Geological Survey, February 2, 2010

1.79 mm per yr or 0.6 ft (7.2") per century

Data courtesy of NOAA CO-OPS

2.1 mm/yr

(1947-2006)

2.0 mm/yr

(1929-2006)

1.8 mm/yr (1912-2009)

1.8 mm/yr (1926-2001)

Documented Sea Level Rise

Based on measurements, about 7-8”

(0.6-0.7 feet) of sea level rise has

occurred along the Maine coast.

IPCC 3rd Assessment (Tech. Summary of Working Group I Report, Fig. 24, p. 74., 2001 )

Satellite altimetry (1992-2010) = global sea level 3.2 + 0.4 mm/yr

Portland during same time period = 1.9 mm/yr http://sealevel.colorado.edu/

Hugo Ahlenius, United Nations Environment Programme, 2007

http://maps.grida.no/go/graphic/projected-sea-level-rise-for-the-21st-century

Coastal Sand Dune Rules (Chapter 355 NRPA)

In response, in the coastal sand dune system, Maine is planning

for 2 feet of sea level rise over the next 100 years, which is

generally a “middle-of-the road” prediction for global sea level rise.

P.A. Slovinsky, MGS

“Coastal wetlands” means all tidal and subtidal

lands; all areas with vegetation present that is

tolerant of salt water and occurs primarily in salt

water or estuarine habitat; and any swamp, marsh,

bog, beach, flat or other contiguous lowland that is

subject to tidal action during the highest tide level

for each year in which an activity is proposed as

identified in tide tables published by the National

Ocean Service. Coastal wetlands may include

portions of coastal sand dunes.

Coastal wetlands

Using the Sea Level Rise Simulation Tool

Steps:

1)Demonstrate accuracy of LIDAR in representing

ground conditions.

2)Demonstrate accuracy in simulating existing

conditions using tidal elevations to define

marsh habitats and inundation

3) Simulate potential impacts of sea level rise on:

a)Marsh Habitat

b)Existing Infrastructure

4) Identify at-risk areas

5) Identify adaptation strategies

Assumptions:

Open Water generally exists below mean sea level.

Low Marsh generally exists from mean sea level to mean high

water.

High Marsh generally exists from mean high water to highest

annual tide.

Data is limited to where we have LIDAR data coverage.

Represent Marsh Boundaries

Using Tidal Elevations

Marsh Habitats

Scarborough River, Scarborough

Saco Bay

“Groundtruthing”

Identify marsh boundaries

Overlay LIDAR

Identify using tidal elevation ranges

High Marsh = Above MHW and below HAT

Low Marsh = Above MSL and below MHW

Open Water = Below MSL

Use #1: Simulate Existing Conditions in Marshes

Open water (<MSL)

Low Marsh (MSL – MHW)

High Marsh (MHW-HAT)

Use #2: Simulate Potential Future Marsh Conditions

Use #3: Identify low-lying uplands for marsh

transgression

Flooding and Inundation

Ocean Park, Old Orchard Beach

Simulation of Existing Conditions

Use #4: Simulate Existing Inundation

92.8 acres

Use #5: Simulate Inundation under Future Conditions

169.2 acres (83% increase)

Flood Depths (ft)

HAT + 2 ft SL rise

depth, ft

-8 - -7

-7 - -6

-6 - -5

-5 - -4

-4 - -3

-3 - -2

-2 - -1

-1 - 0

Examine Storm Impacts

2007 Patriots’ Day Storm = HAT+2 ft

Indicator of Future Conditions!

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

01002003004005006007008009001000

Distance

Floo

d de

pth

(ft)

Flo

od

De

pth

(ft)

Distance (m)

2007

2007 Patriots’ Day Storm

HAT+2 = Pats’ Day Flooding

Memorial Library

Temple St.

Temple St.

2-3 feet flooding

Memorial Library

2-3 feet flooding

Images courtesy of Bill Edwards, www.mainecoastimages.com and NOAA NWS

Memorial Library

Temple St.

2007

2007 Patriots’ Day Storm

HAT+2 = Pats’ Day Flooding

Memorial Library

Memorial Library

Use #7: Simulate potential future storm

impacts

2007 Patriots’ Day Storm

Plus 2 feet of Sea level Rise

Show Visualization Techniques (CanVis2.3)

Memorial Library

Simulation of Mapped Flood Conditions

Use #8: Simulate impacts to FEMA

FIRM static floodplains

.

50

050

25

Mete

rs

Existing A-zone (9 ft)

.

50

050

25

Mete

rs

Future A-zone (11 ft)

Use #9: Simulate impacts

on volumetric increases at culverts

Route 1, Scarborough, ME

Culvert

Almost a 3x increase!

Some Potential Regional

Adaptation Techniques

Open Space Designation/Acquisition

“Future” Flood or Wetland Areas

P.A. Slovinsky, MGS

April 16, 2007, approximately10:00 am

Images courtesy of Bill Edwards, www.mainecoastimages.com and NOAA NWS

Emergency Access Rerouting

Stormwater Improvements

Tidal Flow Control…elevation, sizing

New locations?

P.A. Slovinsky, MGS

Elevation and sitingP.A. Slovinsky, MGS

Sea Level Rise as

Future requirement?

P.A. Slovinsky, MGS

Utility Relocation

P.A. Slovinsky, MGS

Selective Structure Improvement

P.A. Slovinsky, MGS

Regional Sediment

Management

Beach nourishment

Dune restoration/creation

• RSM Within the

Region (inter)

2 federal projects

• Northerly drift

• RSM within the

community (intra)

Developing a Regional Approach…SLAWG

Hazards do not follow

geopolitical boundaries!