where they work & where they...

Shoreline Stabilization & Landscape Strategies:

Where they work & where they won’t

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Agenda • 5:45PM | Eat Dinner & Chat with Your Neighbors

• 6PM | Welcome, Intro, & Next Steps Post-workshops

• 6:15PM | Why We Are Flooding, How Landforms Help

Us, and Why Your Site Matters

• 6:45PM | Strategies for Shoreline & Land Management

• 7:45PM | Evaluations

• 8PM | Optional Small Group Discussions with Panelists

• 8:30 | We’re Outta Here

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Is This Really The End? • SHEA follow-up with Hampton BoS

• based on workshop comments and issues discussed

• fill out your evaluation forms if you have an issue you’d like included in communication

• Monthly or bi-monthly network meetings • to share ideas, lessons learned, and coordinate requests to the town

• SHEA will help organize, schedule and host these meetings and help bring in experts, as needed

• Site visit to your property in Fall 2018/Spring 2019

Sign up sheet for network meetings & site visits is being passed around.

WHY ARE WE FLOODING?

Kirsten Howard

Coastal Resilience Coordinator

NHDES Coastal Program

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What causes coastal flooding?

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GROUND WATER

WIND

Nor’easter Season 2018

Winter Storm Grayson January 4, 2018

Winter Storm Riley March 2-5, 2018

Nor’easters + Astronomical Tides

• Storm surge = back marsh flooding • Waves = Atlantic Coast damage

• Multi-day build up

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What about last week?

• Between 2000-2015, frequency increased by 75% (from 3.4 days to 6 days/year) along Northeast Atlantic

• 2017: highest nation-wide average frequency ever measured

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Why is coastal flooding on the rise?

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Why is coastal flooding on the rise?

0.6 – 2.0 ft. by 2050

1.6 – 6.6 ft. by 2100

PROJECTIONS

HOW TO PREPARE

1. Select time period

2. Commit to manage intermediate high

3. Adjust if necessary

Example: If the design time period is 2050-2100, commit to manage 3.9 ft. of sea-level rise, but be prepared to manage and adapt to 6.6 ft. if necessary.

www.nhcrhc.org

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HOW LANDFORMS HELP US

Dr. David Burdick

Jackson Estuarine Lab

University of New Hampshire

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Dunes are one of our most valuable storm protection assets

Protection from flooding Protection from coastal erosion Plant growth to support food

webs Plant structure to provide habitat

Support of biodiversity Tourism Education Self-sustaining ecosystem

Slide credit: David Burdick, UNH

Why we love sand dunes

Where We Live

Year Area Percent of historic (1776)

1776 293.0 ha (724.0 acres) 100 %

1894 170.4 ha (421.0 acres) 58.2 %

1934 94.4 ha (233.2 acres) 32.2 %

2005 48.0 ha (118.7 acres) 16.4 %

Sand dune extent over time

Provide sand for beaches

Protect landward properties/infrastructure during storms

Site of sand capture and storage for next storm Dunes are sacrificial

How sand dunes work

Natural dune widths can recover Narrower dunes need our help – Why?

Dunes are one of our most valuable storm protection assets

Slide credit: David Burdick, UNH

Why we love sand dunes

When in dynamic equilibrium, dunes, beaches and offshore bars respond

to Sea Level Rise by building elevation

Photo: Kiki Evans

UNH Cooperative Extension/Sea-Grant and partners have been working with local communities to strengthen dunes

Resources for local action: plants, consults, regulatory changes

Why we love salt marshes

• Plant growth supports food webs

• Secondary production (fish and

shellfish!)

• Plants provide habitat

• Support of biodiversity

• Carbon Storage

• Protection from flooding

• Protection from coastal erosion

• Removal of sediments and excess nutrients

• Aesthetic, Recreational & Educational

values

• Self-sustaining ecosystems

CONCEPTUAL MODEL OF SALT MARSH

Or . . . How Salt Marshes Work

USGS FS-091-97 Global warming, sea-level rise, and coastal marsh survival

Regular flooding with salt water Sediment supply

Sea level driven marsh expansion in a coupled model of marsh erosion and migration, Volume: 43, Issue: 9, Pages: 4366-4373, First published: 19

April 2016, DOI: (10.1002/2016GL068507)

Salt marshes are a balance of building and eroding processes

Marshes grow in elevation as Sea Level Rises

Why we love salt marshes

BS:2.9mm/yrR²=0.94

HF:2.1mm/yrR²=0.74

HP:1.9mm/yrR²=0.83

R1:2.6mm/yrR²=0.97

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Elevation(mm)

SETElevation- Hampton-SeabrookEstuaryAveragerate=2.26+ 0.15mm/yr

101:2.2mm/yrR²=.70

WR:2.3mm/yrR²=.81

How have our salt marshes changed over time?

Approximately 30% of NH salt marshes have been lost to filling

Tidal Restrictions are slowly destroying another 20%

Salt marsh impacts – tidal restrictions

Salt marsh impacts – ditches

Salt marsh impacts – sea level rise

Photo: Amy Hansen NHCAW King tide photo contest 2nd place

So, Storm surges too high for marshes to protect from flooding, but still the marshes have completely prevented erosion

THE SALT MARSH SQUEEZE

Marsh migration

+

Shoreline stabilization

=

salt marsh squeeze

From Kirsten Howard, NHCP

WHY YOUR SITE MATTERS

Kirsten Howard

Coastal Resilience Coordinator

NHDES Coastal Program

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Site: Beach Structure Dominant coastal hazards: storms, waves, wind, surge

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Site: Beach Structure Dominant coastal hazards: storms, waves, wind, surge

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Site: Low, back marsh/estuarine properties

Dominant coastal hazards: extra high tides, surge

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Site: Low, back marsh/estuarine properties

Dominant coastal hazards: extra high tides, surge

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Site: Coastal bank structure

Dominant coastal hazards: gradual or aggressive erosion

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Site: Coastal bank structure

Dominant coastal hazards: gradual or aggressive erosion

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Site: Low, inner properties

Dominant coastal hazards: stormwater, groundwater rise

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Site: Low, inner properties

Dominant coastal hazards: stormwater, groundwater rise

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STEP 1 FOR ALL: understand YOUR risk before you decide what strategies will work for you. If you don’t, you might end up spending a lot of $ on a “solution” that doesn’t fix your issue.

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Strategies for Shoreline & Landscape MGMT

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Keep the Water Out

Live with the Water

Get Out of the Water’s Way

Panelists:

Dr. Dave Burdick, UNH Jackson Estuarine Lab Kirsten Howard, NHDES Coastal Program Dr. Tom Ballestero, UNH Stormwater Center Alyson Eberhardt, NH Sea Grant and UNH Cooperative Extension

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Keep Water Out (protect)

From an ecological perspective, what’s the first thing you can do to keep the water at bay?

Strategy 1: Keep Water Out (protect)

Erosion Cycle

Gradual slope Steep Bank

What do marshes need to remain healthy and help prevent flooding?

• Tidal flooding • Sediment source • Space to migrate into

upland buffer

How should we manage and restore marshes in the near

future? • Remove barriers to hydrology • Remove barriers to sediment supply • Remove shoreline barriers (e.g., Seawalls) • Provide areas for marsh migration

What do Beaches and Dunes need to remain healthy and help prevent flooding?

• Sand that can be windblown • Vegetation (and fencing) to catch sand • Offshore sand bars and dune storage

How should we manage and restore dune in the future?

• Beach nourishment (add sand) where needed • Help narrow dunes store sand (plant and fence) • Maintain high ridge (walk-overs for beach access) • Regulations to relax height restrictions for lifting homes

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Can you enhance or create new salt marshes or dunes?


Use natural materials including plants, fiber, shell and rock along a shoreline

exhibiting erosion to dissipate wave energy and

to collect naturally deposited sediment. Living

shorelines maintain continuity of the natural

land–water interface while protecting against coastal

hazards.

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Install a living shoreline

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What are some examples of living shorelines and where might they work best?


Living shorelines protect properties when there is distance and elevation

between the asset you want to protect and the water.

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How effective are living shorelines?


Living Shorelines: better than walls?

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Gittman et al. 2014

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Can you keep the water from entering your structure?


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Install Dry Floodproofing

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What kinds of flood protection barriers exist? Pros and cons?


• Structural options • Levee/berm – compacted

earthen structure

• Walls – engineered structure

• Tide gates – throttle for incoming water

• NOTE: our permitting regime does not allow many walls to be put in place. Must first check with federal, state, and local regulations

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Barrier Systems

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Barrier Systems

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Barrier Systems

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Barrier Systems

Nantucket, MA

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Barrier Systems

Extreme?

Important Considerations:

• Height/Elevation of expected flood level

• Site topography

• Draining the landward side of the barrier

• Groundwater conditions

• Access over/through barrier

• Visual impacts

• Inspection and Maintenance

• Permitting

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Barrier Systems

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Barrier Systems

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Barrier Systems

Plum Island, MA

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Barrier Systems

Plum Island, MA

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Barrier Systems

Revere, MA

Tide Gates • Throttle incoming water

to reduce water elevation landward of the gate

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Barrier Systems

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Barrier Systems

Tide Gates • Waterway Size Dictates Gate Size

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Barrier Systems

Every property surrounded by walls

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Barrier Systems

Flood proof and zombie proof

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Barrier Systems

How far do we go?

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Temporary Barrier


Barrier Systems

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Barrier Systems

Permanent Barrier

In regional systems, decisions need to be made about who is in and who is out…

Strategy 2: Live with Water (accommodate)

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What can you do to get ready for a flood?

Live with Water (accommodate)

Up your reaction time (tide gauge—link in resource handout, HSEM emergency alerts, inform guests/renters)

Make a plan (evacuation plan, emergency kit, back up power, tie down trash cans/chairs/BBQ, move utilities upstairs, plan for extended absence)

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Get Prepared


Make a back up plan for your plan (boat, roof access)

Maintain a flood insurance policy

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Get Prepared


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Your driveway floods, can you continue to park there?


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Options for your car

Hamer car lift

Homeowners getting creative in Houston during Harvey

Extreme Vehicle Protection (EVP)


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What design changes can you make to your structure to live with water?

Elevate / Secure Equipment

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Live with Water (accommodate) Structural / Design Changes

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Elevating entire foundation/structure

Structural / Design Changes

Usable Space on Ground Floor

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Wet Floodproofing

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Sump Systems

Sump System Considerations:

• Where is water inflow?

• What is the design scenario? • Empty a full basement

• Keep up with water entering

• Intermittent groundwater control

• Foundation seepage

• Back-up power supply

• Where is discharge point?

• Inspection and maintenance

• Alarms/notifications

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Can stormwater BMPs help with coastal flooding?

• Reduce volume of runoff (infiltration)

• Reduce peak runoff flow (capture, slow release)

• Improve water quality

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Live with Water (accommodate) Stormwater Management

Rain Gardens

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Rain Gardens


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Permeable Pavements


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Permeable Pavements


Pavers Asphalt Concrete

Key Considerations Along the Coast

• Submerged systems do not function

• Underdrains may back up

• Already high groundwater may be exacerbated by stormwater infiltration

• Stormwater management does not control or affect sea level

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Strategy 3: Get Out of the Water’s Way

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Have people already had to move out of the way of water?


• Hampton’s 10 foot tide parking program (handout)

• Parking or staying at a friend or family member’s house

• Staying at a hotel or other property

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Some Common Temporary Examples


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What can you do to your property or structure?

Rearrange your land use

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Get Out of the Water’s Way Property / Structural Solutions

What would you move?

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Elevate Structures

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Relocate Structures

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What approaches have people taken to sell their property?


• Active flood insurance policy can be transferred

• Selling in and of itself doesn’t eliminate the flood risk

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Sell the Property


• Voluntary, market value buyout programs • Needs to be set up by town/other gov’t body (Hampton has not

set this up).

• In most cases the purchaser commits to returning the properties to flood storage space.

• In many cases the properties have suffered repetitive losses and the owners are at that point voluntarily willing to sell.

• Can be created using FEMA Hazard Mitigation Grant Program funds, but match is required.

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Sell the Property


• Example: Blue Acres Buyout Program following Superstorm Sandy, Woodbridge, New Jersey

• Homes bought at pre-storm value, redevelopment blocked forever

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Sell the Property

Credit: Grant Delin

Agenda • 5:45PM | Eat Dinner & Chat with Your Neighbors

• 6PM | Welcome, Intro, & Next Steps Post-workshops

• 6:15PM | Why We Are Flooding, How Landforms Help

Us, and Why Your Site Matters

• 6:45PM | Strategies for Shoreline & Land Management

• 7:45PM | Evaluations

• 8PM | Optional Small Group Discussions with Panelists

• 8:30 | We’re Outta Here

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BUILDING A FLOOD SMART SEACOAST Ways to Protect Your Property from Coastal Flooding

SUMMER 2018 WORKSHOP SERIES

8-8:30: Small Group Discussions

Brought to you by the Seabrook-Hamptons Estuary Alliance & NHDES Coastal Program

www.shea4nh.org

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