SCIENCE TO SUPPORT COASTAL RESILIENCE:

THE ROLE OF NATURAL SYSTEMS

Denise Reed, Chief Scientist Restore America’s Estuaries November 2014

COASTAL RESILIENCE IN 2014

Business as usual isn’t working

THE ROLE OF SCIENCE

What can we really provide?

THE ROLE OF SCIENCE

How much better can we be?

Lightbody & Nepf, 2006

THE ROLE OF SCIENCE

Concepts based on sound science • What might work where?

Site specific analyses • What should work here?

CONCEPTS BASED ON SOUND SCIENCE

Concepts based on sound science • What might work where?

Site specific analyses • What should work here?

WHY are we using/expecting performance from ‘natural’ features? HOW do ‘natural’ features compare to ‘traditional’ approaches?

Geomorphology

Low High Resistance to change

Low

High E

nerg

y R

egim

e Reducing Erosion by Waves

Seagrass

Salt marshes

Oyster Reefs

Barrier islands

Beaches

Coral Reefs

Freshwater wetlands

Seawalls/ revetments

Groins Breakwaters

Example Conceptualization

SLR/Durability

Urb

aniza

tion

Low

High

Low High

Current Future

Storm Impact

Salt marshes

Barrier islands

Beaches

Coral Reefs

Dunes

Maritime forests

Surge Barriers

Nonstructural

Seawalls/ revetments

Breakwaters

Storm Damage Risk Reduction

Example Conceptualization

Mangroves

Different Species With mangroves

Without mangroves

Without mangroves

With mangroves

Increasing age of trees

Brinkman, 1997

Mazda

Mazda et al., 2006

Quartel et al., 2007

Suzuki et al., 2012

Cyclone waves Varying factors for roots, stems and canopies

Mangroves

Coral Reefs Gelfenbaum et al. 2011

High tide - low tide Roughness

Marshes

Loder et al. 2009. Idealized marsh simulations: Sensitivity of storm surge elevation to seabed elevation. ERDC/CHL CHETN-I-78.

0

100

200

300

Janu

ary

Mar

ch

May

July

Sept

embe

r

Nov

embe

r

Man

grov

e bi

omas

s (t

ons

hect

are

-1)

0

5

10

15N

umbe

r of t

ypho

ons

2001

to 2

005

mangroves

typhoons

0

200

400

600

800

1000

Janu

ary

Mar

ch

May

July

Sept

embe

r

Nov

embe

rSeag

rass

bio

mas

s (g

m-2)

2

3

4

5

Max

imum

ave

rage

win

d (m

s-1)

seagrasswind

Koch et al., 2009

When do the events occur? When does the ecosystem act to reduce the effect?

Examination of the effect of landscape character/restoration on storm surge & waves

Cobell et al, 2013

Cobell et al, in press Distance (Km)

300m flume experiment Real marsh sods

‘The higher than expected rates of storm wave dissipation and the fact that marsh surfaces are able to withstand larger wave forces without substantial erosion effects increase their reliability as part of coastal defence schemes and shifts debates about marsh stability and resilience to those locations where the marsh profile is exposed. In such settings, lateral retreat (for example, cliff undercutting/collapse on marsh fronts and channel widening) may be enhanced by the presence of vegetation, for example, when roots become exposed to wave impact. The long-term balance between vertical and lateral marsh dynamics thus becomes a key area for further study’.

Moeller et al., 2014.

W H A T D O W E N E E D , W H E R E ?

Weinstein & Reed, 2005

What do we want our coasts to do for us? Where can we apply different measures? How can they work together?

Role of coastal marshes in response to increases in relative sea level. (A) Contemporary natural

shoreline. (B) Natural shoreline w/SLR. (C) “Holding the line” (D) Hybrid interventions

where space is allowed for the maintenance of natural coastal defenses

Spalding et al., 2013

C O M M U N I T I E S A N D L I V E L I H O O D S AT R I S K

Predicted Future Flooding from a 100 Year Flood Event Future Without Action

Potential for damages to reach $23.4 billion annually

Increasing threats to lives, jobs, communities and the economy

2 0 1 2 C O A S TA L M A S T E R P L A N

CONCLUDING THOUGHTS

The stakes are high • Coastal systems are changing, risk of erosion and storm damage is

increasing

There is a lot of useful scientific information on the role of natural features in risk reduction • More for erosion control/wave attenuation than for storm surge damage

reduction

We need to capture the information we have and use it to guide coastal managers • Where/when do natural features make sense • Where/when do natural features NOT contribute to risk reduction

THANK YOU

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