Hydrodynamic Limitations and the Effects of Living Shoreline Stabilization on Mangrove Recruitment Christian Pilato1, Kelly Kibler2, Melinda Donnelly1, Linda Walters1

1Department of Biology2Department of Civil, Environmental, and Construction EngineeringUniversity of Central Florida

Stabilization and Mangrove Restoration

Lewis, 2005; Samson and Rollon, 2008

Replace pic

• Success = self sustaining

• Sensitive to local hydraulic conditions

• Hydrodynamic thresholds not well defined or considered

• Often fails• Mostly due to hydrologic issues• 50% average survival in “developed” countries,

11% survival in “developing” countries

De Soto National Memorial: 2017

De Soto National Memorial: 2017

150 meters of shoreline restored:• 270 mangroves• 1800 oyster shell bags

Contributors:• Coastal and Estuarine Ecology Lab• National Park Service• Coastal Conservation Association• 80 local volunteers

Shell bags as wave breaks

Pro

pag

ule

s p

er 0

.25

m2

±(S

.E.)

Seasonal propagule release begins

Res

tora

tion

Hur

rican

e Irm

a

NaturalRestoredRevetment

Seasonal propagule release begins

2017-2018 Monitoring

Seed

lings

per

0.2

5m

2 ±

(S.E

.)

2017-2018 Monitoring 2017-2018 Monitoring

Hydrodynamic Thresholds to Recruitment

Photo: Bywater et al., 2015

Are hydrodynamic forces limiting recruitment?

~3 month old black mangrove

Limitations to Recruitment

Ɵ

Hand-

powered

winch

FD (drag force)

Avicennia germinans

Rhizophora mangle

Avicennia germinans

Rhizophora mangle

Hand-winch

Load cell

Seedling5cm 5cm

Greenhouse test

Greenhouse Results

R. mangleA. germinans

Forc

e to

Rem

ova

l (kg

*m/s

2)

Below-ground biomass (g)

50 kg*m/s2 = ~11 pound-force

R. mangleA. germinans

Forc

e to

Rem

ova

l ±S.

E. (

kg*m

/s2)

Month

Mean Force to Removal through Time

R. mangleA. germinans

Bel

ow

-gro

un

d B

iom

ass

±S.

E. (

g)Month

Mean Below-ground Biomass through Time

Greenhouse Results

CANA 1

CANA 2

De Soto 1

De Soto 2

De Soto 1

Avicennia germinans

Rhizophora mangle

Field Results

Below-ground Biomass (g)

Forc

e to

Rem

ova

l (kg

*m/s

2)

Force to removal (95% CI)

R. mangleA. germinans

50 kg*m/s2 = ~11 pound-force

Sediment Graph

Field ResultsFo

rce

to R

emo

val ±

S.E.

(kg*

m/s

2)

R. mangleA. germinans

R. mangleA. germinans

Forc

e to

Rem

ova

l (kg

*m/s

2)

Surrounding Vegetation Cover (%)

Sediment Grain Size: D84 (mm)

Effects of Vegetation Cover (95% CI)Effects of Sediment Grain Size

0.5 m

Calculating Velocities

Drag force

Drag coefficient

Frontal area

Velocity of the fluidDensity of

the fluid

Uprooting Critical Velocities:• Mazda et al., 1997: 1.41-7.07 m/s• Tanino and Nepf, 2008: 1.62-3.31 m/s• J. Struve et al., 2003: 4.19-4.52 m/s, Extreme: 2.01 m/s• Ni, Y., 2014: 4.08-8.94 m/s

Avicennia germinans Rhizophora mangle

Mean frontal area= 10.69 cm2

Mean frontal area= 53.47 cm2

Caveats:• Erosion not considered• Grouped estimates for both species• Account for plant flexibility• Test more drag coefficients

Grouped Mean Frontal area= 32.08 cm2

=

Avicennia germinans

Rhizophora mangle

Uprooting Critical Velocities (red mangrove):••••

Acknowledgements