martecchini great marsh symposium presentation duxbury beach - 11-13-2014
TRANSCRIPT
Great Marsh Coalition
2014 Sea Level Rise Symposium
Duxbury Beach – A Case Study
November 13, 2014
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Duxbury Beach
Duxbury Bay
Saquish
Gurnet
Cape Cod Bay
Powder Point Bridge
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• Owned by the Duxbury Beach
Reservation, Inc., a 501c(3) non-profit
• Formed in 1975, but evolved from
organizations dating back to 1919
• Leases much of beach to the Town of
Duxbury
• Maintains access to Gurnet/Saquish
• Funding provided by Town Lease
($600k), beach pavilion and parking
receipts, donations and grants
Duxbury Beach
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DBR awarded a CZM Green Infrastructure
for Coastal Resilience Grant in June 2014
Grant includes three projects:
• Restore cobble berm
• Construct two beach grass nurseries
• Eradicate invasive Japanese Knotweed
on the dune
CZM Grant
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CZM Grant
Task Estimated Cost
Engineering $ 9,788.00
DBR Construction
Management/Inspection $ 10,000.00
Cobble Berm Restoration $ 79,980.00
Create Beach Grass Nurseries $ 10,162.00
Eradicate Japanese Knotweed $ 6,000.00
Total Estimated Project Cost $ 115,930.00
Less DBR Match $ 28,983.00
Grant Amount Requested $ 86,947.00
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Cobble Berm Restoration
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Cobble Berm Restoration
Cobble
Berm
Berm Restoration Length ≈ 2,090 ft.
Channel
Access
Road
• Cobble berm originally placed in 2006/2007
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Cobble Berm Restoration
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Cobble Berm Restoration
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Cobble Berm Restoration
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Cobble Berm Restoration
What is a Cobble Berm?
• A moderately sloping
ramp of cobble-sized
stone (3” – 6”)
• Cobble must be well
rounded and free of sand
• Also known as “dynamic revetment” or
“rubble beach”
• Natural or “Green” form of Coastal
Protection
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Cobble Berm Restoration
Why a Cobble Berm?
• Porous cobble dissipates wave energy
by allowing wave “uprush” to percolate
through large spaces between stones
which move and reshape themselves
• Dynamic rather than static like a massive
stone revetment
• You can hear stones moving as waves
pass through
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Cobble Berm Restoration
• Rounded cobble tends to move up a
beach during high waves unlike sand
which moves seaward
• A cobble berm will find its natural slope
angle (8° to 14°) - as long as there is
material it will create a natural slope
• Cobble tends to move up a beach during
high waves rather than sand which moves
seaward
• Lower cost alternative to hard revetments
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Cobble Berm Restoration
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New Beach Grass Nurseries
3 essential elements
of a healthy dune
system:
• sand, wind and
vegetation
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New Beach Grass Nurseries
• DBR plants 15,000 to
30,000 culms of beach
grass every year as part
of normal maintenance
• After major storm
damage, up to 500,000
culms were planted
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New Beach Grass Nurseries
• DBR’s main supplier of beach grass is
Church’s Beach Grass in Cape May,
NJ
• After Hurricane Sandy, beach grass
was in short supply
• For first time this year, also had to
use a nursery in North Carolina
• DBR concerned that after another
major storm, beach grass might not
be available when needed
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To help ensure a local supply of beach
grass, this grant is helping DBR develop
two local beach grass nurseries
• Silver Lake High School Horticultural
Department (≈ 300 sf)
• Town of Kingston Conservation
Commission (≈ 5,000 sf)
New Beach Grass Nurseries
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• Cape American Beach Grass
(amophilla) will be grown
• Sand brought in to a depth of 1ft. - 2 ft.
• Culms planted at about 1 ft. on center
• Propagation rate of 10 – 20 culms per
year from original culms
• Potential yield of 53,000 – 106,000
culms / year
• Culms are separated for beach planting
New Beach Grass Nurseries
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• Silver Lake High School already planted
and is growing beautifully
• Working on a MOU with Kingston
Conservation Commission
• Grass will be sold at market price
• DBR will get right of first refusal
• DBR will maintain for 2 years
• Will plant in the spring of 2015
New Beach Grass Nurseries
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New Beach Grass Nurseries
Silver Lake High School Nursery
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New Beach Grass Nurseries
Silver Lake High School Nursery
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Eradicate Japanese Knotweed
• Approximately ½ acre of invasive Knotweed
• May have been brought in during cottage
reconstruction
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Eradicate Japanese Knotweed
• Rodeo herbicide will be used
• “Cut and Drip” or “Glove” technique will be
used by a licensed herbicide applicator
