Duxbury Beach Reservation, Inc. – Cobble Berm Restoration, Construction of Nurseries for Native Beach Grass Cultivation and Japanese Knotweed Eradication Andre Martecchini, Principal Engineer, Kleinfelder, Inc.

1. 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

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Thank You!
Andre Martecchini, PE
Kleinfelder
617-498-4658
amartecchini@kleinfelder.com