Town of Oak Bluffs Coastal Sediment Transport Study Project Update - - PowerPoint PPT Presentation

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town of oak bluffs coastal sediment transport study
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Town of Oak Bluffs Coastal Sediment Transport Study Project Update - - PowerPoint PPT Presentation

Jan 29, 2024 484 likes •734 views

Town of Oak Bluffs Coastal Sediment Transport Study Project Update Applied Coastal Research and Engineering Mashpee, Massachusetts John S. Ramsey, P.E. Sean W. Kelley, P.E. Bathymetric and Shoreline Change Analyses Bathymetric change

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Town of Oak Bluffs Coastal Sediment Transport Study

Project Update

Applied Coastal Research and Engineering Mashpee, Massachusetts John S. Ramsey, P.E. Sean W. Kelley, P.E.

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Bathymetric and Shoreline Change Analyses

  • Bathymetric change based on

CLE 2008 survey and 2000 LIDAR

  • Shoreline analysis uses data

from historical T-sheets, aerial photography, and 2009 GPS survey

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Bathymetric Change Analysis

  • Small-scale beach and

nearshore erosion

  • Results also may show

seasonal shifts in beach shape

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Shoreline Change 1846 to 2005

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SLIDE 5

Shoreline Change1846 to 2005

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Shoreline Change 1846 to 2005

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SLIDE 7

Shoreline Change 1955 to 2005

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Shoreline Change 2003 to 2009

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Coastal Model Development

  • Wind data from CMAN platform in

Buzzards Bay, 1985 through 2008

  • Bathymetry from NOAA

(GEODAS database supplemented with chart data) and CLE

  • Open ocean waves from

USACE WIS database

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Coastal Processes Modeling

Wave model of Nantucket sound used to determine wave climate along the Oak Bluffs Shoreline

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Coastal Processes Modeling

  • Local grid with 5-meter

grid resolution nested within Nantucket Sound regional model

  • Local wave model

includes

– CLE 2008 topography and bathymetry – Harbor Jetties, Steamship Pier, and Groin at Pay Beach

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Sediment Transport Potential Modeling

  • Transport potential along

study area is typically ~10,000 cubic yards per year

  • Actual transport is less

due to sediment starved condition of the shoreline and groins

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Potential Shoreline Protection Options

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Potential Shoreline Protection Options Historical Shore Protection USGS 1941

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Potential Shoreline Protection Options Historical Shore Protection U.S. Army Corps 1965 Report

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Example 1: Inkwell Beach

  • 50 ft-wide nourishment
  • 8,000 cubic yards
  • Fill lasts longer with

rehabilitated groin

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Example 2: 2300 ft Nourishment

  • 50 ft-wide nourishment
  • 70,000 cubic yards
  • Rehabilitation of 4 groins
  • Added protection to base of

revetment

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Environmental Concerns

  • Eelgrass beds 250 ft to 300

ft offshore

  • Regulatory agencies have

recently allowed permanent impacts to eelgrass in Woods Hole (direct dredging of the resource)

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Environmental Concerns

  • Example of recently

permitted hydraulic placement of sand within ~150 ft of existing eelgrass bed

Figure: courtesy of Leslie Fields

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Beach Nourishment as a Shore Protection Option

  • Dead Neck (Barnstable)

nourished since 1985

  • Most recent large-scale

nourishment in 1999 Pre-1999

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Beach Nourishment as a Shore Protection Option

  • ~200,000 cubic yards

placed in 1999

  • In 2009, approximately

50% remains 1999

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Summary

  • Sediment-starved shoreline
  • History of “hard” shoreline

armoring

  • Long-term shoreline

management using combination of beach nourishment and structures

  • Possible “structure trading”

as a regional approach

  • Environmental concerns

are manageable

  • Long-term sediment

sources…