Three Years After The 2011 Nourishment Project Performance, Dune - - PowerPoint PPT Presentation

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three years after the 2011 nourishment project
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Three Years After The 2011 Nourishment Project Performance, Dune - - PowerPoint PPT Presentation

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TOWN OF NAGS HEAD BOARD OF COMMISSIONERS MEETING 7 JAN 2015 Three Years After The 2011 Nourishment Project Performance, Dune Growth, and Hot Spots South Nags Head 23 Dec 2014 Photo By David Ryan 2011 Nourishment The largest locally

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SLIDE 1

Three Years After The 2011 Nourishment – Project Performance, Dune Growth, and Hot Spots

TOWN OF NAGS HEAD BOARD OF COMMISSIONERS MEETING – 7 JAN 2015

South Nags Head – 23 Dec 2014

Photo By David Ryan

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SLIDE 2

The largest locally funded beach nourishment accomplished to date in the United States.

  • 4.6 million cubic yards
  • Along 10 miles
  • Over 100 borings to discover

pristine sand source offshore

  • Project budget of $37 million
  • Unit Price – $6.56 per cubic yard
  • 5 years of environmental reviews
  • 5 months of summer construction

between 24 May and 27 Oct 2011

2011 Nourishment

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SLIDE 3

Project Performance – Volume Changes

4.6 MCY

Dune Growth

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SLIDE 4

South NH – 2 mi ~30% loss NH R1&2 – 8 mi >10% Gain

Project Performance – Volume Changes by Reach

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SLIDE 5

Project Performance – Summary @ 3 years

  • Sediment Compaction Results
  • No different than native beaches
  • No tilling required
  • Nourishment Sand Remaining
  • Over 1 million cy more sand between dune and dry beach
  • 96% sand remaining to -19 ft NAVD (FEMA Offshore Limit)
  • North 8-mi of NH gained ~10%, south lost ~30%
  • Upcoast and Downcoast Changes
  • Upcoast gained ~230,000 cy to -19 ft NAVD
  • Downcoast gained ~170,000 cy to -19 ft NAVD
  • Biological Studies
  • CZR Study confirmed rapid recovery of organisms and no

significant differences between project areas and unnourished areas

“Wildlife thrives after Nags Head beach replenishment”

Source: Virginian-Pilot (23 Jun2014)

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SLIDE 6

Dune Management Plan – Beach Width

One-mile average dry-beach width in June 2014 between the toe

  • f dune and the edge of dry sand (between +10 and +5 ft NAVD).

Reach 1: 60-68 ft Reach 2: 83-89 ft Reach 3: 85-132 ft Reach 4: 85 ft

73.5 85.6 89.4 82.6 102.7 132.1 68.2 66.7 65.0 60.5 62.9

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SLIDE 7

Dune Management Plan – Category 1

Place sand fencing close to the stable vegetation line, and re-vegetate bare areas

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SLIDE 8

Dune Management Plan – Category 2

If the berm is >75 ft wide, place sand fencing ~25 ft seaward of the structure and promote dune buildup via fencing and vegetation.

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SLIDE 9

Dune Management Plan – Category 3

Fencing should not be installed on the seaward side unless there is >75 ft of dry-sand beach seaward of the structure.

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SLIDE 10

Erosion Hot Spots

10333 S. Old Oregon Inlet Rd. on 23 Dec 2014 (By D Ryan) 27 Oct 2014 (By C Ogburn)

  • Re-exposed sandbags
  • Dune erosion
  • Low-elevated beach

Sta 1012+00

  • E. Seagull Dr

Sta 995+00

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SLIDE 11
  • S. Nags Head on 27 Oct 2014 (By C Ogburn)
  • S. Nags Head on 31 Oct 2014 (By CSE)
  • E. Tern Street

Sta 1009+00 Reach 3/4

  • E. McCall Ct

Sta 1019+00 Reach 4

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SLIDE 12

Erosion Hot Spots – Causes

  • South Nags Head has

higher historical erosion rate than north Nags Head

  • Project End-losses
  • Profile Adjustment
  • Rhythmic Shoreline
  • Migrating versus persistent

hot spots

Recommendations

  • Additional survey in Fall 2015
  • Short-term solution (eg. sand

scraping)

  • Long-term solution (periodic re-

nourishment) – Start permitting!

  • Most cost-effective long-term

solution (combine nourishment with sand retaining structure)