impact of hurricane irene on pivers island shorelines carolyn currin, noaa nos objective: provide...
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PIE
PIW
PIN
Impact of Hurricane Irene on Pivers Island ShorelinesCarolyn Currin, NOAA NOS
Objective: Provide data on resiliency of ‘living shorelines’ to storm impacts
•Installed 6 horizon makers at each PI site, at lower, middle and upper edge
•Read SETS at PIW (Sill) and PIN (NAT) post –storm
•Examined hardened structures for evidence of erosion
PIE marsh-oyster restorationPIW marsh-sill
Sediment deposition layer (mm)
Elevation Plot PIE PIW PIN
Lower 1 2.65 4.19 1.97
4 0 . NA
Mid 2 4.78 . .
5 5.49 0.55 .
High 3 13.82 . .
6 . 3.73 .
Sediment accretion in Pivers Island Marshes
Hurricane Irene resulted in net sediment deposition to PI sites
Erosion behind west-facing bulkhead(consistent with R. Gittman assessment of stabilization structures in Bogue Sound)
Erosion of bank behind riprap
Minimal erosion of unvegetated sediment bank
Intact upland border adjacent to marsh
20 yr old Oyster reef – marsh project‘Dredge Island’
October 2011 post-Irene
Conclusion: Marsh – oyster reefs provide an effective shoreline stabilization alternative
Additional data on Hurricane Irene impacts to estuarine shorelines
South shore of Dredge Island restoration site
Dredge Island wave exposure setting
Salt marsh
Carteret Co. marsh width vs. wave energy
Two other assessments :
J. Fear NERRS: marsh sill projects -little damage, wrack deposition -ome adjacent erosion of shoreline
R. Gittman UNC: bulkheads, sills, marshes in Bogue & APES
-bulkhead erosion more prevalent than marsh erosion
Sill structures showed no damage with marsh intactSome accumulation and sediment trapping by larger structures. Design matters.
Bulkheads and upland revetments showed some damage and scour – often overtopped.
Slope is important. Unvegetated sediment banks eroded
Intact marsh-upland boundaries showed no upland erosion or marsh loss.
Oyster reef-marsh shorelines showed no erosion.
We documented net sediment gain in Pivers Island shoreline marshes.
Summary of observations on Irene impact on shoreline stabilization projects
Pivers Island transplanted marshOyster cultch addition DMF