Impacts of Beach Scraping and Human Modifications to the … · 2010. 4. 22. · This presentation...
Transcript of Impacts of Beach Scraping and Human Modifications to the … · 2010. 4. 22. · This presentation...
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Impacts of Beach Scraping and Human Modifications to the Coastal System, Fire
Island National Seashore
Cheryl Hapke (U.S. Geological Survey)
Meredith Kratzmann (U.S. Geological Survey/University of Rhode Island)
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Introduction
- Moderate coastal development
- Land loss due to erosion
Protective measuresProperty protection and erosion mitigation through beach scraping, beach replenishment
This presentation
Quantitative comparison of scraped vs. non-scraped beaches
- National Park Service Technical Report 2008/131- In Press article in Journal of Coastal Research
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Human Modification
Development
Beach replenishment Beach scraping
Sand fencing
Photo: Erika Lentzhttp://www.fiyrra.com/fiyrra/FIRenourishment03.html
http://www.fiyrra.com/fiyrra/FIRenourishment03.html Photo: Meredith Kratzmann
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Assess morphological change on decadal to sub-decadal timescales
Isolate and assess the effects of beach scraping on dune/beach morphology
Quantify beach volumes, shoreline change, differences in beach profile characteristics
Approach
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Beach profile analysis
Objective: isolate impacts of beach scraping
Photo: Erika Lentz
Profiles collected as part of permit-required monitoring
Communities: Kismet, Davis Park
Statistical analysis of beach profile characteristics: scraped vs. non-scraped
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- Digitized hard copy profiles, identified characteristics, conducted statistical analysis
Profiles: Land Use Ecological Services, Inc.
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Davis Park
Kismet
CW
CW
CE
CE
SC
SC
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Western control Eastern control
Scraped locationKISMET
Profile envelopes1998-2007
Distance (m)
Distance (m) Distance (m)
Elev
atio
n (m
abo
ve N
AVD
88)
Elev
atio
n (m
abo
ve N
AVD
88)
Elev
atio
n (m
abo
ve N
AVD
88)
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Western control Eastern control
Scraped location
Distance (m)
Distance (m) Distance (m)
Elev
atio
n (m
abo
ve N
AVD
88)
Elev
atio
n (m
abo
ve N
AVD
88)
Elev
atio
n (m
abo
ve N
AVD
88)
DAVIS PARKProfile envelopes 1997-2000
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KISMET - August 2006
Scraped
profile
Western
control
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Conclusions Beach scraping can accelerate downcoast transport by:
- Scraped beach is lower and narrower (waves reach dune more easily)
- Loose pile of sand more erodible than beach or natural dune
Downcoast beaches benefit: recipients of mobilized material
Ineffective protection in chronically eroding areas (areas with low volumes and dune elevations) – inadvertently accelerates erosion
An assessment of long- and short-term beach behavior may provide indication of success of proposed scraping