Coastal Processes 101 & The Regs · A beach undergoing net longterm retreat will maintain its...
Transcript of Coastal Processes 101 & The Regs · A beach undergoing net longterm retreat will maintain its...
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Coastal Processes 101 & The Regs
Greg Berman
(Woods Hole Sea Grant & Cape Cod Cooperative Extension)
March 26, 2019
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Outline: • ~15 min talk
• Coastal Processes
• What is Erosion?
• Regulations
Coastal Processes 101 & The Regs
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Glacial History
(Shaw et al., 2002)
25,000 yr ago 400’ below SL, ~1 mile thick By ~ 15,000 ice was gone.
11,000 years ago 6,000 years ago Present Day
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Coastal
Processes
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General Coastal Processes
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Beach Profile Adjustments Large waves, which tend to occur in the winter in Massachusetts, cause the beach to temporarily change its profile.
Images adapted from Natural Hazard Considerations for Purchasing Coastal Real Estate in Hawaii - A Practical Guide of Common Questions and Answers, by University of Hawaii Sea Grant College Program, 2006.
Winter
Summer
Daily/Seasonal Variability
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A beach undergoing net longterm retreat will maintain its natural width.
Beach loss eventually occurs in front of a seawall for a beach experiencing net longterm retreat.
Images adapted from Natural Hazard Considerations for Purchasing Coastal Real Estate in Hawaii - A Practical Guide of Common Questions and Answers, by University of Hawaii Sea Grant College Program, 2006.
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Seasonal VS Long Term Erosion
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Seasonal VS Long Term Erosion
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Seasonal VS Long Term Erosion
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Seasonal VS Long Term Erosion
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Seasonal VS Long Term Erosion
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Seasonal VS Long Term Erosion
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Seasonal VS Long Term Erosion
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Seasonal VS Long Term Erosion
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Barrier Beach
Town Beach
System migrates landward across the shelf and SL as rises.
Perpendicular to Shore
1st appeared as ridges (far out on continental shelf) flooded by SLR
Rising SL breaches the beach ridge and floods behind creating a bay.
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Overwash: Storms push sand across the island and into the lagoon area beyond. Barrier `rolls over on itself.‘
Coastal Processes: Barrier Migration
Perpendicular to Shore
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Coastal Processes: Barrier Migration
Perpendicular to Shore
Adapted from http://www.nasa.gov/vision/earth/lookingatearth/katrina_poststorm.html
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Peggotty Beach 2016
Video by Peter Miles
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General Coastal Processes
Sea level rise
has been
occurring for
thousands of
years. During
this time barrier
beaches have
migrated
landward
through natural
coastal
processes and
have avoided
“drowning in
place”.
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Evidence of Coastal Processes
“Transgressive” = a beach migrating landward and upward, covering the water body or salt marsh that lies behind it.
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General Coastal Processes
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Longshore Sediment Transport
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Longshore Sediment Transport
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Longshore Sediment Transport
Google Earth Engine: Timelapse is a global, zoomable video that lets you see how the Earth has changed over the past 32 years. It is made from 33 cloud-free annual mosaics, one for each year from 1984 to 2016, which are made interactively explorable by Carnegie Mellon University CREATE Lab's Time Machine library.
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What is Erosion ?
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The Erosion Problem: Education Perspectives
It’s all sediment transport! What is Erosion???..... just more leaving than coming in
Erosion Accretion Dynamic Equilibrium
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Parallel Transport…….Blocked LST
Downdrift
Direction ofLongshore Current
Coastal Structure
Direction ofLongshore Current
Erosion
Deposition
+5’/yr+8’/yr
+4’/yr+3’/yr
-2’/yr
-2’/yr
0’/yr
-1’/yr
Source: MORIS: CZM’s Online Mapping Tool
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Perpendicular Transport…….Blocked input
1.3mi
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Coastal Processes: Key Points
1. Erosion of glacial landforms is the MOST important source of sediment for dunes and beaches in Massachusetts.
2. Wind and waves then transport sediment.
3. Without erosion and then longshore re-deposition there would be no beaches.
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Coastal Processes: Key Points
1. Erosion of glacial landforms is the MOST important source of sediment for dunes and beaches in Massachusetts.
2. Wind and waves then transport sediment.
3. Without erosion and then longshore re-deposition there would be no beaches.
Thanks for contributing sand to our coastal resource areasThanks for contributing sand to our coastal resource areas
Thanks for contributing sand to our coastal resource areas
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Erosion Control Structures
Designed to extend the “usable life” of a property.
Towns: Engineered structures may require nourishment
310 CMR 10: “no new coastal engineering structure on a coastal beach/dune/bank to protect a structure built after 8/10/1978”
Scientists wrote letter in 1970’s... MA “needs” erosion.
General practice 1920s – 1950s.
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The Erosion Problem: Regulatory / Legal Perspectives
1. Post 1978 house 2. Scarp 50-60’ from house 3. Poorly maintained fiber rolls 4. Several OOCs included “no CES”
Is it acting as a sediment source?...only needs to “play a role”. Local ConCom permitted a rock revetment (CES). Abutters/Stakeholders appealed to State DEP
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The Erosion Problem: Regulatory / Legal Perspectives
“No…you don’t understand…my house is going to fall in!”
1. Mix of Pre and Post 1978 houses 2. Scarp 5-50’ from houses 3. Revegetation of coastal bank attempted 4. Several OOCs included “no CES” 5. Town owned conservation land 6. Beach had Wetlands Restriction Act 7. Erosion down drift
Is it acting as a sediment source?...only needs to “play a role”. Local ConCom denied project. Likely changes/appeal coming soon.
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Natural Heritage and Endangered Species Program The Natural Heritage & Endangered Species Program (NHESP), part of the DFW, is
responsible for the conservation and protection of hundreds of species that are not
hunted, fished, trapped, or commercially harvested in the state. The Program's highest
priority is protecting the 176 species of vertebrate and invertebrate animals and 259
species of native plants that are officially listed as Endangered, Threatened or of Special
Concern in Massachusetts.
State: Potential Habitat = historic and currently acceptable habitat
Towns: Potential Habit = historic habitat
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2009 2013 2014 2016
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Coastal Processes 101 & The Regulations
Questions ?
↑ Resilience ≠ ↓ Natural Systems