HomeMy WebLinkAboutPublic Shoreline Management Alternatives_201401231559377527Public Shoreline
Management
Alternatives
Rebecca Haney
Coastal Geologist
Massachusetts Office of Coastal Zone Management
Coastal Management Challenge
•Balance protection of natural resource function with
human use.
Coastal Management Needs Analysis
•What is the goal?
•What are the causes of erosion/damage?
–Tides
–Waves
–Currents
•Options to address causes?
–Upland Runoff?
–Vegetative Stabilization?
–Reconfigure uses?
–Need for stabilization?
•Impacts
•Benefits
•Costs
Shore Parallel Structures
•Erosion continues
•Cuts off sediment source
•Causes end scour
•Causes increased erosion
•Can be overtopped
•Requires monitoring
•Requires mitigation
•Costly to maintain
End Effects of Walls
Shore Perpendicular Structures
•Constructed with rock,
wood, concrete or sandbags
•Design minimum length,
width and height necessary
•Traps sediment moving
alongshore
•Starves downdrift beaches,
unless filled to entrapment
•Reflects wave energy
•Can have rip currents
adjacent to them
•Reduces erosion of beach
nourishment projects
•Requires monitoring
•Requires maintenance to
keep filled to entrapment
Offshore Breakwaters
•May reduce local
erosion rate
•Interrupts longshore
transport of sediment
•Used with beach
nourishment
•Requires monitoring
Sand-filled bags
•Stops erosion of sediment
source
•Reflects wave energy
•May be marine debris
hazard
•End effects
•Vegetation often can’t
establish in them.
•Requires monitoring and
maintenance.
Bioengineering: Coir
Rolls & Vegetation
Before
During Construction
10 Years later
• Reflects less wave
energy than rocks or
sandbags
•Limits erosion of
sediment sources
•Can be used to re-
establish vegetation
Bioengineering – Natural Fiber Blankets
•Blankets stabilize soils
while vegetation gets
established
•Use in conjunction with
coir rolls and vegetation
•Do not use synthetic
fibers
Nourishment
•Add sediment to
the beach, dune, or
nearshore to
enhance natural
storm damage
protection system.
•Requires
monitoring.
•Beach
Nourishment: Mass
DEP’s Guide to
Best Management
Practices for
Beach
Nourishment in MA
(2007).
Dune Nourishment & Artificial Dunes
Artificial Dune
•Construct dune seaward
of an eroding coastal
bank/bluff
•Sacrificial
•Use coarser sediment for
increased longevity
Dune nourishment
•Add compatible sediment
to eroded dunes
•Vegetation
Vegetation
•Use native, salt-
tolerant plants with
extensive root
systems
•Establish stable slope
•Address invasives
Runoff Control
•Remove and reduce
impervious surfaces
•Redirect water
•Minimize maintained lawn
areas
•Use swales and rain
gardens
Sand Fencing
•Thin wood slats &
twisted wire preferred
•Site landward of
annual storm waves
•Avoid plastic, metal,
fences that become
structures
Modified Public
Access
Brewster
Coastal Management Needs Analysis
•What is the goal?
•What are the causes of erosion/damage?
–Flooding
–Erosion
–Waves
•Options to address causes?
–Upland Runoff?
–Vegetative Stabilization?
–Reconfigure uses?
–Need for stabilization?
•Impacts
•Benefits
•Costs
Site-Specific Analysis
•Shoreline Change Rate?
–Short and long-term
•Flood Zone(s): type and elevation(s)?
–V zone, A zone
•Dry beach width?
•Resource type?
–Beach, dune, bank, floodplain
•Function?