Sea Level Rise: Natural Resource Impacts and Considerations for Great Marsh Community Resilience

1. Sea
Level
Rise:
Natural
Resource
Impacts
and
Considera8ons
for
Great
Marsh
Community
Resilience
Julia
Knisel,
Coastal
Shoreline
and
Floodplain
Manager
Kathryn
Glenn,
North
Shore
Regional
Coordinator
Massachuse8s
Office
of
Coastal
Zone
Management

2. Coastal
Inunda8on
Mapping
Elements
• Water
Level:
– Local
@de
ranges
– Sea
level
rise
data
&
projec@ons
– Flood
event
data
(surge
&
precipita@on)
• High
Resolu8on
Eleva8on
Data:
– Topographic
&
bathymetric
LIDAR
– Digital
eleva@on
models
referenced
to
@dal
datums
• Natural
&
Human
Responses:
– Current
ecosystems
(beaches
&
wetlands)
– Landform
changes
(erosion
&
accre@on)
– Physical
barriers
to
migra@on
(development,
seawalls,
culverts,
etc.)

3. Cri8cal
Parameters
for
Modeling
Marsh
Migra8on
Marshes
on
the
Move,
2011
• If
sediment
accretes
(traps
on
surface
or
accumulates)
as
fast
as
sea
level
rises,
then
marsh
may
avoid
being
converted
or
submerged

5. Mean
Higher
High
Water
Tidal
Datum

6. Sea
Level
Rise
Scenarios

7. Historic
Rate
of
Sea
Level
Rise
(Boston
Tide
Gauge)
• Mean
range
(MHW-­‐MLW)
=
9.5
feet
• Record
=
1921-­‐2012
(91+
years)
• Sea
level
rise
=
0.9
feet/100
years

8. Historic
Sea
Level
Trends
from
1921
to
2006-­‐2012
(Boston)
•
Linear
mean
sea
level
rates
(
)
&
95%
confidence
intervals
(mm/yr)
calculated
from
1921
to
recent
years
(2006-­‐2012)
at
the
NOAA
Boston
@de
gauge
sta@on
• Values
are
trend
of
en@re
data
period
up
to
that
year

9. Great
Marsh
Sediment
Accre8on
•
•
Marshes
accrete
by
trapping
sediment
&
by
organic
ma8er
accumula@on
from
roots
&
rhizomes
Maximum
accre@on
for
Great
Marsh
currently
recorded
~
6
mm/yr
Courtesy
of
Anne
Giblin,
Marine
Biological
Lab

10. Wetland
Types
Eleva@on
66%
wetland
Majority
Mean
High
Water
Spring
Mean
High
Water
Mean
Tide
Level
Mean
Low
Water
Water
Unconsolidated
Salt
Shore*
Marsh
Brackish/
Freshwater
Transi@onal
Wetlands
Dry
Lands
*includes
silt,
sand,
or
gravel
that
is
subject
to
inunda@on
and
redistribu@on
due
to
the
ac@on
of
water;
substrates
lack
vegeta@on

21. Marsh
Migra8on
Limited
by
Development
&
Infrastructure
(Newbury)
Current
75-­‐Year
Time
Horizon
(2080)
Net
marsh
impact
=
MHHW
+
4.5
l
sea
level
rise
–
1
l
accre@on

22. Marsh
Migra8on
Limited
by
Development
&
Infrastructure
(Salisbury)
Current
75-­‐Year
Time
Horizon
(2080)
Net
marsh
impact
=
MHHW
+
4.5
l
sea
level
rise
–
1
l
accre@on

23. Marsh
Conversion
to
Unconsolidated
Shore
(Gloucester)
Current
75-­‐Year
Time
Horizon
(2080)
Net
marsh
impact
=
MHHW
+
4.5
l
sea
level
rise
–
1
l
accre@on

24. Marsh
Conversion
to
Unconsolidated
Shore
(Salisbury)
Current
75-­‐Year
Time
Horizon
(2080)
Net
marsh
impact
=
MHHW
+
4.5
l
sea
level
rise
–
1
l
accre@on

25. Marsh
Migra8on
Modeling
Resource
www.csc.noaa.gov/digitalcoast/publica@ons/marshesonthemove

26. Applying
SLR
Data/Mapping
• Great
Marsh
communi@es
are
currently
grappling
with
retrofinng
areas
that
were
developed
before
SLR
and
climate
change
issues
were
recognized

27. Applying
SLR
Data/Mapping
• Past
experience
• What
do
we
know
now?
• What
can
we
do
differently?
• What
have
we
learned?

28. Altera8ons
that
Limit
Natural
Resilience
• Development
in
flood
prone
areas
• Impervious
floodplains
• Culverted
streams
and
rivers
• Tidal
restric@ons
• Armored
river
and
coastal
banks
• Hardened
shorelines
• Barriers
to
marsh
migra@on
NOAA
photo

29. Altera8ons
that
Limit
Natural
Resilience
• Development
in
flood
prone
areas

30. Altera8ons
that
Limit
Natural
Resilience
• Impervious
floodplains

31. Altera8ons
that
Limit
Natural
Resilience
• Confined
stream
and
river
beds

32. Altera8ons
that
Limit
Natural
Resilience
• Tidal
Restric@ons
• Causeways
• Low-­‐lying
roadways

33. Altera8ons
that
Limit
Natural
Resilience
• Armored
river
and
coastal
banks

34. Altera8ons
that
Limit
Natural
Resilience
• Hardened
shorelines

35. Altera8ons
that
Limit
Natural
Resilience
• Barriers
to
marsh
migra@on
Photo:
Maine
Sea
Grant

36. Altera8ons
that
Limit
Natural
Resilience
• Dams
• Culverts

37. Sea
Level
Rising/Climate
Changing:
Key
Resource
Func8ons
to
Consider
• A8enua@on
of
flood
waters
• Ability
of
storm/flood
waters
to
recede
• Sediment
availability
and
transport
• Energy
dissipa@on
• Natural
resource
adapta@on
• Ecosystem
con@nuity

38. AXenua8on
of
Flood
Waters
• Limit
impervious
areas
• Preserve
open
space
in
developments
• Incorporate
LID
• Avoid
hardening
stream
and
riverbanks
• Rethink
new
development
in
flood
prone
areas

39. Ability
of
Storm/Floodwaters
to
Recede
• Limit
new
impervious/
incorporate
LID
and
• Address
restric@ons
and
inappropriate
culvert
designs
• Dam
removal
• Preserve
open
space
in
developments
• Where
do
floodwaters
go?
• Consider
ousall
loca@ons
AP
photo
Reuters
photo

40. Sediment
Availability
and
Transport
• Unarmored
banks
• Bioengineering
alterna@ves
• Re-­‐nourishment
• Open
pilings
for
development
• Re-­‐vegeta@on

41. Energy
Dissipa8on
• Protect
dune
stability
• Sediment
supply
• Maintain
floodplain
func@on
• Sol
bank
stabiliza@on
techniques

42. Natural
Resource
Adapta8on
• Marsh
migra@on
and
accre@on
• Barrier
beach
migra@on

43. Ques8ons?
Julia
Knisel
CZM
Coastal
Shoreline
and
Floodplain
Manager
617-­‐626-­‐1191;
julia.knisel@state.ma.us
Kathryn
Glenn
CZM
North
Shore
Regional
Coordinator
978-­‐281-­‐3868;
kathryn.glenn@state.ma.us