• Variances

• ID areas where flood boundaries exceed zoning (e.g. jurisdiction of marsh act)

• MMRA Mandate = protect agricultural land (allows periodic flooding)

• boundary based on HWL (CGVD28 datum) from 1950s, unique to each marsh body

Tregothic Marsh (Windsor):• Total assessed value = $31,003,300 • yet agricultural land ~0.6%, majority commercial or government infrastructure

Legislative Boundaries

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Two animated slides removed to reduce file size.

Assessment & EngineeringCrest Elevations & Footprints

• ‘critical’ elevation determined for each marsh body (based on HWL & exposure)• ‘construction’ elevation = 2 ft + critical

Storm surge & return periods Relative Sea Level Rise (m) Combined (SLR + surge)Hants HWL Crit. const. 1:10 1:25 1:50 1:100 2025 2055 2085 2100 2055 & 2085 & 2100 &

NS # Name (m) (m) (m) 0.85 0.96 1.04 1.13 0.16 0.45 0.85 1.1 1:100 1:100 1:1008 Grand Pre 7.9 8.2 8.8 8.8 8.9 8.9 9.0 8.1 8.4 8.8 9.0 9.5 9.9 10.1

41 Habitant 7.9 8.2 8.8 8.8 8.9 8.9 9.0 8.1 8.4 8.8 9.0 9.5 9.9 10.156 Wellington 7.9 8.2 8.8 8.8 8.9 8.9 9.0 8.1 8.4 8.8 9.0 9.5 9.9 10.157 New Minas 8.1 8.1 8.7 9.0 9.1 9.1 9.2 8.3 8.6 9.0 9.2 9.7 10.1 10.365 Bishop Beckwith 8.0 8.2 8.8 8.9 9.0 9.0 9.1 8.2 8.5 8.9 9.1 9.6 10.0 10.2

• in order to maintain slope, as increase height, must increase footprint

• Original Fundy design: • 1:3 seaward• 1:2 landward

• 210 m < critical• 3.7% of dyke length• foreshore mean = 220 m

Town of Wolfville

ErosionAccretion

Dyke toe instabiliity

Erosion of outer and/or inner slope

Piping

Sliding of outer and/or inner slope

Instability of shore protection element

Overflow & wave overtoppinga)

b)

c)

d)

e)

f)

Mechanisms of Dyke Failure

Assessment & Engineering

Erosion & foreshore marsh

Bishop Beckwith

Starrs Point

• foreshore marsh is critical for erosion protection & source of material (borrow pit) for dyke topping to decrease cost

• 1 m water depth – wave dissipation in 80 m

Assessment & EngineeringLegislative Boundaries

• Important to re-examine marsh body boundary

• In many areas, strong match with historical HWL survey and lidar analysis.

• However, HWL determined from 1940s and did not consider CC

• Extend boundary if minimal development

Adaptation Options

Protect

Type of Property Suggested Flooding Frequency Allowance

High-yield agricultural land flooded by freshwater 1:10 High-yield agricultural land flooded by freshwater

but with high investments 1:25

High-yield agricultural land flooded by salt water 1:50 – 1:100 Individual houses 1:50 – 1:100 Complete town 1:500

Big cities, industrial areas essential services (ie: airports railways) 1:1000

Source: Pilarsky, 1998

• hold the line & protect assets• topping requires increase in

base footprint, potentially extend dyke

• source of material (cost)• armouring (toe of dyke or

foreshore)• cost benefit analysis required

Dyke heightening (cm)

Cost

of

heig

hte

nin

g o

r d

am

ag

e (

M$

)

Example of cost assessment for dyke heightening in the Netherlands (van Alphen, 2012)

The economic optimum level of protection is where the sum of investments in dikes and residual damage (continuous line) shows a minimum, i.e. where further increase of dike height doesn’t outweigh the related avoided damage anymore.” (van Alphen, 2012).