Dr. Danika van Proosdij & Greg Baker

Department of Geography, Saint Mary’s University

Coastal Vulnerability Assessment

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Rationale

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Coastal zones are dynamic – leads to conflict between natural variability & economic, social & cultural activities

Anse Source D’Argent, La Digue Petit Sable, Mauritius

Rationale

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Adaptive capacity of coastal communities directly linked to availability of physical space, shore zone stability & knowledge

Lack of consistent polices often leads to the systematic use of hard engineering structures without consideration for either coastal dynamics or socioeconomic factors

Point d’Ensy Road to Grand Sable, Mauritius

Coastal Vulnerability

4 Photo: Sam Page, 2012

Exposure Condition • fetch • dominant wind/wave direction • shoreline orientation • tidal state

Biophysical State • geomorphology • built features • erodibility • slope • elevation

Resilience Condition • eco-morphological resilience capacity • sediment budget • relaxation time

Adaptive Capacity • political • financial • cultural/social

Adaptation Response/ Adjustments • hold the line (shore protection) • retreat (incl. set backs) • abandon

Understanding the complexities of current and future coastal exposure-sensitivities and adaptive strategies is one of the central themes of the ParCA & GIVRAPD projects.

Research Approach

GOAL: Assess and compare coastal vulnerability (exposure – sensitivity) to current and future coastal erosion and storm surge and associated adaptive capacity within the ParCA and GIVRAPD study areas in Canada, the Caribbean and Indian Ocean.

Field Characterization & Assessment

Modelling & Visualization within GIS

Research Approach: Field

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Anse Royale

• Line segmentation @ changes in backshore, foreshore and nearshore

• Notable point features (e.g. groyne, fishing access, drain, pier)

• Geotagged enabled camera

Trimble Yuma Field Tablet

Blue Bay

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• hierarchical decision key integrated into GIS

• Includes form type, height, slope,

material, vegetated, condition/state • Multiple lines permits multiple,

complex queries (e.g. slope with beach vs no beach)

Decreasing Stability

Research Approach: Field

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• Modified Emery Board method

• Beach width, slope, wave E proxy • Profiles perpendicular to coast

Research Approach: GIS

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Input: • LIDAR bare earth model (elevations) • Resolution dependent on provider (e.g.

2 m vs 10 m) • Orthophoto • Topographic base data • Digitized layers as needed

Processing: • ArcGIS 10.1 • Spatial & 3D analyst • GRASS/QGIS (open source)

Projected 90 yr RSLR – Mauritius (1.32 m); Seychelles (1.23 m) based on Forbes et al., 2013 – incorporates vertical crustal movement & meltwater fingerprinting

Output: • Flood extent & area • Connectivity (e.g. id of ‘weak’ spots) • Flood water depth • Intersection of flood depth with buildings, road segments and agriculture areas

Field Assessment Example: Grand

& Petit Sable, Mauritius

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• 82% foreshore coarse sand, low gradient, stabilized, evidenced by significant wrack material & garbage

• Shore protection only in backshore (55%), min engineering (except park), opportunistic use of materials – all evidence of disrepair or failure

• Query level of understanding of mangrove planting as useful – evidence of use of cut wood for field stakes

Flood Analysis: Anse Royale, Seychelles

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• Projected 90 yr RSLR = 1.23 m • 152 buildings flooded • 1.16 km road • 16.13 Ha agricultural land flooded behind Anse

Royale • Primary conduit under Bazaar bridge & wetland

PARCA: Negril characterization & assessment post Sandy

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Antropogenic Feature

!> Culvert

Artifical Reef

Breakwater

Gate

Groyne

Road

Run-off Trench

Sill

Wall

Wharf

Tourist Amenity

¼= ATM

J Airport

"# Bank

"ñ Fire Station

I8 Fuel

ÆP Hospital

ÆI Park

"î Place of Worship

ca Police

Ó" Post Office

_ Resort

"n School

Backshore Form Type

anthro

cliff

outcrop

platform

slope

waterbody

wetland

Backshore Conditions

high stabilized

not stabilized

partially stabilized

unconsolidated over solid

Physical Vulnerability Analysis

13 Analysis conducted by S. Letourneau

Challenges: Accommodation Space

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Example: Anse Source D’Argent

Key tourist destination, widely advertised , iconic beach – min area to ‘roll back’

Challenges: Accommodation Space

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• Limited space for relocation of agriculture or built structures due to coastal topography

• Query creation of conflict for land resources & equity of access – social & governance issue

Adaptation vs Maladaptation

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Key to adaptation is choosing a solution that does not create additional problems (e.g. undermining structure or neighbouring structures or interrupting supply of sediment) Does not need to be costly, just designed with coastal process in mind & not all techniques are appropriate in all areas Encourage use of soft/living or hybrid shoreline where appropriate however will require a longer time to realize benefits compared with ‘immediate’ result of rock armouring

Innovations & Opportunities

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Natural planting of hybrid options

Restrict or modify development to permit migration of coastal landforms & coastal processes Use future predicted HWL rather than exisiting

Education, training, outreach & community engagement

Beach nourishment appropriate if sand sustainably obtained Requires consideration of longshore transport

Recommendations

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• Maps provide basis for dialogue & community decision making - protect/accommodate/retreat – ID priorities & options

• Critical to consider planning at littoral cell level (e.g.

coastal component of sediment transport – see Cuzes-Duvat and Robert (2001) for maps) to avoid maladaptation choices (e.g. groyne which cuts of sediment supply)

• Increase education & outreach on cost - effective design of coastal protection structures – including outreach to agricultural & fishing communities

• Integrate local knowledge and experience

where possible – share experiences between island communities

Acknowledgements

• Field work would not have been possible without the logistical assistance of colleagues (& impromptu field assistants) in Mauritius, Seychelles & Canada particularly Ministry of Environment & Energy (Seychelles)

• Data access facilitated through Ministry of Housing and Lands (Mauritius) & Ministry of Land Use and Housing (Seychelles)

Geomatics & cartographic support provided by B. Perrott, G. Matheson and S. Letourneau from Saint Mary’s University

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