resilience of Vulnerable Coastal Areas and Communities to - - PowerPoint PPT Presentation

“Enhancing resilience of Vulnerable Coastal Areas and Communities to Climate Change in the Republic

• f Gambia”

Jonathan McCue and Jeremy Hills

PPG Work Programme

WORK “PHASES” EXPECTED DATES Project PPG Approval February 2012 Procurement of Consultants and Approval March to July 2012 PPG Inception Phase August 2012 Consultation Phase (Vulnerability Assessment and Feasibility) August to September 2012 Result Compilation October 2012 Project Document (Draft) compilation November 2012 Project Document Draft Workshop Presentation December 2012 (11-18 Dec?) Final Acceptance

• f

Project Document and submission to GEF January 2013 Anticipated start July 2012

Issues linked to Coastal Protection decision making in Gambia

• Is there mechanical equipment available for construction purposes?.
• If a project requires earth moving equipment (trucks or loaders) they

would have to be shipped in at considerable expense.

• What are the locally available materials for a coastal structure ?.
• Are large rocks available for armour stones?

Issue (cont)

• Construction projects may rely only on manual labour; hence, the

size and quantity of rock which can be moved is limited.

• Supervision of construction projects in remote areas can be an

issue,

• Mechanical equipment, brought in from outside, is very expensive
• Need to use local material and local labour - benefit of the project

can be economically felt in the local area.

Issue (cont)

• Rubble mound walls are the least reflective but require specific

rock sizes and precise construction supervision.

• Artificial nourishment of a beach is a soft solution with no negative

effects on the beach.

• Artificial nourishment must be repeated periodically (often not

understood by local land owners).

• Artificial nourishment requires a adequate supply of sand and

equipment to move it onto the beach.

Living with the Sea - Possible intervention techniques

1. Shore Management Plan 2. Use of dredged material to construct embankments or for intertidal recharge 3. Construction of realigned earth embanked defences within lagoons (managed realignment) 4. Sand bag offshore breakwaters 5. Sediment bypassing at lagoon entrances (beach recycling) 6. Adaptive Mangrove/tree planting Techniques

The need for a Shoreline Planning Framework for Gambia

• A Shoreline Planning Framework is needed to help strategically plan

for the suitable implementation of sustainable sea defence

management (soft and hard) and other maritime works.

• It can be used by GoG when considering applications for reclamation
• r for new private development proposals on islands.
• Help to enforce environmental permits and EIA regulations

Shoreline Planning for Gambia

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Adaptive Options for a “Road” scenario

Sediment Dynamics – Cape Point

Sediment Dynamics – Cape Point

Setback Policies?

150m?

Intervention Measure 1 - Beach Replenishment

• Sand pumping and beach replenishment, commonly takes place
• Consider wider geographic impacts of the practice and how this might alter

the prevailing sediment budget.

• Localised remedies often lead to neighbouring island problems.
• High monitoring costs and maintenance commitment
• Alteration to sediment budgets
• “Relic” footprints that are left behind by sand pumping (depression hollows)

which can increase the risk of unstable footing.

Trinidad

Appropriate locations All locations, including those with limited blown sand for natural recovery. Costs Low to moderate, but requires

• ngoing

maintenance (US$2000- US$40,000 /100m length plus fencing, transplanting, etc, with similar repeat costs).

Effectiveness Short term defence against erosion, and enhancement of natural recovery. Moderate resistance to single storms. Enhanced by fencing and vegetation transplanting, and can be successfully used to bury hard defences. Benefits Accelerates natural recovery of beaches and provides short term defence against single severe storms. Problems Removes material from other sites, possibly transferring erosion or environmental damage to a different frontage. May introduce beach debris, non-indigenous sediment and/or vegetation, potentially damaging local ecology. Applicability to Gambia? Useful low cost solution to localised problems in specific areas. Needs to be combined with a robust monitoring framework to be able to deduce and predict volumes and timing of recycling.

Beach Recycling and Reprofiling

Associated measure: Sediment bypassing at river outlets (beach recycling)

Intervention Measure B : Sand bag revetment or related structures

Structural Measure : Sand bag revetment

Intervention Measure C : offshore breakwaters

A Multi-Purpose Reef is a type of coastal structure that can reduce erosion, enhance marine habitat and provide a valuable recreational resource. The key to the effectiveness of a Multi-Purpose Reef is the formation of a salient – a wider, more stable section of a beach caused by the reef. Multi-Purpose Reefs actually consider the value that beaches provide to local communities by serving to protect the beach itself. Seawalls and other forms

• f coastal armouring do not actually protect the beach; they only protect the

land behind it.

Coastal Engineering Design - Recommendations

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Trinidad

Artificial Offshore Reefs

Appropriate locations Exposed beach of high ecological and landscape value. Costs Moderate to high, and may need some shoreline maintenance (USS40,000 to US$120,000/100m of structure, plus minor works for unprotected areas). Effectiveness Causes lee side accretion, but least effective during storm surge conditions. Unlimited structure life. Benefits Natural processes are only partly disrupted, allowing beach to stabilise. Rocks create new intertidal habitat. Problems May cause navigation hazard for local fisherfolk. Visually intrusive at low tide. Disrupt amenity use of beach. Applicability to Gambia Likely to disrupt natural beach replenishment of

• ffshore sand bar stores. Also would be visually

intrusive and impact on beach and surfing recreation activities

Associated measures : Sand bag, timber

• r rock groynes

Trinidad

Timber Revetments

Appropriate locations High value sites suffering modest and periodic erosion. Costs Moderate (US$4000 to US$100,000/100m frontage length) – See Appendix C. Effectiveness Provide good protection if only occasionally exposed to waves. 5-30 year life. Benefits Normally acceptable to the public. Less expensive than seawalls or rock revetments Problems Limited life, particularly where exposed to wave

• action. Visually intrusive. Alters beach-beach

processes as sand interchange is disrupted. Applicability to Gambia? Not appropriate as shore normal groynes on the foreshore, or as foreshore breastwork (see Figure 21), possible consideration as a backshore sand trap structure using local hardwood and assist with

• ther timber designs as part of the Master Plan.

Groynes and Jetties

• ensure appropriate consideration is given to the spacing,

composition and height of coastal structures.

• It is apparent that most groynes, jetties and breakwaters

constructed are not based on quantitative information that relates to the hydrodynamic conditions of the immediate area.

• Consider the aesthetic appeal of the local environment!!!

Intervention Measure D : Construction

• f realigned earth embanked defences

within the estuary (managed realignment)

Integrated aquaculture with sea defence measures

Sea level Land level Road Level

• Ag. land level

Sea level Land level Road Level

• Ag. land level

Fish Ponds Sea Defense System

Intervention Measure E : Adaptive Mangrove/tree planting techniques

Trinidad Beach Grass Planting

Appropriate locations Above normal limit of wave run-up at any location with available blown sand. Unlikely to succeed where erosion is severe. Costs Low, but labour intensive with on-going management (up to $4000/100m length for each visit). Effectiveness Enhancement to natural beach recovery. Reservoir of sand held in planted beach will provide a buffer to resist storm erosion. Benefits Compliments natural system. Can be used to improve other management options. Potentially self sustaining. Problems Normally requires beach fencing or thatching to achieve

• success. May be completely lost to storm erosion.

Applicability to the Nile Delta? Native beach grasses, are needed. Hardy species and can be used to help assist beach sediment binding as part of the structure particularly on the seaward face of structure.

Beach Grass Planting

Trinidad

Beach “Thatching”

Appropriate locations Above normal limit of wave run-up at any location with available blown sand. Unlikely to succeed where erosion is severe. Costs Low, but labour intensive and requires ongoing

• maintenance. (US$400 – US$4000/100m length

plus cost of transplanting and annual maintenance) Effectiveness Enhancement to natural beach recovery. Modest resistance to storm erosion. Enhanced by vegetation transplanting. Benefits Minimal impact on natural system. Materials are all natural, degradable and low cost. Problems Without maintenance thatching will last no more than 1 year. Materials are often used to build bonfires. Applicability to Nile delta? No benefit ahead of grass planting – only applicable to the backshore area to prevent wind blown sand wind.

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Site template for a tidal wetland (flood storage) restoration site

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Floating breakwaters (to encourage fish culture)

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Intervention Measure 5 – Gabion Baskets

Future Exercise 1 – Which Technique??

Dividing the Gambian “Coast”

• Coastal “stretches” for possible intervention and technique selection

(Proposed Exercise for consultation discussion – multi-criteria analysis)

Gambian “Coastal Stretches”

“Enhancing resilience of Vulnerable Coastal Areas and Communities to Climate Change in the Republic

• f Gambia”

Dr Jeremy Hills

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“Adaptation Through Learning”

Vulnerability Assessment Table

Socio-economic themes Vulnerability Arguments Agriculture High

• Deterioration of terrace and irrigation system
• Depletion of water sources mainly driven by extension of qat crops
• Deficient market infrastructure and resulting crop losses

Pastoralism Moderate

• Limited contribution to GDP
• Decrepit market infrastructure resulting in low productivity and added value
• Conversion of pasture into arable land

Water management High

• Excessive use for agricultural purposes (more than 90% of total consumption)
• Limited water resources and growing water consumption
• High municipal water losses
• Low understanding and skills in water resources management

Health Low

• Sector vulnerability stems from other sources than climate change

Tourism Moderate

• Significant tourism potential located on its coastal areas
• Tourism related to water sports and recreation

Linking Climate Change with Total Vulnerability

14 12 10 8 6 4 2 9 8 7 6 5 4 3 2 1

Total-vulnerability CC-vulnerability

Urbanisation In-migration. Out-migration Health Water management - extraction Water management - conservation Waste management Transport - marine Transport – terrestrial Tourism Industry & Ports Fisheries Pastoralism Agriculture