Manzanilla-Mayaro Road Repair Works

8/10/2019 Manzanilla-Mayaro Road Repair Works

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Manzanilla-Mayaro Road

Repair Works

Water Management - Drainage Interventions


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ON THE GROUND(17THNOVEMBER 2014)

COASTAL CONDITION SURVEY


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Breach #1

High Beach Dune relative to

road level


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Breach #4

Overflow from wetland flowing

across and under the road.

Lack of interceptor drainage


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AERIAL SURVEY



7/28High beach dune

Overflow from wetland


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Breach


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BREACH LOCATIONS/OUTFALLS



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OUTFALL #1


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OUTFALL #6


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OUTFALL #12

Photo taken looking

towards shoreline

Photo taken lookingtowards the road


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OUTFALL #16

Major breach at the location of the damaged

house.

Sandbag being used by homeowner to protection

against ongoing erosion. Sandbag located on

northern side of breach (Outfall 16)


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OUTFALL #17

Major breach. At this location the entire road

cross section failed. No vehicular traffic beyond

this location


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PROPOSED DRAINAGE WORKS

MANZANILLA-MAYARO ROAD REPAIR WORKS


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Manzanilla-Mayaro Road Repair Works

Problems Opportunities

Solution

(Mimic the natural

drainage processes)

Failed sections of the roadway rendering the route

impassable

High topography of the beach dune

provides a natural defence against

coastal inundation or run-up by the

sea

Construction of interceptor drains (on

western side of the road) and

collector drains (on eastern side of the

road)

Paucity of drainage (natural and/or anthropogenic) Channels created during the flood

event can provide drainage from

inland runoff

Construction of culvert crossings to

channel flow from interceptor drains

(western side of the road) to collectordrains (eastern side of the road)

Relatively high topography of the beach dune in

comparison to the existing elevation of the Manzanilla-

Mayaro Road creating a natural impediment to drainage

Permanent establishment of 7 8

major breaches using green

technology (marine cells/marine

mattresses)

Ongoing coastal erosion threatening critical areas along the

Manzanilla-Mayaro Road, that is high water mark is less

than 15 meters from the existing roadway

Installation of inline check valves or

tideflex values to prohibit the

intrusion of saltwater into the wetland

Intense rainfall over a relatively short period (e.g. 371mm

over 9 days). It is noted that the long term (30-year) rainfall

depth for the month of November is 227.8mm

Residential and resort properties have been constructed

between the Manzanilla-Mayaro Road and the shoreline.

In many cases the structures are close to the roadway. This

provides a challenge for widening and elevating the road


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In line check valve or tideflex valve. Allowing only

one direction of flow at this point along the culvert.


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Breach #1

Breach #4

Breach #8

Breach #10

Breach #12

Breach #16

Breach #17


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COASTAL INTERVENTION

MANZANILLA-MAYARO ROAD REPAIR WORKS


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Proposed Coastal Intervention South Cocos

Proposed protection measures for the four shoreline sections

Sect.Road to be

protected against Proposed protection measure

Flooding Erosion

1 Yes Yes

Reinforcement of existing concrete seawall and

a new rubble mound seawall

2 Yes Yes Seawall type structure landwards of the

coastline3 Yes Yes

4 Yes No

Dyke located relatively close to the road to

allow natural coastal processes to take place

but preventing flooding of the road. This

involves gradual sacrificing of the coconut

plantation

Risk classification for coastal flooding and for coastal erosion

for the 1200 m long project stretch

Section Distance to

road [m]

Risk for

flooding

Risk for erosion

of road of road

1 0 Critical Critical

2 0 to 35 Critical Critical

3

25

Critical

Critical

4 50 to 60 Critical Not critical

Documents

Manzanilla-Mayaro Road Repair Works