department of infrastructure castletown tidal flooding & sea defence august 2014

Department of Infrastructure

CastletownTidal Flooding & Sea Defence

August 2014

2002 • Tide model created• Storm Surge Model • Flood Maps• 2002 prediction

accuracy +- 500 mm Meters

• 2014 prediction accuracy +- 50 mm

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January 2014

• Flooding areas– Hope Street– Back Hope Street– Springfield Terrace– Victoria Road– Milner Terrace– Athol street – Brewery Walf

• Tidal Overtopping– Douglas Street– The Promenade

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January 2014 Structural Damage

• Damage to sea wall at St Mary’s Car Park

• Damage to breakwater

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Lessons Learnt/Improvements

• Shortage of sandbags

• Poor communication– Government – Businesses,

Residents and LA’s

• Understanding of the flooding routes

• Drains, Lanes, Roads

• Area Protection works

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February 2014

• Improved flood protection at end of Hope Street.

• Gullies and manholes covered to prevent backing up.

• Early deployment of sandbags and increased availability

• Improved communication with businesses, residents and local authorities

• Pre-planned road closures, advertised in advance

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St Mary’s Car Park

• Castletown Commissioners reconstructed the sea wall and car park

– 250T of temporary rock armour to protect the area

– Construction of new retaining wall– Improved land drainage– Increased car parking– Viewing area being created

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Tactical Improvements Since January• 20,000 filled

sandbags• Flood barriers• Portable flood

barriers• Maintenance of

non-return valves to harbour

• Pre-planned road closures

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Portable Flood Barriers• Demountable flood

defence barrier• Rapidly deployed• Flexible, easy

connection to walls• Pods fill with rising

flood waters• 900 mm high units• No bolting or

construction work needed

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Fixed Flood Barriers• Permanently fixed

wall channels• Lightweight

aluminium panels• Durable rubber

seals• Units locked in

place with compression screws

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Policy and Strategy Development• A high level cost

benefit analysis complete

• Investigation of defence options and budget costs commissioned

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Up Coming Tides• Tide height

– 10-15 August 14– 13th- Chart 4.15 m– 8-12 September 14– 11th Chart 4.21 m

• Castletown Harbour typically 0.40-0.50 lower than above

• This only starts to be predictable 36 hours out

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