Skip navigation


This information is being maintained for archive/historical purposes only.
It will not be updated.

 


You are here:

Homepage> Archive> Friday 11th March 2005> Ivan’s Impact on Cayman
 

Ivan’s Impact on Cayman: Facts From the Storm

Government and private sector representatives recently attended a presentation on the impact of Hurricane Ivan. The meeting was chaired by the National Hurricane Committee (NHC) Deputy Chairman Donovan Ebanks.

The presentation was based on a United Kingdom Department of International Development (UK-DFID) study, which was undertaken in conjunction with the Cayman Islands Government. It aimed to provide a scientific assessment of the hazardous phenomena (wind, storm surge) that occurred during Hurricane Ivan, and to present data on the impact on the physical infrastructure in order to learn lessons to be applied to future mitigation efforts.

Dr. Simon Young, principal consultant for GeoSY and Mr. Tony Gibbs, also of GeoSY, conducted the study for the UK-DFID. Dr. Young presented the flowing findings:

What happened island wide on September 12, 2004?

Wave damage in West Bay: Onshore winds at the end of the storm produced major wave damage on the south-facing coast. This highlights the Seven Mile Beach vulnerability to westerly-driven winds.

Flood damage on West Bay Road: Ivan’s strongest easterly winds drove surge water across West Bay Road, causing 4-5 ft. of flooding and widespread damage to roads and buildings. Hundreds of cars were also washed away.

Wind damage in George Town: Winds of 130-135mph did little structural damage; exceptions were poorly secured roofs, un-reinforced masonry walls and long-span galvanized steel sidings. Loss of lightweight cladding, small areas of roof damage and poorly fitted windows allowed rain to enter, causing severe internal damage. Storm shutters and hurricane-strapped roofs saved many residential structures from more damage.

Storm surge in North Sound The saucer-like geometry of North Sound created a 6-9ft storm surge peaking in the NE winds around 5:00am. Later, as winds strengthened and swung to the east, the surge and waves caused damage to coastal property and breaching of the island across to Seven Mile Beach. Cayman Kai had only 1-3ft of surge and was protected from wave damage.

Wave damage and flooding from South Sound A short break in the reef protection at Milford’s Bay along South Sound enabled waves to break on the low-lying shoreline after winds came onshore from the SE around 11:00am. This caused extensive damage to beachfront properties and added to flood water depths inland. Further east, houses along Sea Spray Drive, another unprotected stretch, fared much better due to their higher elevation (30ft above sea level).

Wind and surge damage at Bodden Town The Civic Centre at Bodden Town was the only shelter that had to be evacuated during Ivan. Its roof was already known to be a weak-point. Along the beachfront, many properties were inundated and badly damaged by storm surge flooding carrying sand.

Wave damage at High Rock The exposed iron-shore at High Rock results from harsh wave action through the ages, due to lack of reef protection. Large rocks at 30ft above sea level, hundreds of feet from shore, are evidence of past hurricane action (e.g., 1932). During Ivan, almost all of the property along this stretch was damaged or destroyed, even houses 500 ft. from, and 25 ft. above, the sea.

Surge and some wind damage along East Coast Storm surge of 4-6 ft. brought water and sand into the ground floor rooms of the Morritt’s Tortuga Club and moved houses in East End. Winds lifted some standing seam roofing from tall structures.

Double Surge

Eyewitness accounts suggest two surge peaks —a n early (4-5:00am) peak from the North Sound wind-driven surge and another at 11:00am, coinciding with peak winds blowing onshore in the Spotts-Prospect area. The second peak was associated with heavier waves, especially in areas lacking reef protection (e.g., Mariner’s Cove and Ocean Club).

Dr. Young said that while many residents and officials were surprised by the 6-9ft storm surge, it was not unprecedented for Grand Cayman. Breaches in the Newlands, Red Bay and Prospect areas have occurred at least four times in the past 100 years. Early morning northerly and northeasterly winds caused the wind-driven element of the storm surge to be much higher than normally anticipated.

Eyewall replacement

Microwave imagery shows that Ivan was going through an eyewall replacement cycle as its centre passed within 30 miles of George Town around 9:00am. An intense, compact inner eye started breaking down early in the morning and by 10:00am the strongest winds were in the outer eyewall. Peak winds were felt AFTER the centre of the storm had passed closest to the island—meaning that there was only a slow swing in wind direction.

Storm damage to Property:

Wind damage (residential): Shingles fared better than they would in a Category 5 storm. Roof damage was highly variable within small areas, suggesting that small differences in roof installation were very important.

Wind damage (commercial): Long-span galvanized sidings and roofs are compromised in Cat 2 and Cat 3 storms. Poor roofs on several older “strip malls” led to total destruction. Plastic venting covers beneath balcony overhangs did badly and led to roof compromise and water ingress where it wouldn’t otherwise have happened. Standing seam roofing did very well – but there some peeling off at edges in the most exposed areas.

Main Conclusions:

  • Post storm scientific analysis is vital—none of the ‘quoted’ maximum wind speeds were verifiable.
  • Ivan produced low to moderate Cat 4 winds across western Grand Cayman, Cat 3 in the east. These winds were sufficient to do major damage to a poorly prepared island (peak winds were higher in Grand Cayman than in Grenada).
  • Good building code and strong enforcement, plus generally good residential housing stock, were main reasons for avoiding worse wind damage.
  • Wave damage was severe in areas encountering onshore winds but unprotected by shallow reefs.
  • Water ingress, via rain entering through breaches in the building envelope and through salt-water flooding, was the dominant damaging agent.
  • Low elevation and lack of preparedness for degree of flooding exacerbated the impact of water.
  • Long duration of storm (almost 18 hours at hurricane force) added to the degree of damage.

Ivan “Quick Facts”
September 12, 2004

Wind strength over the day
Wind 90mph from NE at 7:00am
Wind 110mph from East at 8:00am
Wind 135mph from East at 9:00am
Wind 125mph from SE at 11:00am
Wind 90mph from SSE at 3:00pm

Peak winds: 130-135mph in George Town and 110-115mph in East End.
Peak surge: 6-9ft causing inland flooding up to 5ft
Peak waves: probably 15-20ft
Rainfall: probably 15-18 inches