Tuesday 3 September 2019

The New World - Howard Chin, Member Jamaica Institution of Engineers

In the Sunday Gleaner (1 September 2019) there are two articles on drought, and one extremely powerful (possibly a new record) hurricane in the news. This is to be expected, based on the IPCC report some years ago. The higher temperatures predicted increases the dryness of the soils, raises the sea levels, and increases the sea temperature which results in higher hurricane winds. Years ago, I proposed McCarry Bay, south of Vernam Field for the site of the logistics port when Goat Island was being considered because the IPCC report was taken into consideration in its selection: the elevation of the land is over 6 meters above sea level near to the coast, probably good to beyond the end of the century. Also, the Vernam Field International Airport will survive well after Norman Manley International Airport and Sangster International Airport are submerged, as well as the Port of Kingston.

Similarly, with regards to energy, seawater pumped storage was the preferred method of supporting the large amounts of renewable electricity to be produced in the near future. The more common freshwater pumped storage was not considered because the IPCC said that the Caribbean would be net drier. As a consequence there would be insufficient fresh water routinely available to fill the high level reservoirs.

The severity of the dryness has caught me a little off guard, with rivers drying up, and underground water being threatened. The progression to near desertification seems to be well ahead of schedule, so the government’s plans to even consider allowing mining land considered part of the Cockpit Country which supplies water to a good part of western Jamaica seems imprudent, to say the least.

As the Earth heats up, the Saffir-Simpson scale for hurricanes will need to be brought up to date with 2 new categories added, Category 6 would seem to be needed in the next few years as Hurricane Dorian is already almost there:-

Category 6:- Sustained winds:- 210 to 295 mph, Types of damage due to hurricane winds:- Near apocalyptic damage, all framed buildings will be destroyed**. Some reinforced concrete buildings may be damaged. Most large trees will be broken down to stumps, or uprooted and blown away**. Most of the area will be uninhabitable for many months to a year+.

Category 7:- Sustained winds:- 296 mph  or higher. Types of damage due to hurricane winds:- Apocalyptic damage. Most conventional reinforced concrete structures will be damaged either directly or by flying debris. Thick walled monolithic structures with sloping sides and deep foundations will survive. All large trees will be broken down to stumps, or uprooted and blown away. The land will be scoured. Flexible, low plants such as grasses may survive**. This area should be evaluated if continued habitation is feasible.  [** This is what happens with now in the most severe tornados.]

Government should be designing systems for decades ahead, not month to month or even to the next year, expecting far more than 1.5 degrees C global temperature rise as seems to be likely.




Category
Sustained Winds
Types of Damage Due to Hurricane Winds
1
74-95 mph
64-82 kt
119-153 km/h
Very dangerous winds will produce some damage: Well-constructed frame homes could have damage to roof, shingles, vinyl siding and gutters. Large branches of trees will snap and shallowly rooted trees may be toppled. Extensive damage to power lines and poles likely will result in power outages that could last a few to several days.
2
96-110 mph
83-95 kt
154-177 km/h
Extremely dangerous winds will cause extensive damage: Well-constructed frame homes could sustain major roof and siding damage. Many shallowly rooted trees will be snapped or uprooted and block numerous roads. Near-total power loss is expected with outages that could last from several days to weeks.
3
(major)
111-129 mph
96-112 kt
178-208 km/h
Devastating damage will occur: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes.
4
(major)
130-156 mph
113-136 kt
209-251 km/h
Catastrophic damage will occur: Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Fallen trees and power poles will isolate residential areas. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months.
5
(major)
157 mph or higher
137 kt or higher
252 km/h or higher
Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months.
  

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