The Big One is coming

Avec le soutien de
The SSR Botanical Garden, in Pamplemousses, was unrecognizable after cyclone ‘Gervaise’ hit Mauritius in 1975.

Published in August 2016 in l’express, The Big One is Coming, written by Abbas Currimjee
remains relevant. Especially at this time when cyclone Berguita, a threat of the same ilk as Carol or Gervaise, is heading to Mauritius.

The last decade and a half have given us a reprieve from something that has been part of Mauritian life ever since the beginning of human activity here: serious storms. And though some sunny optimists are crediting the effects of climate change on the absence of cyclone activity, there is no actual scientific evidence to back up the claim – only the lucky streak of near misses that we’ve enjoyed since ‘Dina’ did significant damage in 2002.

While we’ve basked in our unusually sustained good weather, we’ve been busy developing the island. Since 2002, we have modernized and expanded. Since ‘Dina’ hit land, we have erected Ebene Cybercity, constructed a modern glass-covered airport, expanded electricity grids, built significant road infrastructure and installed a fiberoptic internet network covering most of the island. Some of it has never been tested by anything more serious than a low intensity perturbation.

Given the scientific evidence, I’ve become convinced that as a nation, we have let our guard down and are now sleepwalking into a dreadful situation. Over the last months I’ve spoken with some of the top Mauritian experts in engineering, infrastructure, weather and disaster management, both on the government payroll and in the private sector, both on the record and off. The picture that has emerged is scary: in the worst – but statistically not unlikely – scenario, we could lose power for several weeks, the water system could be affected temporarily, food supply chain thrown out of gear, public buildings could be damaged and out of use and the airport – our fastest link with the outside word – could be compromised. Just as bad, if less immediately visible, our internet communication with the outside world could become blocked, the mainframe computers holding all our data – banking, government social security, etc – could become corrupted.

‘State of climate change 2015’

(Bulletin of the American Meteorological Society)

Notable findings from the report include:- Greenhouse gases, global surface and sea surface temperature as well as global upper ocean heat content were the highest on record. Global sea level rose to a new record high in 2015. Tropical cyclones were well above average, overall. There were 101 tropical cyclones total across all ocean basins in 2015, well above the 1981-2010 average of 82 storms. The Eastern/ Central Pacific had 26 named storms, the most since 1992. The North Atlantic, in contrast, had fewer storms than most years during the last two decades. The Arctic continued to warm; sea ice extent remained low.

It is reasonable to deduce that Mauritius is well overdue for a major cyclonic event, based on the law of statistical probability and irrefutable scientific evidence.

Heavy Toll

As shown on the table below, ‘Dina’ was the last very intense tropical cyclone (category 4 Saffir- Simpson Scale) which passed at its nearest distance of 50 kms North of Cap-Malheureux; intense cyclone ‘Carol’ passed over Mauritius between Feb 25th to 29th 1960, 56 years ago!

Cyclone ‘Dina’ it would appear from the data available would have exceeded ‘Carol’ in wind velocity, and very likely in its destructive capacity, had it come directly over Mauritius. It was a near miss! Fortunately its small diameter and eye and the 50 kms distance from Cap-Malheureux spared us the worst?

However the toll was heavy, nine fatalities were attributed to the cyclone, five in Rodrigues and four in Mauritius. There was extensive damage to agriculture and property. Electricity supply was seriously affected, as was the telecommunications sector, including the mobile network, about 25% of the island was without water for several days.

The ‘Université De La Réunion – Laboratoire de l’Atmosphère et des Cyclones’ in a case study on ‘Dina’ concludes :- ‘‘2 500 personnes en centres d’hébergements, 180 000 personnes sans eau, 107 000 foyers sans électricité, 13 500 foyers sans téléphone, cellulaire hors-services, rafales de vent à plus de 200 km/h, maisons dévastées, routes emportées, rivières en crues, plantations détruites, le cyclone tropical intense ‘Dina’ a ravagé la Réunion.’’

‘‘Si Dina était passée 25 km plus au sud lors de son passage au plus près de la Réunion, la vitesse des vents aurait été supérieure de 50 km/h à ce que nous avons observé,’’ analyse Philippe Caroff, chef prévisionniste à la station Météo France du Chaudron. En clair, notre île a eu beaucoup de chance. Si on se reporte aux valeurs de vent enregistrées on s’aperçoit que l’on aurait pu flirter par endroits avec les 300 km/h. “Nous avons échappé aux vents les plus violents, confirme Philippe Caroff. La force du vent étant proportionnelle au carré de la vitesse lorsque cette dernière est multipliée par deux, la force est quadruplée”.

Since ‘Dina’, we have had five tropical cyclones and severe depressions in the region, but as mentioned, without any serious damage having been caused.]


 

Cyclone ‘Fantala’

I take the case of ‘Fantala’ separately, it amply merits this distinction. Very intense cyclone ‘Fantala’ was the strongest tropical cyclone in the South West Indian Ocean in terms of sustained wind speeds, the most destructive phenomena.

Late on the 17th April, the Météo-France office on Réunion (MFR) estimated peak 10-minute winds of 250 km/h (155 mph), making ‘Fantala’ the strongest tropical cyclone of the basin in terms of 10-minute sustained winds. The Joint Typhoon Warning Centre estimated peak 1-minute winds of 280 km/h (175 mph), equivalent to Category 5 on the Saffir-Simpson scale and tied only with ‘Agnielle’ from November 1995 as the strongest on the record in the South-West Indian Ocean.

Having followed an unusual trajectory which on the 22nd April 2016 constituted a potential threat to Mauritius had it continued on its course, finally changed direction to head North West and eventually disintegrated as it approached the coastline of Tanzania. What would have happened if ‘Fantala’ had flirted our shores can only be conjectured?

The highest gusts recorded were 350 K.P.H and the highest 10-minute sustained wind speeds were of the order of 250 K.P.H. The lowest pressure was 910 hPa.

‘Carol’ by comparison had the highest gusts of 257 K.P.H. (Fort William) the highest 10-minute sustained were of the order of 190 K.P.H. The lowest pressure was 943 hPa.

Cyclone (Part II)

  • Probable scenario post Cat.5 – Very Intense Tropical Cyclone coming very close (20-30kms) or over Mauritius

The devastating effects of the cyclonic winds would be simultaneous and possibly span over a 24/36 hour period. I list below the impact in relation to the maximum number of our citizens who will be affected by such a calamity affecting various services and sectors.

(C.E.B Electrical Supply)

In my opinion, the Central Electricity Board (CEB) is a well-managed, technically competent and responsive utility, assuring us reliable and constant supply of electricity day and night. I am confident that on an international scale they would rank very well.

However our vulnerability in the event of a major occurrence remains high. The absence of a long term integrated plan, the frequent change of top management, political exigencies, not to mention interference, have deprived the CEB of the opportunity to develop the required resilience in its infrastructural network which is paramount for an essential service the whole country is so dependent upon.

Presently, Mauritius has some 300 km of 66 K.V lines and 3,000 km of 22 K.V distribution. The low tension network amounts to about 5,000 km island-wide. Serious damage to this network will impact severely on the normal functioning of our society, and after a relatively short period of non-availability of electrical supply, there would be considerable social and economic distress.

Based on my discussions with Senior Management at CEB, it transpires that in case of a severe cyclonic occurrence, the CEB network could be restored in about 3 to 4 weeks. This figure is indicative and many imponderables preclude a more accurate estimate.

It is interesting to note thatquasi-complete re-establishment of supply post Hollanda in 1994 took one month with the assistance of the Indian and U.S. Naval Engineering Corps. Also it should be borne in mind that the CEB network in 1994 was substantially smaller than it is presently. Considering that reliable electrical energy supply is the backbone  of our socio-economic fabric (Central Water Authority largely depends on reliable electrical supply), we must, as a nation, embark urgently on rendering the electrical supply/ distribution as resilient as is possible.

The above should constitute a topmost national priority. This will possibly require the ‘undergrounding’ of several thousand of kilometres of our network, presently highly vulnerable to cyclonic damage. It will most likely also require the strengthening/replacement of high tension towers. All this will entail substantial but very worthwhile capital expenditure, so as to ensure strong foundations for the resilience we must provide for a sustainable future for Mauritius.

  • The ‘Domino’ effect of relatively prolonged interruption to our electrical supply can be extensive, nefarious and costly in human and economic terms:

(CWA water supply)

I am given to understand that presently about 100 boreholes supply water to different areas of the country, besides, of course, the reservoir dams. Although they have autonomous standby generators in case of need, it is but normal that they cannot replace the reliability of regular CEB supply, and consequently water shortage, and increased interruption  of supply could be a frequent occurrence.

(Cold food supply chain)

Many of the smaller/medium-sized outlets and supermarketsselling chilled/frozen foods would have to cease this activity until re-establishment of CEB supply. Most households would be deprived of refrigeration capacity resulting in the need for a change in dietary and eating habits, further adding to the disruption of normalcy.

(Health and social implications)

Lack of electricity, shortage/ interruption of water supply, dislocation of normal food availability, including vegetables, etc., will impose undue stress on society and the medical facilities will have to bear their fair share of this phenomena as epidemics are quite likely to occur at such periods.

(Communication networks)

The communication networks will be impacted not only at the transmission level but as the majority of users will not have electricity, Internet, fixed and mobile communications will virtually come to a halt ! It would possibly constitute an ‘overskill’ were I to carry on with the list of hardships that would ensue in the event of non-supply of electrical energy for several weeks.

Some other issues of major concern

(Ebene Cybercity)

This is a post Dina development and consists of moderately high rise structures which may be generally referred to as High Tech in the local context. They have a high percentage of sub-structural components, which are best described as a ‘no-man’s land’, falling between the responsibilities of the Engineer, Architect, Builder and Owner. The responsibility in case of failure, at present, will be apportioned in a court of law, whereas in fact it simply arises from a clear lack of adequate Regulations/ Codes – the Australian example covers this amply.

In the course of my discussions with numerous colleagues, I brought up my favorite concern, ‘sub-structural damage’ and there was unanimous consensus on this issue. This un-regulated ‘No man’s land’ potentially constitutes a major and serious danger to many recent so-called High Tech structures. The integrity of the skin of the structure which has often been a supply and fix item, installed and designed by the main contractor or sub-contractor, contains inherent risks of failure, in such a situation it is difficult to determine until after the event has occurred, “la tisane après la mort”.

My personal experience perhaps will elucidate my concern more convincingly.My two brothers, my sister and myself decided to build a block of apartments for ourselves at J.F. Kennedy Avenue, Floreal, about five years ago. We selected a team of reputable and competent consultants and proceeded with our project. As is quite often the case, the project had its generous share of problems but fortunately my experience as an architect came to good use (I was one of the clients, not the architect for the project).

Upon my return from a month’s holiday, I noticed that the roller shutters, which were there to protect all the major rooms to our apartments, were being installed. The contractual responsibility of this most reputable, and probably the largest sub-contractor in this sector, was to supply and install roller shutters designed to withstand 300 K.P.H winds. What I saw clearly did not seem to satisfy the criteria required. I instructed for a load test under the supervision of an acceptable and qualified structural engineer. The test established that the maximum wind speed beyond which there would be failure of the shutters was 125 K.P.H. instead of the 300 K.P.H. asked for! I wonder how many such instances are waiting to be tested in a real cyclone across the built-up landscape of Mauritius.

Highly important data, sophisticated and expensive hardware and fixtures are housed in these buildings. It is difficult to estimate the damage potential, but the risk is real and major. Two very importantsectors, finance and ICT are housed in these buildings and the possibility of major localized failure cannot be ignored, impacting very negatively on these crucial poles of development.

(S.S.R International Airport)

My concern extends to this attractive ‘bijou’ of a structure built of seemingly solid steel, but covered extensively with a glass roof. It is difficult to comprehend the design logic or the lack of it, in designing such an important and strategic building, the only airport in Mauritius, with a glass ceiling. However well-designed, it runs the risk of serious leakage and ‘sub-structural’ impact damage, with possibly substantial disruption to the functionality of this essential facility.

‘High tech’ designs such as these, however well resolved in the design office, and in theory, have to be realized on the construction site. Their successful outcome depends very much on highly skilled and disciplined labour and rigorous observation of specifications and construction methodology. There is far less margin for error as compared to the more conventional forms of construction, concrete being an excellent example. Presently skilled labour and supervision are not in abundance in the country!

The Swami Vivekananda International Convention Centre roof failed at wind speeds of about 140 K.P.H. causing millions of rupees of damage to the interior and five months of non-use. I admit that my apprehension is only the result of what I often refer to as my ‘gut feeling’. This feeling is the product of 50 years of professional experience as an architect practicing in Mauritius, having lived through enumerable depressions and cyclones and being passionate about the unpredictable and destructive capacity of the relentless and untiring winds of an intense cyclone.

I humbly suggest that a thorough and highly professional structural and ‘substructural’ audit be carried out on the S.S.R Airport building to validate the existing design, and if required, make remedial recommendations. I consider, again in my lay opinion, that this matter be treated with the urgency that is dictated by the approaching cyclone season and the indispensability of our sole airport.

(Storm sea surge)

Global rising sea levels are synonymous with the threat of climate change. They have been the cause of massive dislocation and migration of many vulnerable populations tosafer areas. During Intense Cyclones, these same seas generate massive sea surges which encroach inland with waves of up to 6/7 metres and more, generating relentless destructive energy. A category 5 – Very Intense Tropical Cyclone, with the confluence of wind direction, high tide and very low atmospheric pressure would wreak unprecedented damage to our coastal zones and assets.

In view of our dependence on the above, which would include the Port installations, Port-Louis Waterfront, major hotels and the countless houses, authorities should commence with plausible preemptive actions.

Singapore’s leadership already realized in 2007 that rising sea levels was a major challenge that had to be met to assure its very survival. Its Prime Minister, Lee Kuan Yew, personally headed a highlevel committee that was soon set up to address this existentialist issue. “We are already in consultation with DELFT in Holland,” said Lee Kuan Yew in a press interview a few days after the first deliberation of the newly formed committee. An outstanding example of political will, clear thinking and expeditious action. DELFT Hydraulics, a research institute and consulting firm specializing in water management issues, is considered to be world leaders in this sector.

“We feel we have strong reasons to be concerned but no reasons for panic,” said Vladan Babovic, director of the Singapore Delft Water Alliance, a $43 million research center opened in February between Delft, the National University of Singapore and the country’s water management agency, PUB Singapore. “We will be able to resolve these challenges,” he said.

  • Building regulations and codes

A building code, building control or building regulations, is a set of rules that specify the minimum standards for constructed objects such as buildings and non-building structures. The main purpose of building codes are to protect public health, safety and general welfare as they relate to the construction and occupancy of buildings and structures. The building code becomes law of a particular jurisdiction when formally enacted by the appropriate governmental or private authority.

Our building regulations date back to 1954, we do not have Codes that regulate the structural, and specially the ‘sub-structural’ integrity of buildings. Design, Engineers in Mauritius generally refer to British Codes of Practice for engineering design purposes.

A most relevant example of what a situation as the above mentioned can result in is the catastrophic impact that was suffered by the town of Darwin, Australia, in December 1974. It was the worst disaster due to building failure in Australian history, and it was an engineering failure. Today every building built in Australia embodies major lessons learnt from cyclone Tracy’s experience.

The insurance industry was also seriously impacted and the Government took little convincing that it was not in the national interest to expect the private insurance companies to bear such risks and thus put the whole insurance industry at risk of insolvency.

Tracy, although one of the greatest disasters to afflict Australia since European settlement, its impact has led to greatly improved practices in the building and insurance industries which have substantially increased the resistance of Australia’s built environment to extreme wind events.

Mauritius urgently needs to totally update its building regulations and elaborate relevant and thorough Codes for  the building and construction industry. There is no need to re-invent the wheel, the Australian experience and expertise surely can be made available by an appropriate request to the Australian Authorities.

Presently in Mauritius, the absence of a Code for the building/construction sector results in what I consider to be a highly precarious and dangerous situation, whereby important elements of a building which do not constitute the main structure, such as windows, large glass panels, protective shutters, cladding to buildings, even block walls between structural elements, are not the responsibility of  the structural engineer under his normal professional terms of engagement unless the design engineer has been specifically requested to look into the matter. The engineers’ responsibility is to ensure the main structural integrity of the building. The remaining, but very important, elements which I refer to as ‘sub-structural’ and which assure that the structure has an envelope which is also resistant to wind and related impact forces. A building with outer skin failure would not only be non-functional but dangerous for its occupants and destructive for its contents.

The way forward

The above issues are significant, they need to be addressed with the seriousness and urgency that is warranted. The list is not exhaustive for some, the path to even partial ‘resolution’ will be long and arduous.

The challenging period ahead offers us an exceptional opportunity for nation building. We will all be affected by adversity in a democratic manner, the forces of nature do not discriminate! There is one common threat, this will demand in turn our common, concerted response.

Focused leadership, the mobilization of the best available human and substantial financial resources, both local and foreign, all managed with clarity and probity will be necessary for such an ambitious endeavour that can also be the spark to “re-ignite the engines of growth” to quote Rama Sithanen with thanks!

Legacy fund

A suggested strategy to finance the infrastructure upgradation that will be required to face the challenges ahead, whilst sensitising the Mauritian population and creating a sense of solidarity around the effort, is the issuance of a ‘Cyclone Infrastructure Enhancement Bond’. This bond would be issued by the Government of Mauritius, the proceeds of which would be 100 % directed to finance the key sub-sectors of our country’s infrastructure that would suffer the most damage.

The Bond would enjoy full government guarantee, be interest-bearing and redeemable after 5 years, 7 years and 10 years, with higher coupon rates for longer durations. It would target both private and institutional investors. In addition, a special marketing effort would be undertaken to raise capital from the wider Mauritian population in order to create nation-building awareness around this important initiative. A higher interest rate for private investors on a capped amount could be structured to encourage the participation of the population. Tax incentives for institutional investors should also be studied. A successful example is the ‘Great Millennium Dam Bond’ issued by the Government of Ethiopia to part-finance the construction of the ‘Grand Ethiopian Renaissance Dam’, the largest hydro-electric dam in Africa. By targeting Ethiopians locally and abroad, it created a sense of solidarity around this ambitious nation building project.

The views expressed in the article are my own and, where applicable, based on verified and verifiable data. I acknowledge with thanks the time and attention given to me by the following friends and colleagues who encouraged my initiative:-

Pierre DESJARDINS

Chartered Structural Eng. F.I.E.M Iqbal Limbada Structural Eng. M.I.E.M – Limbada & Limbada

Nuvin HOOLOOMAN

Quantity Surveyor FRICS – Hoolooman & Associates Ltd

Michael SEW

Director-Civil Engineer. ARUP Engineers

Vassen KAUPPAYMUTHOO

Oceanographer (MSc Oceanographer, Canada), Environmental Engineer (MSc Ecole des Mines, France Professional Diver CMAS 3*

C.E.B

Senior Officials

Others

Who wish to remain Anonymous

Note for table:

The average interval period between intense cyclones is found to be 6.3 years Only cyclones of gusts 200 km/h or above are being considered Dynamic pressure refers to the pressure that the gusts will be exerting on the façade wall/glass per m2

Publicité
Publicité
Rejoignez la conversation en laissant un commentaire ci-dessous.

Ailleurs sur lexpress.mu

Les plus...

  • Lus
  • Commentés
  pages consultées aujourd'hui Statistiques et options publicitaires