BY JUDE NJOKU & LAIDE AKINBOADE
MRS. Vero Paul lived in a dilapidated building near the canal that links Amukoko and Sari-Iganmu, two slummy neighbourhoods in Lagos. She had earnestly prayed to raise enough funds to enable the family move out of the flood-prone ghetto, but her efforts yielded little or no dividend.However, the early rains and attendant wind-aided destructions in most parts of Lagos on February 13, served as a wake-up call on the family that something must be done urgently. Mrs. Paul had to send a save our soul (SOS) appeal to friends and relations to raise the necessary funds to rent a room in a more conducive environment.
Indeed, the events of July 10, 2011 and February 13, 2012 are two incidents most residents of Lagos would earnestly pray that should not reoccur. Reason? July 10 last year was a dark day when flood swept through the mega-city leaving in its trail the loss of lives and property worth several millions of Naira while February 13 will remain evergreen in their memories as the coastal parts of the bustling commercial mega-city of Lagos experienced a most severe wind/rain storm unprecedented in its history.
With a projected wind speed of about 60-90 kilometres an hour and driving rains that lasted for almost an hour, the rainstorm blew off several roofs and telecom masts and upturned trees. Even boats in motion reportedly capsized resulting in substantial loss of lives and property.
NIMET’s rainfall predictions
Presenting the 2012 Seasonal Rainfall Prediction (2012 SRP) in Abuja, the Director General of Nigerian Meteorological Agency NIMET, Dr. Anthony Anuforom, said there would be irregular flooding and erosion in some parts of the country, especially the coastal zone and river catchment areas.
Anuforom urged the relevant emergency agencies, state governments and the Federal Government to create awareness in order to reduce damages and loss of lives and properties.
He said there would likely be a normal onset of rainfall in 2012 in most parts of the country between late February (in the southernmost part of the country), and last week in June (in the northernmost part of the country).
The Agency predicted that the length of planting season would vary from 90 -270 days with most parts of the country experiencing normal growing season.
Warri will have the highest length of rainfall season with 247 days and 2,649mm of rainfall, which starts from March 7 to November 8, 2012, followed by Ibadan with 246 days and 1,275mm. The rains in Ibadan are expected to start from March 26 to November 27, 2012 while Nguru has the shortest length of rainfall season of 93 days of 1,675mm. This will run from June 30 to October 3, 2012, followed by Potiskum with 113 days of 494mm of rainfall. The rains are expected to start from June 23 last till October 2012.
Anuforom stated that “for the hydrological and water resources sector, this implies adequate water and stream-flows which may affect the dam storages for municipal water supply, hydropower generation and irrigation. Hence, development and regular maintenance of dams for dry season irrigation and water supply should be accorded high priority”.
He stated that episodic flooding and erosion in the coastal zone and river catchment areas may be inevitable and as such adequate publicity would be required to reduce damages and risk of losses of life and property, especially in areas prone to river bank overflows.
Furthermore, he stated that the predicted normal rainfall may result in flash flooding particularly in the northern states. It should also be noted that wet spells and flash floods could occur even in areas with a likelihood of near normal to below normal rainfall.
Such flash floods may lead to physical damage to crops in the field, agricultural equipment and structures (such as dams), as well as physical damage to infrastructure – roads, railway lines, telecommunication networks, loss of lives and displacement of large population due to disruption of agricultural activities as a result of extreme weather is very likely.
“As expected during the onset and cessation period of the rainy season, rainstorms accompanied by strong winds are expected over the country. The likely increase in the frequency and intensity of these extreme weather event in the coastal areas will cause flooding and erosion which may result in landslide and loss of lives and property.
Hence, there is need for sensitization of National Emergency Management Agency, NEMA, and other relevant agencies to ensure adequate emergency preparedness for associated risks,” the NIMET boss said.
The growing season, he said, is expected to be normal and would vary from 90-270 days. The rainfall amount would be from 300mm to 1100mm in the northern half of the country and in the South, 1200mm – 2700mm which may lead to high surface runoff and flash flooding.
”Farmers in the extreme northern parts of the country and environs are likely to face attacks of grasshoppers (desert locust), flower-feeding insects, millet head miners and grain eating birds (quela birds and other environmental related crop diseases). The necessary measures to address such threats should, therefore, be put in place by relevant agricultural extension services.
But high agricultural yields are likely over the savannah regions as a result of adequate rainfall expected over the area. In southern region where adequate rainfall is also expected, good cereal and root crop yields are likely. Farmers in this region and the central part of the country should plant tuber crops immediately the predicted dates are attained,” he advised.
According to the Minister of Aviation, aviation safety would depend on weather prediction. “Accurate and timely weather information is critical for achieving these objectives. In particular, aviation safety is heavily dependent on accuracy and timeliness of weather information available to the pilot.
These NIMET predictions which are in line with the growing worldwide climatic change, according to a Lagos-based architect, Mr. Emeka Izuwah, pose new challenges for architects, engineers and builders. He listed a number of design considerations that should be adopted to avert or mitigate further damage.Design storm resistant buildings: According to him, building designs must now respond to climatic challenges. “In earthquake prone areas, building designs should be earthquake-resistant while building materials should be made to resist adverse weather situations. Building designers in Nigeria must now respond to the challenges of climate change.
“The use of concrete facia, stone-coated steel roofing with generous pitches must be encouraged. Minimum gauge of 0.55mm for Long-Span Aluminium roofing sheets must be enforced while the iron anchorage that holds the tie beam preventing wind uplift must be used. The use of glass must also be regulated with a minimum of 0.5mm thickness as the minimum standard,” he said.
Mr. Izuwah who is the managing partner of Archiplex Consult, a firm of architects and builders stated that a “cursory study of the roof affected during the February 13 episode, showed that most of them lacked iron anchorages to their tie beams and had breakable roof covering with low pitches.” He charged telecom companies to ensure that their masts are firmly anchored to the ground with sufficient steel bracing to counter wind uplift.
The image maker of the Nigerian Institute of Building, NIOB, Mr. Kunle Awobodu, described storm as a phenomenon which is “an obvious threat to our buildings that we have no control over”. He stated that rebuilding a house brought down by storm is defeatist and should remain unacceptable. The attitude should be that of constructing buildings that will withstand storm, not rebuilding.
He sid: “In the design of buildings and other related structures, meteorological data, in the face of global changing climate, are very essential at determining the design variables. Isopleths of basic wind speed in Nigeria rate the coastal area less susceptible to hazardous wind effect. Wind pressure in the northern region is quite higher. Hence, roof design and construction in the northern part of the country consider wind resistance more than the southern roofing system. But erratic wind speed of present time calls for greater prevention.
“The wind velocity prior to the Lagos rainstorm was generally calm and as low as 02 knots. Then emerged the drown daft that was ossified by kinetic energy, resulting in maximum wind gust called squall. The three meteorological stations in Lagos recorded the squall as 45 knots at Stranchan Street, Lagos Island; it reduces to 40 knots at Oshodi and 35 knots at the Murtala Mohammed Airport. The least of these is strong enough to knock down a structure not designed and constructed to withstand squall.”
He called for a result-oriented synergy among building construction professionals to ensure that such occurrences are nipped in the bud. Against this backdrop, the NIOB’s publicity secretary, sought a working relationship between built environment professional bodies and researchers to create a platform for the needed synergy. Such a synergy will lead to scientific strides to confront the rising weather challenges.
Need for period maintenance
Apart from designing wind-resistant buildings, Izuwah decried the poor maintenance culture in Nigeria. Said he: “While a level of maintenance culture has been achieved in car maintenance, the same cannot be said of building maintenance. Just as cars need to be regularly maintained so also do buildings need to be maintained.
“Most home owners do not know that roof coverings and other building members have a specific lifespan after which they must be replaced. Some building members need to be replaced with age to prevent damage. Building maintenance must go beyond mere re-painting and other window dressing measure.”
Enhanced development control and monitoring
The Archiplex Consult boss stated that to permit building development without prudent development control is to invite disaster. “Government must empower its development control authorities to monitor and ensure compliance with statutory building standards and regulations.
“Material testing must become an integral part of building construction while the country’s building code must become enshrined in the curricula of all building related institutions. The influx of untested and probably sub-standard materials into the country is not in the long term best interest of the nation,” he said.
Early warning and detection
Mr. Izuwah posited that while designers must upgrade their building techniques, early warning and detection must be put in place. He said: “The nation’s Maritime authorities may have informed us of the probability of heavy rains, they will need to go a step further by giving us precise early warning and detection.
“If the path, date and time of Hurricane Catrina in the US was diligently charted so that people took precautionary measures, it then stands to reason that severe wind or rain can be accurately predicted and people warned so that lives and property can be saved”.
But, the NIOB image maker noted that according to the Central Forecast Office of the Nigerian Meteorological Agency, the rainstorm was of micro-scale system, that is, unexpected; thereby it can happen again without warnings. “In this peculiar circumstance, the onus is now on the professionals in the built environment, and with the support of the government, to ruminate on how best to mitigate losses resulting from extreme weather,” he said.
Lagos experienced severe flooding due to unusual rainfall of 233.3mm on July 10, last year. Ibadan had a similar experience on August 26, 2011 though with the rainfall recording 88.2mm. Fourteen years ago, (June, 1997) Lagos was heavily flooded following a rainfall value of 237.3mm. The latest NIMET prediction has warned Nigerians of impending heavy rains and the concomitant flooding.
The builders who attributed the frequency with which extreme weather condition returns nowadays to climate change noted that “in a science-oriented society, experts would begin to work assiduously in order to find solution to challenges of nature.
“As at today, Baca, a London-based firm of architects, who are also flood specialists, has developed Britain’s first amphibious house. The house, if struck by flood would rise with the water and come down to its original position when flood recedes. With this construction ingenuity, communities on flood plains are bracing up to the challenges of climate change rather than accept defeat in a relocation.
“Japan, in the face of frequent earthquakes, rose up to the challenges with innovations. Buildings that could overcome destructive effect of earthquakes were designed and constructed. Compliance with standard construction could reduce effect of natural disaster on buildings. Haiti was known for substandard building construction.
“Hence, when the country was hit on January 12, 2010 by 7.0 magnitude earthquake, greater damages on buildings were recorded if compared to the 2010 Chile’s experience of 8.8 magnitude earthquake on Richter scale.”
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