The year 2012 might well go down after all as Nigeria's "annus horribilis", the year of horrors when Nigeria's fabled good luck deserted her precipitously as one calamity after another cascaded downwards upon the nation in torrential manner. Perhaps a parallel in the intensity of misfortunes might be found in the case of the biblical Job who God handed over to Satan for intensive trials and tribulations with the sole pre-condition that his life be spared.
However we should not push the similarity too far, because while Job was acknowledged as righteous by both God and man with the exception of Satan, Nigeria does not have such a sterling reputation in the assembly of nations and even in the minds of its own citizens. A stronger case may in fact be made for a much closer fit between Nigeria and the twin evil city states of Sodom and Gomorrah. We all know the sad end to which their impenitence led them. Is it possible that God has handed Nigeria over to Satan without any pre-condition? Your God-forbid prayer is as good as mine.
The latest tragedy to befall Nigeria, the great and unprecedented flood of 2012 has badly exposed Nigeria's rump and particularly the state of unpreparedness of the Nigerian state to cope with natural disasters. After the initial shock and awe, accusations are now flying left, right and centre like heat-seeking missiles about who and what caused the flood. The government has responded in the only manner it knows best, it has doled out =N=17.6 billion to rehabilitate the victims. It has also set up a committee to raise more cash with much fanfare.
Soon more accusations will start flying about how the monies earmarked and raised were squandered. In typical Nigerian fashion, thousands of hardened criminals and con men including many from non-riverine communities deep in the hinterland will soon make their crooked ways to the resettlement centres and gradually outnumber the genuine refugees all in a bid to lay their greedy hands on the presidential largesse. A number of genuine refugees upon receiving their very little and ultimately not so fair share of the resettlement payouts at a heavily discounted rate drawn in favor of the paymasters will soon be kidnapped until they cough out what little they have received.
There would soon be strong clamor about non-observance of federal -, state -, local government -, village -, family -, sex -, age, or even sibling - character in the disbursements. More noise would be raised. Otherwise sterling characters would be rubbished. Then another panel would be set up to probe how the monies were disbursed. While the new panel would still be gathering facts and memoranda from a shocked and not so shocked public, the Great Nigerian Flood 2.0 (2013 version) would come upon the nation. More lives and properties would be lost. A new uniquely Nigerian, vicious cycle of flood - resettlement -payout - protests - probe - flood - resettlement - payout - etc. would emerge to employ many Nigerian idle hands and wicked souls for many decades to come.
Do not get me wrong. As a short term palliative measure, rehabilitating genuine flood victims or other victims of natural or man-made disasters is a noble thing to do. But equally as important is taking other short, medium and long term measures to ensure that such a disaster does not recur or even if does, that it does not meet us as unprepared. We must improve our national flood control infrastructure. But more importantly we must take care in erecting this flood control infrastructure because if its foundation is not solid and if it is not laid immediately all our best efforts will come crashing down again and again.
It is not an easy matter to fight an opponent you cannot easily identify and characterize. This is exactly the challenge Nigeria is facing with the Boko Haram terrorists. In a similar manner to provide an effective bulwark against flooding of the type witnessed this year we must first of all study and characterize our major natural water resource systems.
As simple as it sounds, the absolutely essential foundation upon which any successful flood control system must be built is a comprehensive and adequate network of recording rain gauges and stream gauges. Like in other areas of our national life, this is an area Nigeria is failing grievously. That Nigeria is desperately under - served by recording rain gauges and automatic stream gauges is an indisputable fact.
But first what is a rain gauge and what is a stream gauge? Simply put, a rain gauge is a device that collects and measures the amount of rainfall within a given period. Discounting more modern but not as yet fully reliable approaches of rain measurement such as radar based methods; there are two types of conventional rain gauges. There is the manual rain gauge which is read manually at a definite time interval often after every 24 hours. The other is the automatic rain gauge which automatically records the amount of rainfall continuously all year round.
Now as everyone knows, rainfall is a random or more technically, a stochastic event. And there are different forms of rainfall. We have high intensity rainfall as well as low intensity rainfall. We have long duration rainfall as well as short duration rainfall. We also have all possible combinations of the various types. For instance we might have low intensity, long duration rainfall or high intensity, short duration rainfall and vice versa.
Therein lies the superiority of the recording rain gauge. For while the manual rain gauge can only tell you the amount of rain that fell in between readings i.e. daily rainfall, it cannot tell you whether it was from single or multiple rainfall events or the intensity of each rainfall event.
On the other hand, a recording rain gauge can not only tell you the number of distinct rainfall events within any given period, be it 1hr, 3hrs, 6hrs, 12hrs or 24hrs etc. More importantly, it will also tell you the intensity of the rainfall such as '25mm of rainfall per hour for 2 hours starting from 10.30 pm' or '10mm of rain per hour for 6 hours starting from 6.00am followed afterwards by 5 hours of 20mm rainfall for 1 hour'.
In order words from a recording rain-gauge device you can count the number of as well as characterize distinct rainfall events. This helps engineers to build up the so called IDF or rainfall intensity-duration-frequency curves. This difference has significant implications in rain fall modeling.
Another important fact to note is that the value of the data from a rainfall station to be used in rainfall event modeling varies directly with its age that is the number of years of useful historical rainfall data it has generated. In other words the longer the period it has been in continued use, the more valuable the data from a rainfall station is prized. Long periods of data apart from reducing the possibility of statistical bias enable one to identify underlying rainfall trends.
The World Meteorological Organization minimum standard for the spatial density of rain-gauges is 600 - 900 square kilometers per rain-gauge for flat areas in tropical regions and 100 - 250 kilometers per rain gauge in mountainous tropical regions (WMO, 1974). If for the sake or argumentation we even consider a below threshold density of 1000 square kilometers per rain gauge, then Nigeria with a land mass of about 923,770 square kilometers as quoted by the World Bank roughly requires about 924 say 925 rain gauges.
Unfortunately this writer does not have information concerning the number of active rainfall measurement stations in Nigeria at his disposal. The National Assembly is in a better position to demand this information from the Nigerian Meteorological Agency, the Ministry of Water Resources and other relevant agencies. What I can however say is that a significant proportion of our oldest and existing rainfall gauges are of the manual type!!
A couple of years ago, this writer under the auspices of my civil engineering consulting firm, Strategic Research Consortium Limited, was privileged to consult extensively for the Nigerian Railway Corporation in the study and engineering design of major flood/gully erosion control projects at 9 separate locations nationwide. These locations are Akerri railway station in Niger State; Bomala to Zongoma railway stations in Gombe State; Eziama Gully, Aba in Abia State; Amuzuku Gully in Umuahia Abia State; Emene Railway Bridge, Enugu; Gangara, Fagan Baza, Nahuche and Kasuwa Daga villages all in Zamfara State.
Needless to say at or near most of these locations, there were no reliable rainfall stations and one had to extrapolate rainfall data from data originating from the nearest yet relatively distant rainfall stations in Maiduguri, Bauchi, Zaria, Gusau, Bida, Minna, Port Harcourt and Enugu. Thankfully most of these stations had about 20 years or more of daily rainfall data recovered from manual rain gauges. It was a case of half bread being better than none.
A stream gauge on the other hand is a device that indirectly measures the discharge or quantity of flow of a river or stream within a particular time interval (say in units of cubic metres of water per second) at a particular station along the river course. Although there are devices which can measure the discharge directly, it is prohibitively expensive to do so on a continuous basis, so what is pragmatically done is to measure the level of water in a river or stream at a particular station and then use so called stage-discharge curves to estimate the discharge.
Stream gauges measure the water level continuously so that the discharge through the stream can be ascertained continuously at that particular location. The stage-discharge curves are established or calibrated by physically measuring the actual discharge at known stages or water levels corresponding to very low and very high flood conditions several times a year. Since major flood conditions reconfigure river beds and cross-sectional profiles via scouring or silting, after any major flood condition such as that of this year, the stage discharge curves should inevitably be revalidated or recalibrated.
Again as for rain gauges, the longer the period of continuous observation or use of a stream gauge (10 years is the minimum threshold recommended while 30 years of data is preferred), the more valuable and the more reliable is its data. Modern stream gauges using telemetry involving aerial satellites are able to transmit real time information 24/7 about stream water levels to flood control centres where the river or stream discharge can then be automatically computed and posted in real time. The delay between automatic reading and the free availability of the result to end users is put at about 10 to 15 minutes.
The United States has about 7400 active stream gauges. One county Mecklenburg County in North Carolina alone funds about 55 stream gauges in the county or in the vicinity of the county (according to a United States Geological Surveys report dated October 2006). Now a county in the United States is roughly equivalent to a local government in Nigeria. Sadly to say I have very serious doubts if Nigeria has as many active, well calibrated stream gauges as this single U.S. County!!
What is more as noted earlier, streamflow information is absolutely free in the United States. The USGS (2006) quotes that a National Research Council (NRC) study in 2004 characterized stream flow information, 'as a public good because (1) those who have not paid for the service are not excluded from using it and (2) the marginal cost of servicing additional individuals is zero, because if individuals safely cross a stream during a flood, travelling on a road way bridge that is properly sized to span the high water, no cost is incurred instead the cost is borne as a component of the national investment in economic development and social well-being)'.
In Nigeria, the reverse is the case. It may not surprise readers to learn that during the course of my design studies for the Nigerian Railway Corporation projects referred to earlier, my firm paid a steep price for access to the relevant rainfall data. Whether the amount paid was remitted to the coffers of the National Meteorological Agency or was pocketed is unknown. Your guess is as good as mine. In the Akerri flood control project for instance, since the adjacent River Mariga to the best of my knowledge then was not gauged, this writer had to calculate an estimate of the river discharge using empirical methods.
What was more frightening was the absence of digital maps for a majority of the Nigerian Railway Corporation project locations. In a few cases where the digital maps were available from the Office of the Surveyor-General of the Federation, (OSGOF) the cost of the maps being touted was astronomical. I ended up purchasing digital maps of Nigeria from the United States!!
It may also surprise Nigerians to learn that even though our maps are currently being digitized by OSGOF, the digitization is essentially based on old Colonial maps. You may not be able to get an official topographic Nigerian map, paper based or digital, for Umuahia area today because the area was not mapped during colonial times!!
The reader might now be wondering how all this stuff can prevent or protect against flooding. The answer is that taken together, the various bits and pieces of information provided by "mature" rainfall and stream gauges enable engineers to answer very crucial life and death questions as well as safely design structures exposed to water resource systems such as dams, bridges, levees, dykes, culverts, gully control works etc.
For instance consider a catchment basin that feeds a river and has an adequate number of "mature" rainfall gauges spatially located within its perimeter. Assume that there is a couple of "mature" and well calibrated stream gauge stations located along the river course before and after the catchment discharges into it. Then engineers can establish with reasonable confidence, the incremental discharge to expect and when to expect that discharge in the river after a single or multiple specific rainfall events within the catchment basin. These rainfall events may either be real or virtual.
In other words once such information is available through these measuring devices, then with appropriate skills one can even model various rainfall events that have not even occurred. Such hydrograph and other regional river models can alert you when the discharge will exceed the river's conveyance capacity. Engineers can now carry out flood plain mapping and tell you what areas would be flooded downstream, as well as when and to what height the river would rise at various downstream locations based on these real or assumed rainfall events. The analysis of a river's response mechanism given all these real and virtual scenarios is now within the realm of engineering capabilities.
This is precisely the sort of information, the National Emergency Management Agency (NEMA) could not provide. It is true that NEMA alerted the nation about the impending forced release of water from several dams within and without Nigeria (i.e. Cameroon) and warned all those living near the river banks to evacuate immediately.
This was a timely warning but it was not actionable by the various State Governments or anybody else apart from the naturally prudent, because the flood plain of River Niger was not hitherto mapped and so the flood line and more importantly flood height as well as almost precise timing information could not be given in conjunction with the alert.
If the residents of say Oko-Anala village near Asaba had been forewarned that, the level of river Niger would rise to say 2m (or roughly say 6ft) above its normal rainy season level on say September 29th 2012 around 10pm say, even without flood plain mapping, the inhabitants of Oko-Anala village would need no one to tell them to evacuate their families and valuables.
As they say in my Asaba (Igbo) dialect, 'adi agwa ochinti na aya esu go'. This translates literally to 'you don't need to tell a deaf man that war is around the corner for once he sees others running, he too would sprint for dear life in the same direction'. In fairness to NEMA there is no way it would have been able to issue this specific warning, because the engineering hydrology cum river hydraulics infrastructure to generate such a warning is crucially absent in Nigeria.
But as civil engineers would testify, the value of an adequate and comprehensive recording gauge and stream gauge system goes far beyond generating such warnings. The very first thing a civil or structural engineer learns during the course of his studies, is to respect the forces of nature for these are things engineers grapple with daily. Natural forces do not come much greater than flood water, wind storms, fire and earthquakes.
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