FLOOD DISASTERS IN NIGERIA: BEYOND CLIMATIC BORDERS

By

Emmanuel Ajayi OlofinProfessor of GeographyBayero University, Kano

Text of a Public Valedictory Lecture

Introduction

One believes that a valedictory lecture is a sort ofgoodbye summary of some aspects of what a Professor hasbeing doing academically up to the point of his departure,laced with policy implications and an agenda of what needsbe done by those in his field of study. Thus, there shouldbe some connection between the inaugural and valedictorylectures. Consequently, this valedictory lecture has someelements of matters arising from the Professorial inaugurallecture delivered 21 years ago (Olofin 2000). That lectureaddressed the issue of “The Gains and Pains of Putting aWater-Look on the Face of the Drylands of Nigeria.” Statedin other words, the lecture addressed the advantages anddisadvantages of water development in the drylands ofNigeria through the construction of dams and the greening ofthe farmlands in the region through irrigation.

At that time, some of the pains (disadvantages)identified in the downstream reaches were the drying out ofthe fadama land and the cessation of annual silt deposit onthe fadama land, while in the irrigated areas yet-to-becritical built up of salinity was also identified. Impoundedfarm land, soil erosion and deforestation were a few of thepains identified in the reservoir basin and at the upstreamcatchment areas as settlements expanded and new farmlandswere established in such areas. Indeed, the drying up of thefadama land was not regarded as a complete pain; it checked

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the pre-dam excessive floods in some downstream reaches suchas in the Hadejia valley complex only that after over tenyears of crop production pain, the system of irrigation(residual moisture utilization) had to give way to both dryseason irrigation through tube-wells and wash bores and wetseason farming by rain-fed cultivation.

Without any warming, there came an end to the perpetualdryness of the fadama land downstream of many of theNigerian dams, particularly in the Sudano-Sahelian zones.Periodic, but more devastating floods emerged downstream ofthese dams; all connected to the hydraulic structures thatwere supposed to be flood-preventing! Consider the BagaudaDam burst of 1988 spreading disaster through the Kano Riverfloodplains all the way downstream to the Hadejia valley;the Alau Dam dyke breach of 1994 sending flood waterstearing through parts of Maiduguri; the annual rituals offlooding downstream of Shiroro Dam in the Niger State anddownstream of Kainji-Jebba Dams in Niger and Kogi states;the periodic flooding of the Hadejia Valley since theemergence of Chalawa Gorge Dam in 1992, sacking most of Auyoin 2001 and 2004 and the recent devastating floodsdownstream of the Gonroyo Dam since 2010. This may make oneconclude that too much “water-look” is being put on the faceof the Nigerian drylands.

However, dam-induced floods have not been limited tothe drylands. The first dam-related flood occurred in thehumid south, downstream of the Ojirami Dam in 1980 in thethen Bendel State. For many decades the Ogunpa flood atIbadan has been an annual event, though this is not as aresult of any dam upstream. One recalls also that before anydam was constructed on the Ogun River, the river overflowedits banks at Majidun in 1963, but now the management of thereservoir on it sends flood torrents down its channel toLagos on annual basis.

It is generally agreed that the most intense, mostwidespread, and most devastating of the floods that haveever affected Nigeria is the 2012 flood, which as usualoccurred downstream of a number of dams located in the dryand semi-humid areas. It is strange, therefore, that with

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all the dam-related evidence before us, the floods inNigeria within the last decade, particularly those of 2012are being explained off as the consequences of climatechange that have brought about excessive rainfall. Relyingon one’s previous researches, up-to-date secondaryinformation and recent personal experience and fieldobservations one plans, in this lecture, to answer somepertinent questions which include:

(a) What are the effects of Climate Change on therainfall regime in the last decade or so in some partsof Nigeria?

(b) Given that there have been some increases inrainfall amounts; can the margin of increase explainthe devastation of some of the recent floods,particularly those of 2012?

(c) What other factors, beyond climate change, musthave contributed to the floods?

(d) What must we do to prevent and/or ameliorate theeffect of future occurrences?

Before these questions are tackled we shall give a briefreview of the current status of the debate on Climate Change– the causes and consequences of which are yet to beuniversally agreed.

Climate Change: Cause and Characteristics Climate Change is the variation in climatic conditions

that is showing some irreversible characteristics. In otherwords, it is a condition that shows a trend towards aparticular condition of more or less. Thus, climate changeis seen today as a situation that is pointing to a change inthe contemporary climate in an irreversible manner to a newtype of climate in all parts of the earth (Olofin 2011b).The concern for Climate Change started earnestly in the late1960s to early 1970s – a period that is significant in WestAfrica because it coincided with that of the great Sudano-Sahelian drought in the region. This concern prompted thefirst World Summit on the Environment in Stockholm, Sweden,in 1972. There have been many other global summits and

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conventions on the global environment since then, includingthe greatest of all in Rio de Janeiro, Brazil in 1992, thefollow up referred as Rio + 10 in Durban in 2002 and the Rio+ 20 in 2012 at the venue of the 1992 summit.. The summitsconcern the changes in the earth’s atmosphere that arebelieved to be causing changes in the climate of the world.The initial arguments were on a greenhouse effect caused bythe accumulation of greenhouse gases and the depletion ofthe ozone layer caused by the interaction between thegreenhouse gases and other emissions on the one hand and theozone in the stratosphere on the other.

The debates over the years have produced some schoolsof thoughts. All schools agree that there are some changesin the global climatic conditions but disagree on whether ornot it amounts to climate change, as well as on what thecauses are and on what to do about it. There is theanthropogenic cause theory, the conspiracy theory and thegame theory. The anthropogenic cause theory otherwise knownas the Catastrophic Anthropogenic Global Warming (CAGW)Theory forms the basis of the argument of the pro-climatechange scientists, particularly the Intergovernmental Panelon Climate Change (IPCC). This theory holds that globalwarming is largely caused by human activities, particularlythose associated with industries and fossil fuel extractionand combustion which emit a lot of CO2. Specifically, theIPCC (2007) indicated that the current warming of theclimate system is unequivocal, and scientists are more than90% certain that most of it is caused by increasingconcentrations of greenhouse gases produced by humanactivities such as deforestation and burning of fossilfuels. It went further to assert that these findings arerecognized by the national science academies of all themajor industrialized countries. In a more objectivestatement, which sounds quite reasonable to this presenter,a relatively neutral commentator observes that:

Some people are under the false impression that global warming isa theory that still has to be confirmed. They do not realize that

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scientists are in complete agreement that a continual rise in theatmospheric concentration of greenhouse gases will inevitably leadto global warming and global climate changes (CampusColloquia, retrieved April 18, 2013)

The theory also holds that if nothing is done to abateor adapt to the consequences serious disaster (orcatastrophe) awaits humanity through an irreversibledegradation of the Earth’s environment. In supporting theirpoint of view, the theorists indicate that human activitiesdistort and accelerate the natural process by creating moregreenhouse gases in the atmosphere than are necessary towarm the planet to an ideal temperature. Thus, it is thestrengthening of the greenhouse effect through humanactivities known as enhanced (or anthropogenic) greenhouseeffect (Nova, 2006; and Kiehl, et al, 2007) that isdangerous. The increase in radiation forcing from humanactivities is attributable mainly to increased atmosphericcarbon dioxide levels (Nova, 2006).

In opposition is the Global Warming Conspiracy Theory(also known as Global Warming Denial Theory or Climategate)which fuels the argument of the people not in support ofglobal warming and the acclaimed scientific consensus of theIPCC (2007). The supporters of this theory state that theCAGW theorists are mere alarmists who are fraudulentlydeceiving the world by doctoring data for personal,political and economic reasons. There are those who are ofthe view that the global warming conspiracy theory is acollection of allegations that, through worldwide acts ofprofessional and criminal misconduct, the science behindanthropogenic global warming has been invented and is beingperpetuated for financial or ideological reasons. Proponentsof such allegations refer to the scientific consensus as a"global warming hoax", or "global warming fraud”.

The conspiracy theorists are quick to point out thatthe greenhouse effect is not a bad thing under natural ornormal conditions and that it has been occurring since theEarth came to existence and that, indeed, the greenhouseeffect is necessary to give the Earth the type of natural

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climate it has, thereby keeping the Earth habitable.Emphasizing this point, West (undated: retrieved August2012) asserted that “the ‘greenhouse effect’ often gets abad rap because of its association with global warming, butthe truth is we couldn't live without it”.

In between are those who are neither here or there butbased their inaction on what is known as the Game Theory.Cornell University Networks (2012) indicated that the GameTheory in Global Warming describes the economic forces thathinder moving toward a greener planet. In spite of thearguments against global warming, most people and countriesseem to have acknowledged that there is a problem withglobal warming.  Countries are working towards fixing thisissue, but the talks are very tedious and it is difficult tomake progress, despite the fact that some of the effects ofpollution and global warming are already visible and canonly get worse.  Countries agree that the best outcome wouldbe to invest in cleaner technology in order to controlemissions. 

However, the feeling and calculation of each country isthat if a single country were to defect from the effort toreduce emissions, it would not significantly increase thetotal emissions. As such, the money required for switchingto cleaner technologies can be saved while reaping all ofthe benefits of overall lower global emissions, if othersshould reduce their emissions.  In other words, it ischeaper to produce goods without regard to the side effectson the planet and factories in the defaulting country wouldnot have to worry about installing filters or investing innew methods of production. Thus the goods being produced inthe defaulting country would be cheaper and be morecompetitive in a global market.  This way the country thatdoes not decrease emissions gains a significant advantage inthe market place while still benefitting from a cleanerplanet.

On the other hand, if only one country tries todecrease emissions while the rest of the world does not,that country will hurt itself by making their goods lesscompetitive while only making a small impact on global

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emissions. This has been the line of argument of theAmerican (US) Presidents “It would hurt our economy, ourindustries”, has always been their response to theimplementation of the Kyoto Protocol (Olofin 2011a).

This results in the Game theory of who “bells the cat”where all countries analyzing this situation come to thesame conclusion – a dominant strategy to have cheaperproduction and lower standards for emissions, despite thefact that the world would be better off if all of thecountries were to choose greener production.

It is instructive that all the theorists agree thatthere is an increase in the emission of greenhouse gases anda rise in global temperature, whether or not it is duemainly to human activities is not the most important point.Furthermore, judged by what is happening around the world –the extremes of climatic events, the thinning of arctic ice,the rising of sea level and extreme floods and others – itis certain that global warming would result in seriousdisasters which may or may not be as catastrophic as theCAGW theorists have predicted. Indeed when the existingreports about the effects of global warming are considered,one cannot agree more with Connor (2007) that no one can goaway with the impression that climate change is aconspiratorial hoax

Effects of Climate Change on Rainfall in NigeriaAgreed that there is global warming ushering in climate

change, it is important to know how much it has affected therainfall in Nigeria. Generally, it is argued that theresponse of climatic parameters to global warming variesfrom one place to another. Most climate change modelspredict an increase of extreme events associated withincreased irregularity and decreased predictability (Nori.,et al. 2008).

In the tropics, the specific effects are listed toinclude: increasing incidents of drought and aridity; thedecline in agricultural productivity, and the incursion ofdesert-like conditions, among others (UNEP, 1987).Similarly, Issar (1998) contends that while the effects of

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global warming may be flooding and humid conditions in sometemperate areas, "the predicted global warming willcause ...further drying up" in the arid and semi-arid areas.However, West Africa (Nigeria inclusive) is described as oneof the regions of the world that presents the mostuncertainty, and the most disagreement among models, asregards future trends in precipitation (Anderson 2008). Anaverage of the major models suggests a modest increase inrainfall for the Sudano-Sahelian zone with little change onthe Guinean coast, while there are models which predicteither strong drying or strong moistening. Thus, thedrylands of Nigeria can experience both droughts and floodsevents. Based on this argument, the effect of global warmingexpected in Nigeria is a further drying of the semi-aridzone in the long run with short-term increase in rainfall,but hardly any change in the humid Guinea coast. In otherwords, if the climate becomes more humid, more floods shouldbe expected. Conversely, if the climate becomes drier, asituation that would be worse than that for drought periodswould prevail. Thus, it is important to examine if theclimate has become more humid or more arid in the last fewdecades in Nigeria.

While these researches have shown a steady increase inthe temperature over the years, the trend in rainfall hasbeen one of variations with an overall decreasing rainy daysand shorter duration of the rainy season, particularly inthe Sudano-Sahelian zone of the country. For example,Ibrahim (1998) has shown that where the rainy days used tobe 120, they have reduced to 90 days and, in the extremenorth, where there used to be 90 rainy days there are only60 in recent years. The implication of this is that if theamount of rainfall remains the same or increases, theintensity would have increased thereby leading to increasedrainfall runoff and floods. On the other hand, Adelalu(2012) used rainfall, temperature and the discharge of RiverBenue at Jimeta, Yola, for a period of 49 years (1960 –2008) to examine the response of river Benue discharge toclimate change and found great fluctuations of the elementsabout the long-term mean. Overall, the temperature

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increases, but both runoff and rainfall total decreased. Aperiod of increase in rainfall leads to increase indischarge and vice-versa. In his study, Buba (2009) foundthat there was a very dry period in the northern Nigerianstations up to 1996 and a slight build-up since 2001,particularly in Kano.

Thus, the trend in rainfall has not shown a clearunidirectional increase or decrease (Figures 1 and 2).Rather what appears to be is variation about the averagerainfall amount, with the last decade showing more ofincrease in some locations and decrease in Yola, Sokoto,Kaduna and Makurdi, even though there was a rise in Kadunaand Makurdi in 2012. Table 1 shows monthly rainfall inselected stations between 1989 and 2000 on the one hand andbetween 2001 and 2012 on the other, while Table 2illustrates the annual rainfall within the same periods inthe stations. Both tables indicate a slight increase in themonthly rainfall during the latter period, particularly inKano. In all the cases, the rainfall of 2012 is not thehighest. For example, the wettest years in Kano are 1998 forthe first period and 2001 for the second with 1998 being theoverall wettest. For Sokoto, the wettest years are 1998 and2010 respectively with 2010 being the overall wettest whilefor Kaduna 1991 and 2003 were the wettest with 2003 beingthe overall wettest. For Ibadan, the wettest years arerespectively 1999 and 2008 with 1999 being the overallwettest year. Finally, the two wettest years in Makurdi were1998 and 1999 with 2012 in the third position and 1999 beingthe overall wettest. Of these wettest years, only Kano 2001and Sokoto 2010 are noted for devastating flood events aidedby releases and/or breach of structure.

In a collaborative study of climate change scenariosin Nigeria, The Nigerian Environmental Study/Action Team,NEST (2004) compiled the average rainfall for the threemonths of July, August and September (JAS) between 1960 and1999 and came up with Figure 3. In that figure the averageof the rainfall for those months in Kano lies about 550 mm,Sokoto 450mm and Ibadan about 600mm. This parameter has beenadopted in this study. The results in Figure 3 compare well

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with those of Ibadan and Sokoto in Table 1, but very lowcompared with the JAS figures for Kano in the Table. Thisindicates an increase in the rainfall of Kano in recentdecades.

0200400600800100012001400160018002000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Years 1989 - 2012

Rainfall (

mm)

KANOSOKOTOIBADANKADUNAMAKURDI

Figure 1: Annual Rainfall Trend in Selected Stations 1989 -2012SOURCE: Computed From NIMET Data

Figure 2: Annual Rainfall Trend and Departure from Long-Term Meanin Yola (1960 – 2008)SOURCE: Adelalu (2012)

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Figure 2: Average Rainfall (mm) of July, August and September (JAS) 1960 – 1999SOURCE: NEST (2004)

Table 1: Monthly Rainfall (mm) in Selected Stations 1989 – 2000 and 2001 - 2012Month (a) KANO (b) SOKOTO

1 2 2012 2013 1 2 2012Jan

0.00 0.00

0.00

0.0

0.00

0.00

0.00

Feb 0.00

0.00

0.00

0.0

0.23

0.00

0.00

Mar 0.14

0.00

0.00

0.0

1.08

0.00

0.00

Apr 14.17

13.91

0.00

14.8 2.78

8.70

0.00

May 59.14

65.88

71.90

40.0 50.13

59.91

56.70

11

June 141.08

202.03

436.40

77.6 90.09

83.09

83.20

July 271.54

367.04

466.10

157.3 195.39

197.98

178.20

Aug 358.03

395.29

646.90

440.1 192.60

215.60

140.70

Sep 169.26

197.75

123.50

178.1 119.72

109.88

93.20

Oct 20.91

16.47

19.60

10.3 12.39

35.28

82.90

Nov 0.00

0.00

0.00

0.0 0.00

0.00

0.00

Dec 0.00

0.00

0.00

0.0 0.00

0.00

0.00

Year 1034.27

1278.37

1764.40

918.2 664.41

710.44

634.90

JAS 798.83

960.06

1236.40

775.5 507.71

523.46

412.10

Table 1 ContinuedMonth

(c) KADUNA (d) MAKURDI

1 2 2012 1 2 2012 2013Jan

0.00 0.00

0.00

2.71

4.35

0.00

0.00

Feb 0.00

0.24

0.00

0.63

0.04

0.05

0.00

Mar 5.18

1.63

0.00

10.08

9.15

0.00

44.20

Apr 40.48

45.61

61.60

95.32

91.79

143.20

122.90

May 113.65

121.33

212.80 123.13

137.34

145.20

183.40

June 168.61

156.81

100.30 209.69

172.66

160.60

141.80

July 216.0

243.12

225.60 168.13

162.66

351.90

243.60

12

2Aug

293.34

287.57

346.20 240.18

210.73

174.30

131.00

Sep 266.71

248.91

403.30 246.39

213.92

290.70

285.30

Oct 83.13

79.88

135.10 132.08

152.13

199.10

125.50

Nov 0.11

0.00

0.00

6.13

9.05

27.30

0.00

Dec 0.00

0.00

0.00

0.00

0.13

0.00

10.10

Year 1187.23

1185.09

1484.90

1238.49

1155.35

1492.80

1287.80

JAS 776.07

779.60

975.10

654.67

587.31

816.90

659.90

Note: 1 = 1989 – 2000 2 = 2001 – 2012 Source: Presenter based on NIMET’s Data

Table 1 ContinuedMonth (e) IBADAN

1 2 2012 2013Jan

3.23 4.94

0.00

3.3

Feb 42.95

37.53

20.60

64.4

Mar 93.36

70.17

36.20

139.0

Apr 112.65

120.37

125.10

184.0

May 156.90

178.87

215.90

115.3

June 171.65

222.49

215.00

54.7

July 206.52

154.85

218.20

173.1

Aug

13

151.87 121.36 93.30 52.4Sep

174.07 243.04

218.20

213.1

Oct 171.61

188.36

141.30

131.2

Nov 13.35

35.44

54.90

11.0

Dec 13.75

2.87

0.00

28.7

Year 1311.91

1380.09

1336.70

1170.2

JAS 532.46

519.25

529.50

438.6

Note: 1 = 1989 – 2000 2 = 2001 – 2012 Source: Presenter based on NIMET’s Data

Table 2: Annual Rainfall (mm) in Some Stations 1989 – 2000 and 2001 - 2012

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Table 2 Continued

(a) KANO FARM CENTRE (IAR)+

(a) KANO AIRPORT (NIMET)@

Year Rain Year Rain Year Rain Year

Rain

1989 598.2

2001 982.0

1989 700.2

2001

1786.4

1990 540.7

2002 543.2

1990 568.7

2002

1035.7

1991 904.8

2003 886.3

1991 1017.0

2003

1419.2

1992 918.3

2004 756.3

1992 912.5

2004

1243.6

1993 802.0

2005 905.4

1993 921.5

2005

1336.6

1994 778.4

2006 909.6

1994 791.6

2006

1308.8

1995 555.7

2007 818.0

1995 691.2

2007

1099.2

1996 766.4

1996 1064.0

2008

1035.9

1997 760.7

1997 1226.7

2009

992.2

1998 1249.5

1998 1802.2

2010

1047.6

1999 791.1

1999 1384.7

2011

1220.6

2000 643.8

2000 1024.0

2012

1764.4

Mean Mean Mean 1034.3

Mean

1278.4

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Table 2Continued

(d) MAKURDI @ (e) IBADAN@Year Rain Year Rain Year Rain Year Rain1989 1244.

32001 1082.

41989 1345.

62001 1289.

71990 1120.

92002 1281.

51990 2002 1515.

31991 1122.

42003 761

.51991 1369.

32003 1226.

21992 972

.72004 972

.61992 1088.

72004 1328.

41993 1217.

12005 871

.31993 1257.

32005 1569.

51994 973

.22006 1343.

01994

995.12006 1260.

21995 1172.

12007 1339.

91995 1537.

72007 1290.

61996 1324.

92008 1050.

51996 1653.

72008 1740.

61997 1335.

72009 1402.

51997 1121.

42009 1702.

21998 1556.

92010 1115.

31998

920.62010 1539.

51999 1618.

02011 1151.

01999 1814.

22011 1639.

92000 1173.

72012 1492.

82000 1244.

52012 1336.

7

(b) SOKOTO (NIMET)@ (c) KADUNA (NIMET)@Year Rain Year Rain Year Rain Year Rain1989 522.

82001 731.

71989 1002

.02001 1186

.61990 654.

02002 768.

01990 1022

.02002 1307

.41991 771.

52003 790.

21991 1411

.42003 1543

.61992 549.

02004 649.

51992 1118

.82004 1380

.01993 637.

72005 639.

61993 1242

.52005 1148

.01994 762.

12006 716.

91994 1105

.52006 898

.71995 509.

82007 636.

01995 1151

.62007 865

.01996 729.

92008 610.

61996 1217

.22008 811

.51997 645.

52009 638.

11997 1293

.62009 1217

.91998 861.

22010 1146

.71998 1109

.42010 1276

.31999 711.

62011 657.

81999 1286

.12011 1094

.12000 732.

62012 634.

92000 1302

.62012 1484

.9Mean 664.

4Mean 710.

4Mean 1188

.6Mean 1184

.5

16

Mean 1235.5

Mean 1155.35

Mean 1311.9

Mean 1380.1

SOURCES: + Danjuma (2008) based on IAR, Kano (2008)@ Presenter based on NIMET’s Data

Increases in Rainfall Amounts and FloodsGranted that there have been some marginal increases in

the rainfall amounts that also come in high intensities, itis important to be certain that the increases are arisingfrom Climate Change conditions and to determine how much theincreases have contributed to the floods in Nigeria. Oneagrees that heavy rainfalls lead to floods and some floodsexperienced in the country could be related to such heavyrainfalls, directly and indirectly. However, some of thesefloods occurred before the decades of climate changedetection.

One example is the Ogun River flood of 1963 andperhaps, the annual floods of Ogunpa River. Also, in thelast decade, some rivers in the Federal Capital Territoryhave been flooding the bridges and/or the roads annuallymore than they did previously (Personal Observations). Thesefloods are not caused mainly by the heavy rainfalls, butrather they are caused by a combination of the heavyamounts, high intensities and low infiltration capacitiescreated by anthropogenic activities related to urbanizationand agriculture. One believes that where there had been nofloods before, even with heavier rainfalls, and floods startto occur, like those in the Federal Capital Territory, theanthropogenic forcing must be seen as the main cause. Ofcourse, one can agree that the fewer rainy days leading tohigher rainfall intensities can be linked to climaticvariations associated with climate change. Also, it has beenshown that the rainfall of the three critical months (July,August and September – JAS) in 2012 was highest in Kano ofall the other stations. Yet, the 2012 floods of the Hadejiavalley where Kano is located in the headstream did not hitthe headlines like those of 2001 and 2010! Indeed, whenenumerating the most disastrous floods in the Hadejia RiverBasin, the flood of 1998, when the basin received its all

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records heaviest rainfall of 1249mm, is never mentioned.Also, none of the states in the basin drew as much attentionas the four leading category A states for the 2012 flooddisaster even though 2012 was the third wettest year inKano. Thus, the notable flood disasters in Nigeria arecaused by other factors in addition to heavy rainfalls asshall be demonstrated presently.

Factors besides Increasing Rainfall Causing Floods inNigeria

At this point it is pertinent to recall some of theflood disasters in Nigeria and identify their main causes.Excluding the 2012 floods, the floods known to thispresenter through field studies, observations and literaturesearch are as follows:

The Kano River flood of 1988 caused by the Bagauda Damburst of 1988; it is noted that beside this flood, noother serious flood has been recorded in the River Kanofloodplain between the Tiga Dam and the Kano-Chalawaconfluence;

The Maiduguri food of 1994 caused by Alau Dam dykebreach as a result of the diversion of water from theYadzeram basin to the Ngada basin;

The annual rituals of flooding downstream of ShiroroDam in the Niger State and downstream of Kainji-JebbaDams in Niger and Kogi states as a result ofoperational releases from the reservoirs;

The periodic flooding of the Hadejia Valley since theemergence of Chalawa Gorge Dam in 1992 sacking most ofAuyo in 2001 and 2004 due mainly to operationalreleases from Chalawa Gorge Dam;

The recent devastating floods downstream of the GonroyoDam in 2010 due mainly to the breach of the dam,

The 2010 floods downstream of the Oyan Dam on OgunRiver that affected parts of Lagos metropolis duepartially to operational release from the reservoir and

Flood disasters in several metropolitan areas of thecountry due to inefficient and/or blocked drainagesystems and construction of structures on water ways.

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Thus, while heavy rainfalls have contributed (marginally,one would say) to these flood disasters, the main causes arefar from the heavy rainfalls. The identified causes may beclassified as follows:

The failure of hydraulic structures such as the breachof Bagauda Dam (Ahmed and Musa, 1991); Alau Dam dykes(Olofin 1997); and, to some extent, Gonroyo Dam;

The transfer of water to unsecured dykes as in the caseof Alau Dam;

The poor management of reservoir water leading touncontrolled emergency releases as in the other cases(Shiroro, Kainji-Jebba, Chalawa-Gorge, Gonroyo andOyan)Besides these are (a) deforestation in reservoir

catchments leading to increased runoff, (b) soil erosion andreservoir sedimentation beyond what was predicted in thefeasibility studies; (c) construction on water ways andfloodplains; all capped by (d) a poor knowledge of thecountry’s fluvial dynamics. One can conclude from thisexamination that flood disasters occur in Nigeria more fromanthropogenic forcing than from heavy rains resulting fromclimate change, or not.

Causes of 2012 Floods in NigeriaFrom the argument so far, it should be clear that the

2012 floods in Nigeria are not caused mainly by climatechange driven heavy rains as currently believed because themarginal increase in rainfall amount, the reduction in rainydays and the decrease in the duration of the wet seasonleading to high rainfall intensities cannot be the maincauses of the flood experienced in Nigeria in 2012. Therainfall amount, duration, rainy days, etc of 2012 are notmuch different from those of previous years. Indeed, theamount is lower in several instances than the one inprevious years. We have shown that previous floodsdownstream of Chalawa Gorge, Shiroro and Kainji dams whichwere devastating were not caused mainly by heavy rains.

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The point one is making here is that if we are seriousabout preventing or reducing the intensity and negativeeffects of future floods, we should start to look beyondheavy rainfalls resulting from climate change. One stands tobe corrected, but makes bold to declare that the main causeof the 2012 floods in Nigeria is not heavy rainfall arisingfrom climate change. Perhaps if we do our study well,rainfall storms (heavy or not) might have contributed about10 – 15% to the cause. The remaining 85 to 90% of the causerelates to faults in the management of land and water withinthe drainage basins.

Let us pause at this stage to recall some photographsof the effects of flooding caused by emergency releases ofwater from the Shiroro Dam around 2000 in downstreamlocations in Niger State and compare these with some of thephotographs of the effects of the 2012 floods (Plate 1 a -d). The main difference is that nobody was bewailing climatechange as the cause of the Niger State floods (a) and (b)(around 2000) when the photographs were taken.

Dams are expected to reduce or prevent floods indownstream locations and not to worsen their occurrence.This they did until we started to release unknown quantitiesof reservoir water into the affected floodplains, yieldingfloods which usually remain a week or so at particularpoints during when they would have wiped off the nutrientsof valuable fadama land. The Niger State Directorate ofInformation (c2000) illustrated this point very clearly aspresented in Box 1

From 2000 Niger State Floods

From 2012 Floods inNigeria

(a) In Sunlati Village (c) At Etsako, Edo State

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Source: Directorate of Information

Source: saharareporters.com

(b) Submerged School,Mokwa

Source: Directorate ofInformation

(d) Flooded Naval Base, LokojaSource: ecojournalism.org

Plate 1: Pictures of Flood Disasters: Niger State 2000and2012 Floods

Box 1Floods of Horror

Hitherto [that is pre-dam], seasonal floods on theNiger-Kaduna plains and their numerous tributariesbrought hopes of good fish and rice harvests andtherefore prosperity. Such were the floods whichhit their peak at the height of the rainy seasons,in August. Such floods are characterized by fishreproduction and migration. They are the floodsthat would not submerge the various species ofpaddy rice, that have been introduced to theseareas in the course of the first half of thiscentury, to boost rice production in particularand Agricultural production in general. Such floods would leave the environment around theplains marshy and swampy, an environment to whichthe communities had become adapted forgenerations. Not the present phenomenon of flooding [that ispost-dam]. This is the flooding that comes withopening of spillways of the hydro-electric dams.They arrive when the water level hits its peak

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from the rains. Communities along the plains aresubmerged in its wake and farms are washed away. These are the floods that breed famine,destitution and emptiness in the lives of the tensof thousands, who inhabit the plains or live byit. They are the FLOODS OF HORROR, not of hope.SOURCE: Niger State Directorate of information (c 2000)

The management of our reservoirs leaves much to bedesired. Annually we release water from these reservoirs asan emergency solution to the perceived threats to the damsas we assume that the water level in the reservoirs isapproaching or has reached the red alert. The capacity ofthe downstream channel into which the water is released isnot taken into consideration. In most cases, the capacity isnot even known. Similarly, the total amount of water beingreleased is not determined. The panic echo is “save thedam”! True, if the dam should give way, it would cause moredisasters than the floods we cause by the panic releases,but there are safer ways of handling the reservoirs thanwaiting until a crisis point is reached. It is doubtful ifthe management of the reservoirs ensures that the capacitiesof these reservoirs are maintained at more or less the samelevel as declared at the time they were commissioned. It isnot certain if the authorities are monitoring the rate ofreservoir sedimentation as well as the rate of sedimentgeneration in the catchments. Thus, the amount of waterthought to be behind the dams may be much less than assumed.

Indeed, one believes strongly that this is thesituation with the reservoirs, Kainji inclusive. Forexample, in April 2012 or there about, power generation wasstalled at the dam because of a reported low water levelwhich drove sands into the works (Television News). Thus,silted reservoirs leads to quick filling up of thereservoirs to danger levels warranting panic releases, butwith very little amount of water really stored. Manyfactors are responsible for the increased sedimentgeneration rates in the catchments than envisaged at

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inception. Many of the watershed source areas lose initialvegetation cover due to increased human activities such ascultivation, expansion of settlements, fuel wood extractionand others in the headstream areas.

Secondly, these releases require careful management interms of timing, warning and preparation; ingredients whichone suspects are currently lacking. It is not enough togive people downstream two weeks repeated warning ofimpending releases as the authority claimed in connectionwith the 2012 releases from the hydro-dams in Nigeria.Efforts should have been made to assist the would-be victimsto know exactly what to do as well as the level and timingof the expected flood at particular points along the river;estimated to within a few metres and minutes. One is notcertain that the authorities releasing water from thereservoirs ever studied the speed at which such excess waterflows so as to determine when a particular flood water wouldreach a particular point and how long it would affect thepoint! No wonder Chuka (2012) bemoaned the level of theunpreparedness of Nigeria to handle natural disasters.Specifically, he wrote:

The latest tragedy to befall Nigeria, the great and unprecedentedflood of 2012 has badly exposed Nigeria's rump and particularlythe state of unpreparedness of the Nigerian state to cope withnatural disasters

Commenting further, he contended that the warning ofNEMA was a timely warning

but it was not actionable by the various State Governments oranybody else apart from the naturally prudent, because the floodplain of River Niger was not hitherto mapped and so the flood lineand more importantly flood height as well as almost precise timinginformation could not be given in conjunction with the alert.

What compounded the flood of 2012 in Nigeria, however,is the release of water from the dam on the Benue inCameroon under similar poor reservoir management conditionsas operate in Nigeria. Indeed, Nairaland (2012) emphaticallystated that: “Nigeria flooding in 2012 was caused by [the]

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opening of [the] Lagdo Dam in the northern Province ofCameroun… The flooding is the worst since 1958”. Tchotsoua,Moussa and Fotsing (2008) had predicted the potentialflooding dangers the dam portends for the Benue Basin. Theystated, among other things that:

From an analysis of maximum daily rainfalls and thecorresponding flooded surfaces, it follows that a height of 200 mcan only be reached with exceptional rainfalls or the rupture of thedam. In such cases, the flooded surface would be close to 160,000hectares, with a total of 193 villages and about one third of thetown of Garoua underwater.Garoua is located 50 kilometres downstream of the Lagdo

Dam and part of that town was flooded by the 2012 release.Of course, the authors only envisaged “exceptional rainfalland the rupture of the dam”; none of which occurred. Theydid not envisage an emergency release of water that would begreater than what a minor rupture would cause.

The flood generated by that release was making its waydownstream, heading to the confluence with the Niger. Hence,apart from the havoc it caused in Cameroon itself (whichNigeria did not consider to be important), the first weheard about its effect was in Adamawa State, where therampaging flood water received more water from the releasesfrom Dadin Kowa and Hawal reservoirs on the Gongola Rever atNuman (Personal Discussion with colleagues from Yola) beforeheading to Ibi Taraba State. The tell-tales at Ibi werestill fresh when Makurdi got hit. At this point, theAuthorities of the hydro-dams in the River Niger basin wereissuing notices of the impending releases of water from thereservoirs without recognizing the speed at which the floodon the Benue River was moving. One believes that the floodgenerated by the release of water from the dam in Cameroon,intensified by the releases on the Gongola – all in theBenue basin – and flood generated by the releases in theNiger River basin reached the confluence of the two riversat the same time, causing the unprecedented floods,including a back flow up the Niger channel since the Benueflood was apparently stronger. That back flow breached theLokoja Road, making some people wonder how the Niger Bridge

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remained standing! From the confluence, the combined floodwater tore its way downstream to the Niger Delta.

Flood Mitigating Measures for the FutureSince the 2012 flood disaster occurred, a lot of

suggestions have been flying around as to how to preventfuture floods and mitigate their effects. Some havesuggested dredging the entire channel of the Niger River,perhaps from the immediate downstream of the hydro-dams; itis not specified. Dredging is like treating the symptoms ofan illness without touching the illness at all. We are stillto know what the 2012 floods did to the previous dredgingundertaken with billions of naira in the Niger channel. Onecan make an educated guess that a substantial amount ofsediments removed from the channel must be back in thechannel now.

Others believe a permanent relocation of the dwellersof the flood-prone areas is the solution. That move wouldreduce the disaster and leave flooding at a risk-managementlevel. One would like to know if these people would berelocated permanently; thereby abandoning their fadama landto a flood that comes only once a year. One would also wantto know how much fadama land would be rendered idle in thisway and what it would mean to Nigeria’s effort towards foodsecurity and the attainment of the Millennium DevelopmentGoals (MDG).

There is also the suggestion that the construction ofmore dams is the answer – a solution strongly recommended tothe President by some of his advisers and placed in hisspeech at Lokoja (Television News). Theoretically, this is asound suggestion because managed appropriately, theconstruction of more dams could reduce the intensity offloods. However, I believe that more dams, managed in thesame way as the existing ones, would only lead to more flooddisasters occurring in more areas of the country. This pointis clearly explained by the Niger State Directorate ofInformation (c 2000) more than a decade before the 2012flood. Consider the Statement in Box 1 again.

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The correct approach to solving this problem lies insustainable land and reservoir management that will reducethe rate of reservoir siltation, thereby maintaining optimumcapacities of the reservoirs and limiting the necessity toundertake emergency releases from the reservoirs. In thepursuit of sustainable land and reservoir management, thereare two ways to follow: (a) adapting to the occurrence offloods when they cannot be prevented completely and (b)adoption strategies that prevent and/or reduce the intensityof floods.

Adaptation strategies suggested by (ISDR, 2008) forfloods and storm surges include the assessment of floodrisks based on available knowledge and the predictions ofthe impact of climate change; preparation of flood hazardand flood risk maps and the formulation of risk managementplans based on the results of specific studies. Theseinternational adaptation strategies had earlier been echoedby the recommendations of the Hadejia-Komadudgu-Yobe BasinTrust Fund, HKYBTF (2007) on coping strategies for adaptingto floods in the basin, as illustrated in Box 2.

The content of Box 2 is clear and the purpose of eachsuggestion can easily be seen. The issue of community flood-watch is an important one that would enable communities, inflood-prone areas, to decide on evacuation on their ownwithout waiting for outsiders to make the decision for them.Another important adaptation strategy is to have designatedsafe havens that would-be victims can move to immediatelythe decision for evacuation is reached. This is line withbest practices in adaptation to natural disasters. Forexample, Japan has a number of fortified bunkers to whichpeople move when a more-than-normal earthquake occurs in aparticular community.

Finally, a thorough study of past events is necessaryin order to obtain results that would aid proper adaptationto and mitigation of future flood events. To this end, itwill be worthwhile to commission a study, including mapping,of the movement of the 2012 floods on the Benue and NigerRivers in order to chart their speed, their arrival pattern,their extent and other characteristics that would help

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adaptation and appropriate response to future floodingevents in the basins.

The second approach is the adoption of strategies thatcan prevent and/or reduce the intensity of floods. Thesewould include conservative activities such as thepreservation of stream source areas by establishingvegetation cover that would increase infiltration capacityof the headstream areas and reduce the amount of overlandflow as well as prevent soil erosion that increases the rateof generation and accumulation of sediments. Besidesdredging the river channels, it is equally important to de-silt the reservoirs, release appropriate volumes that therelevant channels can evacuate safely without resulting inoverbank discharges, and remove all structures that blockthe free-flow of the rivers. Also, along the river channelsit is important to establish buffer vegetation zones offsettlements and construct artificial levees withinsettlements to prevent flood water from spreading too faroff the channels even when under floods.

Box 2ARTICLE 19 – Flooding

1. Each Basin State shall develop and maintaindata inventory on flood prone areas andestablish a functional flood data bank.2. Liaise with relevant Ministries/Agencies topromote and strengthen the establishment ofmeteorological and river gauging stations togenerate adequate data for flood forecasting.3. Develop emergency preparedness plan formonitoring, evaluating and mitigating flooddisasters in collaboration with the NationalEmergency Management Agency (NEMA).

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4. During actual flood situations, the Basinstates shall:(a) Liaise with operators of dams to minimizethe adverse impacts of released flood water;(b) Put in place appropriate mechanism andstructures for flood control and waterconservation;i) Device strategies for informing and managingthe population during flood in collaborationwith NEMA; andii) Monitor all activities that could increaserunoff and/or block water channels.

SOURCE: HKYBTF (2007)

. .One of the points made here needs further elaboration.

This is the release of appropriate volumes of waterdownstream of dams in the natural channels. Specifically,reservoir managers need not wait until danger is knockingbefore releasing water from the reservoir. Indeed, onerecommends early and/or perennial release of knownquantities of water downstream of dams. Apart from theBagauda burst of 1988, releases from Tiga Dam on River Kanohave hardily contributed to the floods in the HadejiaValley. The releases from the Chalawa Gorge Dam have alwaysbeen the problem. The reason is that an appropriate volumeof water is released on a perennial basis downstream of theTiga Dam. In effect, according to Olofin (1987), the KanoRiver that was seasonal before all dams (at time t), beingdry for five months, changed to a perennial stream at time t+ 1 (after the major dams). Also, the variations between theseasons had been narrowed down from a pre-dam range of zeroto 164 m3/sec to a post-dam range of 7.1 to 28.0 m3/sec,while the mean annual discharge decreased from 37 to 13.2m3/sec, giving the following relationship:

Qt + 1 = 0.36Qt Eq. 1

where Qt + 1 is mean discharge after the dams;

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and Qt is mean discharge before the dams.

Martins and Olofin (1992) indicated that the mostaffected parameter is the average maximum flow in the wetmonths from June to September. This parameter measuresthe mean flood flow of the river during the mostsusceptible period of flooding. The mean flood flow (Qf)decreased from a pre-dam (time t) 383.3 m3/sec to 65m3/sec in the post-dam (time t + 1) period, giving thefollowing relationship:

Qft + 1 = 0.17Qft Eq.3

The emphasis here is on an appropriate volume, which in thecase of hydro-dams must not compromise the volume of waterrequired in the reservoir for power generation. What isappropriate for each channel must be researched, calculatedand maintained in order to eliminate or reduce the necessityto resort to emergency releases during the peak of the wetseason when all parts of the river basin are alreadysaturated.

ConclusionFrom the presentation in this lecture one can safely

conclude that the flood disasters in Nigeria in general andthe 2012 floods, in particular, are driven principally byfactors beyond climatic borders. While heavy rainscontribute directly and/or indirectly to the flood eventsother factors such as poor reservoir and land management inthe river basins are the main anthropogenic causes. Thesedimentation of reservoirs and channels needs closemonitoring and be minimized to ensure that the initialcapacities of such reservoirs and channels are not impaired.This would involve watershed stabilization and protection.One can also conclude that the face of the drylands ofNigeria has not been affected by too much “water-look”.Indeed, more water-look is required with maximum gains and

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controllable minimal pains through proper adaptations andmitigations.

Acknowledgement

I wish to express my gratitude to the Acting Manager of theNigerian Meteorological Services (NIMET), Kano Station, Mal.Isyaku Ibrahim, who made available rainfall data for Kano,Kaduna, Sokoto and Ibadan stations free of charge, and Mr.Idris A. Adaji, NIMET Makurdi, for providing up-to-daterainfall data for Makurdi at a minimal cost.

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