Flood Mitigation

1. 1
Prevention and Managing thePrevention and Managing the
Occurrence and Impact of FloodOccurrence and Impact of Flood
in the City of Ibadanin the City of Ibadan
Adelere Ezekiel Adeniran, Ph.D, FNSE
August 2012

2. 2
Introduction
 I am not sure if I have ever met Mr. Kunle
Akinyele whose memory we are honouring
today.
 I am sure that as a Christian who would want
to save other souls he would like to do
anything like Paul that ... he may be able to
safe others even after his death.
 This lecture series will surely raise both
technical, social, emotional and economic
awareness that may possibly prompt our
Governments and our people into taking
positive action.

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Why Me?Why Me?
 I am not sure while I was chosen to deliver the first in the series of
this memorial lecture.
 Is it because I was born and raised in Ibadan and lived with the
dirty waters of Ibadan streams (onipasan, oluyoro, beyerunka,
agbadagbudu, gege olorun, ogunpa, kudeti, tabi elege, ogbere, omi,
odo ona etc) for the first 21 years of my life?
 Or because I have studies rivers, hydraulics, hydrology, river
modelling and waste and storm water disposal for almost 37years
of my life?
 What ever the reason for my choice, I am humbled and wish to
thank the organisers for this most undeserved honour. The Lord
that we serve will surely reward you.

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Mathematics without Equations!Mathematics without Equations!
 The organisers have put me in a very difficult
position.
 I am faced with delivering a lecture on a highly
technical subject to a mixed audience some of whom
may not understand the language of hydrology or
hydraulics or (mathematics) of floods
 I have the task of speaking in plain language to
benefit generality of the audience without trivialising
the subject and.
 I will try my best to strike a balance. May God help
me

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Ibadan City and Its Rivers

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Ibadan Land

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Ogunpa River: Statistics
 The Ogunpa River river system is a third-order stream i.e. it
falls into the 3rd
category on a scale of 12. In order word
Ogunpa is a small stream in order of ranking!
 Channel length of 21.5 km and area 73.3 km2 draining the
densely populated eastern part of Ibadan Nigeria
 The city of Ibadan in south western Nigeria (7º23’ N, 3º5’ E)
is the largest urban centre in Africa south of the Sahara
 Ogunpa River is known to be highly polluted receiving
untreated storm waters, domestic sewage and solid waste.
 Ogunpa river is septic.

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Ogunpa and Ogbere StreamsOgunpa and Ogbere Streams
CatchmentsCatchments
Ogbere
Ogunpa

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Disaster Records of Ibadan Floods
1960 More than 1,000 residents became homeless
1963 • More than 500 houses were damaged
1978 • 32 bodies retrieved; 100 houses destroyed.
1980 • "Ogunpa" became notorious internationally
• More than 100 bodies were retrieved from the debris of several
collapsed houses and
• Many vehicles washed away by the flood
1999 Several properties and houses were lost to yet another Ogunpa flood
August
26, 2011
• Ogunpa struck again Claiming the life of our dear Mr. Kunle
Akinyele
• Destroying houses, roads, culverts and bridges
• Creating emotional trauma
• Leaving behind colossal economic woes
• It was a National disaster of monumental dimension
• 26,000 houses have been marked for demolition

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Floods:
Hydrology and Hydraulics of Floods

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Floods
 A form of natural disaster when there is more
water than the lakes, rivers, oceans, or ground can
hold.
 Many different types of floods named for how
often they occur
There're 10 years floods,
100 years floods,
500 years floods,
Floods can be seasonal or sudden.

12. 12
Causes of Flood
 Natural Causes
– Excesive rains.
– Overflowing of rivers, lagoons, lakes,etc
 Human Causes
– Bad agricultural practice
– Bad infrastructures location
– Obstruction of Stream paths
– Solid Waste Disposal
– Deforestation (Removal of Igbo Agala)
– Urban population increase

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Causes of Flood Continued….
 Reduction in Carrying Capacity of the river
– Encroachment in river and tributaries banks
draining into the rivers
– Disposal of Debris and solid wastes including
plastics
 Lack of Remote Rain Gauging and Telemetric Early
Warning System
 Rapid and unco-ordinated Urban growth due to
rural to urban migration (lack of rural development)

14. Refuse Disposed into Ibadan
Streams
14

15. Constructions on RiverConstructions on River
Banks in IbadanBanks in Ibadan
15

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Encroachment of Flood Plain of
Kudeti Stream

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Spatial Growth of Ibadan
20102010

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Direct Effects
I. Displacement of Families in the river banks
II. Destruction of private property on the river banks
III. Destruction of Biodiversity on the river banks
IV. Disruption of Transport and communication
systems
V. Destruction of drainage and sewage system
VI. Eroding of river banks
VII. Adverse effect on Public Health

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Flood Damages
 Injuries and loss of life
 Social disruption
 Income loss and Emergency
costs
 Physical damage
– Structures, utilities, autos,
crops, etc.
 Lost value of public services
– Police & power poles, water
mains, hospitals, etc
Damaged PHCN and Water at Apete, Ibadan
Bridge Washed away: Emergency Foot Bridge improvised

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Homelessness and Losses

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Colossal Lost of Properties

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Discomfort and Fear

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Hydrology
 Genesis 1:6-7: “Then God said, Let there be a firmament in
the midst of the waters, and let it divide the waters from the
waters. Then God made the firmament and divided the waters
which were under the firmament from the waters which were
above the firmaments”
 Ecclesiastes 1:7 “All the rivers run into the sea, yet the sea is
not full; to the place from which the rivers come, there they
return again”
 I submit to the Almighty and Omniscience God, before
continuing, that to Him belong all the knowledge.
 Indeed He designed the hydrology of the world and we
humans have made a mess of it.

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25. 25
Hydrologic Cycle
Excessive Runoff,
FLOOD
Precipitation, P(t)

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Stream flow and Flood Hydrograph
Peak
RisingLimb
RecessionLimb
Time
Discharge,Q
Beginning of
Direct Runoff
Baseflow
Recession
Baseflow
Recession
Centroid of
Precipitation
Basin Lag
Time
of Rise
End of
Direct Runoff
Inflection
Point
Baseflow

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Flood: Excessive Storm Runoff
 Rainfall – Divided
1. Direct runoff (Pe) (Flood)
2. Initial loss (before DRO, Ia)
3. Continuing loss (after DRO, Fa)
Time
Precipitation
pt
aI aF
eP
aae FIPP ++=

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Ibadan Flood - 2011
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
Time (hr)
Runoff(cfs)
0
1
2
3
Precip(in)
Precipitation
Streamflow
Flood High Point

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Hydraulics: Channel Capacity
 Q = VA (Carry Capacity)
 More water than the
channel can carry will
result in flood
 Reduction in the area of
the channel will increase
the velocity and thus result
in channel overflow or
flood

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Flood Hydraulics
Debris

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Flood
Management

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Stages of
Flood Management
 Mitigation
 Preparedness
 Response
 Recovery

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Phases of Emergency
Management
Prevention-Mitigation Preparedness
ResponseRecovery

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Emergency
Operation Plan
Precipitation
Prediction
(nowcasting)
Threat
recognition
system
Information
dissemination
system
Data acquisition and
transmission system
Forecast
modeling system
(forecasting uncertainty
estimate)
?
Emergency
Operation Plan
Precipitation
Prediction
)
Threat
recognition
system
Threat
recognition
system
Information
dissemination
system
Information
dissemination
system
Data acquisition and
transmission system
Forecast
modeling system
(forecasting uncertainty
estimate)
?
A Model for Flood Disaster Management

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Flood-Damage Reduction Measures
Measures that
reduce damage
by reducing
discharge
Measures that
reduce damage
by reducing
stage
Measures that
reduce damage
by reducing
existing damage
susceptibility
Measures that
reduce damage
by reducing
future damage
susceptibility
Reservoir Channel
improvement
Levee or
floodwall
Land-use and
construction
regulation
Diversion Flood proofing Acquisition
Watershed
management
Relocation
Flood warning
and preparedness
planning

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Effect of Flood Management Measures
Impacted Relationship
Stage -
Discharge
Stage -
Damage
Discharge -
Damage
Discharge -
Frequency
Damage
-Frequency
Reservoir ✓ ✓
Levee ✓ ✓ ✓ ✓ ✓
Channel
improvement
✓ ✓ ✓ ✓
Diversion ✓ ✓
Flood
Forecasting
✓ ✓
Flood Proofing ✓ ✓ ✓
Relocation ✓ ✓ ✓
Flood warning ✓ ✓ ✓
Land use control ✓ ✓ ✓ ✓

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Response and Preparedness

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Engineering Measures for Disaster Management
 Increase in River carrying capacity by
– Dredging to remove silt
– Excavated Debris can be reused eg sand
for construction
 Protection
– Construction of protection wall to protect
major flood prone areas

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ACTION PLAN FOR FLOOD
FORECASTING & DISASTER
MANAGEMENT
1. Installation of Remote Rain Gauging, level
gauging and telemetry system for early warning
to control peak discharge
2. Prevent encroachment of the river and streams
by declaration of Biodiversity Restoration Zones
along the banks
3. Creation of Green belts on river banks for
stabilisation and allow percolation of water

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Mapping and Delineation of the flood-prone area by use a probability-based
analysis wherein systematic records and historical information on past flooding are
used to develop a relation of probability of occurrence versus magnitude.
Designation of Floodway (River Channel) and High Flood Level Components
High
Flood
LevelFloodway
Development Zone
Submersible ZoneDevelopment
Zone
Subm
ersible
Zone

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Flood Forecasting Methodologies
 hydro-meteorological data acquisition and
transmission system
 forecasting modeling system
 precipitation prediction
 forecasting uncertainty estimate
 threat-recognition and information dissemination
system

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 Comprehensive Non Structural Flood Management System
 The proposed system can be divided into three important sub
systems viz.
 Telemetry System
 Management Information System
 Decision Support System

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 Telemetry System gathers hydrological and meteorological data such
as
 Rain fall data from rain-gauge stations in the catchment
 Water level data from river gauge stations
 Reservoir level data from level sensors installed at the reservoirs
 Data is gathered without any human intervention
 Collected data is then presented to the Management Information
System and the Decision Support System
 Based on the received data and the pre-fed conditions/parameters/rules
the system computes information required for controlling discharge of
water

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Future Directions
 Encourage and consolidate knowledge networks
 Mobilize and train disaster volunteers for more
effective preparedness, mitigation and response
 Increased capacity building leads to faster
vulnerability reduction.
 Learn from best practices in disaster
preparedness, mitigation and disaster response

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Boys Scout: Be Prepared
 Be Prepared : Preparedness and Mitigation is
bound to yield more effective returns than
distributing relief after a disaster.
 Create a Culture of Preparedness and
Prevention.
 Evolve a code of conduct for all stake-holders

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Invest in Preparedness
 Investments in Preparedness and Prevention
(Mitigation) will yield sustainable results, rather
than spending money on relief after a disaster.
 Most disasters are predictable, especially in their
seasonality and the disaster-prone areas which are
vulnerable.
 Communities must be involved in disaster
preparedness.

47. RecoveryRecovery
47

48. Recovery StrategiesRecovery Strategies
 Relief/Support schemes for flood victimsRelief/Support schemes for flood victims
 Reconstruction of damagesReconstruction of damages
 Recovery Strategies must lead to actionsRecovery Strategies must lead to actions
leading to prevention and/or minimizationleading to prevention and/or minimization
of effect of future floodsof effect of future floods
» General flood mitigation Master PlanGeneral flood mitigation Master Plan
» Action Plan StrategiesAction Plan Strategies
» Research and Development of actions andResearch and Development of actions and
regulationregulation
» Enforcement of RegulationsEnforcement of Regulations 48

49. Re-Construction of BridgeRe-Construction of Bridge
over Ogunpa at Agodiover Ogunpa at Agodi
49

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 Installation of Remote Rain Gauging, level gauging and
telemetry system for early warning to control peak
discharge from the streams in Ibadan
 Prevent encroachment of the river and streams by
declaration of Biodiversity Restoration Zones along the
banks
 It is necessary to create a regional (SW) centre for Regional
Warning Management for Flood
 A National Data Bank for collection and dissemination of
stream flow data should focus more on design and modeling
and simulation.
Recommendations

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Conclusions
• In view of the general global warming and the
general terrains of Ibadan, we will always have
the tendency for Ibadan streams to overflow
their banks, but to reduce the impact of the
effect of the flood, we must put in place:
• Mitigation policies
• Preparedness attitude
• Response Mechanism
• Recovery Techniques

52. 52
ThankThank
YouYou

53. 53
Brief ResumeBrief Resume
Dr. Adelere Ezekiel Adeniran, FNSE, Ph.DDr. Adelere Ezekiel Adeniran, FNSE, Ph.D..
• Dr. A. E. Adeniran, the current Director of Works & Physical Planning of the University of Lagos, Nigeria, also lectures
and supervises research works in the Department of Civil and Environmental Engineering of the University as a Senior
Research Fellow.
• A UNESCO scholar in alternative water and wastewater options, Dr. Adeniran holds a B.Sc.(Hons.) degree in Civil
Engineering from the University of Lagos, Nigeria; a M.Sc. degree in Water & Wastewater Engineering from
Loughborough University, UK and a Ph.D. degree in System Dynamics Modeling with specialization in Water Supply
Systems from the University of Ibadan, Nigeria.
• He is a visiting scholar to the Capella University, USA.
• He has presented peer-reviewed papers in many local and international academic and professional conferences. He has
also authored and co-authored academic and professional articles in learned local and international journals. He is an
editorial member of the International System Dynamic Journal based in MIT, USA.
• He received the 2010 World Federation of Engineering Institutions for the Best Innovative Research award in Water
Resources for a paper in presented in Rio De Janeiro, Argentina.
• He has served and still serving as consultant to UNDP on sustainable water projects and the World Bank as Analyst for
Procurement of Water supply projects.
• Dr. Adeniran, who was a former Chairman of Ibadan Branch of the Nigerian Society of Engineers, is a member of
American Waterworks Association, American Water Resources Association, International Water Association, Fellow of
the Nigerian Institute of Civil Engineers and a Fellow of the Nigerian Society of Engineers.
• He was born in Ibadan and married to Olayinka Adeniran. He is blessed wit four children who are all University