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Prevention and Mitigating the Occurence and Impact of Flood in the City of Ibadan


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Flood Mitigation

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Prevention and Mitigating the Occurence and Impact of Flood in the City of Ibadan

  1. 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. 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.
  3. 3. 3 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.
  4. 4. 4 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
  5. 5. 5 Ibadan City and Its Rivers
  6. 6. 6 Ibadan Land
  7. 7. 7 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.
  8. 8. 8 Ogunpa and Ogbere StreamsOgunpa and Ogbere Streams CatchmentsCatchments Ogbere Ogunpa
  9. 9. 9 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
  10. 10. 10 Floods: Hydrology and Hydraulics of Floods
  11. 11. 11 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. 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
  13. 13. 13 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. 14. Refuse Disposed into Ibadan Streams 14
  15. 15. Constructions on RiverConstructions on River Banks in IbadanBanks in Ibadan 15
  16. 16. 16 Encroachment of Flood Plain of Kudeti Stream
  17. 17. 17 Spatial Growth of Ibadan 20102010
  18. 18. 18 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
  19. 19. 19 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
  20. 20. 20 Homelessness and Losses
  21. 21. 21 Colossal Lost of Properties
  22. 22. 22 Discomfort and Fear
  23. 23. 23 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.
  24. 24. 24
  25. 25. 25 Hydrologic Cycle Excessive Runoff, FLOOD Precipitation, P(t)
  26. 26. 26 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
  27. 27. 27 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 ++=
  28. 28. 28 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
  29. 29. 29 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
  30. 30. 30 Flood Hydraulics Debris
  31. 31. 31 Flood Management
  32. 32. 32 Stages of Flood Management  Mitigation  Preparedness  Response  Recovery
  33. 33. 33 Phases of Emergency Management Prevention-Mitigation Preparedness ResponseRecovery
  34. 34. 34 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
  35. 35. 35 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
  36. 36. 36 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 ✓ ✓ ✓ ✓
  37. 37. 37 Response and Preparedness
  38. 38. 38 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
  39. 39. 39 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
  40. 40. 40 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
  41. 41. 41 Flood Forecasting Methodologies  hydro-meteorological data acquisition and transmission system  forecasting modeling system  precipitation prediction  forecasting uncertainty estimate  threat-recognition and information dissemination system
  42. 42. 42  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
  43. 43. 43  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
  44. 44. 44 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
  45. 45. 45 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
  46. 46. 46 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. 47. RecoveryRecovery 47
  48. 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. 49. Re-Construction of BridgeRe-Construction of Bridge over Ogunpa at Agodiover Ogunpa at Agodi 49
  50. 50. 50  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
  51. 51. 51 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. 52 ThankThank YouYou
  53. 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