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Management of Floods / Disaster

Presentation to the Portfolio Committee: Water & Environment. Management of Floods / Disaster. Presentation by Mr L Z Maswuma Director: Hydrological Services. PART I Update on recent floods in the Country. 2. OVERVIEW OF THE FLOOD MANAGEMENT IN RSA (1).

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Management of Floods / Disaster

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  1. Presentation to the Portfolio Committee: Water & Environment Management of Floods / Disaster Presentation byMr L Z MaswumaDirector: Hydrological Services

  2. PART I Update on recent floods in the Country 2

  3. OVERVIEW OF THE FLOOD MANAGEMENT IN RSA (1) RSA is a semi-arid country and rainfall is spread unevenly – floods & drought predominately. This presentation is limited to recent flood situation in the country The Department’s Regional Offices assume responsibility for the management of localised floods 3

  4. OVERVIEW OF THE FLOOD MANAGEMENT IN RSA (2). National Office is responsible for flood management of the Vaal and Orange River System covers Gauteng, FS, NW & NC.This System comprises 49% of the total area of RSA. The National office also monitors and coordinate information on floods occurring on other river systems that impact to neighbouring countries – Moz & Namibia. These river systems include Inkomati, Limpopo and Olifants 4

  5. AREAS AFFECTED BY FLOODS (1) KwaZulu Natal 5

  6. AREAS AFFECTED BY FLOODS (2) North West 6

  7. AREAS AFFECTED BY FLOODS (3) Free State 7

  8. AREAS AFFECTED BY FLOODS (4) Free State 8

  9. AREAS AFFECTED BY FLOODS (5) Free State 9

  10. AREAS AFFECTED BY FLOODS (6) Free State 10

  11. AREAS AFFECTED BY FLOODS (7) Limpopo 11

  12. AREAS AFFECTED BY FLOODS (7) Mpumalanga & Northern Cape Floods causes major damages Water levels are still very high in most cases and assessment work on damages is ongoing Important:Eastern Cape and Western Cape Major concern is drought 12

  13. CURRENT SITUATION (1) We do daily update on the situation at the four large dams in the Vaal Orange River system. Below is the update as at 26 January 2011 @ 14h00 and new report has been issued this morning and will be updated today at 14h00 Vaal Dam: Vaal Dam capacity is currently at100% The current inflow is 1200m3/s with an outflow of 680 m3/s with six (6 ) gates open 13

  14. CURRENT SITUATION (2) Bloemhof Dam: Bloemhof Dam capacity is currently at92% The current inflow is 1200 m3/s (to increase to 1800 m3/s on 2011/01/29) and the outflow is 1300 m3/s Gariep Dam: Gariep Dam is currently at 115% (to increase to 123% on 2011/01/29). The inflow is 4200 m3/s (to increase to 5000 m3/s on 2011/01/27) and the outflow is 2100 m3/s (to increase to 3200 m3/s on 2011/01/29). 14

  15. CURRENT SITUATION (3) Vanderkloof Dam: Vanderkloof Dam capacity is currently at 110% (to increase to 116% on 2011/01/31) The inflow is 2100 m3/s (to increase to 3200 m3/s on 2011/01/30) and the outflow is 1700 m3/s (to increase to 3000 m3/s on 2011/01/31). 15

  16. CURRENT SITUATION (4) Lower Orange River Predicted high flow at Upington of 4500 m3/s (stage 7.3m (0.5m lower than the flood earlier this month)) on 2011/02/03 A flow of 4500 m3/s is forecasted for the Lower Orange River. The high discharge is mainly from the Orange River. 16

  17. CURRENT SITUATION (5) Limpopo, Olifants and Inkomati River Systems Water levels are table and expected to rise as wetaher services forecasted 60% chance rainfall – catchments are very wet and high flows are expected. 17

  18. CURRENT SITUATION (6) uThugela, Umgeni, Hluhluwe river systems Water levels are table and the uThugela river is expected to rise as weather services forecasted more than 30% chance of rainfall – catchments are very wet and high floors are expected. 18

  19. CURRENT SITUATION (7) uMsundusi and Fish river systems Water levels are normal and may rise as more rains are expected. 19

  20. CONCLUSIONS (1) Minister issued a press statement on how we are responding on Disaster and has put aside R20million for repairing of water resources infrastructure Assessment of damages is still continuing whilst river levels are lowering Department is a member of the NATJOC and is providing info on daily river flow levels and weekly state of dams. The information is also accessible by public on internet 20

  21. CONCLUSIONS (2) Disaster management strategy which include management of hydrological risks and extremes is being finalised and it is informed by National Disaster Management Act - River levels in the Inkomati, Olifants, Thugela and Limpopo River systems are lowering Orange river levels are rising and it pose risks in the lower orange – Gariep and Vanderkloof dams have no flood gates hence overflow can not be manually controlled to keep more water in the dams 21

  22. CONCLUSIONS (3) More rainfall I still expected in most parts of the country towards March 2011 22

  23. PART 2 Flood management in the Vaal-River System 23

  24. INTRODUCTION (1) Management of extreme floods in the Vaal / Orange River system is an event driven activity done by the Department of Water Affairs in consultation with SAWS on daily weather Information and COGTA (NDMC). The “Flood Room” in Pretoria serves as an information centre to collect, process and distribute rainfall, stage and flow data Information is then sent through to NDMC – daily and other institutions in the 24

  25. INTRODUCTION (2) The main objectives of flood management is to: protect the life of people and minimisation of infrastructure damages Ensuring that the dams are 100% full at the end of the flood 25

  26. Vaal / Orange River System VAAL- ORANGE RIVER SYSTEM Vaal- Orange System is about 49% the size of South Africa, excluding Lesotho 26

  27. MONITORING STATION IN THE VAAL-ORANGE RIVER SYSTEM 50 Gauging stations collecting near real time flow and / or rainfall data - available on the Hydrology real time Web Site 27

  28. VAAL- ORANGE RIVER SYSTEM MODELLING Rainfall runoff, flood routing and dam optimisation models are used to operate Vaal Dam. Aim to minimise the flow in the system and to get rid of excess water in the system as soon as possible 28

  29. ROUTING TIMES IN VAAL- ORANGE SYSTEM Flood warnings can provide time for people to take action to protect their property as well as allowing emergency services to prepare and plan for evacuations and other emergency actions

  30. MANAGEMENT OF INFLOW/OUTFLOWS (1)

  31. MANAGEMENT OF INFLOW/OUTFLOWS (2)

  32. MANAGEMENT OF INFLOW/OUTFLOWS

  33. MANAGEMENT OF INFLOW/OUTFLOWS (4)

  34. CONCLUSION (1) In the recent floods almost double the volume of Vaal Dam and four times the volume of Bloemhof Dam flowed through the dams Short, medium and long term weather forecasts, satellite and radar images and 24 hour rainfall figures play a major role in operating decisions during the flood

  35. CONCLUSION (2) Apart from possible dam failure and loss of life, incorrect or poor dam operation could lead to billions of Rands in flood damage. (Example: the Zuikerbosch and Vereeniging pump stations are insured for about R 2.4 billion and property along the river in Vereeniging for about R 10.2 billion) 35

  36. THANK YOU 36

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