Management of Floods / Disaster

Presentation to the Portfolio Committee: Water & Environment

Management of Floods / DisasterManagement of Floods / Disaster

Presentation byMr L Z Maswuma

Director: Hydrological Services

PART I

Update on recent floods in the Country

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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

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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

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AREAS AFFECTED BY FLOODS (1)

KwaZulu Natal

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Municipality & Specific Area

Impact on water supply

Proposed Intervention & estimate costs

uThukela District Municipality•Bergville

submerged the water abstraction pumping station

Tankering & an est.cost R900 000 is required

AREAS AFFECTED BY FLOODS (2)

North West

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Municipality & Specific Area

Impact on water supply

Proposed Intervention & estimate costs

Lekwa Teemane Local Municipality

submerged the water abstraction pumping station

Alternate source identified & is being used

Water borne diseases reported

Funding requirement not yet quantified for health & hygiene campaigns

AREAS AFFECTED BY FLOODS (3)Free State

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Municipality & Specific Area

Impact on water supply

Proposed Intervention & estimate costs

Dihlabeng Local Municipality•Fouriesburg•Bethlehem•Rosendal•Clarens

Loose pumps and motors washed away

Funding is required to repair pumps and estimate cost is R1.5 mil

AREAS AFFECTED BY FLOODS (4)Free State

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Municipality & Specific Area

Impact on water supply

Proposed Intervention & estimate costs

Moqhaka Local Municipality•Kroonstad•Viljoenskroon•Steynsrus

Raw water pump station flooded and water infrastruture damaged

Not yet quantified, funding is required

AREAS AFFECTED BY FLOODS (5)

Free State

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Municipality & Specific Area

Impact on water supply

Proposed Intervention & estimate costs

Nala Local Municipality•Monyakeng and Wesselsbron take-off points

Raw water pump station flooded and water infrastruture damaged

Not yet quantified, funding is required

AREAS AFFECTED BY FLOODS (6)

Free State

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Municipality & Specific Area

Impact on water supply

Proposed Intervention & estimate costs

Nala Local Municipality•Wepener•Dewetsdorp

pump station blocked and also overflowing, this also affected the treatment plant

Damage not yet quantified, funding is required

AREAS AFFECTED BY FLOODS (7)

Limpopo

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Municipality & Specific Area

Impact on water supply

Proposed Intervention & estimate costs

Capricon DMVhembe DMWaterberg DMMopani DMSekhukhune DM

Historically, affected by cholera outbreaks that usually follow the flood season are managed.

Community awareness campaigns;Cholera packs &Potable treatment plants

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 CapeMajor concern is drought

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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 at 100% The current inflow is 1200 m3/s with an outflow of 680 m3/s

with six (6 ) gates open

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CURRENT SITUATION (2)

Bloemhof Dam:Bloemhof Dam capacity is currently at 92% 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).

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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).

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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.

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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.

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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.

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CURRENT SITUATION (7)

uMsundusi and Fish river systems

Water levels are normal and may rise as more rains are expected.

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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

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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

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CONCLUSIONS (3)• More rainfall I still expected in most parts of

the country towards March 2011

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PART 2

Flood management in the Vaal-River System

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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

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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

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Vaal / Orange River System

Vaal- Orange System is about 49% the size of South Africa, excluding Lesotho

VAAL- ORANGE RIVER SYSTEM

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

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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

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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

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MANAGEMENT OF INFLOW/OUTFLOWS (1)Vaal Dam

0

500

1000

1500

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2500

3000

Date

Dis

ch

arg

e

85

90

95

100

105

110

115

Ca

pa

cit

y (

%)

Vaal Dam Inflow Vaal Dam Outflow Vaal Dam (%)

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MANAGEMENT OF INFLOW/OUTFLOWS (2)Bloemhof Dam

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500

1000

1500

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2500

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3500

4000

Date

Dis

ch

arg

e

85

87

89

91

93

95

97

99

101

103

105

Ca

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cit

y (

%)

Bloehof Inflow Bloemhof Outflow Bloemhof (%)

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MANAGEMENT OF INFLOW/OUTFLOWSGariep Dam

0

500

1000

1500

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3500

4000

4500

Date

Dis

ch

arg

e

85

90

95

100

105

110

115

120

125

Ca

pa

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y (

%)

Gariep Inflow Gariep Outflow Gariep (%)

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MANAGEMENT OF INFLOW/OUTFLOWS (4)Vanderkloof Dam

0

500

1000

1500

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2500

3000

Date

Dis

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arg

e

85

90

95

100

105

110

115

Ca

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%)

vd Kloof Inflow vd Kloof Outflow vd Kloof (%)

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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

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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)

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THANK YOU

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