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FLOODING IN SADC:

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FLOODING IN SADC: AN OVERVIEW Eugene Poolman South African Weather Service OUTLINE OF PRESENTATION Global perspective of floods Flooding in SADC - Historical patterns ... – PowerPoint PPT presentation

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Title: FLOODING IN SADC:


1
FLOODING IN SADC AN OVERVIEW
Eugene Poolman South African Weather Service
2
OUTLINE OF PRESENTATION
  • Global perspective of floods
  • Flooding in SADC - Historical patterns
  • Flooding in SADC Future patterns
  • Status of flood forecasting in SADC
  • Way forward

3
Global Perspective of Floods
4
The number of flood disasters by country from
1974 to 2003
5
  • Floods are worldwide a major hazard
  • Cause death of on average 7000 people every year
  • WMO of all natural hazards
  • Floods has greatest damage potential
  • (over 1/3 of total damage)
  • Affect the greatest number of people (over 2/3
    of people affected)
  • Impact is increasing rapidly

6
Frequency of worldwide flood disasters
7
Impact on Developing Countries
  • Developing countries are more vulnerable
  • Social and economic vulnerability
  • Reduced coping mechanisms
  • Rural people are most vulnerable
  • 95 of deaths occurred in least developing
    countries
  • 8 SADC countries are least developing countries

8
Flooding in SADC Historical Patterns
9
Flooding events between 1985 and 2002
  • Occur mostly along southern and eastern parts of
    the subcontinent
  • Caused by
  • tropical weather systems moving westwards in
    summer
  • Cold fronts and cut-off lows in winter

10
  • In SADC Floods follows second to epidemics in
    frequency
  • Third to drought and wind storms on damage caused
  • Wind storms mostly tropical cyclones, and winter
    frontal systems that also cause floods
  • R7,000 million flood damage caused by tropical
    cyclone Eline and Gloria in 2000 in Mozambique
  • 3 times their 1999 export

11
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12
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13
Impact on SA, Mozambique, Zambia
  • Frequency of natural disasters
  • Most frequent natural disaster in SA and
    Mozambique, second to epidemics in Zambia
  • Deaths from natural disasters
  • Mozambique 37 of deaths, SA 62, Zambia unclear
  • Affecting people (injured, displaced)
  • Drought affects most people (slow and
    long-lasting disaster)
  • Floods second in Zambia 50 (about 3 million
    people) and in Mozambique 33 (about 8 million
    people)
  • In Mozambique about 30 people per square km stay
    in flood prone river basins

14
Trends of flood occurrences in SADC
  • Following global trends, floods have increased in
    SADC
  • 1984 - 1988 9
  • 1994 1998 26
  • 1999 2003 59
  • Dramatic increase in number of people affected
    and died
  • 1984 1988 4000
  • 1998 2003 13000
  • Particularly elderly, women and children are
    affected
  • This upward trend is due to
  • Growth in urban population
  • Population growth in flood prone river basins
    (nutritious and water rich)

15
Flooding in SADC Future Patterns
16
From reports by the IPCC Assessment Report 4, and
WMO
  • Great deal of uncertainty on the impact of
    climate change on flooding in SADC
  • Flood risk is also controlled by other factors
  • Changes in economic and social systems
  • Changes of hydrological aspects such as
    vegetation and soil moisture in basins
  • Land-use changes
  • Deforestation
  • Reduction in wetlands

IPCC Intergovernmental Panel on Climate Change
17
  • IPCC Precipitation intensity expected to
    increase virtually everywhere (though parts of SA
    expected to be drier and warmer)
  • A warmer climate with increased variability will
    increase the risk of both floods and droughts
  • Increase in precipitation intensity and
    frequency will lead to increase in risk of
    flooding and droughts in many areas
  • Flood magnitudes and frequencies are likely to
    increase in most regions

18
Status of Flood Forecasting in SADC
19
  • Distinguish broadly between two kinds of floods
    Large scale river floods, and Flash floods
  • Large scale river floods
  • Occur in large river basins from large scale
    heavy rain (Orange, Vaal, Limpopo, Zambezi
    Rivers)
  • Long response time (6 hours to many days) between
    heavy rain and flooding
  • Complex hydrologic models calculating river
    levels as the flood moves down the river over the
    next few days
  • Situation in SADC
  • Outside SA there is a general lack of river
    forecast systems due to limited rainfall data and
    river monitoring data
  • SA is implementing a river forecasting system in
    the Vaal River
  • USA developed a crude satellite based system for
    Limpopo following 2000 floods
  • Some effort in Zambezi

20
Limpopo River Basin
21
  • Flash floods
  • Occur in small river basins (50 200 square km)
  • Quick response (lt6 hours) between heavy rain and
    flooding
  • Traditional hydrologic models ineffective due to
    small lead time
  • Rainfall measurements on hourly basis using rain
    gauges and weather radars and satellites are very
    important
  • Promising system implemented in Central America
  • Situation in SADC
  • There is currently no flash flood warning system
    operational
  • Real time rainfall measurement only in South
    Africa
  • Very few weather radars outside SA (Mozambique
    has 2, Botswana has 1) and their coverage not
    sufficient
  • SA is investigating implementation of Central
    American system under radar coverage in flood
    prone regions

22
Example of the Central American flash flood
warning system
23
Way Forward
24
1. Integrated Flood Management as a comprehensive
solution
  • Munich Re It is not possible to prevent
    disasters, we rather need to learn to live with
    them
  • WMO developed an Integrated Flood Management
    program as part of a holistic disaster risk
    management approach
  • Early warning systems
  • Socio-economic activities to balance needs and
    risks
  • Structural solutions such as levees and dams
  • Non-structural measures such as land-use
    regulation
  • Awareness raising of population and governments
  • This approach should be strongly supported

25
2. Early Warning through Flood Forecasting
  • WMO emphasizes that the most critical aspect of a
    flood-loss reduction strategy, lies in emergency
    preparedness and response, particularly a flood
    forecasting and warning system
  • This requires collaboration between
    meteorologists, hydrologists and disaster
    managers, and between countries

26
  • Forecasting for large scale river floods
  • Development of comprehensive hydrologic river
    forecasting models for the large basins (Limpopo,
    Zambesi, etc)
  • Long-term solution
  • Depends heavily on the improvement of rainfall
    measurement and river level monitoring in all
    riparian countries of river basins
  • An example is the efforts by the Limpopo Basin
    Commission
  • Investigate more crude interim measure such as
    the US satellite based system to provide some
    kind of guidance
  • Easier to implement since it does not depend on
    surface data
  • But, it is less accurate because it uses only
    remote observations by satellite and not real
    data

27
  • Forecasting for flash floods
  • South Africa is investigating the implementation
    of a flash flood warning system based on the
    Central American system
  • Can operate under the radar coverage in flash
    flood prone basins of 50 to 100 square km
  • Complement the SAWS current early warning system
  • WMO is planning the development of a global flash
    flood warning system (FFGS) based on the Central
    American system, but using only satellite
    information
  • Can be rolled out where no surface data exists
  • Can only work for larger basins of about 200
    square km
  • Will be implemented on a regional basis (like
    SADC) in 2010
  • SAWS as a RSMC can play a pivotal role in this
    activity

28
3. Enhancing data measuring
  • Reliable weather and hydrological data is an
    essential system for flood forecasting systems
  • Particularly rainfall and river flow and water
    level monitoring
  • WMO operates the SADC-HYCOS program aimed at
    improving hydrological monitoring.
  • National meteorological services must
    continuously improve their existing rainfall
    networks substantially
  • This depends heavily on funding levels

29
FOR THERE IS NO NOAH AMONG US For there is no
Noah among us, let us do it ourselves. Let us
not attempt to cross flooded rivers. Let us not
build our homes on river banks. Let us not build
our homes on low land. Let us fill gullies and
stop them from becoming rivers. For there is no
Noah among us, let us protect ourselves from
floods Poem by Nokuthula Ndou Grade 6
Pupil Shashi Primary School Maramani Communal
Areas Beit Bridge Zimbabwe
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