FLOODING IN SADC:

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FLOODING IN SADC AN OVERVIEW
Eugene Poolman South African Weather Service
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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

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Global Perspective of Floods
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The number of flood disasters by country from
1974 to 2003
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• 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

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Frequency of worldwide flood disasters
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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

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Flooding in SADC Historical Patterns
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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

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• 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

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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

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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)

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Flooding in SADC Future Patterns
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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
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• 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

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Status of Flood Forecasting in SADC
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• 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

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Limpopo River Basin
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• 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

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Example of the Central American flash flood
warning system
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Way Forward
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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

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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

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• 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

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• 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

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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

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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