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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 Flooding in SADC – Future patterns Status of flood forecasting in SADC Way forward. Global Perspective of Floods.

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slide1

FLOODING IN SADC:

AN OVERVIEW

Eugene Poolman

South African Weather Service

slide2

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
slide5

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
impact on developing countries
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
slide9

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
slide10

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
impact on sa mozambique zambia
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
trends of flood occurrences in sadc
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)
from reports by the ipcc assessment report 4 and wmo
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

slide17

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
slide19

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
slide21

Flash floods:

    • Occur in small river basins (50 – 200 square km)
    • Quick response (<6 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
1 integrated flood management as a comprehensive solution
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
2 early warning through flood forecasting
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
slide26

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
slide27

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
3 enhancing data measuring
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
slide29

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 NokuthulaNdou

Grade 6 Pupil

Shashi Primary School

Maramani Communal Areas

Beit Bridge

Zimbabwe