ICSU Dark Nature

The mega-flood meeting in Bobole focused chiefly on floods in Equatorial East Africa and Southeast Africa. This declaration is mainly based on the African experience:

FLOODS:

• Are the most frequent of all natural catastrophes
• Affect almost every part of the World
• Affect a great part of the World's population because so many people live along rivers and on flood-plains
• Have castastrophic effects that are closely linked to the man's manipulation of natural systems

During the history of humankind, the Earth's surface has experienced alternations between dry and wet periods. Floods and droughts along river floodplains and deltas have disrupted lives for the people living there. Catastrophic floods have recently occurred in almost all populated areas of the World. At the same time, many catchments are becoming drier, with reduced river flow. Climate models indicate that both floods and droughts may become more frequent and more severe during global warming. The mega-flood in Mozambique in 2000, as well as the recent catastrophic flooding along the coast of the Gulf of Mexico, showed that societies everywhere are unprepared to meet the challenge of such events.

CATASTROPHIC FLOODS ARE NUMEROUS IN EAST AND SOUTHEAST AFRICA:

Examples from Equatorial East Africa, Lake Victoria Basin:

• 1961: Famine and waterborne epidemics
• 1997/98: The worst flood ever recorded in Equatorial East Africa
• 2004: Floods displaced 24,000 people Examples from southeast Africa:
• 1984: Cyclone Domoina caused large floods on the coastal plain of Maputaland in northeast South Africa and southern Mozambique
• 1987: Large flood in eastern South Africa
• 2000: Cyclone Eline caused the largest recorded flood experienced in Mozambique, also large floods in Zimbabwe, Swaziland and South Africa. Nobody was prepared for it and the impact was catastrophic

UNDERSTANDING OF POSSIBLE FUTURE MEGA-FLOODS:

The listed floods in Equatorial East Africa were all related to El Niño events. Some floods in Mozambique were related to El Niño events, while others were not. The mega-flood in 2000 was not related to any El Niño or La Niña event. Floods in South Africa during the past 50 years have not been related to El Niño events at all. Flood records dating back more than 50 years are almost non-existent in many African countries. This leads us to draw the following conclusions:

• Studies of the relation between climate cyclicity and floods are needed.
• Very little is known about the possible maximum magnitude of future mega-floods.
• Statistical analyses of long flood-records cannot be used to estimate such extremes. They may be orders of magnitude larger than registered floods.
• Sediment records from floodplains and deltas, and the geomorphology of river valleys indicate that pre-historic floods have been much larger than those experienced in historical times.

MANIPULATION OF RIVER SYSTEMS:

River systems are becoming more and more influenced by man:

• Dams
• Levees along artificially channelled river courses
• Bridges
• Extraction of groundwater from river plains
• Construction of heavy buildings and roads related to large cities
• The recent flood in New Orleans has taught us that even highly developed countries are unprepared to cope with floods related to systems strongly altered by man.
• In many African countries the rivers systems are still almost natural. There is a great need to know the impact of future man-made manipulation of these rivers.

ACTIONS NEEDED:

The Workshop in Bobole 2004 urges decision makers to:

• Improve research on past environmental change and its effect upon river systems. This knowledge is needed to understand what can be expected in the future. Societies must be prepared for catastrophic flood events larger than hitherto experienced
• Increase the expertise needed to study flood sediments in African countries. Training in sedimentology and past climate history are basic elements related to such expertise.
• Integrate with scientists to make assessment plans, in order to be prepared for mega-floods, to respond during the flood event and to act in the best possible way after the flood event itself.
• Make plans to allow existing data, collected by international researchers, to become available for national experts. We call upon university and research funding agencies to ensure that:
• In coming to terms with rapid landscape changes, interdisciplinary research is strengthened.
• Funding agencies and the academic organisations increase their support for efforts to link different disciplines.
• More credit is given to young researchers who work with interdisciplinary teams and publish their work on the Internet and in non-specialist journals and books.
• Efforts are made to strengthen links between researchers and the media.
• Research that takes place in Africa is always carried out with the participation of local people, with the results communicated fully to them.

WORKSHOP CONCLUSIONS:

• Catastrophic floods are an integral part of the hydrological cycle Ð they are recurrent events and will occur again.
• Catastrophic floods cannot be accurately predicted or fully controlled anywhere in the world
• River plains are the most fertile areas. People will recolonise the same areas after floods. Local communities must be prepared for new floods. There is, therefore, a strong requirement for flood assessment plans in Africa.
• These plans must be based on realistic ideas about the largest possible flood.
• Therefore, knowledge about past mega-flood records is needed

Sponsors of the meeting:

• International Council for Science (ICSU)
• International Union of Geological Sciences (IUGS)
• IUGS Initiative on Geoindicators
• International Union for Quaternary Research (INQUA)
• Norwegian Universities Collaboration with Developing Countries (NUFU)

About 40 participants attended the Workshop, 23 of them participated in the Workshop training course. The participants were from First Nations, Developing Countries: governmental institutions and universities, and included decision makers, geologists, meteorologists, geographers and ecologists.