"It's raining more now in the Sahel than it was in the 30 years before," said Sylwia Trzaska, a climatologist at Colombia University's International Research Institute for Climate and Society in New York. "From the early 1970s until the 1990s when the region was very dry people started settling in areas that used to flood where there were no settlements before. Now these areas are flooding again."
Already in early June, one month before rains usually start in the region, heavy rains flooded the homes of 5,900 people in northern Burkina Faso. According to the Red Cross, the province of Kouritenga, 100 km east of the capital Ouagadougou, was the worst hit, with 155mm of rain in 24 hours. More than 680 households have been affected.
Last year more than 129,000 people's homes were flooded in Niger, Burkina Faso, Senegal, Mauritania and Guinea, the UN Office for the Coordination of Humanitarian Affairs (OCHA) said.
One of the most devastating inundations occurred in Niger where 17,000 people were flooded out of their homes in the remote desert town of Bilma in the north of the country, after 63mm of rain fell within just a few days; this is roughly equal to the total rainfall the town has had over the last 10 years.
And in Burkina Faso 6,000 people in the ancient northern oasis town of Gorom-Gorom were flooded out of their homes in August 2006.
No country in the region can assume it is immune from flooding, said Jerry Niati, Regional Disaster Manager at the International Federation of the Red Cross (IFRC) in Dakar, who advises countries on preventing and mitigating the effects of natural disasters. "Regions that never used to be affected by floods are now being caught by surprise."
The concern that disaster management experts like Niati have is that some Sahelian countries lack contingency plans. "Where some countries have been using mitigation measures and are well prepared, others never expect to see floods so they are not."
He said that UN country teams and non-governmental organisations working in the Sahel must be ready to react rapidly when floods occur and should be preparing now. "They should draw up contingency plans and practice disaster scenarios," Niati said.
Disaster preparedness organisations also need to disseminate information about the threats of flooding so that communities can be ready to respond. "Countries will have to depend on what local resources they can muster," he said.
Researchers say some parts of the region that have normally been wet might actually be getting drier. In the Volta Basin in central Ghana, where massive hydroelectric dams generate much of the power used in Ghana, Togo and Benin, researchers have found temperatures to be rising and rainfall decreasing. The drying has already affected electricity generation throughout the region.
But elsewhere in Ghana major floods in early June affected over 1,600 households in the capital Accra, where 500 people were made homeless, according to OCHA.
"West Africa is and always has been prone to large natural variability," Romain Guigma, national coordinator for disaster readiness and response at the Burkina Faso Red Cross, said.
Yet climatologists say they do not have enough data to know whether the change in rain pattern is directly related to global warming or the result of a natural boom-bust pattern of drought and intense rainfall.
Trzaska of Columbia University said that data on the Sahel's climate over the last the 50 years has been too "patchy" to tell. Dave Rowell at the Meteorological Office in London agrees, although he said that it was a "certain prediction" that within 20 years climate change will make the region more disaster prone.
Most people in West Africa still rely on subsistence agriculture and use the rainy season to grow as much food as possible to see themselves through the rest of the year. When floods wipe out crops, domestic animals and homes, people are affected for the whole year and sometimes longer.
Many of the victims of last year's floods in northern Niger are still living in tents and need food, blankets and mosquito nets. A recent OCHA evaluation mission in the Gorom-Gorom commune of Burkina Faso showed that the 6,000 people there would need humanitarian assistance "at least" up to the next harvest in September 2007.
Joseph Instiful, who also works at the Meteorological Office in London, said that disaster managers need to pay more attention to floods than to droughts. The World Meteorological Organisation is installing a monitoring station in West Africa as the infrastructure for forecasting rains there is "not well developed," Instiful said.
Currently signs of impending drought can be detected far in advance compared to high-impact floods, Instiful added.