Tropical valley bottoms are a special environment, with high potential for agricultural development due to water availability, fertility and numerous ecosystem functions. In addition to their agricultural potential, valley bottoms fulfil various economic, ecological and social functions.

These areas are rich in biodiversity. They play an important role for grazing throughout the seasons, wood supply and foraging, and water supply for livestock and domestic and artisanal uses. They contribute significantly to food security and the financial stability of households. Yet less than one third of these strategic areas, representing approximately ten million hectares in Africa, is currently cultivated. Valley bottoms have specific constraints linked to their limited size, irregular water resources and flood risks. These specificities have implications on the modes of development action and management choices to be proposed, and call for a renewed engineering approach. These factors are the basis for our choice to address valley bottoms in West Africa.