Dakar area landscape is mainly characterized by the existence of the ＂niaye＂-or agricultural depressions located in the sand dunes system. In these depressions, the top-table of quaternary sand groundwater reaches o...Dakar area landscape is mainly characterized by the existence of the ＂niaye＂-or agricultural depressions located in the sand dunes system. In these depressions, the top-table of quaternary sand groundwater reaches or overflows the soil surface. Because of a recent groundwater level drop, some of the niayes have become runoff-gathering sites. This water ensures various economical, environmental and social services, i.e. urban agriculture, drinking water supply of Dakar and formation of ecosystems supporting biodiversity. Given that rainwater infiltration is the only natural ＂input＂, conception and implemention of rainwater management PPP （Politics, Plan and Program） must necessarily take into account this interrelationl Nowadays, two acute problems are observed in the Dakar area. On the one hand, the niayes are threatened by a hydrological drying process due to the insufficiency of rainwater refill. On the other hand, the dramatic social pressure on the environment has led to the urbanization of these bottom-lands. Furthermore, because of the pluviometry decrease, a worsening of the nuisances （floods and malaria） related to surface waters occurs. Consequently, an appropriate runoff management should integrate both the ＂risk＂ and ＂resource＂ dimensions, thus allowing the protection of natural resources and a secure living environment. According to the limits of＂classicai＂ solutions, this paper provides approach elements for building a sustainability plan focusing on emergent concerns, which would control rainwater in urbanized zones.展开更多
文摘Dakar area landscape is mainly characterized by the existence of the ＂niaye＂-or agricultural depressions located in the sand dunes system. In these depressions, the top-table of quaternary sand groundwater reaches or overflows the soil surface. Because of a recent groundwater level drop, some of the niayes have become runoff-gathering sites. This water ensures various economical, environmental and social services, i.e. urban agriculture, drinking water supply of Dakar and formation of ecosystems supporting biodiversity. Given that rainwater infiltration is the only natural ＂input＂, conception and implemention of rainwater management PPP （Politics, Plan and Program） must necessarily take into account this interrelationl Nowadays, two acute problems are observed in the Dakar area. On the one hand, the niayes are threatened by a hydrological drying process due to the insufficiency of rainwater refill. On the other hand, the dramatic social pressure on the environment has led to the urbanization of these bottom-lands. Furthermore, because of the pluviometry decrease, a worsening of the nuisances （floods and malaria） related to surface waters occurs. Consequently, an appropriate runoff management should integrate both the ＂risk＂ and ＂resource＂ dimensions, thus allowing the protection of natural resources and a secure living environment. According to the limits of＂classicai＂ solutions, this paper provides approach elements for building a sustainability plan focusing on emergent concerns, which would control rainwater in urbanized zones.
