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Hydrological risk analysis with optical remote sensing and hydrogeological modelling: case study of Dakar flooding area (Senegal)

The present study uses remote sensing, geographic information systems, groundwater levels and hydrogeological modelling to evaluate the influence of urbanization and modification of water pumping rates on groundwater and related inundations. Evidence of the fast urban expansion was investigated using time series aerial photos and satellite images interpretation (1966, 1978, 1989, 2000 and 2006). Results show that urban occupation increases from 36 km2 in 1966 to 150 km2 in 2006. However, areas affected by flooding were mainly located in Guediawaye and Pikine districts (municipalities). Daily groundwater monitoring levels using “Thalimede Orpheus mini” recorders and chemical data investigation support relatively high recharge values in the periurban areas. Groundwater recharge evolution is modelled using FEFLOW software. Predictive simulations of groundwater pumping as a solution to fight against floods at rates of 19 000 m3/d and 9 000 m3/d respectively for infrabasaltic and Thiaroye aquifers cause a decline in groundwater levels ranges between 0.6 m and 3 m in piezometer Pz7 (Guediawaye); 0.5 m and 2.9 m Pz4 (Pikine) and 0.5 m and 2.6 m Pz21 (Yeumbeul). These results show that groundwater pumping is an effective way to fold the piezometric levels. Results analyses suggest also that the flooding phenomena are due to some factors such as urbanization combined with spontaneous occupation of lowland, rainfall events accumulation, groundwater level rising caused by waste water infiltration due to the absence of drainage sanitation and a significant decrease of pumping rate.

Auteur(s) : Diouf, O.C., Faye, S.C., Dieng, N.M., Faye, S., Faye, A., Englert, A., Wohnlich, S.
Pages : 2327-4581
Année de publication : 2013
Revue : Geoinformatics & Geostatistics: An Overview S1
N° de volume : S1-011
Type : Article
Mise en ligne par : DIOUF Ousmane Coly