Modeling and Verification of the Effect of Dikes on the Spatial Extension of the Flood Plain of the Mananjeba River (Marivorahona, Madagascar)

摘要

During the passage of cyclone Eliakim in March 2018, the overflow of the Mananjeba River (Ambilobe, DIANA Region, Madagascar) had led to a large flood that had caused material damage, loss of life and cut off the road between Ambilobe and Diego-Suarez for several months. Dikes were then planned to mitigate the effects of this flooding and to protect the destroyed and rebuilding infrastructure. In this work, we modelled the floodplain of the Mananjeba River in the vicinity of the village of Marivorahona, without and then with the dykes, and this modelling was based on solving the flow equations according to a finite-difference method in generalized curvilinear coordinates and using a constrained numerical interpolation scheme (CIP) for the advection terms. This resolution was performed with the Nays2D Flood solver which is available in the iRIC software suite due to its low requirement for measured field data. It was concluded that the models thus developed reproduced the spatial extent of the flood quite accurately. It was also found that the effect of dykes on flood attenuation for infrastructure protection was not fully effective. Nevertheless, the models used in this work could be improved by carrying out field measurements in order to fix certain parameters and to increase their accuracy.