Propagation of flood waves on the N ziriver (Bandama, Côte d’Ivoire)

Floods are random natural phenomena with often disastrous consequences. To the recurrence of these events, the understanding and monitoring of flood propagationmechanisms along the main rivers of Côte d Ivoire become a way of watershed management and flood prevention. The aim of this study is to know the evolution of the flood waves along the N’zi, the main tributary of the Bandama River, which every year is subjected to flood sometimes exceptional. The highlight of rainfall and flow relationship shows that N zi floods are mainly generated by precipitation and that the watershed s response is immediate. The spatial heterogeneity of the rains and their intensity variation disrupt the evolution of the waves which is done either by amplification or by attenuation. The determination of the physical parameters of the bed and the propagation parameters of the flood point by the analysis of the hydrographs revealed the attenuating nature of the floods especially around Bocanda: 50% on the M bahiakro-Bocanda section and 83% between Bocanda and Dimbokro. The weakness of the slope, the sinuosities and the roughness of the bed contribute greatly to the attenuation of the flood waves with a low celerity (0.6 m/s).