This work present the recent advances on the numerical simulation of flood dynamics in Nechi (Colombia) caused by the failure of a marginal dam located at the left side of the intersection beteween Cauca and Nechi rivers. Specifically, the flood scenario caused during La nina (2010-2011) event is analyzed in space and time. A 2D numerical simulation. Besed on a shallow water approximation is taken as a plataform of analysis. Where it is assumed that the dynamics of the floos ocours mainly in the horizontal direction, and a hydrostatic pressure gradient in the vertical direction. The model was built with the finite differences based ISIS2D computer software which allows the evalutaion of the free Surface elevation and the velocity dynamics. So what risk of flooding of the area of interest can be determined. Field measurements of free Surface elevation are taken from limnigraphic stations in Cauca river, and were imposed as boundary conditions for the numerical model at the points of the marginal dam failure. The behavior of the flooding within the one hoyr was analyzed for three cases of failure of the marginal dam. The obtained results show that the flood propagation, base don the velocity vector feld and frees Surface elevation, affect the urban area of the municipality just when there is failure of closest breaker to it. A discussion on the effect of the lack of information in that specific area is presented, as well as the strategies used to overcome that problem. Finally, future work needed to increase the level of detail of the model is presented.