We are interested in simulating rainfall overland flows on agricultural fields, because they may have some undesirable effects such as soil erosion and pollutant transport. The model used for these simulations is the system of Shallow Water (SW) or Saint-Venant system as in (Esteves et al. 2000 and Fiedler and Ramirez 2000). In this context, we can meet some numerical difficulties due to dry/wet transitions and to steady states. This work is divided into two parts. First we present the numerical method for the resolution of the Shallow Water equations integrated in FullSWOF_2D (Full Shallow Water for Overland Flow : an object oriented code in C++). This method is based on a hydrostatic reconstruction scheme (Audusse et al. 2004 and Bouchut 2004) to cope with dry/wet transitions and steady states, coupled with a semi-implicit friction term treatment (Bristeau and Coussin 2001). In the second part, FullSWOF 2D is tested and by comparison with experimental field observations validated on several real events measured by IRD on two different runoff plots in Niger (West Africa).