Three dimensional numerical modeling ofidealized sand dunes was used to assess the capability of various modeling formulations to capture the flow structure and resistance introduced by bed forms which are similar to those in the Lower Mississippi River. The selected models were: ECOMSED (HydroQual), MIKE 3 [Danish Hydraulic Institute (DHI)] and H3D (Hayco). The study revealed that the hydrostatic versions of models did not capture the flow separation at the crest of the dunes; however, they did respond to the presence of bed forms and gave a total resistance similar to the nonhydrostatic models. Three dimensional numerical modeling ofidealized sand dunes was used to assess the capability of various modeling formulations to capture the flow structure and resistance introduced by bed forms which are similar to those in the Lower Mississippi River. The selected models were: ECOMSED (HydroQual), MIKE 3 [Danish Hydraulic Institute (DHI)] and H3D (Hayco). The study revealed that the hydrostatic versions of models did not capture the flow separation at the crest of the dunes; however, they did respond to the presence of bed forms and gave a total resistance similar to the nonhydrostatic models.