A Large eddy simulation of the flow around a bend of a river that has been found to be the habitat of a rare species of vegetation in Japan has been conducted.  The river reach consists of a sharp bend, point bar that is submerged under water during large floods, large boulders and vegetation and appears to be a challenge for conventional two-dimensional analysis.  The results of LES have been critically compared with the conventional two-dimensional analysis considering various effects that may contribute to the differences or the similarities between the two results.  While the strong secondary flow exists downstream of the bend that can only be correctly reproduced by a three dimensional analysis, the results of the two-dimensional analysis around the gravel bar near the inner bank of the bend where the vegetation habitat is, are not much different from the three-dimensional analysis and the observation.  Some analysis into the conditions is made that may clarify the limitation and the accuracies of depth-averaged flow analysis and the large eddy simulation.