The effect of dam flushing events on the channel morphological evolution was investigated in this paper. The study area encloses an alternate bar system, which is a typical example of harnessed mountain rivers regulated by hydro-power reservoirs. Topographic point measurements were acquired at the experimental site before and after the studied dam flush events. The field survey strategy consists of a measurement of a cross sections set reinforced by the acquisition of a relatively high dense data describing transverse channels and breaks in the slope. Afterwards, a set of DEMs were derived based on multiple breaklines defining the complex morphological features of the gravel bar. Changes in morphology were assessed by DEM differencing. The DEM methodology based on the morphological unit scale provides an explicit identification of spatial patterns of erosion and deposition. The different morphological response of the reach to similar flushing events is explained by the severe incision of the main channel observed after the 2008 flood which was accompanied by the transformation of the upstream bar to an island and therefore a change on flow direction.