<p>In this parameter study, the effect of local river widening on the attenuation and delay of flood waves is investigated using two-dimensional hydrodynamic numerical simulations. In addition, the affected hydraulic parameters, such as flow depth and velocity, are analyzed. Realistic parameter combinations are used to define 240 simulation scenarios. Under subcritical flow conditions, the considered river widening setup leads to an acceleration of the upstream flow, accompanied by a partial reduction of the flow depth, which can extend over several kilometers. At the beginning of the local widening, flow depth reductions of up to 50 % are analyzed. At the end of the widening, a significant rise in water level is observed due to the reduced discharge capacity. The reduction in downstream flow depths corresponds to the degree of retention achieved by the widening. Regression analyses show an almost linear relationship between the relative wave peak and its delay, with the steepness of the regression line depending on the discharge load. Peak reduction is approximately inversely quadratic with the discharge load. The study shows that the potential of local river widening to reduce flood peaks is very small, with maximum calculated peak reductions in the order of a few per thousand. However, a significant delay in the peak flows can certainly be achieved.</p>