flood risk, HEC-RAS, hydraulic model, restoration, stream morphology

Stream restoration projects are often presented as a part of flood protection management. In practice are restoration realised often on small streams for hundreds meters long sections. How much are these projects effective in flood risk reduction can be estimated by mathematical hydraulic models without actual realization. This approach was applied on Jasénka stream located at Czech Republic for 1, 5 km long section of channel. The effect of current state of channel morphology on potential flood waves was compared to proposed variants of new channel morphologies. New variants of morphology were proposed with preserving original trace but with lower capacity and with new meandering trace. By method of unit hydrograph were estimated potential flood waves with probability of reocurece 5, 20 and 100 years. For current and proposed morphologies were established two dimensional hydraulic models in software HEC-RAS. Then were simulated all designed flood waves. The results showed that the effect of the proposed modifications to the flood waves attenuation from the current state is evident just for 5yr flood wave where restored morphology cased delay of peak flow. For flood waves with higher flows the effect is not significant compared to current state.