Summary:

Recent field measurements of mobile-bed roughness in selected streams in Czech Republic are described. The results are collected in a database organized to a www catalogue. The field results of the bed roughness in two gravel-bed streams under flash flood conditions are discussed. A methodology is suggested for evalua-tion of the bed roughness of straight channels transporting sediments.
A prediction of the bed roughness under the condition of intense sediment trans-port in the upper plane bed regime is demonstrated on the results of laboratory pressurized-pipe tests. An application to flood conditions in a steep mountain creek is shown in a case study.