Nagaoka city area in an alluvial fan is dangerous in flood control, because the Shinano River flows fast, meanders and attacks the area. Safety of levees is a serious problem. After the alignment of low water channel was examined in a hydraulic model experiment as well as a training levee, a low water revetment has been executed the work since 1975. About 25 years have passed, the site observationresults were compared with the hydraulic model experiment results about changes of a riverbed and reduction of flow attacking effect. The effect of training levee, which is main concern of this planning, is evaluated by numerical simulation.