Flood threat to the territories below the water dam in conditions of occurrence of extreme hydrological phenomena
The course of the flood in July 2001 and passage of the freshet wave through the water reservoir Chańcza on the Czarna Staszowska River was analyzed. Culmination of this wave equaling 418.62 m3·s-1 was two times higher than the estimated flow of 1% probability for what the reservoir was designed. Water management during the flood forced a higher than forecast water discharge during culmination. The paper aims at determination of water level situation on the territory at maximum water discharge from the reservoir during the flood equaling 122.75 m3·s-1 and showing possibilities of flood threat reduction. The range of the inundation zone at this discharge flow on the territory below the dam at the length of 3 km was determined taking into regard the influence of vegetation in the valley and in the zone adjacent the channel and bridge. The cause of inundation of the valley on the studied river sector is a rather low channel capacity equaling from 20-60 m3·s-1. It was found that the bridge does not influence the leveling of the analyzed flow and the reserve in the bridge light, determined as the difference of ordinate of the underlay of the span beam and ordinate of the water level under the bridge 0.92 m. Calculations of the channel capacity were also carried out in the case of renovation treatments consisting in removing stiff and soft vegetation and decrease in the inundation range of the valley was demonstrated.
Determination of channel capacity of the Mokelumne River downstream from Camanche Dam, San Joaquin and Sacramento Counties, California
