Effect of reservoir on floodwave transformation

Abstract

Reservoir effects on floodwave transformation were calculated based on the concrete research. The procedure was based on the definitions of the distribution of inflow and outflow hydrograph time bases. The inflow-outflow hydrograph was divided into time intervals. The volume of inflow water in the reservoir was calculated for each interval, as well as the volume of water released from the reservoir. Lag time was calculated as the time between peak inflow to the reservoir and peak outflow from it at the spillway. The study analysis can be used as a guideline for the calculation of correct dimensions and the protection of earthfill dams from overtopping. In this way, especially in earthfill dams, a significant saving of material incorporated in the spillway parts is achieved, and general stability of earthfill dams is ensured. Based on the conducted research, it can be concluded that there is a transformation of the inflow floodwave through the reservoir. In the case when the reservoir is full, i.e. the elevation of water level in the reservoir at the moment of floodwave arrival is at the elevation of the spillway crest, the reduction rate of the outflow hydrograph is 25, 73%. Calculation is possible only based on the volume method or reservoir filling within a given time period. The increase in the water level at the spillway is in the function of inflow-outflow volume of water and the surface of water table in the reservoir.