Author(s): E. I. Daniil; L. S. Lazaridis
Linked Author(s):
Keywords: Rainfall distribution; Flood; Dam sizing; Hydrographs; Return period
Abstract: The design engineer is often called upon to make decisions relating to the sizing of major hydraulic structures with essentially minimal data. Design for a given return period is not uniquely defined and may vary considerably depending on the selection of the parameteres and methodologies involved: choice of appropriate idf curve, rainfall distribution, rainfall height and duration, unit hydrograph type. Implementing the worst profile distribution may result in twice the design discharge, compared to the one resulting from rainfall heights computed by the idf curve without redistribution. Sizing of spillway, diversion tunnel and cofferdam are all significantly affected by the choice of the rainfall distribution. Using a rainfall height distribution that tends to maximize the peak discharge in essence corresponds to a lower probability of occurrence that is not quantified at present and is not discussed. Thus, although not admitted the return period is increased. Combining higher discharges that calculated in previous stages of a project with topographic restrictions and cost issues may render the whole project non-feasible. It is proposed that in such cases a range of computations is performed and the final design can handle the higher discharges with reduced freeboard. Two case studies of reservoirs in greek islands are discussed.
Year: 2003