Risks in Hydrologic Design of Engineering Projects

By using the probability theory it has been shown that for any hydrologic design with a certain return period and expected life of a project there is always a calculated risk of failure involved. For a time invariant hydrologic system this simple risk can be computed. Conversely, if the expected project life and the simple risk are known, the corresponding design return period can be determined. Such a determination of the return period is independent of the type of distribution and the plotting position of the hydrologic data. Furthermore, there are additional risks and uncertainties involved which should be considered in hydrologic design of engineering projects such as those due to limited record of data available, using rainfall records to synthesize runoff information, stochastic nature of the hydrologic system, and the techniques utilized in the mathematical processing of the data.