Return period and risk for nonstationary hydrologic extreme events

Return period and risk for nonstationary hydrologic extreme events Conference

Salas, JD, Obeysekera, J. (2013). Return period and risk for nonstationary hydrologic extreme events . 1213-1223. 10.1061/9780784412947.119

Standard practice for designing hydraulic structures generally assumes that extreme events are stationary. However, it has been shown that in some cases hydrologic records exhibit some nonstationarity features, such as trends and shifts. Human intervention in river basins, the effect of low frequency climatic variability, and climate change due to increased greenhouse gases in the atmosphere have been suggested to be the leading causes of changes in the hydrologic cycle of river basins, which may also influence changes in the magnitude and frequency of extreme floods and sea levels that have been observed in certain parts of the globe. Various approaches have been used to analyze nonstationarity in hydrologic extremes, for example by application of frequency analysis where the parameters of a model vary with time. Basic methods used in designing flood-related hydraulic structures, such as return period (T) and risk (R), assuming a stationary world, can be extended into a nonstationary framework using the geometric distribution and changing exceedance probabilities over time. Building on previous developments suggested in literature, we present a simple and unified framework for estimating T and R for nonstationary hydrologic events along with an illustrative example. © 2013 American Society of Civil Engineers.