Frequency of Recurrent Extremes under Nonstationarity: Fid-Bau Portal

Frequency of Recurrent Extremes under Nonstationarity

Obeysekera, Jayantha / Salas, Jose D.

The concepts and methods for planning and design of hydraulic structures subject to hydrologic extreme events that arise from nonstationary conditions have emerged in the last few years. The traditional approaches such as return period, risk, and reliability assume that extreme events are stationary and they are being reformulated for applications under nonstationary conditions. For this purpose, some of the previous developments have been based on the nonhomogeneous geometric distribution. The particular importance of this paper relates to the frequency of extreme events as time evolves, say for a given time period $n$ . For stationary extreme events, the number of events exceeding the design quantity (e.g., design flood) over the design life of the project, say $n$ , can be determined from the binomial distribution. The main objective of the research reported in this paper is to develop a conceptual framework so that the frequency of extreme events when the extremes are nonstationary can be determined from the Poisson binomial distribution. In addition, the use of the number of extreme events in the future as an alternative metric for hydrologic design is proposed with potential applications in flooding associated with both riverine and sea level extremes in coastal regions. The application of analytical concepts is demonstrated by using the annual flood maxima of the Assunpink Creek in New Jersey. Results suggest that the frequency of extreme events as an alternative metric for hydrologic design has a significant potential for applications in risk-based economic analysis of projects.