Revisiting the Concepts of Return Period and Risk for Nonstationary Hydrologic Extreme Events
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Material Information

Title:
Revisiting the Concepts of Return Period and Risk for Nonstationary Hydrologic Extreme Events
Series Title:
American Society of Civil Engineers Journal of Hydrologic Engineering
Creator:
Salas,Jose D.
Obeysekera, Jayantha
Affiliation:
Colorado State University -- Department of Civil and Environmental Engineering
South Florida Water Management District -- Hydrologic and Environmental Systems Modeling
Publisher:
American Society of Civil Engineers
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Sea Level Rise ( lcsh )
Climate Change ( lcsh )
Hydrology ( lcsh )

Notes

Abstract:
Current practice using probabilistic concepts and methods applied for designing hydraulic structures generally assume that extreme events are stationary. But many studies in the past decades have shown that hydrological records exhibit some type of nonstationarity such as trends and shifts. Human intervention in river basins (e.g. urbanization), the effect of low frequency climatic variability (e.g. Pacific Decadal Oscillation), and climate change due to increased greenhouse gasses in the atmosphere have been suggested to be the leading causes of changes in the hydrologic cycle of river basins. As a consequence changes in the magnitude and frequency of hydrologic events such as extreme floods and extreme sea levels have been observed in certain parts of the globe. To tackle the various types of nonstationarities in hydrologic extremes several statistical approaches have been proposed in literature such as frequency analysis where the parameters of a given model (e.g. the Gumbel model) may vary with time. The aim of this paper is to show that some basic concepts and methods used in designing flood-related hydraulic structures such as return period and risk assuming a stationary world can be extended into a nonstationary framework. In particular, the concepts of return period and risk are formulated by extending the geometric distribution to allow for changing exceeding probabilities over time. Building on previous developments suggested in the statistical and climate change literature, we present a simple and unified framework to estimate the return period and risk for nonstationary hydrologic events along with examples and applications so that it can be accessible to a broad audience in the field. The applications demonstrate that the return period and risk estimates for nonstationary situations can be quite different than those corresponding to stationary conditions. They also suggest that the nonstationary analysis can be helpful in making appropriate assessment of the reliability (risk) of a hydraulic structure during the planned project life. Some possible extensions of the proposed methods are also discussed.

Record Information

Source Institution:
Florida International University
Rights Management:
Please contact the owning institution for licensing and permissions. It is the user's responsibility to ensure use does not violate any third party rights.
Resource Identifier:
10.1061 ( doi )

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Sea Level Rise