Dynamic rating curve assessment in unstable rivers using Ornstein‐Uhlenbeck processes

Abstract

The procedure of fitting rating curves in channels where the stage‐discharge relationship is subject to changes driven by morphological processes remains one of the major unsolved problems in hydrometry. This paper addresses this issue by formulating the stage‐discharge relationship as a steady flow, one‐segmented power law model with parameters that are viewed as stochastic processes with characteristics associated with the temporal instabilities of the channel elements governing the stage‐discharge relationship. A Bayesian analysis with informative priors and time‐stage‐discharge measurements as forcing data is used to determine the most plausible model and its posterior parameter distributions using Markov chain Monte Carlo simulation techniques and particle filtering. The proposed framework is applied to data from gauging stations in two unstable rivers and one stable river in Norway.