Stage-discharge relationship in tidal channels

Abstract

Long-term records of the flow of water through tidal channels are essential to constrain the budgets of sediments and biogeochemical compounds in salt marshes. Statistical models which relate discharge to water level allow the estimation of such records from more easily obtained records of water stage in the channel. Here, we compare four different types of stage-discharge models, each of which captures different characteristics of the stage-discharge relationship. We estimate and validate each of these models on a 2-month long time series of stage and discharge obtained with an acoustic Doppler current profiler in a salt marsh channel. We find that the best performance is obtained by models that account for the nonlinear and time-varying nature of the stage-discharge relationship. Good performance can also be obtained from a simplified version of these models, which captures nonlinearity and nonstationarity without the complexity of the fully nonlinear or time-varying models.