Introduction of a stochastic approach in the development of a numerical model for tidal–fluvial interaction analysis and design

Abstract

The interaction of tidal surges and fluvial flows in any river system results in a prevailing combined condition that requires accurate consideration in the reaches of the system not directly influenced by either phenomenon. The combined return period of the system should be deduced based on the combined effects of the two phenomena, which may usually be considered independent of one another. It is therefore imperative to consider both the return periods of the upstream flood condition and the downstream tidal surge condition to determine the combined return period for design flood analysis in tidal river systems. The task of obtaining a suitable and practical combination of the two phenomena encompasses preparation of an interactive scenario most closely and practically verified against the actual design event. In the present research, a combination coefficient has been introduced using the joint probability method. The combination coefficient is used to combine return periods of tidal surges and fluvial floods. A numerical and stochastic model has been developed for hydraulic routing in tidal rivers. The model is applied to the Karun River in Iran and the Severn River in the United Kingdom. The model can generally be utilized for river management and determination of safe bank height for tidal rivers.Key words: combination coefficient, tidal surges, river floods, joint probability method.