Estimating river flow capacity in practice

Estimating water level underpins almost all river flood risk management (FRM) tasks from identifying routine channel maintenance actions to developing comprehensive sustainable FRM measures. Research over the past 50 years has seen considerable advances in estimating flow capacity; however, much of this knowledge has not been transferred into industry practice. This paper introduces the Conveyance and Afflux Estimation System (CES/AES) software, the primary output from two UK Environment Agency Research projects, which aim to bridge this gap between science and practice. The focus is the conveyance element, which provides a means for estimating flow capacity for a range of channel types, flow conditions and vegetation and substrate cover. An overview of the methodology and testing is given, together with a practical example of its use in decision making. The method is applied to 16 river sites from the United Kingdom, New Zealand, Argentina and Ecuador, exhibiting model performance for a wide range of channel and flow conditions. Simulations of depth-averaged velocities at four sites are compared with observations, improving confidence in the underlying methods. The CES/AES toolset is also used in assessing flood risk versus ecological objectives for a small UK river, where vegetation is of significant conservation value but impacts flow capacity.