Continuous simulation for design flood estimation—a review

Developments of systems for continuous simulation of streamflow are traced from manual systems in the middle of the 20th century to present day computer-based systems. A profusion of different systems from very simple to very complex are in use. Systems in operational use in UK/Europe, USA, South Africa and Australia are reviewed. There are several different runoff generation processes used in these systems such as saturation overland flow, subsurface stormflow and infiltration excess. These processes demonstrate different approaches to hydrological modelling in different areas. Other differences include the use of processes such as snowmelt and transmission loss that are significant in some areas but not in others. A feature of many modern systems is the use of stochastic rainfall generators that allow for very long streamflow sequences to be generated from which long-term flood statistics can be extracted. Only a few studies have compared continuous simulation with other methods of design flood estimation, and no significant studies have been made comparing different continuous simulation systems. Most of the available systems use recorded streamflow data for calibration and there is little information available for the use of continuous simulation systems on ungauged catchments