Defining the state-of-the-art cold regions river engineering practice with fluvial morphology concepts

English Abstract:

Cold region river engineers work in an environment that is rarely accurately defined in textbooks. In cold countries, the formation of ice at the drainage system scale can depress the downstream discharge by over 50%, hydro-production peaking can generate a river ice breakup event, frazil ice can block water intakes, about 30% of all flooding events are caused by ice, the development of an ice jam may cause the water level to rise faster than 1 m/min, and ice jam release events can generate flow velocities up to 10 m/s. From freezeup to breakup, multiple river ice processes directly affect sediment transport rates, sediment supply and the overall stability of cold region channels. Because hydraulic conditions can explain the occurrence of specific ice processes, it is logical that a retroactive link exists between such winter processes and the morphology of a channel. This link has been documented in recent years and it is now possible to predict how an ice cover will form along a given channel knowing its morphology and simple climate parameters.

The impact of this research advance on cold regions river engineering is significant. Indeed, understanding the retroactive link between ice processes and the channel morphology fills up a gap in the engineering practice because identifying potential ice cover formation and breakup patterns is the first important step towards (1) the efficient monitoring of river ice processes using field instrumentation, (2) the accurate simulation of river ice processes using numerical ice-hydrodynamic models (in which multiple parameters need to be imposed) and (3) the appropriate design of hydraulic structures (for flood protection, transportation, hydro production, water consumption, ice control, etc.) and floodplain infrastructures (flood resilient constructions, transport systems, etc.). In past decades, the overdesign, failure, low efficiency, or unexpected undesirable effect of hydraulic and floodplain infrastructures due to river ice processes could be excused by a lack of scientific knowledge. In a nearby future, with the advances now documented in this field, cold region river engineers will become liable for their designs and decisions. Fluvial morphology concepts undoubtedly represent an important piece of the state-of-the-art cold regions river engineering puzzle.