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Ice jams in the Grasse River have caused the erosion of capping material designed to prevent the resurfacing of the bed sediment in the polychlorinated biphenyl (PCB)-contaminated area. Two in-stream ice-control structures are proposed to avoid the jam-induced erosion of the capping material. These two ice-control options are a pier-type ice-control structure and a reconstruction of a small hydropower dam upstream of the capping site. A numerical model study using the DynaRICE model is conducted to evaluate the effectiveness of the proposed design. Flow and ice conditions corresponding to the 100-year return period of ice jam events obtained from analyzing historical breakup ice jam data are used in the evaluation. The results showed that these ice-control structures could reduce the ice discharge downstream and the size of the ice jam at the capping site to prevent the erosion and scour of the PCB-contaminated bed. [ABSTRACT FROM AUTHOR]

This study examines the possible effect of the record ice jam of 1984 in the St. Clair River on river bed changes and conveyance. Numerical simulations were made to examine the flow and bed shear stresses during the jam formation and release periods. Simulation results indicate that the ice jam in the river did not cause a significant increase in bed shear stress compared to pre- and post-jam open water conditions. The insignificant change on bed shear stress during the ice jam period is the result of the large flow depth and the limited jam thickness. The bed shear stresses are much less than the critical shear stress for bed particle movement. This implies that the jam may not have had a significant impact on the channel conveyance. Key words: bed erosion, ice jam, mathematical modelling, river ice dynamics, St. Clair River. La presente etude examine les effets possibles des embacles observes en 1984 sur la riviere Sainte-Claire sur les modifications du lit du cours d'eau et sur l'ecoulement de ce dernier. Des simulations numeriques ont ete realisees pour etudier le debit et les contraintes de cisaillement exercees sur le lit de la riviere lors les periodes de formation d'embacles et pendant les debacles de glaces. Ces simulations montrent que les embacles de la riviere n'entrainaient pas d'augmentation significative des contraintes de cisaillement exercees sur le lit du cours d'eau, si l'on compare ces dernieres a celles enregistrees dans la riviere avant et apres la formation des embacles. Les tres faibles variations de contrainte de cisaillement observees dans le lit durant la formation des embacles s'expliquent par la profondeur importante de la riviere et par la faible epaisseur de la glace au niveau des embacles. Les contraintes de cisaillement exercees sur le lit sont bien inferieures aux contraintes de cisaillement limites liees au mouvement des particules du lit. De ce fait, les embacles pourraient ne pas avoir d'impact significatif sur l'ecoulement du cours d'eau. [Traduit par la Redaction] Mots-cles: erosion de lit, embacle, modelisation mathematique, dynamique de la glace de riviere, riviere Sainte-Claire., Introduction The conveyance of the St. Clair River, which connects Lake Huron and Lake St. Clair (Fig. 1), has attracted much attention because of its impacts on upper Great Lakes [...]

Ice processes in general, and ice jams in particular, play a dominant role in the hydrologic regime of Canadian rivers, often causing extreme floods and affecting the life cycle of many aquatic, terrestrial, and avian species. Various numerical models have been developed to help simulate the formation and consequences of these very dynamic and often destructive jam events. To test and compare the performance of existing models, a series of three tests have been devised and coordinated by a task force appointed by the Committee on River Ice Processes and the Environment (CRIPE). The results indicate that the overall performance of the models is good when calibration data are available, but considerably more varied when the models are applied in uncalibrated or 'blind' mode. However, the diversity of results in the blind mode may be attributed more to the variations in perceptions of the physical processes by the users, as compared to the mechanics of the numerical computations. Key words: Calibration, case study, field data, ice jam, model testing, numerical model, river. Les processus de glaces en general, et les embacles en particulier, ont un role predominant dans le regime hydrologique des rivieres canadiennes, causant souvent des inondations extremes et touchant le cycle de vie de plusieurs especes aquatiques, terrestres et aviaires. Plusieurs modeles numeriques ont ete developpes pour aider a simuler la formation et les consequences de ces evenements d'embacle tres dynamiques et souvent destructeurs. Pour verifier et comparer le rendement des modeles existants, une serie de trois essais a ete concue et coordonnee par un groupe de travail assigne par le CRIPE (Committee on River IceProcesses and the Environment). Les resultats indiquent que le rendement general des modeles est bon lorsque les donnees d' etalonnage sont disponibles, mais varie considerablement lorsque les modeles sont appliques en mode << aveugle >> ou non etalonne. Toutefois, la diversite des resultats en mode << aveugle >> peut etre attribuee plus aux variations dans les perceptions des procedes physiques par les utilisateurs, que par la mecanique des calculs numeriques. Mots-cles : etalonnage, etude de cas, donnees de terrain, embacle, essai de modele, modele numerique, riviere. [Traduit par la Redaction], 1. Introduction Ice processes play a dominant role in the hydrologic regime of Canadian rivers and are intimately related to the life cycle of many aquatic, terrestrial, and avian species. [...]