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Major ice jams that occasionally form in lower Peace River generate extensive flooding, which helps replenish the perched basins of Peace-Athabasca Delta, a Ramsar wetland of international importance and a UNESCO World Heritage Site. This complex and dynamic ecosystem has experienced prolonged dry periods since the late 1960s, coincident with the construction of the W.A.C. Bennett hydroelectric dam in British Columbia. Physically-based and paleolimnological studies differ with respect to the impact of regulation on flood frequency. This issue is examined herein, based entirely on the historical record of observed ice-jam flood events. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Presents a case study of midwinter ice jams on the upper Saint John River in Canada. Background on the environmental effects of ice breakup and jamming; Analysis of several ice breakup and jamming events in the area during the 1990s; Results and implications for planning flood control measures.

The article discusses several inconsistencies in the treatment of the angle of internal friction in the modelling of dynamic ice-jam processes. It highlights the laboratory test conducted by researchers G. W. Timco and A. M. Cornett to eliminate uncertainties and errors arising from limitations of the study "Ice and sedimentation processes in the Saint John River, Canada." It is concluded that the findings concerning the spatial variability of the angle of internal friction is tenuous.