Journal of Cold Regions Engineering

River ice is an integral and important component of the flow regime in cold-regions environments. From a hydrologic perspective, it is known to produce many extremes, such as low-flows and floods, that far exceed those possible under open-water conditions. It can also significantly modify a number of other geomorphic and chemical processes that have important biological implications, such as the erosion and deposition of sediment or the production and transport of oxygen. This paper reviews our current state of knowledge in these areas at various stages of ice-cover development, including freeze-up, main winter, and breakup. Included is a comprehensive reference list, the most complete ever assembled on this subject. This manuscript also provides the context for a companion paper that discusses the biological conditions created by river ice.

River ice is an integral and important component of the flow regime in cold-regions environments. As demonstrated in a companion paper, it can significantly affect many of the hydrologic, geomorphic, and chemical characteristics of a river. Building on such a physical template, this paper reviews the related biological effects at all stages of winter ice cover, including the period of autumn cooling, initial freeze-up, main winter, and breakup. Special focus is placed on the role of ice in seasonal movements and avoidance behavior of fish and benthic organisms, the creation of unique in-channel and riparian habitats, the modification of aquatic and floodplain vegetation, and some river-ecology theories, including disturbance ecology and flood-pulse theory. Included is a comprehensive reference list, the most complete ever assembled on this subject.

Presented here are detailed descriptions of ice-jam processes at river-channel confluences. The descriptions are based on observations obtained from a small-scale hydraulic model of variable geometry and on field observations interpreted from published and unpublished accounts of ice jams in the vicinity of confluences. It was found that, in addition to three straightforward jamming processes, several relatively complex processes may lead to ice jams in channel confluences: (1) the merging of ice runs; (2) hydrodynamic pressure from a confluent flow impacting an ice run from the second confluent channel; (3) ice congestion at a confluence bar; and (4) ice grounding on confluence deltaic bars. The presence of a confluence bar, for example, is a significant factor triggering ice jams at the confluence of the Mississippi and Missouri Rivers. Tentative formulations of the three jam processes are proposed. The following three straightforward processes cause ice jams at river confluences: (1) a stationary ice cover exists immediately downstream of a confluence; (2) large ice pieces arch in the confluence; and (3) channel flow below the confluence is sluggish (e.g., the special case of flow entering a reservoir or lake).

A counterrotating flume housed in a cold room was used to study anchor ice growth. The rate of anchor ice growth was monitored and quantified over time using a digital image processing system. The laboratory experiments were conducted over Froude numbers ranging from 0.18 to 0.76 using air temperatures of −15 and −20°C. The data suggest that the rate of anchor ice growth and the density of the resulting anchor ice have a dependence on the Froude number. The rate of anchor ice growth is observed to be a maximum at a Froude number of approximately 0.27. The qualitatively observed density of the anchor ice increases with increasing Froude number. The release of anchor ice is related to the Reynolds number; anchor ice was released for Reynolds number less than approximately 42,000, but remains attached for larger Reynolds numbers.