Abstract
During the breakup of river ice covers, a greater potential for erosion occurs due to rising discharge and moving ice and the highly dynamic waves that form upon ice-jam release. Consequently, suspended-sediment concentrations can increase sharply and peak before the arrival of the peak flow. Large spikes in sediment concentrations occasionally occur during the passage of sharp waves resulting from releases of upstream ice jams and the ensuing ice runs. This is important, as river form and function (both geomorphologic and ecological) depend upon sediment erosion and deposition. Yet, sediment monitoring programs often overlook the higher suspended-sediment concentrations and loads that occur during the breakup period owing to data-collection difficulties in the presence of moving ice and ice jams. In this review paper, we introduce basics of river sediment erosion and transport and of relevant phenomena that occur during the breakup of river ice. Datasets of varying volume and detail on measured and inferred suspended-sediment concentrations during the breakup period on different rivers are reviewed and compared. Possible effects of river characteristics on seasonal sediment supply are discussed, and the implications of increased sediment supply are reviewed based on seasonal comparisons. The paper also reviews the environmental significance of increased sediment supply both on water quality and ecosystem functionality.
Highlights
Ice formation, growth, and breakup affect the flow dynamics of a river or stream and its potential for erosion and transport of sediment [1]
Compared to midwinter periods under a stable ice cover, forces acting to dislodge material from a river bank during the pre-breakup and breakup periods increase, but rising water levels may expose a greater portion of the bank to these forces
This results in increased sediment transport, which can have potential effects on channel morphology, reservoir operations, water quality, aquatic life and habitat, and riparian ecology
Summary
Ice formation, growth, and breakup affect the flow dynamics of a river or stream and its potential for erosion and transport of sediment [1]. The breakup period, characterized by increased water levels and flows, is generally more important with respect to erosion and sediment transport. The effects of breakup ice jams on flow conveyance and direction can increase or lessen flow velocity and tractive force, thereby leading to sediment removal or deposition, with potential localized detrimental effects with respect to the functioning of water intakes and the conservancy of aquatic habitat. Javes (ice-jam-release waves) exemplify the extreme power and erosive capacity of breakup in their heights, rates of water level rise, celerities, and high speeds of associated ice runs [3]. As ice processes on rivers change, e.g., greater occurrence of thermal or midwinter breakups, ice action against channel boundaries may be altered, thereby affecting channel geometry and the supply, transport, and deposition of sediment and resulting in geomorphic and ecosystem changes. The terms “concentration” or “sediment concentration” will refer to the concentration of suspended sediment, unless specified otherwise
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