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Timely release of flow from upstream hydropower generation facilities on the Peace River can enhance potential ice-jam flooding near the drying Peace–Athabasca Delta (PAD), a Ramsar wetland of international importance and homeland to Indigenous Peoples. An important consideration in deciding whether and when to commence a release is the celerity of the breakup front as it advances along the Peace River. Relevant historical data for a key stretch of the river are analyzed to determine average celerities, which can vary by an order of magnitude from year to year. Seven breakup events are identified that might have been candidates for a release, and the predictability of associated celerities is explored in terms of antecedent hydroclimatic variables, including cumulative winter snowfall, snow water equivalent on 1 April, ice cover thickness, coldness of the winter, and freezeup level. It is shown that celerity can be predicted to within a factor of two or less, with the freezeup level giving the best results. Three of the seven "promising" events culminated in PAD floods and were associated with the three highest celerities. The empirical findings are shown to generally align with physical understanding of breakup driving and resisting factors. [ABSTRACT FROM AUTHOR]

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]

Abstract: Since the late 1960s, a paucity of ice-jam flooding in the lower Peace River has resulted in prolonged dry periods and considerable reduction in the area covered by lakes and ponds that provide habitat for aquatic life in the Peace–Athabasca Delta region. To help identify the causes of this trend and assess future conditions under a changing climate, a field observation program was conducted during 1999–2003. Limited data were also obtained during a significant event in 2007. This program has furnished the first detailed documentation of ice processes in the lower Peace. Though focusing on the breakup period, relevant antecedent conditions were also documented. Freezeup often involves formation of thickened ice covers, which lead to high freezeup stages and potentially to enhanced growth of the solid-ice layer during the winter. Ice decay prior to breakup can be moderate to severe, and is manifested in saturation and candling. The type of observed breakup ranged from essential melt-out in 2000, to occasional jamming upstream of the delta reach in 2003, and to a moderate delta flood in 2007. The field observations and measurements, including the only ice jam profile that has been measured in the lower Peace, are shown to be consistent with current physical understanding of breakup and jamming processes. The main factors conducive to ice-jam flooding are identified and their relative importance is assessed using physically-based breakup criteria. Breakup patterns are shown to be strongly influenced by the very low slope of the river, which amplifies the importance of waves generated by ice jam releases. [Copyright &y& Elsevier]

This article discusses the mechanisms that lead to breakup of the ice cover and jamming within the delta reach of Peace River-Athabasca Delta region in Canada. According to the authors, the extremely flat lower Peace River does not generally allow long period waves caused by spring snowmelt to dislodge the winter ice cover. However, major ice jams do occur on occasion form in the middle section of the river and move to the delta via repeated stalls and releases. The releases cause steep waves which amplify the hydrodynamic forces acting on the ice cover and cause it to become dislodged.