Remote data collection on ice breakup dynamics: Saint John River case study

摘要

Dynamic processes that occur during the breakup of river ice covers have important socio-economic and ecological impacts, but development of predictive capability is hampered by the brevity of the event and the ever-changing flow and ice conditions. The spatial and temporal variation of river water levels reflects the evolution of breakup processes and may be used to quantify their characteristics. However, various practical difficulties in measuring such variations have contributed to a scarcity of relevant data. A recently developed technique for remote recording of river levels involves pre-breakup deployment of portable pressure loggers, which are retrieved weeks or months later. Logger memory can accommodate high sampling frequencies, sufficient to capture very rapid water level changes. Application of this technique to document a highly dynamic breakup in the Saint John River, New Brunswick, resulted in an extensive data set. The processed logger output is described in detail and shown to furnish important insights on the chronology of breakup events. Analysis of the water level records that were obtained at different locations resulted in quantification of the hydrodynamic properties of waves generated by ice jam releases, also known as "javes". Jave-induced amplification of flow and shear stress decreased with traveled distance, being between 2.5 and 3.0 at a distance of 11 km. Extensive mobilization of the riverbed during the passage of javes in the study reach is likely. Application of a numerical model to the measured WL profile of a major ice jam resulted in default-range calibration coefficients, further corroborating current modeling capability.