ANALYSIS OF FRAZIL ICE AS A GEOMORPHIC AGENT IN A FRAZIL POOL

Frazil ice forms in open water areas of high turbulent intensity and accumulates downstream along flatter river segments. The activation of production zones, in relation to hydro-climatic parameters, directly affects the infilling of frazil sinks. Past field investigations have described strong relationships between riverbed scour and undercover frazil accumulation but few have documented the dynamics of bed deformation in relation to the accumulation of frazil ice over an entire winter season. Here, we present the chronology of the development of a hanging dam at a pool section over the 2007-2008 ice period. The characteristics of upstream frazil ice production and ice cover growth is documented using a river corridor approach. At a pool section, undercover frazil ice accumulation behaviour, water level variations, hydro-climatic conditions and riverbed deformations are also documented. Innovative dynamic bed-rods integrating three-axis accelerometer pendant loggers were deployed at the bed to obtain a dynamic measurement of erosional and depositional activity over the frazil pool. Data shows a relation between bedform deformation and ice cover formation. Analysis reveals the spatio-temporal variation of physical attributes of ice cover, undercover frazil accumulation and bedforms. Collected data is used to analyse the relationship between riverbed deformation and overlying ice forms. Copyright (C) 2011 John Wiley & Sons, Ltd.