Onset of river ice breakup

Abstract

Predicting whether and where the ice cover of a river is going to break up as a result of increased runoff, is crucial in such concerns as environmental impact assessment of climatic and hydrologic changes, emergency flood warning and mitigation, and winter hydro-power production. The available predictive methods are generally empirical and site-specific. Their utility is limited by the need for local records, and the uncertainty introduced by changes in factors not explicitly accounted for in an empirical correlation. As a first step toward development of more general, transferable, breakup forecasting criteria, five data sets are used to test existing theoretical concepts of how breakup is initiated. One of these concepts results in acceptable consistency among the different sites, and shows promise for further testing. It involves such variables as water surface width, channel curvature, freeze-up stage, and ice competence. In addition to forecasting applications at a particular site, this method has the potential for application over entire reaches to address such problems as where ice jams form, when they release, and the magnitude of the ice clearing discharge.