Ice Jam Formation Processes

Abstract

The various causes, the physical mechanisms involved, and the complex geometries that are important to ice jam formation processes means that ice jams are complex phenomena. The importance of river geometry also means that they are site specific, and variations between ice jam locations will be significant. In this report, approximate parametric relationships are developed to predict the formation of two common ice jam types using the most important physical parameters: river flow velocity, ice thickness, ice roughness, and river width, depth, and curvature. The parametric relationships are developed from an analysis of the important physics of these processes, and are used to roughly determine if an ice jam will form under a given set of conditions. In developing these theories, several descriptive terms are introduced to help clarify discussion. Then the processes responsible for causing a breakup ice jam to thicken are investigated. Thickened ice jams are divided into two general categories, based on their primary formation mechanism: ice block submergence and ice cover collapse. A new method for calculating submergence velocity based upon experimental data of pressure coefficients for flow around a block is presented and tested. In addition, using a 2-dimensional mathematical disk model and physical reasoning, a stability coefficient is developed to estimate the conditions necessary for the collapse of a fragmented ice cover. Finally, the newly developed parametric relationships are tested against six case study ice jams. Considering the approximations inherent in developing these relations, the results of the applications are surprisingly good.