Unsteady Ice Jam Processes
COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
Pagination or Media Count:
Ice jams cause flooding in northern temperate climate areas, usually forming rapidly, often with little warning, constricting water flow and elevating water levels. Consequently, jam formation comprises highly unsteady processes drifting ice pieces are brought to rest, accumulated ice shoves and thickens, and initial water depths and velocities change. Those processes are even more unsteady when a jam collapses. Prior simulations of ice jams, however, treat them as simply stationary, uniformly thick accumulations of ice pieces. No account is taken of the impact forces exerted by moving ice, an estimation that is further complicated by the need to couple equations describing water flow and ice movement. Under the dynamic conditions attendant to jam formation, water flow and ice movement interactively influence each other. This report evaluates the importance of ice momentum on ice jam thickness and thickness distribution using experiments conducted with laboratory flumes and a numerical model in which the equations of motion for one dimensional flow of water and ice are solved as fully coupled. In this regard, the model is unique, enabling simulation of the important unsteady interactions of water and ice, and determination of their effects on jam thickness. Ice momentum should be taken into account for most jams because it leads to significantly thicker jams and affects the thickness profile. A useful dimensionless parameter is identified for generalizing this finding.
- Snow, Ice and Permafrost