Anchor ice effects on river hydraulics

Abstract

Anchor ice can cause significant water level and discharge fluctuations in rivers. This study presents an analysis of anchor ice effects on water level and discharge in the Peace River. Field data collected in two winters from the Peace River are analyzed using a river ice model that include the anchor ice process and effects. The anchor processes considered include the bed elevation change due to anchor ice, the change in discharge due to the mass flux of anchor ice growth and release, and the change in ice-bed roughness due to anchor ice growth and release. The analysis showed that the dominating contributing factor to the water level and discharge fluctuations, i.e. anchor ice waves, by anchor ice is the changing ice-bed roughness. This suggests the need for further studies on developing a formulation on ice-bed roughness. The field data also showed that the anchor ice waves occurred over a longer period towards downstream as the water temperature decreases towards downstream during the freezing period, and the anchor ice wave decays while travelling downstream due to the energy loss, but enhanced by anchor ice waves generated along the way.