Celerities of waves and ice runs from ice jam releases

- Simultaneous observations of water levels and ice conditions over a 52 km river reach
- Observed changes in water waves and ice runs over a longer scale than laboratory tests
- The wave features travelled faster than the ice run features.
- The leading edges of the waves at first travelled close to the dynamic wave celerity.
- The ice runs travelled in front of the peak of the wave for 4 to 8 ice jam lengths.

The release of a river ice jam can lead to rapidly rising water levels and a fast-moving torrent of water and ice that can threaten riverside communities. Two phases are released when an ice jam fails: a water wave and a moving ice accumulation (called an “ice run”). The propagation of the water component of an ice jam release wave is relatively well understood. However, a dearth of simultaneous observations of both the water and ice components of an ice jam release has hampered the development of tools to predict of the effects of these releases. This paper presents a field experiment on the Hay River in the Northwest Territories where both water level and ice condition were observed simultaneously at several locations over a distance of more than ten thousand flow depths. This research shows that the water wave and the ice run travel at different celerities resulting in two distinct, but initially overlapping, features. The celerity of the leading edge of the water wave was found to be higher than the ice components, making the water wave move out in front of the ice after 4 to 8 ice jam lengths of travel.