Study of Ice Jam Events on Missouri River During the Winter Seasons

Abstract

Rivers are hugely affected by river ice processes for a significant portion of the year causing river ice jams in Northern rivers such as the Missouri River in Montana. Ice jamming is an accumulation of ice in a river, stream, or other flooding sources that reduces the cross-sectional area available to carry the flow and increases the water-surface elevation. Several researchers have conducted a variety of river ice studies over the years which resulted in a comprehensive dataset including meteorological, hydrometric, and river ice data. The analyses of these data provide evidence of a highly complex ice regime. This study of ice jam events in the Missouri River is conducted as a part of the project “Studying effects of sub-zero temperatures on the volume of water and discharge in the Missouri River” funded by Northwestern Energy Hydro. The flow analysis using the USGS hydrometric data (discharge, gage height, and water temperature) is carried out from the Holter, MT to Great Falls, MT at the Missouri River which is ~100 river miles. Several ice jam events during the winter from 2014–2022 were analyzed, studying the discharge loss downstream of the ice jam location, gage height increases upstream of the ice jam location, and air temperature during the ice formation event. Flow analysis spreadsheet capable of automatically downloading hydrometric data available at the USGS gage stations from the Holter to Morony Dam is prepared which also downloads the visual crossing website weather data for historical and future periods for Great Falls. This spreadsheet is used to identify a potential ice jamming event from freezing degree hours during any event. The model preparation of HEC-RAS is done for the Missouri River using the Lidar data and USGS data with the bathymetry data provided by Northwestern Energy Hydro. The flow and water temperature simulations are then carried out for Missouri River during the identified ice jam events using the meteorological parameters. The water temperature simulation results show the evidence of ice cover/jam formation as the water temperature stays at 0 oC during the event. Ice jam simulation is carried out in HEC-RAS after knowing the river distance that is covered by ice. The HEC-RAS ice jam simulation model do not consider the meteorological parameters for ice jam simulation and do not consider the dynamic process involved in river ice processes, which is why River1D model is selected for river ice modeling. River1D has the ability to perform thermal ice jam simulation which incorporates the dynamic processes involved in river ice jam formation.