Rivers under Ice: Evaluating Simulated Morphodynamics through a Riffle-Pool Sequence

Abstract

Modeling in ice-covered rivers is limited due to added computational complexity, specifically challenges with the collection of field calibration data. Using River2D, a 2-dimensional hydrodynamic modeling software, this study simulates depth-averaged velocity and shear stress distributions under ice cover and in open-water conditions during varying flow conditions in a small, shallow riffle-pool sequence. The results demonstrated differences in velocity distribution throughout the channel and increases in discharge were found to impact the velocity magnitude under ice cover, while the spatial distribution remained consistent. A recirculating eddy found along the pool’s left bank was exacerbated under ice cover, with potential implications for silver shiner habitat suitability. Bed shear stress magnitude did not vary significantly between ice and open water, although the spatial distribution differed notably. Model validation demonstrated success in simulating water depth and velocities, and the shear stress was estimated within a reasonable margin. Using hydrodynamic models provides valuable insight into seasonal changes in velocities and shear stress when ice is present.

River ice analyses and roughness calculations using underwater drones and photogrammetric approach

“…In cold climates during winter, rive ice is an important element in different hydrological and fluvial processes of the river (Shen, 2010). Ice cover increases the complexity of for instance fluvial processes compared to openchannel flow (Smith et al, 2023). According to Shen (2010), river ice processes are complex and progress through winter from ice formation to its deterioration and breakup.…”

“…The grown flow resistance can have effect on for example water level, flow velocity, flow pattern, channel conveyance and sediment transport (Sui et al, 2010). For instance, Lotsari et al (2017) and Smith et al (2023) have noted, that the flow velocity pattern and velocity distribution is remarkably altered by ice-cover. Demers et al (2011) In open-channel conditions, the highest flow velocities are typically close to water surface whereas in ice-covered channel the point of highest velocity is lowered closer to the channel bed (Lotsari et al, 2017).…”

“…Concerning river ice, as Sui et al (2010) describe, in cold climates during winter hydrology of rivers is strongly influenced by river ice. Ice cover alters river hydraulics and affects for instance flow patterns and fluvial processes (Smith et al, 2023;Sui et al, 2010). This effect on the other hand is highly depended on the type and characteristics of the ice cover, especially on the roughness of underside of the ice cover also referred as ice-water interface (Sui et al, 2010).…”

“…Nevertheless, generally ice-covered areas have remained largely unexplored due to the challenging conditions and difficult access to them (Spears et al, 2014). Field measurements in ice-covered rivers in winter conditions can be time consuming and difficult, which has also limited modelling approaches due to lack of calibration data (Smith et al, 2023). Additionally, ice cover increases the difficulty related to collecting comprehensive data -for instance Smith et al (2023) have identified the difficulty of acquiring data covering large areas as a challenge regarding field measurements in ice-covered rivers.…”

“…Field measurements in ice-covered rivers in winter conditions can be time consuming and difficult, which has also limited modelling approaches due to lack of calibration data (Smith et al, 2023). Additionally, ice cover increases the difficulty related to collecting comprehensive data -for instance Smith et al (2023) have identified the difficulty of acquiring data covering large areas as a challenge regarding field measurements in ice-covered rivers. Similarly, Lotsari et al (2019) describe that conventional methods for analysing ice-covered conditions, such as point measurements through the ice, can produce only spatially sparse measurements.…”