Effects of River-Ice Breakup on Sediment Transport and Implications to Stream Environments: A Review

During the breakup of river ice covers, a greater potential for erosion occurs due to rising discharge and moving ice and the highly dynamic waves that form upon ice-jam release. Consequently, suspended-sediment concentrations can increase sharply and peak before the arrival of the peak flow. Large spikes in sediment concentrations occasionally occur during the passage of sharp waves resulting from releases of upstream ice jams and the ensuing ice runs. This is important, as river form and function (both geomorphologic and ecological) depend upon sediment erosion and deposition. Yet, sediment monitoring programs often overlook the higher suspended-sediment concentrations and loads that occur during the breakup period owing to data-collection difficulties in the presence of moving ice and ice jams. In this review paper, we introduce basics of river sediment erosion and transport and of relevant phenomena that occur during the breakup of river ice. Datasets of varying volume and detail on measured and inferred suspended-sediment concentrations during the breakup period on different rivers are reviewed and compared. Possible effects of river characteristics on seasonal sediment supply are discussed, and the implications of increased sediment supply are reviewed based on seasonal comparisons. The paper also reviews the environmental significance of increased sediment supply both on water quality and ecosystem functionality.

Convolutional Neural Network and Long Short-Term Memory Models for Ice-Jam Prediction

In cold regions, ice-jam events result in severe flooding due to a rapid rise in water levels upstream of the jam. These floods threaten human safety and damage properties and infrastructures as the floods resulting from ice-jams are sudden. Hence, the ice-jam prediction tools can give an early warning to increase response time and minimize the possible corresponding damages. However, the ice-jam prediction has always been a challenging problem as there is no analytical method available for this purpose. Nonetheless, ice jams form when some hydro-meteorological conditions happen, a few hours to a few days before the event. The ice-jam prediction problem can be considered as a binary multivariate time-series classification. Deep learning techniques have been successfully applied for time-series classification in many fields such as finance, engineering, weather forecasting, and medicine. In this research, we successfully applied CNN, LSTM, and combined CN-LSTM networks for ice-jam prediction for all the rivers in Quebec. The results show that the CN-LSTM model yields the best results in the validation and generalization with F1 scores of 0.82 and 0.91, respectively. This demonstrates that CNN and LSTM models are complementary, and a combination of them further improves classification.

Freeze-Up Ice Jam Formation in the River Bend, a Case Study on the Inner Mongolia Reach of Yellow River

Concern has been expressed regarding the impacts of climate change on river ice and ice jam formation in cold regions. Ice jams are easily initiated in bends and narrow channels and cause disasters. In this study, observations and remote sensing monitoring are used to study the freeze-up ice jam formation of bends. Sediment transport and freezing process of the river interact, influencing bed changes profile and sedimentary budget. River ice processes, channel evolution, ice hydro-thermodynamics, and ice jam accumulation are explored. The results show that the channel topography determines the river thalweg, and that the channel elevation interacts with the river ice through sediment transport. The channel shrinkage increases the probability of ice jam, and the sharp bend is prone to ice jam formation. Under the effect of secondary circulation flow in the bend and in the outer bank, the juxtaposed freeze-up and the hummocky ice cover occur in the same location, and frazil ice accumulates under the junction of the main channel and the shoals. Affected by the increase of the hydraulic slope and the velocity downstream, open water reaches develops downstream of the ice accumulation. An open water section is emerged upstream of the bend, due to the ice deposition, and partly cut-off supply of the frazil.

Modelling climatic impacts on ice-jam floods: a review of current models, modelling capabilities, challenges, and future prospects.

River ice is an important hydraulic and hydrological component of many rivers in the high northern latitudes of the world. It controls the hydraulic characteristics of streamflow, affects the geomorphology of channels, and can cause flooding due to ice-jam formation during ice-cover freeze-up and breakup periods. In recent decades, climate change has considerably altered ice regimes, affecting the severity of ice-jam flooding. Although many approaches have been developed to model river ice regimes and the severity of ice jam flooding, appropriate methods that account for impacts of the future climate on ice-jam flooding have not been well established. Therefore, the main goals of this study are to review the current knowledge of climate change impacts on river ice processes and to assess the current modelling capabilities to determine the severity of ice jams under future climatic conditions. Finally, a conceptual river ice-jam modelling approach is presented for incorporating climate change impacts on ice jams.

Impact of the spaciotemporal variability of the snowpack conditions on internal liquid water fluxes

<p>In cold regions, the seasonal snowpack plays an important hydrological role. By storing and releasing solid precipitation, the snowpack gives shape to the yearly hygrogram. In addition, by modulating liquid water pathway and residence time, snowpack internal conditions have a strong implication on the partitioning of meltwater among streamflow, groundwater recharge and soil moisture storage. During rain on snow (ROS) events, snowpack conditions influence timing and amount of liquid water inflow to the surface drainage system, with winter floods and ice jams as potential consequences.</p><p>Recent observations and projections show an increase in ROS frequency in many cold regions of the world. This trend raises concern about a possible increase in winter floods and ice jams events with climate change. In order to better anticipate the hydrological consequences of the increasing ROS phenomenon, a good understanding of the processes and conditions influencing liquid water release from the snowpack is required. </p><p>The present study articulates around a multimethod approach to characterize liquid water storage and movement in a snowpack in a non-mountainous environment. By combining drone-based high frequency GPR, NIR photogrammetry, time domain reflectometry, stable isotopes of water and other manual measurements throughout a winter season, we aim monitoring the spatiotemporal evolution of the snowpack liquid water content as well as the water fluxes at the snowpack margins.</p><p>Preliminary results show that, combining the selected methods allows tracking liquid water storage and movements in the snowpack throughout an entire season.</p>

Floods in Siberia: geographical and statistical analysis for the period of climate change

In Siberia, floods are one of dangerous natural disaster. The danger of floods varies under the climatic and anthropogenic changes, as well as socio-economic development. The aim was to study the current position of problems associated with flood hazard. A key to understanding the flood situation is geographical and statistical analysis of the floods for the period of climate change (1985-2019). Such analyzes addresses the following aspects: study of flood genesis and recurrence, the severity of the impact for floods of different genesis; maxima runoff analysis as the principal cause of floods; analysis of the spatial distribution of settlements vulnerable to flooding; analysis of the ice jams and ice dams as a specific natural factor causing the floods in Siberia; assessment of the degree of danger, and identification of areas with the different integral flood danger. In Siberia, more than 1400 settlements are flooded at regular intervals. Most of them are concentrated in the southern, most developed territories in the Ob, Tom and Yeniseiy basins. In Siberia, rainfall, mixed (from snow melting with rainfall) and ice-dam floods are the most dangerous. They have the highest recurrence and severity of the impact. The greatest floods risk is in the most populated and economically developed southern regions within the Ob, Lena and Yenisey rivers and Lake Baikal basins. Territories with the highest risk of floods were determined. For the Baikal region, one of the most developed territories of Siberia, the flood hazard was determined for all administrative districts. Flood hazard maps for Siberian regions can be the basis for developing the flood adaptation strategies.

To issue of gorges and ice jams in the Kuban river basin

Purpose: analysis of quantitative indicators of actual сongestion and ice jams in the Kuban river basin with subsequent intra-basin zoning of the parameters studied. Materials and Methods: data from hydrometeorological observations of ice phenomena were used. The summary calculation of the quantitative indicators of gorges and ice jams along the river Kuban, as well as for each basin of tributaries of the first order was carried out. Results: as a result of the analysis, it was found that the cases of maximum ice jams above the “0” graph in the river Kuban basin were observed more often than the maximum gorge rises. On the river Kuban the number of jams was 90, gorges – 64; in the river Belaya basin number of jamming phenomena was 96, gorges – 9; in the river Laba basin – 43 ice jams and 18 gorges; on the river Pshish the number of jams – 31, gorges – 6; in the river basin Urup the number of jams is 10, and the number of gorges is 20; the river Bolshoi Zelenchuk basin has 25 jams, and 5 gorges. The maximum rise in the water level during jams was 248 cm on the river Pshish at the Bzhedukhovskaya gauging station. The highest water level during gorge events was also recorded on the river Pshish in the aul Teuchezhkhabl and amounted to 386 cm. Most of the recorded cases of water level rise in the presence of gorge phenomena occur at the end of December and the second decade of February. There are no observational series of gorge events at most gauging stations, but, according to available data, most gorge events occur at the end of January and the second decade of February. Conclusions: gorges and ice jams are very dangerous natural phenomena and therefore require promptness and accuracy of forecasting. The solution of such problems is impossible without a network of hydrological posts and observation points, which is currently underdeveloped. Therefore, thickening and improving the existing observational network is one of the main solutions to this issue.

Hydrometeorological Characteristics of Ice Jams on the Pemigewasset River in Central New Hampshire

Ice jams that occurred on the Pemigewasset River in central New Hampshire resulted in significant localized flooding on 26 February 2017 and 13 January 2018. Analyses of these two case studies shows that both ice jam events occurred in association with enhanced moisture transport characteristic of atmospheric rivers (ARs) that resulted in rain-on-snow, snowpack ablation, and rapid increases in streamflow across central New Hampshire. However, while the ice jams and ARs that preceded them were similar, the antecedent hydrometeorological characteristics of the region were different. The February 2017 event featured a “long melting period with low precipitation” scenario, with several days of warm (~5°–20°C) maximum surface temperatures that resulted in extensive snowmelt followed by short-duration, weak AR that produced ~10–15 mm of precipitation during a 6-h period prior to the formation of the ice jam. Alternatively, the January 2018 event featured a “short melting period with high precipitation” scenario with snowmelt that occurred primarily during a more intense and long-duration AR that produced >50 mm of rainfall during a 30-h period prior to the formation of the ice jam. Composite analysis of 20 ice jam events during 1981–2019 illustrates that 19 of 20 events were preceded by environments characterized by ARs along the U.S. East Coast and occur in association with a composite corridor of enhanced integrated water vapor > 25 mm collocated with integrated water vapor transport magnitudes > 600 kg m−1 s−1. Additional analyses suggest that most ice jams on the Pemigewasset River share many common synoptic-scale antecedent meteorological characteristics that may provide situational awareness for future events.