February 8, 2026
Qizhong (George) Guo
Rutgers University–New Brunswick

Prompted by forecasted warming following prolonged cold conditions and heavy snowfall in early 2026, this brief synthesizes current understanding of river ice breakup, ice jamming, and associated flooding, with emphasis on practical indicators relevant to preparedness and risk awareness. It is informed by early research experience in river ice processes and by ongoing review of developments reported in the literature over the past three decades.

Conceptual Flow of Breakup Ice-Jam Flooding

Conceptual flow of river ice breakup, ice transport, ice jamming, and flooding

Prolonged cold conditions lead to the formation of a continuous river ice cover. Forecasted warming, together with snowmelt and occasional rainfall, can generate rapid increases in runoff and river discharge that trigger ice cover breakup, followed by ice transport, jamming at vulnerable locations, and rapid backwater rise and flooding.

A Brief Reflection on 30 Years of Progress

Extended cold spells since the end of January, followed by warming—such as the warm spell forecast for mid-February 2026—often raise concerns about river ice breakup, ice jams, and potential flooding. Although the warming has not yet arrived, this forecasted transition provides a timely opportunity to reflect on what we know about breakup ice jams and what tools are available to support advance preparedness.

Early Research: Seeing the Whole Process

My research in the early 1990s focused on a basic but unresolved question at the time: how do ice cover breakup, ice movement, ice jamming, and eventual release fit together as a single physical process?

In work published in 1993–1994, I proposed a unified, process-based view in which breakup is not an isolated event, but the first step in a sequence that may—or may not—lead to jamming and flooding.

A key finding from that early work was that, despite the apparent complexity of ice-covered rivers, a small number of physical factors exert dominant control. In particular, the mechanical competence of the ice cover and the ability of broken ice to stall or submerge largely determine whether breakup escalates into a hazardous ice jam.

Progress Since Then

Over the past 30 years, research by many groups has significantly improved our understanding of river ice processes. Subsequent studies refined mechanical criteria for the onset of ice cover breakup, demonstrating that breakup is often triggered by short-term increases in river stage or discharge, rather than by high flow alone. Ice thickness has emerged as a practical indicator that integrates longer-term thermal weakening.

At the same time, numerical modeling has advanced substantially. System-scale models now allow engineers and agencies to simulate ice transport, ice jam formation, and resulting flood levels with much greater confidence. These tools are particularly valuable for floodplain mapping, scenario analysis, and emergency planning, once ice is in motion.

More recently, forecasting and nowcasting approaches have begun to bridge the gap between physics and operations by combining hydrologic forecasts with simple, physically meaningful indicators—such as changes in discharge over several days and observed ice thickness—to assess breakup and ice-jam potential in near real time.

Where Challenges Remain

Despite this progress, predicting when breakup will occur and whether it will lead to dangerous ice jams remains challenging. Many operational models still require the timing and location of breakup to be specified externally, rather than predicted directly from physical conditions.

The central challenge today is integration: linking breakup physics, ice dynamics, and flood modeling into practical, operational tools that support early warning and preparedness, even when uncertainty remains.

What to Watch Over the Next Two Weeks

As cold conditions persist and warming is forecast, the following factors are especially important in assessing the risk of river ice breakup and ice-jam flooding:

  • Rapid warming trends
    Several consecutive days with above-freezing air temperatures can weaken ice cover and accelerate snowmelt.

  • Rain-on-snow events
    Rain falling on an existing snowpack can sharply increase runoff and river discharge.

  • Sudden increases in river stage or flow
    Ice breakup is often triggered by changes in discharge over a short period, not by peak flow alone.

  • Ice cover thickness and continuity
    Thicker, more continuous ice covers are more likely to produce ice jams once breakup begins.

  • Upstream ice movement
    Reports or images of broken ice moving downstream can signal elevated jamming risk farther downstream.

  • Known jam-prone locations
    River bends, channel constrictions, bridges, shallow reaches, and transitions from non-tidal to tidal flow deserve closer attention, as these locations commonly experience flow deceleration and backwater effects that favor ice jamming.

  • Local advisories and observations
    Information from weather forecasts, river gauges, satellite imagery, and local agencies can provide early warning.

Monitoring these conditions together supports informed readiness, even when exact timing and severity remain uncertain.

Key References (Selected)

  • Guo, Q., and Song, C. C. S. (1993).
    A semi-discrete element approach to the river ice breakup and jamming process.
    Proceedings of the National Conference on Hydraulic Engineering, ASCE, San Francisco, CA, pp. 65–69. ResearchGate

  • Guo, Q., and Song, C. C. S. (1994).
    A numerical model for the entire river ice breakup and jamming process.
    Proceedings of the River Ice Seminar, National Weather Service, Minneapolis, MN, pp. 233–243. ResearchGate

  • Guo, Q. (2002).
    Applicability of criterion for onset of river ice breakup.
    Journal of Hydraulic Engineering, ASCE, 128(11), 1023–1026. Link

  • Wang, J., He, G., and Chen, X. (2013).
    Mechanical breakup of river ice cover considering fluid–solid coupling.
    Journal of Hydrodynamics, 25(2), 193–202. Link

  • Lindenschmidt, K.-E. (2017).
    RIVICE—A non-proprietary, open-source, one-dimensional river-ice model.
    Water, 9(5), 314. Link

  • Shen, H. T., and Huang, J. (2025).
    Nowcasting mechanical breakup ice jams based on hydrologic change and ice thickness.
    Hydrology, 12(3), 324. Link

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