Quantifying steep channel freezeup processes

•Water levels associated with steep channel freezeup processes vary significantly.•Steep channel cryologic processes greatly affect the channel discharge.•The average buildup rate of an ice dam during freezeup is about 1 cm/h.•The average breaching rate of an ice dam is about 2 cm/h.•A steep channel heat budget model is presented.

Freezeup processes in steep channels are particularly dynamic and generate important water level, water temperature, and discharge variations. This work presents unique field data quantifying steep channel ice processes during the freezeup period. Water temperature variability and ice dam buildup and breaching rates measured in the Montmorency watershed, Quebec, Canada are reported. The conditions leading to the development and melting of ice dams are discussed. The rate at which water is stored in the drainage system at different channel Strahler orders and the consequent freezeup flooding rates and discharge depressions are estimated.A major contribution of this paper is the formulation and application of an original heat budget model designed to specifically address the particularities of steep channel heat fluxes. The modeled net heat flux is compared with measured water temperature and with the timing of ice dam buildup and breaching events for a second order channel.This work can be of interest for cold region hydraulic and transportation engineers who are responsible for the safe design of bridges and culverts, for cold region hydrologists, for hydroelectric producers and for water intake operators in need of evaluating and forecasting low freezeup discharge conditions. Freshwater and riparian zone biologists can also refer to this work to evaluate the conditions that affect the fauna and flora at freezeup and public emergency services can use this work to quantify the risk of freezeup flooding along steep channels.