Estimation of composite hydraulic resistance in ice‐covered alluvial streams

Abstract

Formation, propagation, and recession of ice cover introduce a dynamic boundary layer to the top of rivers during northern winters. Ice cover affects water velocity magnitude and distribution, water level and consequently conveyance capacity of the river. In this research, total resistance, i.e., ''composite resistance,'' is studied for a 4 month period including stable ice cover, breakup, and open water stages in Lower Nelson River (LNR), northern Manitoba, Canada. Flow and ice characteristics such as water velocity and depth and ice thickness and condition were measured continuously using acoustic techniques. An Acoustic Doppler Current Profiler (ADCP) and Shallow Water Ice Profiling Sonar (SWIPS) were installed simultaneously on a bottom mount and deployed for this purpose. Total resistance to the flow and boundary roughness are estimated using measured bulk hydraulic parameters. A novel method is developed to calculate composite resistance directly from measured under ice velocity profiles. The results of this method are compared to the measured total resistance and to the calculated composite resistance using formulae available in literature. The new technique is demonstrated to compare favorably to measured total resistance and to outperform previously available methods.1. Appropriate water releases from upstream water reservoirs or dams according to the water demands for hydropower generation, and urban, industrial, and agricultural water consumption. 2. Hydraulic measurement issues due to disturbance of stage-discharge relations caused by complete or partial ice coverage of control reach, and 3. Early mechanical breakup due to rapid water staging in ice-covered channels, which can lead to ice jam formation and release which increases the chance of severe flooding. Key Points: Study of hydraulic resistance of river boundaries during ice cover period Evaluation of available methods for composite roughness calculation Introduction of a new approach for composite roughness estimation PUBLICATIONSAmong the important factors that determine a channel's conveyance capacity, hydraulic resistance of a covered reach is a factor that varies directly according to the condition of the ice cover.

Turbulence Structure and Momentum Exchange in Compound Channel Flows With Shore Ice Covered on the Floodplains

“…Thus, the ice-covered floodplain region will have a relatively great boundary resistance. Meanwhile, the study of Zare et al (2016) showed that the ratio n i /n b could be up to 4.0, which demonstrates the ratio n i /n b = 1.17 presented in this study is rational. Besides, it should be noted that the water flow in the experiments does not belong to the shallow flow (D r < 0.33) according to the classification of Nezu et al (1999).…”

“…Ice cover can have a significant impact on society and the economy. For example, the thawing of the ice cover during the spring season may result in a downstream flood, while the floating ice poses threats to hydroelectric equipment, navigation, and municipal drinking water intakes (Morse & Hicks, 2005;Zare et al, 2016). Due to its practical importance, river ice cover has attracted considerable interest from researchers in the past several decades.…”

Analytical Models of Velocity, Reynolds Stress and Turbulence Intensity in Ice-Covered Channels

“…In this study, we define that the inner region inside the lower bed layer starts from the channel bed (z = 0) to 0.2H, and the inner region inside the upper ice layer is from 0.8H to the ice cover (H). Therefore, we used the following logarithmic law to describe the velocity profile in the two inner regions [36]…”

Comment on “Estimation of composite hydraulic resistance in ice‐covered alluvial streams” by Ghareh Aghaji Zare et al.

“…This expectation can be quantified using equation (14) of the authors [Zare et al, 2016a], which derives from application of the velocity defect law to each flow layer (u * denotes shear velocity):…”

“…Throughout the text, the subscripts i, b, and c will be used to denote properties associated with the ice layer, the bed layer, and the composite flow, respectively. Mention of references, figures, and equations will refer to the above noted article [Zare et al 2016a] unless otherwise specified; new references are appended herewith. To avoid confusion, equation numbers in the present text will be preceded by the writer's initials (SB).…”