The presence of ice cover on rivers causes the change in the overall resistance to the flow. The additional boundary formed by the undersurface of the ice cover can be very smooth or extremely rough, and the measurement of the size and distribution of the roughness at the undersurface is normally impossible. This paper presents an improved method for determining roughness coefficient of the underside of ice cover based upon the direct measurement of velocity distribution in the flow under ice cover. It is assumed that velocity distribution has logarithmic character in the regions near the channel bottom and ice cover. The results of the present analysis have indicated that measured velocity profiles can be used to evaluate resistance coefficients of ice-covered channels with more reliable accuracy. The presence of ice cover on rivers causes the change in the overall resistance to the flow. The additional boundary formed by the undersurface of the ice cover can be very smooth or extremely rough, and the measurement of the size and distribution of the roughness at the This paper presents an improved method for determining roughness coefficient of the underside of ice cover based upon the direct measurement of velocity distribution in the flow under ice cover. It is assumed that velocity distribution has logarithmic character in the regions near the channel bottom and ice cover. The results of the present analysis have indicated that measured velocity profiles can be used to evaluate resistance coefficients of ice-covered channels with more reliable accuracy.