Journal of Cold Regions Engineering

An ice-control structure (ICS) for Cazenovia Creek in West Seneca, N.Y., will arrest a breakup ice run and hold the resulting ice jam throughout typical breakup events. While this will reduce downstream flood damages, water levels upstream will be higher than under existing conditions, and upstream property owners must be compensated. We used HEC-RAS to model ice-jam hydraulics upstream of the ICS. Because the extent of the jam dictates the extent of high water, estimating ice-jam volume plays a key role in the modeling. The initial volume was the estimated prebreakup ice supply, less 30% transport losses. At each discharge, we reduced the available ice volume to account for melting by water entering the jam at 0.7°C and washouts through the ICS at a rate of 1% of discharge. These losses significantly reduce the ice-jam length, and thus the extent of high water, as discharge increases. The maximum ice-jam water levels at each discharge form an “elevation envelope” to determine the effect of the ICS on upstream property owners. To our knowledge, these are the first analyses to account for the effects of melting and washout losses on predicted ice-jam water levels.

Ice jam release surges present a unique challenge to the flood forecaster, since the surge released when an ice jam fails is highly dynamic in nature and, therefore, traditional hydrologic flood routing techniques are inapplicable. The problem is analogous to the classic dam break scenario and should be amenable to analysis by hydraulic flood routing techniques. However, previous investigations suggest that the influence of ice on the wave propagation and attenuation must also be considered to achieve accurate results. This study explores the applicability of dynamic hydraulic flow modeling techniques to the ice jam surge propagation problem, presenting the results of numerical simulations of the ice jam release event which occurred on the Saint John River upstream of Grand Falls, N.B., in April 1993. The surge propagation analysis was conducted using a one-dimensional finite element implementation of the Saint Venant equations adapted for natural channel geometries. Even neglecting ice effects, the resulting model is successful in terms of reproducing the observed peak stage and the surge propagation speed. Based on these results, it is concluded that accurate channel geometry is a key factor in effectively modeling ice jam release surge events.

In seeking to promote cycling in wintertime, it is desirable to understand how important the winter maintenance service level is in people’s decision to cycle or not, and methods to compare different road conditions on cycleways are therefore needed. By measuring friction, an assessment of the service level can be achieved, but methods available often involve the use of large vehicles, which can lead to overloading damage on cycleways, and constitute a safety risk for cyclists and pedestrians. A portable friction tester (PFT), originally designed to measure friction on road markings, was thought to be an appropriate instrument for cycleways and was, therefore, tested on different winter road conditions, and on different cycleway pavement materials. In this study, it was found that the PFT is a valuable tool for measuring friction on cycleways. Different winter road conditions, as well as different pavement materials, can be distinguished from each other through PFT measurements. The PFT provides a good complement to visual inspections of cycleways in winter maintenance evaluation and can, for example, be used to determine if desired service levels have been achieved.