Impacts of dam removal on riverine ice regime

The impact of dam removal on the ice regime of northern rivers has largely been ignored in the recent push for removal of dams to restore or improve aquatic habitat. However, dam removal may have significant impacts on the ice regime and has resulted in increased frequency and severity of downstream jams. Lowering of water levels in impoundments containing sediment deposits may result in more frequent or longer duration ice-induced scour and erosion of bed and bank material. Ice-related adverse impacts associated with dam removal can be mitigated through ice control measures. This paper presents a brief overview of the evolution of the typical ice regime, followed by a discussion of potential impacts resulting from dam removal. Examples of the impact of dam removal on riverine ice regime are presented, including two case studies in which dam removal has required the later construction of ice control structures. Recommendations are made for supplemental studies, when dam removal is considered in ice-affected rivers.