RESUMEN
Many small communities across the northern United States are located on small, unregulated rivers that generate impressive breakup ice jams. These rivers generally grow thick ice covers throughout winter. In early spring, rapid increase in discharge from snowmelt and rainfall can suddently break up the ice cover and move it quickly downstream. This ice run may stop abruptly against obstructions such as sharp river bends or solic ice sheets on flatter reaches. The resulting ice jams can block flow so throughly that serious flooding may result within an hour of their formation. This innovative, sloped-block ice-control structure performed well during its first field season. For small rivers with suitable sites, it holds great promise to control breakup ice jams at low cost. Nevertheless, much work remains. Over the next few years, CRREL will assess the structure's performance and its environmental and recreational impacts, determine its range of applicability in terms of river hydraulics and ice conditions, and formulate design guidance for Corps districts to disseminate the technology to interested state and local officials