Author(s): Gun Zachrisson
Linked Author(s):
Keywords: No Keywords
Abstract: The river Tornealven, the unregulated border river between Finland and Sweden, has been subject to several disastrous ice break-ups in the past. The latest ones took place in three consecutive years: 1984,1985, and 1986. In a joint Finnish-Swedish three-year project studies have been performed aiming at finding measures to mitigate the damages from ice jams and flooding during severe ice break-ups. The work within the project was carried out along three lines: 1. Development of a forecasting and warning system based on a conceptual hydrologic runoff model, and including statistical models of date and character of break-up. 2. Compilation and valuation of possible technical measures to influence the break-up process in a positive direction or protect buildings and other objects. 3. Preparation of flood risk maps for the two towns near the river mouth, and a key map showing flood prone reaches along the river. The flood risk maps are based on water level computations with the HEC2-model. Both ice free and ice jam situations are simulated, the latter using the model version including an ice cover. The complete forecasting system was tested 1989 with satisfactory results. In 1990, however, a large, unexpected ice jam was formed in the river mouth, causing flooding during some hours. This incident has emphasized the need for local technical measures, e g weakening of the ice in the river mouth, and improvements in the forecasting methods.
Year: 1990