Ice jam flood forecasting: Hay River, N.W.T.

Abstract

Much of the town of Hay River, N.W.T., is located on the low-lying land of the Hay River delta, and is subject to severe ice jam floods every decade or so. As a first line of defence against these floods, it was proposed that an ice jam flood forecast procedure be developed. The major components of the study included a review of historical flood data, resident interviews, field surveys, and observations of the delta ice regime. It was found that a 1–2 day forecast of discharge in Hay River can be directly determined from discharges measured at a Water Survey of Canada gauging station upstream. From this and from an understanding of the breakup ice regime developed from the study as well as the water level–discharge relations determined for ice jams at three locations in the delta, it was possible to develop a first-generation ice jam flood forecasting procedure that gave a 1–2 day warning of high water at each of the three locations. The procedure was evaluated against the breakup events of 1988 and 1989 with reasonable success. The development and application of this procedure is described in the paper. Key words: rivers, floods, ice jams, forecasting.