The Floods of 1990 and 1996 on Peace River: Fid-Bau Portal

The Floods of 1990 and 1996 on Peace River

Church, Michael / Ayles, Christopher P. / Eaton, Brett C.

Abstract: In June 1990, the flood of record occurred on the regulated Peace River. In the summer of 1996, reservoir drawdown created a flood of comparable magnitude on the upper river, smaller on the lower river, but of greatly prolonged duration. These floods provide an exceptional opportunity to study the effect of flows along a regulated river similar to those experienced under pre‐regulation conditions. The 1990 flood, resulting from an exceptional summer storm, imported a supply of fresh sediment to Peace River from flooding tributaries. Limited change was observed in the British Columbia reach, with aggradation downstream of Pine River. Throughout the Alberta Peace River, where the flood was the largest on record, significant sedimentation occurred in all reaches, but was restricted to the established channel zone. In 1996, the clear water release from the dam changed a significant number of sections in British Columbia from stable or aggrading to degrading for the first time since regulation. In Alberta, modest aggradation occurred in Reach AB1, while Reach AB2, below the Smoky River confluence, degraded. Significant sedimentation occurred in Reach AB3, where chronic sedimentation has occurred since regulation. In these events, the import of sediment from tributaries was a critical factor mediating the response of the river.