Using Ice to Flood the Peace–athabasca Delta, Canada

Flooding of deltas on large, northern rivers is usually the result of spring ice-jam events, as opposed to high flows during the open-water season. Some of the most sensitive components of such ecosystems are the perched basins: small ponds and lakes that are hydraulically isolated from the main flow system. The biological structure and productivity of these basins are highly dependent on flooding and flushing associated with high stage events. Major flooding of the Peace–Athabasca Delta, one of the world's largest and most productive deltas, has not occurred since 1974, the time of the last major ice-jam event. Prior to this, the Delta also experienced an extensive drying period, from 1968–1971, as one of its main rivers became regulated. As a result, extensive changes have occurred in the vegetation regime and associated wildlife habitat. Recognizing the historical role of ice-jam flooding, attempts are being made to induce flooding through regulation of the natural flow system using ice. The changing hydroecology of this flood-dependent ecosystem, common approaches related to regulation effects and river ice covers, and the unique strategies used to construct artificial ice dams and/or initiate ice jams, are all reviewed.