Addressing Chronic Flooding in a Dynamic River System with Freshwater Bivalve Species: Mussel over Muscle

The Lower Ausable River discharges into Lake Huron near the hamlet of Port Franks south of Grand Bend, Ontario. Port Franks has a long history of ice-related flooding problems. The Ausable Bayfield Conservation Authority (ABCA) has conducted several hydraulic studies of the Lower Ausable River in the past to identify critical ice jam formation areas and recommend measures to minimize flooding hazards to properties along the river.

The ABCA has recently undertaken an update of these studies, covering a 9.2 km (5.7 mi) reach that was originally channelized for drainage purposes over 130 years ago. The objective of the study was to identify river sections most susceptible to the formation of ice jams through hydraulic modeling, and to recommend a set of mitigative measures that address the resultant flooding. Key project challenges have included the economy of data collection methodologies (e.g. the use of digital bathymetric soundings and land terrain models, augmented with new GPS survey) as well as addressing new environmental permitting requirements.

This presentation presents a summary of the ice management study procedures and findings, including a summary of the theory of ice jam formation, hydraulic modeling methodologies, the identification and prioritization of susceptible ice jam locations, and an overview of mitigative measures (i.e. structural and operational controls) to minimize ice jam potential. A key highlight of this presentation is a practical guide to addressing new environmental permitting challenges that are affecting many water resources projects throughout Ontario; namely, new government protocols related to sampling procedures and potential relocation plans with respect to native bivalve populations (i.e. mussels).