Does a flood mitigation “dry dam” require an environmental assessment?

This question was raised at the Oldman Watershed Council Annual General Meeting. The “dry dam” proposed for the Elbow River is no small deal. It could be the same type of towering concrete wall that contains permanent reservoirs except that it would usually sit empty. If it is allowed to remain full for long enough to reduce flooding downstream then it might kill the underlying vegetation. The photo of a mountain valley turned into a dustbowl by a similar project elsewhere was one of the more striking images at the meeting.

To figure out whether an environmental impact assessment (EIA) is required you need to find out the height of the dam and how much water it would hold.  A provincial assessment is required for a dam greater than 15 metres in height when measured to the top of the dam “from the natural bed of the watercourse at the downstream toe of the dam.” If the dam isn’t across a watercourse then the measurement is from “the lowest elevation at the outside of the dam.” A provincial assessment is also required for a water reservoir with a capacity over 30 million cubic metres no matter how high the dam is.

Read “Does a flood mitigation ‘dry dam’ require an environmental assessment?” on the ELC blog.

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