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Elevated levels: analysis of economic impact of Kootenay Lake flooding studied

BGC Engineering provided the RDCK with an analysis of economic losses that may result from elevated lake levels in Kootenay Lake — Creative Commons

A small amount of residential properties distributed around Kootenay Lake are expected to suffer the highest proportion of economic losses if the lake were to flood, a study commissioned by the regional district found.

According to the BGC Engineering study — Kootenay Lake Flood Impact Analysis — a disproportionate amount of the losses due to flooding would be concentrated in a small number of properties distributed around the lake.

“Developments along alluvial fans that encroach the lake are expected to experience the highest concentration of losses, including areas such as Balfour, Proctor, Long Beach and Harrop,” noted the BGC report, delivered to the Regional District of Central Kootenay board of directors on Feb. 16.

The purpose of the study was to broaden the understanding of potential lake geohazard impacts to begin to formulate things to prevent (or reduce) economic loss from elevated lake levels.

The properties along the perimeter of Kootenay Lake have the potential to be inundated by lake flooding, the report stated, which prompted the RDCK to “quantify the potential economic losses from these geohazards in order to support RDCK with flood risk management decision making.”

The study estimated economic loss using a three-part procedure with hazard analysis, exposure analysis and loss analysis. The hazard analysis included mapping the range of four lake flooding scenarios between flood stages 534.0 metres (1,752 ft) and 536.5 m (1,760 ft).

The exposure analysis included mapping and characterizing elements at risk surrounding the lake — the footprint of primary buildings on each parcel — while loss analysis included estimating the potential direct and indirect economic losses at each property and building.

The loss analysis was based on the property’s characteristics and depth of potential flooding.

As a result, when considering the types of damages assessed, economic losses for each flood stage could be:

• 534.0 m (1,752 ft) flood stage: less than $1 million;

• 534.9 m (1,755 ft) flood stage: between $2-4 million;

• 535.8 m (1,758 ft) flood stage: between $13-23 million; and  

• 536.5 m (1,760 ft) flood stage: between $29-53 million.

Decisions, decisions

BGC did assert in the report that any decisions made based on the analysis results should consider that:

• loss estimates for individual buildings can be inaccurate without site-specific assessment;

• loss estimates are more accurate at higher levels of aggregation; and

• loss estimates should be considered along-side qualitative impacts that cannot be accounted for in this analysis such as long-term effects, and intangible damages.

Source: Kootenay Lake Flood Impact Analysis


There were some considerations for the regional district, including:

• consider approaches to improve understanding of economic losses from Kootenay Lake flooding, and address limitations and uncertainty of the current study;

• formulate approaches to characterize a broader range of reservoir geohazards than the elevated lake levels considered in this study;

• Kootenay Lake Flood Risk Management: approaches to evaluate actions for reservoir flood risk management in terms of the level of risk reduction gained in relation to effort; and

• summarize deliverables that have applications beyond the current scope of work.

Source: Kootenay Lake Flood Impact Analysis