Design |
Climate redesign
As North American experience is showing, designing flood control infrastructure with a focus on climate-resilience is becoming ever more critical, with the frequency and intensity of flood events on the rise
Above: Flooding in Canada during 2019. An upward trend of recurrent flooding is posing a significant threat to critical structures such as dams and levees
CANADA HAS A LONG history of recurrent flooding. Seven of the ten most costly flood events occurred between 1980 and 2019, and after 2010. This upward trend in flood risk is posing significant threats to critical structure such as dams and levees. However, as Islam et al suggest in recent research published by Discover Applied Sciences, national-level guidance on integrating resilience-based frameworks, and addressing climate risks and uncertainties in existing design flood estimation methodologies for dams and levees, are lacking. The changes in the frequency and intensity of floods anticipated with climate change will be a challenge for conventional design flood estimation methods. As the authors explain, ageing dams in Canada also create an increasing risk. With approximately half of the country’s dams over 50 years of age, many were designed and well-maintained to withstand extreme events but weren’t designed with climate change in mind. In addition, it is claimed that some have deteriorated beyond repair and are vulnerable to failure even during moderate rainstorms and associated overland flows. Such vulnerability is now being exacerbated by the increasing occurrence of massive deluges, often following severe drought, which is a trend projected to intensify over time under climate change. However, as Islam et al state, there currently is a lack of
comprehensive and unambiguous guidance on climate- resilience-based frameworks, leading to confusion among engineers and policymakers. The authors wanted to address this gap by reviewing design flood estimation procedures, the potential impact of climatic trends and regional vulnerabilities to climate change, and the barriers
18 | December 2024 |
www.waterpowermagazine.com
and opportunities for advancing a climate-resilience framework. By studying the vulnerability of Canadian dams and levees to flooding in light of changing regional climatic patterns and associated hydrologic design criteria, the authors have tried to identify areas where interventions are necessary to enhance the climate- resilience of such assets. The increasing trend of destructive floods across
different parts of Canada and the projections of rising frequencies of higher return period floods in a changing climate, have highlighted the need for new regional and national initiatives to update design flood estimates. The authors say the conventional approaches which utilise stationary climatic assumptions are no longer adequate for calculating design values, and therefore new strategies must be developed to not only account for the dynamic behaviour of the climate system, but also alleviate undesirable consequences of future climate change. It is imperative, they add, to continuously update estimates of various risk components, including hydrologic loads, and monitor system response in order to enhance climate-resilience and inform the decision-making process. Islam et al highlighted the various challenges for estimating climate-informed design floods for dams and levees. These include:
Constraints of sample size and event identification difficulties Design flood estimation for dams relies heavily on historical records of peak discharge and extreme
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