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And other “fun” facts…
01
The very first gravity dam, the Jawa dam, dates back to at least 2,500 years B.C. and was built by the Mesopotamians. Built out of gravel and riprap, its design was so strong that its remains can still be seen in Jordan today (1). Dams have served our societies for a long time: irrigation, water supply, leisure and recreation…
However, and despite the age of this technology, impressive and destructive ruptures are observed relatively frequently. For example, on May 19, 2020, breaches at the Edenville and Sanford dams led to the complete emptying of a reservoir of 81 million cubic meters of water in less than an hour and the evacuation of nearly of 11,000 people in central Michigan (2).
The causes of failure are varied, but are most often associated with three main reasons: a misunderstanding of the geological conditions and foundations of the dam; a poor estimate of the structure’s inflow design flood; or a misinterpretation of seismic conditions in the region (3). In the event of poor design, a strong safety culture and strong diligence in carrying out the inspections and modifications necessary to maintain the infrastructure are essential to mitigate the risks.
02
The median mobile component of fishes is estimated at 362 meters, meaning that fish habitats exist on a continuum along a river, with migration and easy transitions playing a significant role in the preservation of fish population (4). Bridges and culverts are common structures found on rivers and for many hydraulics engineers, they became a no-brainer. Yet, because poor and easy designs hinder fish movements by creating hydraulic barriers, culverts and bridges are responsible for many ecological disasters, amongst which the decline of migratory fish species (5, 6).
In Quebec, despite the existence of Design Guidelines for culverts, an inventory of 126 culverts distributed over four major salmon rivers across the province showed that only 35% of culverts were passable (7). Culverts are a perfect reminder of the importance of considering each site as unique and of working with nature to achieve real sustainability.
03
Severe erosion will be observed when significant changes are brought to the hydrology of a watershed, which can result from a change to the use of the land, or from climate change. For example, in Quebec city, an inventory of nine rivers located on the watershed of the city’s main water-supply showed that, on average, 38% of river banks presented significant erosion damages (8). This is the reality of most rivers located in areas of concentrated population.
Erosion in rivers and lakes can be a particular nuisance when those rivers are tributaries to a water-supply, are used by fish for spawning, or when houses and communities are located along their shore. Erosion protection, particularly in rivers, should be designed considering the system on a continuum, with various hydro-morphodynamic processes at play, or else the solutions will only work temporarily or maybe worst, will just move the problem further down the river.
04
Ecohydraulics is still a relatively new discipline, born from a desire to link various fields that seldom talk with each other i.e., engineering hydraulics, biology and geomorphology. The current consensus is that ecohydraulics is a synthesis of ecology and hydraulics, and as a discipline, exists at the interface of the two (9). Ecohydraulics topics include, but are not limited to, the movements, abilities and passage of aquatic organisms; environmental, ecological and instream flows and the restoration of aquatic habitats and ecosystems.
Ròs is a consulting engineering firm specialized in engineering hydraulics and the design of hydraulic structures, with a particular investment in doing it right. As such, all our projects include environmental and ecological considerations, and we aim to partner and work with experts from various fields to achieve real sustainability. We are one of the very few engineering consulting firms who truly speaks the language and understands fish migration needs.
References
- National Geographic Society (2002) Dams.
- DELUZARCHE, Céline. (2020) La rupture d’un barrage aux États-Unis entraîne des inondations catastrophiques.
- ADAMO, Nasrat et al. (2020) Dam Safety: General Considerations.
- RADINGER, J. and WOLTER, C. (2013) Patterns and predictors of fish dispersal in rivers.
- SILVA, A.T. et al. (2017) The future of fish passage science, engineering, and practice.
- TORTEROTOT, J-B. et al. (2014) Influence of Forest Road Culverts and Waterfalls on the Fine Scale Distribution of Brook Trout Genetic Diversity in a Boreal Watershed.
- GAGNON-POIRÉ, R. (2017) Fragmentation de l’habitat du Saumon atlantique (Salmo salar) par les ponceaux routiers et forestiers.
- Organisme des bassins versants de la Capitale. (2022) Bassin de la rivière Saint-Charles/Rivières.
- Ecohydraulics Community Leadership Team. (2022) What is it?