THEME:
STORMWATERMANAGEMENT CRYOFRONT – News, Views and Muse from the Far North
Drainage management
in the Far North Ken Johnson, Stantec The north of Canada is a region with long periods of extremely low temperatures; it is a region that is exceptionally large and remote; it is a region with permafrost and other ground-related engineering challenges; it is a region of small, isolated communities with low population density; and it is a region with a large indigenous population. As much as these different attributes contribute to a diversity of communities in the north, a common element between northern communities is the challenge around surface drainage management.
Drainage management associated with roads, such as ditches, is almost nonexistent in many northern communities.
While the north may be regarded as a region of perpetual ice and snow because of the long and cold winter season, it is the short warm summers and brief shoulder seasons of spring and fall that create the perpetual surface drainage issues that are catastrophic in the extreme case, and a constant challenge year after year. There are no simple, quick fix permanent solutions to surface drainage issues in northern communities. Short construction seasons, remote locations, limited community capacity, and challenging ground conditions amongst other factors create a complex web in which the persistent issues of northern drainage must be addressed. As an example, the logistics involved in the installation or replacement of a simple culvert can be challenging. First, the correct size of pipe must be purchased well in advance of when it is needed. It may need to be delivered by winter road or ship, both of which operate in a narrow seasonal
window. Availability of manpower and equipment cannot be assumed, as these resources might have already been committed to other projects during the summer construction season. Even if all of the resources are available when required, the location, local ground conditions such as the presence of permafrost, and material available will influence how the culvert is installed and how long it might remain functional. The effects of climate change create challenges for the design of drainage systems in the north, where there is often limited climate data available, adding to the risk and uncertainty. In most northern communities, drainage system planning, design, and maintenance are often described as ad hoc processes. Community planners, engineers, and asset managers from across Canada’s three territories, as well as Nunatsiavut (northern Labrador), and Nunavik (northern Quebec) have emphasized that conventional drainage
Only a select few northern communities have buried storm sewer systems and the majority of northern communities have surface runoff systems to manage drainage.
The dynamic ground conditions associated with permafrost cause the earth to continuously move and create difficult conditions for installing and maintaining drainage infrastructure.
Redundancy of drainage is necessary in some cases because of the extreme operating conditions and the limitations in operation and maintenance resources.
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planning, approaches to design, and maintenance practices are inadequately defined and often poorly understood. The result is routine and chronic degradation of community infrastructure across the north. Proper drainage planning, design, and maintenance practices are essential for the protection of community infrastructure. The effects of a changing climate bring additional challenges to the process of planning, designing, and maintaining northern drainage systems. Irregular and, in some cases, extreme events appear to set aside what might have been considered normal in the past. Many professionals agree that the changing climate has and will continue to alter northern weather conditions. All of these weather factors in the north influence how drainage planning, design, operation, and maintenance now need to be done. New tools and adaptation strategies are needed to manage the effects of climate change on community
surface drainage systems. The preparation of community surface drainage plans is only a first step. The results of vulnerability assessment studies that have been undertaken in the north are confirming that existing drainage plans and infrastructure are often inadequate to accommodate the effects of a changing climate. In many instances, service levels are insufficient, and repairs to drainage infrastructure are infrequently and non-routinely conducted resulting in ultimately more expensive repairs in the future. Other conditions often associated with climate change, such as warming and degrading permafrost conditions and pronounced local shifts in hydrogeology, are creating new drainage problems within communities and making existing problems worse. Community drainage systems collect runoff water from snowmelt, ice melt, precipitation, and storm events. These systems convey surface drainage away from community sites, whether an individ-
ual lot, a community block, a community neighbourhood, or the entire community to a point down gradient where it no longer impacts the site. The community’s drainage system needs to be planned, designed, constructed, and maintained with the capacity to handle the aggregate flow of water from all catchment areas within the community, as well as surface water that originates from outside the community that must flow through the community because of topography or other factors. A step forward in assisting northern communities has been the development of a CSA standard entitled “Community Drainage System Planning, Design and Maintenance in Northern Communities.” A committee of northerners representing all three territorial governments, consulting engineers, and consulting planners developed the standard. The standard was released in January 2015, and is available through the CSA website.
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Spring 2017
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