It seems the whole world might wash away. By now you are likely aware, at least cursorily, of the many ramifications of the deluge southwestern British Columbia experienced over the weekend of November 13 to 15. Anyways, here’s a recap: Rain, flooding, and landslides stunned communities across the region. Several locations throughout the region shattered rainfall records, most notably Hope, which received 252 millimetres of rain over the storm (that’s over 70% of the average November rainfall for the community). And with the rain came a torrent of damage to roads and communities. Washouts closed Highway 5, known as the Coquihalla, Highway 1 from Hope to Spence’s Bridge, and Highway 1 on Vancouver Island, known as the Malahat Highway, among several others.
Over the following week, the severe flooding in the community of Abbotsford became the most prominent story of the storm, as the Nooksack River in Washington states overflowed its banks and began, in part, flowing north through the rural area along the east of the city, and eventually recreating Sumas Lake, which was drained to create farmland in 1924. Flooding also caused the complete evacuation of Merritt, and inundated the town of Princeton, events that when combined have likely resulted in billions in damages .
But along with the flooding that overwhelmed several watersheds through the region, damage to the provincial highway and railway systems – damage that sparked social panic over food and gas availability, shaking confidence in our entire goods distribution system – came heavy and often from a series of mudslides and road washouts. Though it will take some time for a full and thorough assessment of what happened, there are several key issues that researchers and policy makers will be considering as they look for an explanation for the damage.
In the days following the storm the irony of enduring unprecedented flooding only a few months after living through an unprecedented heatwave and wildfire season did not escape many. But in addition to the damage to forests (and our psyches), wildfires have cascading effects on the resilience and function of watersheds. Scorched ecosystems are more susceptible to landslides, as the lost trees are no longer able to take up water from the ground (resulting in increased soil saturation), from the loss of structural support to soils from plant roots, and due to the water repellency of scorched ground, which causes water to flow overland quickly, rather than seep into soil slowly.
In the spring of 2018, following the devastating Elephant Hill Wildfire, mudslides and road washouts were common in the area surrounding Cache Creek, BC, – and resulted in the death of one person – as the slopes above roads were no longer stable having lost their vegetation. A number of slides occurred in 2004 following the summer of 2003 when fires caused damage across B.C., most notably in Kelowna; in time, researchers attributed many of these slides to burnt soils. It will take time to determine the extent to which wildfires contributed to this year’s slides, but given the extensive damage to Highway 1 between Lytton and Spence’s Bridge, where just months ago the Lytton Creek Wildfire burned, many research questions remain. In fact, according to Tom Popyk, a reporter for the CBC, the location of the now-infamous Tank Hill washout, was designated “high risk” for a landslide in a report from the British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development.
The effects of wildfire on the stability of slopes are well documented, as are similar effects from another major cause of landscape change: logging. Due to a similar suite of processes, logging increases the peak flow of water (the amount of water that flows through a creek at the wettest time of year) in a watershed. When this effect on waterflow is combined with weakening slopes, logging can contribute to landslides, landslides similar to those that washed over highways 3 and 7, and with “debris flows,” where a mass of mud and debris moves through a creek, similar to many of the more severe road washouts last week. It is important to note that if forestry and wildlife really has contributed to the damage to our highways remains to be seen. But, many researchers are already asking these questions, given the scope and scale of both the logging and wildfires in conjunction with the damage to infrastructure around the region.
It is also worth noting that the effects of wildfires and forestry on our watersheds go beyond acute damage like landslides. The loss of forests on the landscape and changes to soil processes can cause many problems to how we use water. Forestry can reduce the amount of water in streams during low flows in the late summer, and is associated with faster snowmelt in the spring, something that can cause spring flooding and summer droughts. Wildfire also has watershed level effects, such as reduced available drinking water, and reduced water quality. But, relevant to our current situation, healthy forests are key to mitigating water flows, reducing flood risk, and maintaining water quality. Changes to the landscape from fire and forestry have potential to cause serious problems to our watersheds.
The unmentioned dark horse in the issue here – and by dark horse I mean an enormous, charging, menacing horse that literally no one could ignore – is climate change. Extreme weather events such as this summer’s heatwave, hurricanes, or major rain events, are becoming increasingly common. Whatever the catalysts are, be it landscape degradation, incredibly poor planning, or just plain bad weather luck, governments need to dramatically increase their preparation for major weather events and environmental catastrophes. The dramatic landscape of British Columbia, something most residents revel in, makes this province vulnerable to the very calamities we have just experienced. If the province is to weather this storm and the inevitable future ones to come, answering what drives the destruction of our infrastructure will be a major answer we need to find.
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