Colorado Public Works Journal, Summer 2019

by Robert Davis Planning for Future Extreme Weather Colorado’s climate carries an elevated rhythm. The state’s cool, dry air and large seasonal temperature swings from day to night can vary drastically depending on location. The Eastern Plains are typically hot during the summer, but are relieved by afternoon thunderstorms. In the mountains, freezing temperatures at night can be expected year round. For residents like Russ Schumacher, Colorado’s state climatologist, these weather patterns offer renewed opportunities to study the state’s shifting climate. Schumacher studies how certain weather systems produce extreme storms and helps climate organizations develop tools and methods to communicate the climatol- ogy and climate variability of Colorado. His research provides a unique perspective into how transportation departments across the state can adjust their projects to account for Colorado’s future climate challenges. “Most of the issues and threats are going to revolve around water: We live in a dry place and depend on mountain snowpack for water, and a lot of other places also depend on water that originates in Colorado’s snowpack,” Schumacher told Colorado Public Works Journal. “Trends in precipitation and peak snowpack are difficult to detect, in part because there’s naturally a lot of variability from year to year. There has been a trend toward melting happening earlier. But the overall warming trend across the state is much more clear and robust, and there’s high confidence that this will continue.” As winter dissipates, snowpack strays further from the forethought of many Colorado residents. We become less concerned with waking up early to shovel driveways and sidewalks, and wonder even less about when the snow plows will be visiting. Instead, we’re making plans to hike through the high country before it rains. This lifestyle is attracting more visitors and newcomers every year, which is placing increased stress on Colorado’s aging roadway and bridge infrastructure. “If the population in Colorado, and especially on the Front Range, continues to grow at the rate that is anticipated, there will be stresses on these systems even in our current climate,” Schumacher said. Current Issues There’s no question Colorado is warmer now that it was 50 years ago. The scorching heat of yore is now an average summer day while latent snowmelt in the high country overwhelms many of the state’s rivers. The impacts of this climate present broad and wide-reaching problems for Colorado residents and the state economy alike. The Bomb Cyclone that hit Colorado in March 2019 serves as a stark reminder of how extreme weather can catch the most prepared transportation departments off guard. During that storm, 1,386 flights at Denver International Airport were cancelled, at least 335 cars were stranded on I-25 near Larkspur, and another 250 cars were abandoned in the Denver area, according to a report by The Denver Channel. What is even more worrisome is that climate scientists like Schumacher are unsure if these storms will become more prevalent in the future. “There are a couple factors working against each other over land, and it’s not clear which one will ‘win’ in the future,” Schumacher said. “To get cyclones like that, you need a very strong gradient in temperature from north to south. That probably will not happen as often in a future warmer climate. There also needs to be a lot of “latent heat release” – the energy released when clouds form and there is strong upward motion in the atmosphere. This will probably get more intense in the future.” Without a way to predict when the next extreme weather phenomenon will occur, Schumacher suggests that transportation departments around the state should make sure they take the changing climate into consideration as they plan upcoming projects. Reaching out to the local National Weather Service office to open the lines of communication in advance of potential hazardous weather is a great place to start. The American Association of State Highway Transportation Officials (AASHTO) also suggests that local transportation departments translate weather forecasts into metrics that matter to specific types of transporta- tion decision-making. One metric that could greatly affect Colorado’s roads is the stability of its road embankments because they can alleviate the damages from flooding caused by storms and melting snow by pro- viding a drainage network that carries stormwater and small debris away from the roads. Effective embankments often include material that is too heavy for stormwater to remove (stones), established natural vegetation that can hold itself and the embankment in place, and protection from structures like sheet piling, retaining walls, or gabions. Cities in Vermont made significant improvements to their local flood mitigation plans following the devastating effects of Tropical Storm Irene in August 2011. According to the National Weather Service, 500 miles of roadway and approximately 1,200 bridges and culverts were either dam- aged or destroyed, six of which were completely washed away, including the historic Bartonsville covered bridge. Overall, the storm caused $700 million in damages to the state’s infrastructure and private lands. A similar event occurred in Colorado in September 2013 when severe storms caused flood conditions that stretched approximately 150 miles across the Front Range, according to the National Oceanic and Atmos- pheric Administration (NOAA).15 counties submitted federal emergency declarations as a result of the floods. In total, nearly $1 billion worth of infrastructure and private property was damaged. 46 | The Future of Snow Operations

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