When massive flooding hit Colorado's Front Range last September, news focused on the impacts in towns like Boulder and Lyons as rapidly rising rivers engulfed infrastructure like roads and bridges.
Although the nearby Arapaho and Roosevelt National Forests, which cover hundreds of thousands of acres in north-central Colorado and lie just to the west of those flooded cities, may not have received as much attention, they also saw significant impacts.
These forests, which are used as a recreational base for the 3.3 million people who inhabit the Front Range area, have had severe erosion, roads damaged by floods, and bridges and other infrastructure washed out, according to a new report from the Forest Service's Rocky Mountain Research Station -- as much as $44 million in damage.
"There are many roads that are closed. They may have been washboarded before, but now they are gone in places," said Sandra Ryan-Burkett, a research geomorphologist with the research station and a report co-author.
Preliminary assessments indicate that "the floods caused over 250 debris slides and damaged at least 382 miles of roads, 236 miles of trails, several dozen recreational facilities [such as campgrounds, picnic areas, parking areas, and fishing and boating access sites], and four bridges," Glenn Casamassa, forest supervisor on the Arapaho and Roosevelt National Forests and Pawnee National Grassland, said in the report.
Landslides and other hazards still possible
"There was one example where the storm actually traveled down the road and basically re-created another [river] channel down the road," Ryan-Burkett added.
The report stressed that while the flooding is over and much of the infrastructure in urban areas may be repaired or is undergoing repair, the forests will likely continue to see impacts, especially during this spring runoff season.
There is a potential for landslides, rock slides and debris flows, and users of the national forests will need to be aware of those risks, the report states.
"Right away, [National Forest employees] are going to be addressing public and employee safety issues because the landscape has changed quite a bit," said Linda Joyce, a quantitative ecologist and Resource Planning Act climate change specialist with the research station and a co-author of the report.
A challenge for managers will be prioritizing needs for restoration. So far, the forests have received an estimated $4.2 million in special recovery funding after the flood.
In what was perhaps a call for patience from those who use the forest, the report also pointed out that restoration will take place "on different timescales" than recovery of highways and communities.
"There is a lot of work that will have to be done to stabilize, repair and recommission facilities and infrastructure because of the consequences of the flood," Joyce said.
The report notes that although the flooding was unusual, it was not unprecedented. In some areas, the rains equated to a 25-year event; in others, a 500-year event.
A need to plan for a more dynamic landscape
"Although it was an unusual event in the magnitude in those particular drainages, in the bigger picture of things we shouldn't be surprised if we see it again," said Pete Robichaud, a research engineer with the research station and report co-author.
"Living in the western part of the United States where we are still in a wild land, it's not an urban environment, these kinds of things are ... I don't want to say common, but they certainly occur. And the forests are well aware of that," he said.
Robichaud's research focuses on how erosion plays out on fire-damaged landscapes. He noted that national forests are no stranger to flood and erosion damage, particularly after wildfires.
Other research has shown that climate change is likely contributing to a longer fire season and more widespread fires (ClimateWire, April 21).
Forest managers need to be prepared for a dynamic landscape that changes and experiences extremes, Robichaud said.
"I don't think 10 years from now we are going to say we have less flooding and fires than we ever did," he noted.
As forests look to rebuild infrastructure, they can plan for events of a larger magnitude. A simple example is replacing a blown-out culvert with one that could handle the amount of water experienced in the flood, Robichaud said.
Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500.E&E Publishing is the leading source for comprehensive, daily coverage of environmental and energy issues. Click here to start a free trial to E&E's information services.
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