A Discourse of Rivers
Of Fire and Water —
Wildfires and What They Mean for Paddlers
By Tamia Nelson
January 28, 2014
It's been been suggested that to every thing there is a season, and it's probably also true that every season has its storm. In my corner of New York's borderlands, this winter has been notable for a particularly nasty one, an ice storm that left some households without power for days on end. And the weather system that sheathed much of the Adirondacks in ice didn't stop at that. It then crossed the Pond, bringing high winds and widespread flooding to much of the UK.
The result? At the same time that ice‑burdened trees were crashing down around me, hampering utility crews in their efforts to restore service to many of my neighbors, I was listening to BBC reports of flash floods that drove thousands of Britons from their homes. In one particularly poignant instance, a man drowned while attempting to rescue his dog from a rain‑swollen river. The dog eventually struggled to safety on its own, but its master wasn't so fortunate.
We had flooding in New York, too, though nothing on the scale of the floods in Britain. That said, flash floods have captured my attention in the past. I touched on the subject last September in "Keep Your Head Above Water!" The title explains my interest. Flash floods can take sleeping (or feckless) paddlers by surprise — it's happened to me — and the consequences can be dire. It's not hard to see why. Water is heavy. Very heavy. And moving water packs a correspondingly hefty punch. When a lot of water comes roaring down a valley at speed, the outcome is a foregone conclusion.
Here's how I described the consequences in my earlier article:Moving water is always a force to be reckoned with. I've seen lazy summer streams pin a swimming canoeist to a sweeper so securely that it took three of her companions several minutes to prise her free. And I've found dead cows — or what was left of them — hanging high in the branches of tall trees along fast‑flowing rivers. A river in flood is a fearsome thing, and with enough rainfall in a short enough time, even a tiny rill can grow into a raging torrent, inundating whole swathes of lowland forest and sweeping all but the largest trees before it.
The word "awesome" is now used so promiscuously, and in such trivial contexts, that it's lost all of its force, but it doesn't hurt to remember that it had its origin in the power of some things to inspire awe, the humbling realization that we humans are not the measure of all things — that nature can outdo even our most ingeniously engineered efforts at destruction. Floods of any description are impressive, but flash floods are awesome: really, truly, totally awesome.
So much so, in fact, that it's best to appreciate their power at a distance. And just how can a paddler ensure that he (or she) avoids too‑close encounters with the raging waters? In part, by understanding those things which predispose a river to sudden, catastrophic floods — the root causes of flash floods, if you will. Here's a short list, taken from my earlier article:
- Road construction and paving
- Deforestation or extensive clearcutting
- Draining of wetlands
These won't surprise old hands, who know all too well that rivers and their catchment basins are dynamic environments, not to mention complex, interdependent systems. Alter just one element — average soil permeability in a river's watershed, say — and you perturb the entire system. And the consequences can be devastating.
Of course, I didn't intend my earlier article to be a primer on fluvial processes. For one thing, even a cursory introduction to the subject would require tens of thousands of words. Still, I had hoped that my modest efforts were complete and correct, at least as far as they went.
But they weren't. At least they weren't complete. One factor that contributes to the likelihood of flash floods — and the related phenomena of landslides and slumps — was conspicuous by its absence. What was this missing element? Fire. Or, to be more precise, …
Wildfire and the Resulting Slope Denudation
I'm indebted to James Stone for pointing this out. James is a valued correspondent, whose letters have often appeared on these pages. He's also a career wildland firefighter, who's spent much of his working life in the rugged terrain of the mountain West. In other words, James knows whereof he speaks, and he had this to say about the risk of flash floods in the aftermath of fires:Your piece about flash floods is right on, and I enjoyed the flash flood info, but I have to add my two cents. Clearcuts are not the only things that denude hillsides and cause them to move. So do forest fires. I was assigned to the fire that denuded the hillside which later let go because of flash flooding. That landslide covered State Highway 55 with tons of debris. [See below for links to related news reports.] These soils are on the Idaho Batholith: rotten, decomposed granitic soils where the clay has long since washed out and downstream. And the remaining soil is very prone to erode.
Matter of fact, there was a second flood I heard about that happened after a fire I was assigned to, and also the second where there was a year between the flood and the fire. This second flood was near Salt Lake City.
James' letter was, as always, illuminating. It turns out that the consequences of wildfire‑caused slope denudation are an area of active research by geologists and other scientists. Not surprisingly, their findings support James' observations: Recently burned areas are at greater risk of flash flooding and landslides. That's something paddlers, campers, and hillwalkers should know, and I'll outline the implications in a minute. First, though, it would be useful to see how federal land managers deal with the immediate aftermath of a wildfire. And here, too, James can help:It's not as if the feds don't do anything after a fire. They bring in Burned Area Emergency Response teams (BAER teams) that consist of hand-picked specialists [with expertise in each] of the damaged resources — range, wildlife, soils, watershed, and so on. The concern used to be just watershed rehabilitation, but now includes such items as wildlife and forage. The BAER team ... uses "burn intensity" maps and does on-the-ground surveys to check for resource damage. For instance, [they map] the presence of hydrophobic soils (caused by waxy-leafed plants burning and leaving a waterproof residue on the surface of the burnt soil so water can't penetrate)..., the potential for noxious weed growth, erosion, etc.
When the BAER team report is done — anywhere from days to a couple of weeks of the fire being controlled — they make mitigation recommendations and funding requests. Since it's a burn emergency, the funding is approved in all or part (earmarked portions) within six weeks, and the work begins as soon as they can get contractors and boots on the ground.
Of course, since fires tend to be put out by "season-ending events" — in other words, winter — in some cases there isn't a lot of field season to get much work accomplished. Helicopter seeding can be fast, but plants need time to germinate and grow, [so] sidehill felling of trees is done to slow down runoff. (A "sidehill-felled" tree is felled so that it falls normal to the gradient, creating a check dam.) Other measures can help a bit, too, such as the placing of straw wattles on sidehills.
It pays to remember that wildfires are common occurrences throughout Canoe Country. Many are triggered by lightning strikes; a few, by other, rarer natural phenomena (e.g., volcanic eruptions, spontaneous combustion). But the remainder can be traced to criminal conduct or human carelessness (a poorly sited campfire, say, or a discarded cigarette, or a "controlled burn" that gets out of hand). Whatever the cause, however, wildfires can produce widespread alterations in permeability and soil stability throughout a watershed, changes that even heroic efforts at mitigation cannot always address, let alone reverse.
And what does this mean for paddlers? Simply that any canoeist or kayaker whose planned route takes her through a recently burned area must …
Or expect to suffer the consequences. This should go without saying, I suppose, but since few of us have daily contact with the natural environment during the workweek — professionals like James are the obvious exception here — we're often slow to recognize dangers that originate in things outside our everyday experience.
What can we do about this? Well, there's no better place to begin than the trip‑planning stage. And winter is the season for planning. So there's not a moment to be lost. If you have your eye on a particular route, learn all you can about what's been happening in your chosen river's watershed. Fires, floods, landslides, slumps — all of these intimately intertwined hazards are (or should be) of interest to the prudent paddler. And don't limit your research to the last season. Go back at least a couple of years. Google, Bing, and DuckDuckGo are your friends here. Web searches will often yield valuable information that can be had in no other way. Not every wildfire or landslide makes the national news.
And what if your search turns up evidence of a recent wildfire? Does this mean you now have to abandon plans that may have been months in the making? Not necessarily. But you will need to redouble your efforts. Dig out anything and everything that has a bearing on the fire and its aftermath: articles in local papers, blog posts, government agency advisories and official notices, even academic papers, if any are available. (You may get lucky; natural disasters are often research opportunities.) Here again the Web is your ally.
Then, once you're on the river — if you decided not to change your destination in light of information received, that is — keep your brain‑housing group fully engaged at all times. You'll find some hints about warning signs to watch for in my earlier article on flash floods, and the US Geological Survey website also publishes a couple of informative pages that will repay careful study. One is titled "Post‑Wildfire Landslide Hazards"; the other, "If You Live in a Recently Burned Area." And though the second is (as the title suggests) written for people who live in places where wildfires have occurred, paddlers can also benefit. We become temporary residents as soon as we pitch our tents, after all.
Finally, James has more good advice for paddlers whose travels take them through (or near) recent burns:If trees are dead and standing, that increases the chance of them coming down, and plans can be made to protect oneself from danger. How? Don't camp (or take breaks) under them. With firefighters, the guideline is to be 1.5h away from the tree, where "h" is the height of the tree. And don't move downhill from them! I have seen parts of trees travel very long distances downhill — like hundreds of yards — and I've also watched branchless snags that fell directly downhill travel like a rocket sled before jamming into the barrow pit next to the road, hundreds of yards from the stump. It's scary stuff. But being 1.5h away from a dead tree (and alongside it, rather than directly below) is a pretty fair bet to be safe. Unless you are then directly downhill from another one that may fall, that is.
Another thing to consider: Rocks on the surface are loosened when their anchoring ground vegetation burns, and the logs which formerly kept them from rolling downhill finally burn away.
The bottom line? Recent burns are melancholy places at best, but they can also pose a real and present danger to heedless paddlers. The risk of flash floods, landslides, and slumps increases, and there's a greater hazard from falling trees, as well. However great the urge to shut your eyes to the devastation and disengage your brain — this is a vacation, isn't it? — resist the temptation. As a great scientist once noted, fortune favors the prepared mind.
Be prepared. And stay lucky.
The connection between wildfires and flash floods isn't obvious, but it's very real. Watersheds are complex systems. Anything that affects one part of the system affects the whole. And few phenomena have more widespread and pervasive effects than wildfires. So anytime you'll be paddling through a recently burned area, it makes sense to plan ahead. James Stone has spent his working life fighting wildfires, and he makes the point that the danger doesn't end when the flames are extinguished. Furthermore, he's described what paddlers and hillwalkers need to look out for, and he's suggested ways we can minimize any risk. Now we're all better prepared to deal with fire and water.
Related Articles From In the Same Boat
- "Keep Your Head Above Water! A Flash Flood Primer," and …
- Air, Earth, and Water — Natural History for Paddlers, a topical collection of columns, including …
- "The Dynamics of Moving Water: Theme and Variation,"
- "After the Flood: When Rivers Rearrange the Dust,"
- "When Size Doesn't Matter: Self‑Similarity over Scale Changes," and …
- "Current Affairs."
Plus two articles from the United States Geological Survey:
- "Post‑Wildfire Landslide Hazards"
- "If you live in a recently burned area, and there is a rainstorm…."
And these others, from Wikipedia and elsewhere:
- "Flood" (Wikipedia)
- "Flash Flood" (Wikipedia)
- "What Are Flash Floods?" (US National Weather Service PDF)
- "Types of Floods and Floodplains" (US Federal Emergency Management Agency PDF)
Finally, here are two video news reports, suggested by James Stone
(NB Each is preceded by a commercial):
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