A Word on Wood

A slightly shortened version of this post was cross-posted on the Kokatat team blog on March 14, 2021 . -All photos by Leif Anderson.

I have spent a large portion of my professional career thinking deeply about wood in rivers and how important it is for the ecosystems of the world; from the headwaters where logs enter our drainage systems to the estuaries and oceans where they are integral for ocean food webs. I am also a boater and am usually able to feel okay about the wood removal that the boating community does because, in general, it is fairly tactful and minimal while also appropriately mitigating risks. 

Melissa Vaughn with Bryar Skinner and Michael Jonnson, Thunder Creek, WA

 However, this past spring there was a log removal project on one of my local runs that made me pretty sad and upset and this past winter, during the high flow season I have noticed a knee-jerk mentality among my fellow paddlers that all wood, if inconvenient to you, must be removed and chopped up immediately. I am now going to use an example of a particular wood removal project to help highlight my concerns and thoughts on this matter and present some photos of the beauty of wood as a reminder to us all to have some humility when we interact with the natural world.
 
The scenario

In Spring 2020 a large old growth tree fell into the very popular section of my local run during a big wind storm. It lodged into a class II/III rapid with a class II lead in and is clearly visible from upstream. It completely obstructed a narrow canyon with fairly vertical walls making portaging around very inconvenient. Paddlers were having a hard time passing around it. I was involved with one mission to take out just the end of the log to allow clear passage without a portage around on one side. Our particular effort was unsuccessful, but another group managed to remove a few feet off the end of the log, and subsequently the danger was very well mitigated. The log could be easily seen and paddled around by paddlers at the skill level required to do the run. Then, about a month later, the old growth was hacked to pieces by a chainsaw, with the center of the log still in place in the middle of the river. The operation to do this must have been quite extensive and somewhat dangerous given the huge size and position of the log. Large sections of the log were then tethered with ropes, below the high water line, to the canyon walls downstream. 

My response

I recognize that this action was done in good faith and in service to the community, but I would like to detail some of the reasons why this level of intervention does not sit well with me. 

Every time we go boating we assume some level of risk. There is also risk to the natural environment and ecosystems when we intervene in their natural functioning. The log jam, prior to the extensive modification, was not posing a level of risk to boaters beyond what would be expected in the rest of the run. We generally don’t use dynamite to blow out rock sieves, and I suggest we think similarly about wood hazards - not always revert to the reflex that they need to be removed entirely. 

Leif Anderson, Stovepipe, Little White Salmon, WA


The cut log was very unsightly and every time I passed it, it served as a reminder to me that the society we live in pervasively emphasizes a dismissive attitude towards the functioning of natural systems in favor of convenience for humans. I generally go boating to escape this and I like to think that as a boating community we are more considerate of the natural world. 

It takes centuries for big trees to actually enter into our waterways. Once there, they, in their larger forms, are very important for aquatic ecosystems, both in the streams but also once they finally make it to the estuaries and oceans. By chopping them up, we are undoing in an afternoon something that took centuries to happen, and we are shortchanging centuries of future benefits to other life forms from its presence or the presence of jams it could nucleate. 

Greg Lee and Natalie Anderson, Gettin, Busy, Little White Salmon, WA


I do not feel that the modifications that were made actually mitigated any risk, and in fact several of the modifications have added a level of uncertainty that at the time made the wood a higher risk to paddlers, at least in the short term. As far as jams go, the original jam was in a great location due to its positioning in a slow moving section without a major rapid just upstream. The jam could have been useful for keeping the lower section clear of wood because wood coming from upstream would get caught in it. 

Once the log was chopped up, I worried that the large piece in the center was now more likely to move downstream to potentially a worse location due to a reduction in its size and complexity and I worried the chunks of wood tethered with ropes to canyon walls would get torn off and transported somewhere else in the river, now with ropes dangling off of them. Or, they could potentially help de-stabilize a canyon wall. 

 I ended up removing the ropes myself and in the high flows this past winter the pieces have all moved downstream to innocuous locations and the paddling run is very clear of wood, so in that sense the wood removal project was a success. Yet I remain saddened that I won’t be able to experience paddling past that impressive majestic tree and instead I have to paddle by cut-up pieces of it dispersed down the run. I can’t help but wonder: what if it was left in place? What are we missing by taking it out and not letting it run its course? Yes, maybe a large jam would have formed, but that could have been really cool to paddle around the edge of it, knowing that its nooks and crannies were a refugium teeming with life. 

Natalie Anderson sneaking the Oregon Slot, Little White Salmon, WA.

Mitigating wood hazards isn’t just about physically removing them, but taking some effort and time to observe and understand the natural world in which we recreate. The more knowledgeable we are about how and when wood comes in and moves and where it is likely to get hung up, the less likely we will be surprised by a very dangerous piece of wood. So here goes a few insights from my own observations and studies of wood movement in streams. I encourage you to start noticing and observing the dynamics of wood in your own watersheds. Experienced paddlers may have already figured out some version of these same ideas.

  • Most large wood is transported during a very steeply rising limb of a flood and is deposited at or just after peak flows. This means that you should be most alert just after high flow events that have a rapid rise and reached levels higher than any other previous flows yet that year. If you are paddling at flows much lower than the peak, it is very likely that you will be able to duck under logs deposited by the flood. If you are paddling at flows close to the peak then the logs deposited by the flow will more likely be in hazardous positions for you.
  • If the trees in the river (or growing along the banks) are as tall as the width of the river or the span between large boulders, they are more likely to get stuck in hazardous cross-wise positions. If you are paddling at high flows during the rising limb of a hydrograph be VERY alert to quickly coming across a new tree lodged widthwise and at river level.
  • If high flows are very high and sustained, Most wood will be cleaned from the run and flushed all the way into floodplains and bars of lowland rivers or into estuaries. If high flows are short lived, more of the wood will simply be re-arranged, with old jams blown out and new ones formed.
  • Pay attention to how much downed wood is actually present along the margins of your river. If there isn’t much, then there is less risk of finding new wood in undesirable locations after a high flow event. However, if it has been years since a really good flushing event has happened OR there was a lot of wood recently deposited from a large landslide, be alert.
  • Delivery of wood to the river (windfall, bank erosion, death from disease, landslide etc) does not occur at the same time as when they are transported downstream and re-located by flows. So, from a boating perspective, pay attention to how much newly recruited wood there is and whether it has yet been reorganized by flows because newly delivered wood is not stable (even if large) and the next higher flow will likely move it downstream (usually not far) and lodge it into a more ‘permanent’ location (at least until a very big flushing event occurs). New wood that is still attached to the bank or has a large rootwad is unlikely to move but may shift and large pieces of it may break off and move to a new location.
  • Jams often serve as a catch for wood during lower flows and can help keep lower sections clear of wood from upper sections. Jams tend to nucleate on one or two very large ‘key’ pieces or are racked against living vegetation. Key pieces usually have stabilizing rootwads or are ramped onto shore.
  • When wood is recruited to the river faster than the river can flush it through, the river will become wood choked and these wood choked streams will often start forming very large jams of wood. You will see this pattern play out for years in riverbeds following a large fire or in sections of streams downstream of avalanche paths or large landslides. If you are exploring new runs, take note of your surroundings and whether there is evidence of large landslide scars or fires. This will indicate that you may be in for a portage sufferfest.
  • Wood likes to get stuck in more physically complex stream sections that have multiple flow paths (sections with mid channel bars, islands, large boulder obstructions). Also pay attention to outside bends since floating wood in the fast current often gets swooped by here and then caught up on the bank or vegetation. Once one piece is stuck other pieces of wood are more likely to get caught in the same location. If there is anything to take away from this article, it is that I hope that my fellow boaters can start seeing themselves as part of this world in which we live. The natural world isn’t separate from us, nor should it serve us on our every whim. 

Before engaging in a wood removal project, just pause and ask yourself, what is the minimum necessary action to take to mitigate the risk from that piece of wood? And, do you really need to chop it up into tiny pieces? 

Yes, the wood will move downstream and may become a hazard somewhere else, but aren’t we all assuming some risk when we are navigating these natural places? The living world needs those large pieces intact.

Me, surfing on the Spokane River near a log. Photo by Leif Anderson


If you are interested in exploring wood and recreational safety more deeply I recommend reading, Riverine large wood and recreation safety: A framework to discretize and contextualize hazard, A peer reviewed article I wrote with WIll Conley. I will happily engage with you privately and can provide a full version of a paper if you are unable to access the article.

For those of you wanting more on the topic of wood in rivers in general, I recommend viewing this short video about my driftwood research that I put together a few years back, reading the stunning ways driftwood builds landscapes (a short blog that I wrote for National Geographic) and reading The Natural Wood Regime. (a short, open access, overview article in Bioscience that I co-authored).

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