The Dynamic Environment of Rivers – What Happened on the Upper Middle Fork in 2022 and Why It Happened and What it Means
The last few years have dealt us some interesting challenges on the upper Middle Fork of the Salmon River. In a domino effect of fires, storms, and mudslides, we are witnessing first hand the impacts of these events in a dynamic wilderness environment. These geomorphological shifts will change the river flow for many years to come. But don’t worry, in the end, these events are and will continue to have many positive impacts on this amazing river that we love.
In 2021, the lightning-caused Boundary Creek Fire ripped through the upper canyon of the Middle Fork. It burned along the river and through many of its tributaries. If you have floated the Middle Fork, or spent much time in the West, you know that fire is a natural and (mostly) healthy part of our ecosystem. The Boundary Fire caused access issues for boaters in the summer of 2021, but it was nothing we had not seen before and we did our best to adjust. While much of the fire had healthy impacts such as burning the underbrush and leaf litter, there were also sections that burned much hotter, killing large swaths of the forest and scorching the soil. Unfortunately, many of these intense burns happened in some of the steepest and most rugged sections of the canyon. Losing the vegetation and root structures in these steep areas leads to the destabilization of the soil and higher risks of landslides.
August of 2022 brought intense microburst storms and heavy rainfall to the Frank Church Wilderness. These storms released multiple inches of rain within just a few short hours on the fragile, unstable, burned hillsides of the upper river. The power of water should never be underestimated and we witnessed first hand how quickly a landscape can change in a matter of hours or even minutes as multiple canyons and hillsides gave way in large scale blowouts.
Don’t worry, this story has a happy ending.
A debris flow or “blowout” is a geomorphological term for a landslide up a tributary that builds momentum as it continues downstream. With extreme force and speed, this flow of mud picks up debris like rocks, boulders, trees, even bridges along the way. When it finally reaches the river, it spews into the main channel, often carrying enough debris to create an earthen dam capable of rerouting or even blocking the entire flow of the river for a period of time. These events can happen on any scale but the ones we experienced last summer were large enough to cause drastic changes to the river corridor and prevent boat passage for the remainder of the season..
Throughout history, many of the rapids on the Middle Fork and rivers everywhere have been formed by blowouts. A debris flow will block the river, forming a dam. As the river backs up behind it, the force of the water builds and begins carving a path through the debris. Over time, the water will wash away the mud and small rocks and sediment, leaving behind big boulders and other large debris to form a new rapid. This is what we expect to see from the new blowouts on the Middle Fork as well.
This powerful event of nature created a mess for the river users, both commercial and private. The blockages started at mile 5, and the groups on the water above could not pass or go around and had to get their boats and equipment out via helicopter and mules. Trips were canceled and the fishing came to a screeching halt. At that point, all float groups had to readjust and begin flying in all equipment, guides and guests into the Indian Creek Airstrip to launch trips.
About a month after the August blowouts on the Middle Fork, just as the river was almost passable again, another storm system dumped rain on the already destabilized hillsides and we saw a repeat event of large scale blowouts in those same tributaries. The river’s ability to clear a path through the debris depends greatly on the volume of water in the river. With these blowouts happening in August and September during low flows, the river took much longer to cut a new path. Much of the debris that came down was wood. With thousands of trees getting pushed into the river, we were left with multiple impassable log jams. Looking forward to this next river season, we feel optimistic that the spring runoff will have the power to clear out these jams and clear much of the debris to allow boat passage.
Now for the good part! Though this mess created challenges for just about everyone, there is so much more that comes from it. Fire and blowouts have long been a part of the Middle Fork’s ecosystem. Many fun and challenging rapids that we have today were created from them. One of the biggest benefits is all of the added sediment that the blowouts deposit in the river. This sediment and fresh rock is great for the fish and creates optimal habitat for spawning salmon, steelhead and trout. With the Middle Fork being home to the highest elevation anadromous run in the world, spawning for these ocean going salmon and steelhead is critical. The sediment that came down with the logs and boulders provide new irregular sized and shaped substrate and benefits spawning fish, while the added woody debris provide good cover for juvenile fish. Increased spawning activity in the water and the resulting biomass that adds to the ecosystem provides nutrients for the bug life and juvenile fish. This in turn helps all populations of fish and animals in the ecosystem.
Over the next few years we can also expect to see much of the finer sediment washing down stream to replenish the beautiful sandy beaches along the river. The big sandy beaches at Elk Bar, Otter Bar, Parrot Placer and many other loved beach camps should be even more spectacular with this new sand being deposited.
Part of why this river is so special is that it is wild, it is free flowing, and completely untamed. Nobody wants the water to be muddy on their fishing trip, or to have to change their vacation plans. Luckily we do have the option to fly in to launch the trips if we are faced with the issue of the river becoming blocked again. This year’s events posed a substantial challenge to boaters and river visitors, but it is a good reminder that we are simply guests in one of Mother Nature’s most amazing wild places. Come see it for yourself.
– Written by Sadie King and Kelsey Helfrich