Willows for Streambank Restoration
Willows serve many functions in their ecosystem. You can read more about that here. They’re tenacious, resilient, and vigorous. Combined with a willow’s ability to replicate, these traits can be harnessed to naturally repair and replenish our waterways. Here we’ll look at just some of the methods currently being used to do so. The links contained herein will be listed at the bottom if you want to skip ahead to those!
On July 10, 2023, Vermont experienced a massive storm event that caused flooding which resulted in millions of dollars in damages across numerous communities. Raging rivers wiped out many bridges and forever altered the shape of the channels containing them. I’ve personally seen this many times in my work at the US Geological Survey. If you’re reading this, you’ve no doubt seen it too.
There’s a LOT on this subject, so we’ll be speaking broadly here. As always, be sure to do your due diligence before attempting any restoration projects. Get a second opinion. And maybe a third.
What Causes Erosion
Lots of things! Heavy rains washing down streams is the most common, but even simple use from ATVs, hiking, herd animals, etc can damage a streambank. Deforestation and overdevelopment are major contributing factors. Like that old sponge in my first apartment, concrete doesn’t absorb water. Without the ability to permeate the ground, asphalt roads become river tributary sources which cause creeks to rapidly rise and chew away waterways.
What a Willow Does to Help Reduce Erosion
Erosion is typically caused by high flows in rivers cutting the earth out from under vegetation. A willow’s root system reaches out like large claws and grasps the earth under it. The roots mitigate some of the forces from high flows thus reducing damage to the bank under it. Many willows planted closely together grow a dense network of such roots. Willows will also act as a “speed bump” and filter for debris that might wash through a farmer’s field or roadways.
Some Methods Which Incorporate Willows
Live Staking
A stake is a 2-to-3 foot section willow, roughly between 3/4 and 1 inch in diameter. Ideally, it is straight and has had the side growth pruned back. The top of the stake should be flat, while the bottom is cut at an angle to aid in planting and water uptake. The stakes are planted, 2/3 to 3/4 the length of the stake, perpendicularly in to the ground where it slopes. Planting configurations can vary, but are generally one-to-three feet apart. Native willows are often preferred for this.
Check out PennState Extension’s thorough write-up here. They also have a fantastic how-to here.
It’s recommended to incorporate stakes from trees local to your planting site but you must be careful not to overharvest which can cause irreparable harm! Live stakes are available for purchase at our nursery.
Note: salix purpurea is considered naturalized in the US.
Fascine
These are a mélange of materials, both live and not, wrapped in a bundle. They typically consist of willow, dogwood, and poplar. The bundle is then laid down in a shallow trench at particular points in a riverbank. Yes, willow can even grow laying horizontally! Intervale here in Vermont does extensive fascine work using bareroot willows. Our nursery doesn’t carry pre-packaged fascines, or bareroot willow, but we do have rods that can be integrated in to bundles you’re building.
Hedge-Brush Layering
Bring out the neighborhood for this one. And the heavy machinery in some circumstances. This is used when a slope is in danger of becoming a landslide. This takes, well, a layer of cuttings and sandwiches them between earth or other materials to create a bank that takes less time to strengthen than other methods.
Closing
This is just the tip of the iceberg. There are too many methods for me to cover in this space. Besides, other people already have, and quite a bit more extensively! I hope that this article has served as a doorway to discovering a more natural solution to an erosion problem you may be experiencing.
Links
A Willow’s Place in it’s Ecosystem
PSU Live Staking for Streambank Restoration
New York Plant Atlas – s. purpurea