Washington Trails Association
Trails for everyone, forever
Managing rain and water runoff is key to building and maintaining trails that will stand the test of time. Here's how we do it. | By Rachel Wendling
On one of my first days of volunteer trail work with WTA, I was assigned to build a series of ‘drain dips’ alongside a forested trail outside of Issaquah. A friendly assistant crew leader taught a small group of my fellow volunteers the art of drain construction — we worked together to dig out and shape gradual trenches beside the trail tread. By the end of the day, we had completed several of these drains, and I went home feeling accomplished and full of those post-volunteering warm fuzzies. But, I’d be lying if I said I fully understood the impact of my day's work.
That all changed when I volunteered again on a rainy day.
I’m a Washingtonian through and through, but like most people, I wasn’t stoked for a full day of work in the cold rain and mud. I went anyway, knowing that the joy of volunteering would quickly overshadow the weather.
When I arrived, I learned that our project for the day was — once again — drain dips. I was happy to use some of the skills I’d learned on my previous trip, so I quickly grabbed a shovel and grub hoe and headed off to the designated drain site.
As I dug my shovel into the build-up of dirt along the trail edge, a river of water rushed towards my feet, like I had removed a tiny dam. As I continued widening and carving out the mouth of the drain as I had been taught, water poured toward my under-construction drain. I could see the trail in front of me drying out.
The steady rainfall helped me identify puddles that were still forming. That day, I saw the trail in a way I had never experienced before. Through subtle shifts in my drain construction, I was able to address stubborn water patches I might not have noticed on a dry day. After an hour or two of this finessing, I stepped back and admired what, at that moment, felt like my magnum opus of trail work.
During my lunch break, I watched as freshly fallen drops trickled down my newly-built slope and I greeted passing hikers who walked with ease across a now mud-free trail. This was the first time I had seen the impact of my trail work play out before my eyes, and it's a memory I think about often when I pass by the work of others on my hikes.
And let's just say I've been seeking out rainy day work parties ever since.
Working on trails across Washington means Washington Trails Association needs to be an expert in building and maintaining trails that last in different kinds of ecosystems. For much of the state, that means being an expert in managing rain and water runoff so our hard work doesn't disappear with the next rainstorm.
Rain and water runoff is the main contributor to trail washouts and erosion, which can create dangerous or fully impassable sections of trail. Rain also creates puddles of standing water and mud on trails that hikers skirt around, leading to an ever-widening trail corridor that damages surrounding plant life. You may have heard this referred to as trail braiding.
Once established, trail braiding or washouts are a big hurdle to fix. Depending on the severity, it can take days, weeks or even full seasons to bring the trail back to its former glory. And these fixes can eat up a lot of the Forest Service's already-too-small budget. So it's best if the situation never gets that bad.
Much of our volunteer work is focused on preventative maintenance — proactive solutions that will keep water and the trail damage it causes — at bay. This ensures that our trails can last years, and save time, money, and frustration down the road. This type of preventative maintenance is highlighted in our Lost Trails Found campaign, where in addition to saving trails that have already been lost, we also work to identify at-risk trails that are susceptible to damage or disappearing in the future. Our volunteers build the infrastructure to keep trails on the map for generations to come — and our members help make their work possible.
Our trail-saving tactics don't always look like much during the dry summer months when they are often built, but they pull a ton of weight during our wet and stormy winter months. These are just a few of the projects and structures our volunteers regularly build on trail, and although you've likely seen them during a summer hike, you might not have known how they work behind the scenes:
Drain dips are commonplace on Washington’s trails — you might pass by upwards of a dozen drain dips on a single trail without even realizing it. Despite their unassuming appearance, these small pieces of trail architecture are crucial to trail sustainability in a wet and rainy climate.
As the name implies, drain dips work to drive water off the trail surface and into the surrounding environment while maintaining a dry (or at least not too muddy) and walkable trail surface. They’re built similarly to the drain in your shower or bathtub, with a gentle, almost imperceptible, slope that angles water toward the drain. In the summer, dry drain dips don't look like much but come back in the fall or winter and you'll see their usefulness as they fill up with runoff.
From a hiker's perspective, check steps probably look like a very simplified staircase — a series of submerged logs placed perpendicular to the trail that are spread out along an uphill slope. But unlike stairs, they have a bit of a different purpose.
For steeper sections of trail, check steps (sometimes called check dams) are a wonderful tool for erosion control. They work to slow down the speed of surface water, by breaking up an otherwise unobstructed downhill trajectory. Since water can carry material away as it flows, slowing down surface water helps hold the trail itself in place during the winter season rather than allowing it to wash down the hill in heavy rain. You'll often see these steps paired with other drainage methods (like drain dips) to maximize efficiency, too.
When a trail meanders alongside a steep sideslope, it may require a little extra reinforcement to keep the trail tread from sliding right on down the hill in a storm. In come retaining walls.
Retaining walls are usually built with large rocks (often scavenged from the surrounding environment) or on occasion, logs. The rocks are placed in staggered tiers leaning slightly inwards toward the trail itself, and securely hold our trail tread to the sideslope. These walls should be, well, rock solid as they need to be able to withstand the weight of thousands of annual hikers (and in some cases, horses) as well as our annual rainfall.
Retaining walls are truly a sight to behold — though you may need to crane your neck over the hillside to see them. The precise interlocking of rocks into a stable structure is an art form, and when built with care, should last for decades.
In flat areas that are particularly wet or boggy, water diversion tools like drain dips or waterbars simply aren’t enough to keep the trail surface dry. When that happens, we often resort to another common trail structure known as a turnpike.
Turnpikes are essentially just elevated trail surfaces. They are constructed with two parallel logs or rock walls running alongside the trail edge that is then filled with small rocks and mineral soil between them, which raises the tread above the water table. Small ditches are also added along the outer edge of the structure to help lower the water level even further away from our trail surface. Although simple in design, this added boost in height is just enough to keep our feet dry and our tread stable in notoriously wet areas.
The next time you're out on trail, keep an eye out for one of these common water-mitigating structures, or if you're feeling so inclined, join us on a volunteer work party for an opportunity to help build one!