As you may have noticed, the weather has been pretty unpredictable across the Northwest for the past several weeks. Mother Nature can’t seem to make up her mind. One day it’ll be snowy and cold just like one would expect during mid winter, and a few days later it feels warm enough to be late spring, and then a few days later there is now on the ground again. In between the two, we get strange periods of time where both seem to be true. Somehow, its 40 plus degrees and we have 8 inches of snow on the ground still. This tends to wreak havoc on transportation systems and other private and public infrastructure. Rapid freeze and thaw cycles may turn pavement into potholes, burst water lines, or cause flooding. When these temperature changes combine with additional rain or snow the situation can get really nasty pretty quick. An event similar to this recently happened with one of our longstanding and great clients, The Town of Oakesdale, Washington.
Located 50 miles of south of Spokane, Oakesdale is a typical Palouse town with great character and a very rich history. The town was founded around the turn of the 20th century as a farming community in the beautiful rolling hills of the Palouse. Easy access to water was a necessity back then, as it provided the ability to sustain life in a seasonally dry climate that was otherwise uninhabitable for most. Logically, the town was formed near the confluence of McCoy Creek and Trestle Creek, where wells could be hand dug without too much difficulty. However, the presence of these two creeks has been a mixed blessing over the years. While providing a consistent water source, creeks and rivers also surge with storm waters from time to time always pushing downstream towards the sea as fast as gravity will allow. Being that Oakesdale sits at the confluence of two creeks, this location is a particular risk for seasonal flooding. Now, add in 100 years of development, a network of paved roads and ditches and extremely efficient agriculture in the immediate area. Things can get complex pretty quick. Fortunately, the town has been pretty lucky and only had a few instances of flooding over the past several decades. But, like most things, just because an event hasn’t occurred recently, doesn’t mean it won’t.
Now, let’s skip back to that freeze thaw cycle. Snow melt happens every year, it’s inevitable. But under the perfect conditions, things can get extra messy really quick. For instance, when there’s been a significantly long cold spell with a moderate amount of snowfall followed by a much warmer period mixed with rain, or in some cases even without rain. Oakesdale seemed to get the perfect combination of variables during the week of February 10th and no one saw it coming. You see, freezing and thawing doesn’t happen at all once. In this case, most all of the snow around Oakesdale melted quickly as it warmed up pretty rapidly while raining a bit. Temperatures in the area were in the teens on Sunday, and by Tuesday it was close to 40. When a rapid temperature change like this occurs, most of the snow melts but the soil and earth below take quite a bit longer. Because of this, little to no water is infiltrating into the ground, and nearly all is being transported downhill. So an unusually large amount of water is flowing down street gutters and ditches, across fields, and through culverts and piped systems all down into natural drainage channels in the bottom of the valley. On this particular week, it was happening like this all over The Palouse. And for Oakesdale, it meant both McCoy Creek and Trestle Creek were nearly full trying to pass as much water as possible from upstream in the valley.
So what happens when things get too full? We all know the answer to this. We have a big wet and muddy mess. In Oakesdale, some key culverts that pass water through town from the outlying areas and wheat fields backed up because the creek was overflowing its banks and it got worse from there. Within just a few hours that day, water was gushing through back yards and across streets. The few town employees and several townspeople were able to mobilize pretty quickly and get some sand bags setup where they were needed most. Fortunately, only a half dozen or so buildings were damaged. Even that is a pretty big disaster for a handful of people.
So what’s the moral of the story? I guess it is something I am always preaching about and striving for: Awareness. Whether you’re a small town in the Palouse, a property developer in Airway Heights, or a home owner on the Pend Oreille River, you need to be aware of what’s going on around you, particularly when it comes to water and drainage. Conditions will undoubtedly change over time. Municipalities and developers build more roads and place more concrete every year. Ditches are dug, and houses built. Erosion happens and culverts clog up. These all adds to the potential risk downstream, wherever that is. If it happens to be you or your property, or your town, you have a significant investment in what’s above you and below. Or if you are the property owner on top of the hill discharging additional water to other properties, you could be found legally liable for damages.
“And when it rains on your parade, look up rather than down. Without the rain, there would be no rainbow.” –GK Chesterton
Contribution by Matt Wright, P.E., TD&H Engineering, Spokane, WA
Photography courtesy of James Richman Photography
Posted on March 12, 2014