|Trail ruts caused by riding partially thawed trails.|
What's the big deal with freeze-thaw cycles?
Dirt trails are extremely vulnerable to rut damage during the transition to and from winter because colder temps prevent the soil from drying. When soil freezes the growth of ice crystals push soil particles apart leaving large gaps that can fill with water when the ice melts. In a thawed state this dirt is much like a sponge and will absorb large amounts of water. It is also hypersensitive to disturbance by foot/bike traffic and flowing water and will form ruts with little effort. Direct sunlight and above freezing daytime temperatures can thaw the top layer of frozen dirt and create an easily rutted, greasy, muddy mess on the surface. Overnight, lower temperatures refreeze the top surface of the trails, ruts included, and the process repeats when conditions allow (hence the name freeze-thaw cycle).
Why are ruts bad for trails?
When ruts develop along a trail they channel water, causing erosion of the trail surface, and slow the drying process. Rain is highly erosive to trails when the ground is frozen and ruts greatly increase the chances of erosion by flowing water. When the soil is frozen, water can't soak in like normal and flows along the top in large quantities. Ruts on a trail can intercept these flows and divert them along the length of a trail. As the water flows down the trail and picks up speed it also picks up soil particles and washes them away from the trail. This can leave behind deep ruts tens or hundreds of feet long in extreme circumstances. Come springtime, ruts can also hold pools of water on the trail surface and prevent it from drying as quickly. If these puddles are disturbed by bike tires they can quickly turn into large mud pits. Fixing these areas eats up trail volunteer time that could be better spent on other projects. Wet areas like this also prolong trail closures.
Tips for riding during the winter/spring months where temps fluctuate between freezing/above-
Pay attention to the trail status
Don't ride frozen trails when the temperature is above freezing.
Ride frozen trails early in the morning before they have a chance to warm.
Don't ride if the temps are hovering around freezing and it is sunny. Wait until temps are below 25F and even then there may be thawed areas.
If after following all the above guidelines and the trails are still too soft, turn around and come back another time. A single rider can damage many thousands of feet of trail under these conditions.
Please respect the trails during the transition months in the winter/spring so everyone can maximize their enjoyment come springtime!