Winter has finally arrived in WNC and that means we are forced to make a public service announcement about the ‘freeze/ thaw’ cycle. In WNC, this cycle does not occur on a precise schedule. Due to the excessive rainfall the last couple of months, winter moisture is in abundance. When soil freezes all the moisture turns to ice crystals between the particles of the soil and in clay or loam soil they are tightly packed together. As the moisture freezes the crystals expand and tear the clay apart shattering it, then as it thaws the soil becomes more porous and allows more moisture in. This is repeated with every successive thaw, and does not require recent rain or snow. It simply requires moisture to be present, which may have been there months prior. If the trails are dry before the freeze/thaw cycle begins, the trails will not be affected as much. As soon as moisture is added to the system, however, conditions degrade rapidly during each thaw cycle. The general rule here, however, is that if nighttime temperatures get below freezing, you should be safe for an early morning ride, before the sun is up in full force. Usually, if you are off the trails by 10:00am, you should have zero problems. Beyond that, it gets complicated by the presence of snow, sunshine, and wind. Some factors to keep in mind:” ”
• The presence of snow tends to insulate the ground. If snow falls on warm soil, the soil will oftentimes not freeze and even if ambient temps are below freezing, the snow will melt from beneath, creating a muddy mess eventually.
• If snow falls on frozen ground, it works the opposite way, snowpack can keep the ground frozen even when ambient temps are above freezing.
• Sunshine on south-facing slopes can melt snow and frozen soil well into the 20’s. This is why morning rides are most reliable during the freeze/thaw cycle.
• Strong winds can help dry trails more quickly and if it’s cold and cloudy, can help keep them frozen solid for good riding.
• Night rides on trails where night riding is permitted are another option during the freeze/thaw cycle. If ambient temps have dropped below freezing and the sun is gone, the ground will begin to re-freeze.
*This applies to all user groups*. Please help spread the word this time of year. Most of our trail damage occurs during the ‘freeze/thaw’ and creates a back log of maintenance issues come spring. Using common sense will help minimizing impact and will allow our crews to focus on projects that will enhance the riding experience instead of being bogged down with otherwise preventable tread repair from this time of year.