With all the rain, it was no surprise. Mudslides are somewhat common here, and they sometimes close roads. In fact, we were sort of expecting a small mudslide almost in this particular spot right when we got the call about it. The only slight surprise was that it was right next to where we expected it to be. The cliff that we expected to make this sort of mess was still intact under the tarps put over it to deflect some of the rain.
Fortunately, it was a small mudslide that blocked only one lane. We were able to direct traffic through the other lane while the blocked lane was cleared of debris by a small bulldozer.
The top of the cliff slid to the bottom along with a stump of a Douglas fir that was cut down many years ago. The Douglas fir was cut down so that it would not destabilize the soil that it was rooted into as it moved in the wind. However, The soil was destabilized as the Douglas fir roots that held it together decayed. This is actually a common dilemma, since trees sometimes need to be cut down before they cause such problems, but the death and decay of the roots of such trees ultimately cause the same problems.
The sorts of trees that could be coppiced do not do so well in the dry soil on top of cliffs. Otherwise, we could plants willows, cottonwoods or something of the sort, and cut them down as they get too big, without killing the roots. They would be happy to regenerate and continue the process. The sorts of plants that prevent surface erosion do not do much to stabilize the soil. Otherwise, we could put something as simple as freeway iceplant (Carpobrotus chilensis) on top, and let it cascade downward over the unstable area.
1. It was nothing too serious, but just enough to block the inbound lane. Tarps over the cliff that we expected to make this sort of mess are visible above the retaining wall just beyond. My work pickup in the lower right corner of the picture blocked the inbound lane with its headlights and hazard flashers on. I directed incoming traffic around it into the clear outbound lane as it was available. The young man off in the distance moved his pickup out of the outbound lane, and also directed traffic accordingly. When necessary, he stopped traffic while incoming traffic used the outbound lane. We communicated by radio and hand signals.
2. This is the stump of the Douglas fir that was cut down so that it would not dislodge the soil and cause a mudslide. A decayed stump of a smaller madrone tree is to the right. Their rotting roots and the English ivy were insufficient to stabilize the top of the cliff.
3. These significant mudstone boulders on the far side of the road could have done some serious damage to a car if one had gotten in their way.
4. That is where the Douglas fir stump came from, just to the left of the drainage pipe. It did not get very far. That is it at the lower left corner.
5. We arrived about ten. By noon, there was not much evidence of what had happened. We left the cones because the road was slippery with mud.
6. This is supposed to be a gardening blog, so here is an unidentified fern that witnessed the whole ordeal from a stable portion of the same cliff. There is slightly more flora to this story than two dead stumps and a bit of ivy.
This is the link for Six on Saturday, for anyone else who would like to participate: