The objective Friday in Forest Falls was to re-open Valley of the Falls Drive, and squads of county workers, heavy equipment operators and dump truck drivers kept at it as the weather allowed.
More storm cells complicated their work for a second day and many residents who had to leave town earlier waited hours to return.
Hardest hit on Thursday when an estimated 4 to 5 inches of rain fell in a matter of hours was the lower end of Valley of the Falls, below a steep drainage that unloaded onto Prospect Drive.
Two homes were damaged on the downhill side of Prospect, where tons of mud and rock came down a draw and piled up to one home's highest windows, shattering at least one of them.
Most residents who remained in town were upbeat Friday, excited by the power of nature in their neighborhoods but hoping no one would be injured or suffer severe property damage.
The town, which lies in one of the most geologically active canyons in Southern California, can trace its history back more than a century. Although damaging boulder-laden debris flows and avalanches sometimes occur, most homes situated in vulnerable low spots have been removed by nature during previous severe storms, including 1938, 1969, and 1999.
According to geologists, several factors make Forest Falls and Mill Creek Canyon interesting.
- The town is situated linear box canyon astride an active fault.
- Steep ridges, particularly on the south side, loom above most of the homes and those ridges drain toward the primary road in and out of the canyon.
- The ridges are composed of tectonically crushed rock, gravel and sand.
- The topographic setting includes watersheds coming off San Gorgonio Mountain, the highest point in Southern California. Other high ridges help park slow-moving or stationary storm cells, especially during the annual monsoonal thunderstorm season.
- Multiple steep creeks or drainages that have formed naturally over time are now essentially rock avalanche chutes, capable of unloading tons of debris that can reach significant velocities in places.
Douglas M. Morton and Rachel M. Hauser authored the following USGS study after a severe storm event 14 years ago:
A Debris Avalanche at Forest Falls, San Bernardino County, California, July 11, 1999
For more recent Patch reports on Forest Falls see the following links:
UPDATE: Dangerous Beauty: Three More Injured at Falls in Mill Creek Canyon
VIDEO: Forest Falls 16th Annual Chili Cookoff Pays Tribute to Firefighters
PHOTOS: Hundreds in Forest Falls for 16th Annual Chili Cookoff
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