Debris Flow — San Bernardino County Mountains, California

2003-12-25 · San Bernardino County Mountains, California

Wider weather episode

Steady light to moderate rain began falling over the burned areas of the San Bernardino Mountains on 0600 PST 12/24/03. Approximately 24 hours later, mud, rock, and debris flows were being reported along highways and roads leading into the mountain resort communities. By 0800 PST on Christmas Day, more than two inches of rain had fallen at many locations. Between 0800 PST and 1320 PST, rainfall rates increased from 0.20 to 0.70 inches per hour. Between 1300 and 1305 PST, mud, water, and rock slides moved through the Pohl Ranch, located about 1.3 miles south of Crestline. This flow continued down the canyon, moving through a campground at approximately 1309 PST killing 14 people. It then flowed into the main Waterman Canyon, taking out two bridges downstream at approximately 1316 PST. It finally fanned out and filled the percolation basins located 3.5 miles north of San Bernardino City center between 1337 and 1400 PST. Rainfall rates stayed heavy after 1320 PST. At 1335 PST, downstream ofthe south fork of Lytle Creek, water began to rise rapidly. A flash flood moved downstream from Scotland, taking out much of the roadway and causing mud, rocks, trees and other debris to wash across the frontage road next to Interstate 15 near Glen Helen. Between 1400 and 1500 PST, a large mud and debris flow came down City Creek, crossed several roads in Highlands, covered a portion of the runway at the old Norton Air force Base, and deposited 18 feet of mud in the Santa Ana River Basin. Moderate to heavy rain continued until approximately 1930 PST, averaging near 0.70 inches/hour. At 1800 PST, a flash flood/mud slide moved down Cable Canyon, through another campground, killing two people, a bear, and a horse, destroying 32 travel trailers, many vehicles, and roads. Heavy rain began to taper off after 2000 PST, with rain ending about 2200 PST on 12/25/03. In all, 33 of the 34 debris basins along the foothills of the San Bernardino Mountains were filled with rocks, trees, and mud.

Source: NOAA Storm Events Database, event_id 5328281. Narrative written by the NWS forecast office that issued the report.