Flash Flood and Hail in California, September 4, 1997

A severe thunderstorm packing torrential rains and golf ball size hail pummelled the Mill Creek Basin and the Yucaipa Ridge, in the San Bernardino Mountains, sending flood waters rushing down Mill and Little San Gorgonio Creeks. A spotter in Forest Falls reported 2.5 inches of rain in just 45 minutes. The result was a 15 foot high, 150 foot wide, wall of mud and water rushing through the Mill Creek Canyon, and into the town of Forest Falls. On the south facing slope of the Yucaipa Ridge, a 6 to 10 foot high flow of water and debris cascaded down Little San Gorgonio Creek, flooding portions of Oak Glen as well. The Forest Falls area bore the brunt of the damage as tons of mud, boulders, and debris buried roads, mangled automobiles, battered scores of homes, dislodged propane tanks, and stranded residents. Two homes were completely destroyed and 77 others suffered damage, 16 seriously. In Oak Glen, a nursery suffered extensive losses, otherwise the major damage was to roads and drainage facilities. Clearing mud, rock, and debris flows was costly. Two minor injuries were reported. Total estimated damage and debris clean-up was $3.2 million in Forest Falls alone, and another $250,000 in Oak Glen.