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The 1938 flood was termed a 100-year flood, and it prompted the County to establish the Flood Control District to implement measures to avert any such disaster in the future. By 1969 there had been massive construction of channels, settling basins, etc. Those measures undoubtedly prevented the '69 flood from reaching 100-year status. During the '70s the SBCFCD had displayed on the walls of their offices at 825 East Third Street two very large aerial mosaic pictures of the valley--one taken just after the '38 flood, and one contemporary mosaic in which the extensive network of constructed facilities was visible.
In San Bernardino the expanse of water created in the '38 flood by the Santa Ana River reached a few blocks north of Mill Street at Arrowhead Avenue. My husband lived in the first block north of Mill, and his family was the last one on the street rescued on wheels. Everyone after them was evacuated by boat.
By comparison, however, the 1862 flood created a continuous body of water from downtown Third Street in Berdoo to the bench north of Pioneer Street in Redlands. That disaster is ranked a 1,000-year flood. The millions of waterworn boulders you see throughout Mentone and the east end of the valley got there during that flood. Engineers performing core drilling for soil samples out there toward Greenspot Road encounter cow bones and fenceposts 40 feet down; before the 1862 flood it was a rich truck-farming area like the Cooley Ranch (W of I-215 & S of I-10).
One thing I've been interested in noting is how the Santa Ana River canyon east of the valley has during recent decades filled up with deciduous trees, leaving a rather narrow water course. As late as the mid-50s the whole width of the canyon was just rocks and sand, apparently having been stripped of trees by the torrential force of the '38 flood.
I knew an old Forest Service employee who had taken a crew of men upriver for some field work the day the Santa Ana went wild in '38, destroying the highway. They had to find their way out of the mountains on foot, along the sides of the canyon, taking several days to get back to the valley.
One result of the '69 flood that not many people even in Yucaipa know about could be described as a freak occurrence. It started in Oak Glen, above the apple orchards, where a the face of a hill had for centuries enroded down the center, depositing soil against a massive boulder. The accumulation of soil eventually enveloped the boulder, leaving a somewhat level area on the uphill side of it. That level area in the lower reaches of the hillside slowed the water draining down its little ravine, producing a sort of natural settling basin. Well, by the day AFTER the '69 flood, a huge area of those lower reaches of that hillside had reached the saturation point. Liquefaction had occurred, but the liquid mud couldn't go any place because that massive boulder was trapping it in its natural underground basin. Then came the decisive moment when the weight of the liquified soil popped that huge boulder out of the ground, opening the floodgates to a river that burst through Bob Bice's apple trees, sending a several-feet-high wall of mud flowing eventually through Wildwood Canyon clear to I-10, permanently changing the terrain on the north side of the freeway opposite the Live Oak Ranch east of Live Oak Canyon Road. That day a number of people had gone to look at Wildwood Canyon to see how much flooding and damage had occurred where several of Yucaipa's streets cross it. Consequently they were standing there surveying the canyon when the spectacle of that wall of mud came marching down the chasm, enveloping buildings halfway up their windows.
I could go on and on, but I did want you to be aware that 1938 and 1862 were the most major floods in recorded history of the valley.
And another thing. Please don't spell dam "damn." If you'd like, I can edit your whole article and email a cleaned-up version of it to you. Your website serves a very good purpose; but like hundreds of other people I've known over the years, including some with multiple doctorates, English class wasn't your finest moment. And many of you have wound up with your written material on the net, trumpeting your lifelong indifference to the finer points of the King's English.