When a grizzly bear surfs woody debris…
December 1, 2011 § 6 Comments
…you know there’s trouble.
I had originally begun drafting this post as a follow on to Trouble at the Waterworks, which recounted how the significant rains of 1867 sent piles flying and reduced LA’s zanja system to carted water. These rains offer some insight to just how gnarly a 500-year storm could be, something that circulates in the news from time to time. It’s worthwhile to appreciate how much these rains can shift our rivers, when the human hand isn’t busily doing it, that is. Driving that shift: loads of debris from the mountains washing down.
And while for some this story may justify all the debris basin management that included wiping out a century-old oak grove in Arcadia(1,2,3,4), for me it is simply one more cautionary exhibit for adequate floodplain restoration. And, need I say it? Functioning floodplains provide us with many underappreciated (and FREE) benefits.
But back to an unfortunate grizzly near the Whittier Narrows on the San Gabriel River, circa 1867, as recalled in James Reagan’s 1914 Early Floods in Los Angeles County:
Setting the stage:
“In the 1867 flood there were thousands of cords of wood brought down from the canyon and scattered over the country. They were hundreds of teams hauling wood to Los Angeles and the other small towns for weeks. There was a small slough, or branch now filled up, just below his house, that was filled chuck full of cedar and hemlock logs, some as large as three feet in diameter, and he had wood for years.” – Interview by R. A. Borthick of Mr. J.D. Durffy in El Monte, CA
“…a man by the name of Henry Roberts…told him that in the ’67 flood that he lived down below the narrows, and the water very nearly stopped running, and it had been raining hard, and he took his gun and went up on the hills by the narrows to see what had stopped the water, and the water was blocked by logs and drift, and he says some 25 to 50 feet high, and backed up three or four miles, and he says when it went out it made a noise loud enough to be heard two or three miles, and broke logs four and five feet thick…”
Wait for it…
“Mr. Dodson says after the 1867 flood he hauled wood from one place below the Narrows for about two years. There was a patch of ground about two acres in size and from 6 to 20 feet deep with logs that had come down from the jam at the Narrows, and there were lots of logs as large as five feet in diameter that had been broken as if matches. He found a dead grizzley bear out in the center of the pile of logs after he had been hauling from the pile quite awhile. The skeleton of the bear and hide was all there, and he said it looked as if it had been caught in the flood, and tried to save himself by riding the drift wood. Anyway, he was there, and it showed he came down in the 1867 flood.” – Interview by R.A. Borthick of Mr. W.R. Dodson in El Monte, CA
Geomorphologists today consider woody debris to be an important factor in creating dynamic rivers – and ultimately higher levels of ecological function. We have so little information about our Southern California river systems in an unurbanized, unengineered state that it is difficult to imagine wood contributing to channel dynamics, although we are all too familiar with tales of our wandering rivers:
“The thousands of houses of Lakewood were built quickly and cheaply because the land was flat. It was flat because all of it had been, over the preceding geologic era, a temporary bed of the Los Angeles and San Gabriel rivers. They were called “tramp” rivers in the 19th century. In a heavy rain, the rivers might shift their beds by as much as a mile. Or one river would braid a new course, loop it out to capture the flow of the other river, and take the combined flow of both to a new mouth at some indeterminate point on the coast until another season of rain rearranged the landscape.” – D.J. Waldie (and thanks to my colleague Rich Walkling for the quote!)
With today’s understanding of river form, function and dynamics, it may be more helpful if planners could relate to the floodplain as those flats. And, with or without our flood control system, in a large enough storm, we should perhaps expect the rivers to “tramp” around…uh, sorry, Lakewood. But as the grizzly shows us, it doesn’t end well to be in the path of the San Gabriel River.
An old grouch gets the last word:
” …it was mostly the people’s own fault…they would build houses and ditches and dams and fill up the streams and when anybody told them they would get flooded out they would not believe them.” -Bob Watson (Reagan, 1914)