Pioneer Days in California by John Carr

quote from page 293 of the above historical book. They are speaking of a dam near Weaverville over the Trinity River in Northern California. They year I believe is 1862, the year of California's worst floods in history:
Begin quote: "The water in the river had been rising all night, and men were stationed on the bridge with poles to keep logs from striking the piers.  At about 4 o'clock in the morning a large spruce tree came down the river with roots, branches and all. The men seeing it come, and knowing the bridge was doomed, escaped from the bridge before the roots of the tree struck it. It was well that they did, for one of the men who were on the bridge told me the next morning that as soon as the tree sturck the bridge it went through it as if nothing had been in its  way, cutting it completely in two, and the whole structure fell into the river and was soon out of sight." end quote from page 293 from Pioneer Days in California which I believe is now a Google Book online.

New Quote Bottom of 293 and top of 294:
"As soon as daylight came Uncle Joe and I went to the ruins. Not a plank of the bridge was left. The rain was pouring down. The snow was nearly all gone. Everything around the place looked desolate. On the flat where the house was built they had the finest bearing orchard in Northern California. If the river rose but a little more, the trees would be swept away, and the house with them. All the forenoon the river continued to rise, and at last it began to spread over the orchard and wash the black loam away. Finally, as the current became stronger amongst the trees, one after another began to fall, some floating off with the water, and others hanging by the roots. Trinity that morning was playing havoc with the settlers on its banks. It was dreadful to look upon. Standing on high ground, one could see property of all kinds on its way to the ocean. The river itself seemed like some mighty uncontrollable monster of destruction broken away from its bonds, rushing uncontrollably on, and everywhere carrying ruin and destruction in its course.---" end quote.
next quote a few sentences later.
"When the river was at or near its highest, one could see floating down parts of mills, sluice-boxes, miner's cabins, water-wheels, hen-coops, parts of bridges, bales of hay, household furniture, sawed lumber, old logs, huge spruce and pine trees that had withstood former storms for hundreds of years--all rushing donw that mad stream on their way to the boundless ocean. From the head settlement to the mouth of the Trinity River, for a distance of one hundred and fifty miles, everything was swept to destruction. Not a bridge was left, or a mining-wheel or a sluce-box. Parts of ranches and miners' cabins met the same fate. The labor of hundreds of men, and their savings of years, invested in bridges, mines and ranches, were all swept away. In forty-eight hours the valley of Trinity was left desolate. The county never recovered from that disastrous flood."

http://books.google.com/books
Pioneer Days in California by John Carr

If you go to the above web address and then go to the Book name and then the right chapter you can read more for free it appears online. I found it fascinating to find such an apt description of eyewitness accounts of the 1862 Historical Flood in California in this historical book.