[Russell Towle's journal]
Photos from Pickering Bar
May 19, 2001
May 19, 2001
|Petrified wood, revealed in hydraulic mine "diggings" in the Gold Run region.|
Date: Mon, 19 May 2003 10:06:29 -0800
To: North Fork Trails
From: Russell Towle
Subject: Codfish Falls
Various factors have conspired to delay a visit to the 567-foot waterfall in New York Canyon, and also delayed has been an attempt to traverse Giant Gap on the HOUT/SHOUT/Giant Gap Survey route from Canyon creek to Green Valley. However, on Sunday my family and I drove down to Weimar and followed Ponderosa Way to the river.
A couple dozen vehicles were parked along the narrow dirt road. The day was warm and bright, the river, high and fast, with rafters and kayakers enjoying the ride. We set off downriver on the trail to Codfish Falls.
This was my first visit to these pretty cascades. The mile and a half from Ponderosa Bridge makes for a very pleasant walk, with abundant wildflowers. It was interesting to see both the California Poppy and its close relative, the Tufted Poppy, growing in close proximity; most of the poppies along the trail itself are the smaller, yellower Tufted type, while in the broad floodplain of Codfish Creek the larger oranger Californias are seen side-by-side with the Tufteds, both set off against extraordinary masses of blue-flowering lupine of two species.
The trail closely parallels the North Fork for nearly a mile before curving north into Codfish Creek. There the trail follows, successively, the lines of two or three old mining ditches, hardly recognizable, showing that the gravels here were mined heavily, perhaps in several episodes, beginning with the Gold Rush itself. Scattered along this last part of the trail were many white Globe Lilies, in the genus Calochortus, and some very pretty shrubs unfamiliar to me, with showy white pendant flowers and large glossy ovate leaves. These later proved to be California Styrax (or Storax), Styrax officinalis.
The last and highest old mining ditch led us directly to the cascades. Here a zone of more competent rock has resisted downcutting by Codfish Creek, which makes a sharp drop of nearly 100 feet. The rock was fairly heterogeneous, varying over short distances, but my guess is that it is metamorphosed volcanic rock or volcaniclastic sediments; there was often a fine-grained dark matrix, without much in the way of slaty foliations or bedding planes visible, and with occasional clasts of other types of rock embedded within this matrix. The non-slaty, relatively massive (unjointed) nature of the rock seems to be the principle reason it has resisted erosion so well. This is a common theme in these suites of metamorphic rock which make up so much of the Sierra around here. Slaty stuff -> easily eroded, massive stuff -> not easily eroded. Thus from a general standpoint metamorphic rock of sedimentary origin makes for broader canyons, metamorphic rock of volcanic origin makes for narrow canyons and gorges. There are exceptions to this rule.
After exploring up and down the creek and snacking in the shade of the alders below the cascades, we wandered back, leaving the trail, after a while, for a long reconnaissance through the floodplain, with all its wonderful flowers.
At Ponderosa Bridge, a mile up the North Fork, another patch of resistant rock made for a narrow inner gorge of very limited extent, but forming a good bridge site. Just downstream the canyon widens and suddenly a large bouldery gravel bar appears, flanking the south side of the river. The large number of blinding white quartz cobbles on this gravel bar shows that a scant hundred and twenty years ago it was buried beneath hydraulic mine tailings, from the mines at Gold Run, Iowa Hill, Yankee Jims, etc. However, standing farther back from the river is a very well-defined terrace of glacial outwash, perhaps thirty or forty feet high, well-stratified, and apparently freshly nicked and brought into greater visibility by the January 1997 flood event, when an astounding 70,000 cubic feet per second flow was recorded a few miles downstream at North Fork Dam.
This terrace had been the scene of intense mining activity, with large piles of boulders left to gradually darken under coats of lichen, in the many decades following those particular episodes of mining. Then, immediately downstream, more recent mining, perhaps from the 1930s, and by my guess involving some kind of large stationary dredge, had left far fresher piles of gravel, fresher and lighter in overall color and also notable for the large proportion of quartz clasts. Obviously this more recent mining had involved great volumes of hydraulic mining sediments, with their "signature" high incidence of white quartz cobbles. This is not surprising since large amounts of fine gold and even some coarse gold escaped the sluice boxes of the hydraulic mines. Thus a "bar" worked intensively by the 49ers and then again by the Chinese might have been re-enriched by hydraulic mining debris.
This whole complex of near-river-level gravel bar + Pleistocene glacial outwash terrace + mounds of dredge spoils, was around a half mile in length. Then the principal zone of sediment accumulation switches to the north side of the river, where the floodplain of Codfish Creek is really not an artifact of the creek itself, so much as a large embayment cut, by the North Fork, into that area in the Pleistocene, when the river was meandering over an outwash plain. After the glaciers far upstream melted away and the huge sediment load abated, the river cut down through this outwash plain, leaving remnant terraces here and there. The "floodplain of Codfish Creek," then, is really part of the outwash plain of the North Fork itself, and the river has managed to erode and rework and remove much of the outwash in that area, over the past twelve thousand years.
This also helps to explain the signs of intense mining activity near this false floodplain; for one would not expect any significant gold accumulation to have derived from the paltry sediment load carried by Codfish Creek itself.
This broad meadowy area is still subject to high flood stages of the North Fork. It was quite interesting to see a fairly large remnant of hydraulic mine tailings as I neared the North Fork, a terrace of some thousands of cubic yards of sand and gravel with white quartz pebbles much in evidence, and signs that the mass had been nicked and partially removed during the January 1997 flood event.
The era of hydraulic mining provided an interesting real-world, real-time test of the abilities of many local streams and rivers to transport sediment. Millions of cubic yards were dumped into all these canyons. Small streams with steep gradients (i.e., Canyon Creek near Gold Run) were able to clear themselves almost completely from the masses of tailings. Larger streams with flatter gradients have been less able to rip these recent sediments out. The Bear River, for instance, is still deeply clogged with hydraulic mine tailings over much of its course from Dutch Flat to the Sacramento Valley. The North Fork American, in contrast, with its much larger basin, extending, also, to the Sierra crest itself, which the basin of the Bear does not—the North Fork has ripped out almost every vestige of tailings. It develops far higher flows and more severe flood events than does the Bear.
In 1881, as recorded in testimony taken in "State of California vs. the Gold Run Ditch and Mining Co.," one could drive a wagon over the tailings, right up the North Fork, from the Colfax/Iowa Hill bridge to Canyon Creek. At that time the mines at Gold Run were delivering three to five thousand cubic yards of tailings, per day, to the North Fork. Masses of tailings at the Colfax/Iowa Hill bridge are also clearly visible in photographs taken by Eadward Muybridge in 1867. These are long gone, now.
This is all to say that within historic times we have more or less recapitulated the process of Pleistocene accumulation of outwash sediments, followed by early Holocene incision, erosion, and removal of those outwash sediments. It helps to show, for instance, that not only is the North Fork able to transport large volumes of coarse sediments, but it can do so in a very short time. My guess is that a couple thousand years was all that was required, after the glaciers melted away and sediment load diminished, for the North Fork to rip out so much outwash that it reached its essentially modern, present state, with only isolated terraces left to show that a generalized outwash plain ever existed.
Downstream, below Ponderosa Bridge and near Codfish Creek, one sees that a fairly significant amount of tailings remains, but only in those favorable locations where the broadness of the canyon had allowed a large Pleistocene outwash plain to develop, and subsequent incision of the river into a stable channel has allowed terraces to persist, almost untouched by even the highest flows, for twelve thousand years. The lower gravel bars flanking such terraces are themselves reworked masses of bouldery glacial outwash, and are to a lesser extent also protected from further erosion by normal high flows. It is in such locations that we find some proportion of hydraulic mine tailings persisting along the North Fork. However, to me it looks as though the river has fully reoccupied its pre-mining channel.
We regained the trail and returned to Ponderosa Bridge, where a very small girl wading in the so-cold, so-fast river worried me, being a bit too close to rapids just downstream. Her parents were near, but she could have been swept away in an eyeblink. A Placer County Sheriff helicopter came roaring down the canyon, very low to the river, and almost instantly disappeared around a bend downstream; perhaps someone had fallen in the roaring river. Gradually our party arrived at the sunny beach by the bridge, and soon we were in the car, driving home, after a lovely day on the North Fork.