I find this station to be most useful for judging what has transpired recently in our local Wshington jade streams. Over the years I have checked this page a few thousand times to try to understand which flooding conditions make for the best collecting after the water recedes. The belief that the best collecting occurs when the stream is low enough to get far below the high water mark is a fallacy. Most good rough , jade or jasper falls out of the water column about half way between the high water mark ( flood stage ) and the summer-fall low water mark. Where on the gravel bar is a much more important concern and over time you get a very good idea which part of the bars have the best chance of hosting desirable rough. Other experienced collectors know this as well so if you wait until the streams go down substantially the best rough will be largely gone to a more enterprising collector. The amount of time that the flooding event stays at a very high level is also crucial as the turn over of the gravel bars from flooding is incremental, it starts where the velocity is highest , the low water channel, and moves progressively toward the high water mark. The duration of this particular event was marginal but the volume was barely adequate so there will be at least some good picking mostly on the heads and tails of the gravel bars. when the center turns over well you can have days that boggle the imagination. Notice the scale of the graph. Normal low flow is about 800 cubic feet per second and this event reached over ten thousand cf/s. One stream I collect in runs at about 6,000 cf/s and the highest it has been while I collected in the area was an astounding 430,000cf/s! That is as large as the Mississippi river is during a big flood at the measuring spot on the lower river where the emergency diversion channel cuts off to the gulf of Mexico. The 430,000 event cut through foothills 600 feet high and filled the valley about 40 feet deep. The volumes of such events destroy the gagueing stations so to accurately estimate the volume hydrologists survey a cross section of the damaged area of the valley ( to discern the high water marks ) and from the cross section that results they can accurately estimate the volume. Another stream in that event was over 90 feet deep instead of the usual 5 feet. A large cast iron railroad bridge from steam train days was 90 feet above the stream bed and it was washed away with no trace ever found.
