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<br />, <br /> <br />7. Waltonia Fan, 6,500', MM=74.3, 2:20 pm <br />This alluvial and debris fan enters on the right bank of the river and was <br />exposed by the 1976 flood. How can water-flood and debris-flow deposits <br />be differentiated after an unobserved event (deposits in/on fan versus in a <br />stream channel)? What are the implications for flood-plain management <br />if deposits are from a waterflood or debris flow? Radiocarbon dates at <br />the base (corresponding to late Pleistocene or early Holocene flood <br />deposits) yielded dates of 8,000 to 10,000 years before present; part of <br />the mid-fan dates a few thousand years before present. Trees on the <br />surface of the fan are 200 to 300 years old. Is it prudent to use fans for <br />building or recreation sites? <br /> <br />8. *** Handicap Catch and Release Fishing area, MM=72 <br /> <br />9. *** Large 1976 floOd-transported boulders. MM=71.5 <br /> <br />10. Long Gulch, 6.900', MM=71.1, 2:40 pm <br />This left-bank tributary to the Big Thompson River contains typical and <br />interesting evidence of floods (below 7,500 feet). The 1976 flood <br />discharge was 5,500 cfs (1.99 sq. mi). Diseuss the accuracy of flood <br />measurements on small mountain watersheds. Discuss the flood evidence <br />and hydraulic reconstruction of peak discharge using paleoflood <br />techniques. What PSis (paleostage indicators) do you see? How reliable <br />are PSis in estimating the peak stage in 1976? How long might it take for <br />hillslope and channel recovery following the 1976 flood? Effects of <br />climate and other basin factors? <br /> <br />11. House Removed from debris fan, 6,950', MM=70.1, 3:15 pm <br />This left-bank tributary was a conduit for a debris torrent which <br />severely damaged a house, since relocated a short distance downstream. <br /> <br />12. *** Glen Comfort, 7,150', MM=68 <br />This area is near the center of the maximum rainfall. Estimates were <br />12 inches in about 6 hours for such "cloudbursts." How is rainfall <br />measured? How measured or estimated without raingages? Can you think <br />what geomorphic techniques might be used to estimate rainfall amounts? <br />Discuss rates of hillslope erosion in various parts of the Big Thompson <br />storm and relation to long-term rates? <br /> <br />5 <br />