| Abstract: | Historical and geologic records may be used to enhance magnitude estimates for extreme floods along mountain channels, as demonstrated in this study from the San Juan Mountains of Colorado. Historical photographs and local newspaper accounts from the October 1911 flood indicate the likely extent of flooding and damage. A checklist designed to organize and numerically score evidence of flooding was used in 15 field reconnaissance surveys in the upper Animas River valley of southwestern Colorado. Step-backwater flow modeling estimated the discharges necessary to create longitudinal flood bars observed at 6 additional field sites. According to these analyses, maximum unit discharge peaks at approximately 1.3 m3 s~‘ km"2 around 2200 m elevation, with decreased unit discharges at both higher and lower elevations. These results (1) are consistent with Jarrett‘s (1987, 1990, 1993) maximum 2300-m elevation limit for flash-flooding in the Colorado Rocky Mountains, and (2) suggest that current Probable Maximum Flood (PMF) estimates based on a 24-h rainfall of 30 cm at elevations above 2700 m are unrealistically large. The methodology used for this study should be readily applicable to other mountain regions where systematic streamflow records are of short duration or nonexistent. ?? 1998 Regents of the University of Colorado. |
| Genre: | Article |
| ProdID: | 70020107 |
| Citation Author: | Channels, M.; Pruess, J.; Wohl, E. E.; Jarrett, R. D. |
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| Citation End Page: | 50 |
| Citation Issue: | 1 |
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| Citation Language: | English |
| Citation Larger Work Title: | Arctic, Antarctic, and Alpine Research |
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| Citation Number Of Pages: | 11 |
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| Citation Search Results Text: | Methodology and Implications of Maximum Paleodischarge Estimates for; 1998; Article; Journal; Arctic, Antarctic, and Alpine Research; Channels, M.; Pruess, J.; Wohl, E. E.; Jarrett, R. D. |
| Citation Start Page: | 40 |
| Citation Volume: | 30 |
| Citation Year: | 1998 |
| Type: | citation/reference |
| Text: | Methodology and Implications of Maximum Paleodischarge Estimates for; 1998; Article; Journal; Arctic, Antarctic, and Alpine Research; Channels, M.; Pruess, J.; Wohl, E. E.; Jarrett, R. D. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Thu, 1 Jan 1998 00:00 -0600 |
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