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<br />U.S. Department of the Interior, Geological Survey, Water-Supply Paper
<br />1925, Surface-Water Supply of the United States 1961-1965, Part 9,
<br />Colorado River Basin, Volume 2, 1970
<br />
<br />U.S. Department of the Interior, Geological Survey, Water-Supply Paper
<br />2125, Surface-Water Supply of the United States 1966-1970, Part 9,
<br />Colorado River Basin, Volume 2, 1973
<br />
<br />U.S. Department of the Interior, Geological Survey, Water-Resources
<br />Data for Colorado, Part 1, Surface Water Records, 1971-1974
<br />
<br />REVISION DESCRIPTIONS
<br />
<br />This section has been added to provide information regarding
<br />significant revisions made since the original Flood Insurance Study was
<br />printed. Future revisions may be made that do not result in the
<br />republishing of the Flood Insurance Study report. To assure that any
<br />user is aware of all revisions, it is advisable to contact the
<br />community repository of flood-hazard data located at 1060 East Second
<br />Avenue, Durango, Colorado 81301.
<br />
<br />9.1 First Revision
<br />
<br />This study was revised on March 16, 1995, to reflect the effects
<br />of more detailed topography and intermittent channelization along
<br />the Animas River in the vicinity of the James Ranch property. As
<br />a result of these changes, the floodplain and floodway were
<br />redefined for a reach of the Animas River from milepost 78.940 to
<br />milepost 81.419. The hydrologic analysis for this revision was
<br />based on the information found in the Flood Insurance Study
<br />report for La Plata County, Colorado (References 1 and 2). The
<br />revised hydraulic analysis for this reach, which was developed by
<br />Goff Engineering and Surveying, Inc., and presented in their
<br />technical report, entitled "Floodway and Flood Elevations
<br />Modifications, Animas River, MP 78.940 to 81.419, La Plata
<br />County, Colorado," dated November 10, 1992 (Reference 16),
<br />utilized the U.S. Army Corps of Engineers (USACE) HEC-2 computer
<br />program (Reference 17). Known starting water-surface elevations
<br />and Manning's roughness coefficients were taken from the
<br />effective Flood Insurance Study report. Cross-section
<br />infor.mation was taken from aerial work maps. The floodway
<br />presented in this revision was computed on the basis of equal
<br />conveyance reduction from each side of the floodplain and on
<br />user-defined encroachment locations. As a result of this study,
<br />the base (100-year) flood elevations both decreased and increased
<br />throughout the revised reach, and the 100- and 500-year
<br />floodplains and 100-year floodway were revised. Topographic maps
<br />at a scale of 1"=200' with a contour interval of 2 feet, produced
<br />by Goff Engineering and Surveying, Inc., dated November 10, 1992
<br />(Reference 16), were utilized to produce the new boundaries as
<br />shown on Flood Insurance Rate Map Panels 0259, 0267, and 0278 and
<br />Flood Boundary and Floodway Map Panels 0259 and 0267.
<br />Profile Panels 14P, 15P, and 16P and the Floodway Data Table
<br />(Table 2) for the Animas River have been revised.
<br />
<br />37
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