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<br />INTRODUCTION
<br />Battlement Mesa Partners (BMP) is requesting a Letter of Map Revision
<br />(LOMR) for certain drainageways delineated and outlined on the January 3,
<br />1986 FEMA Flood Insurance Rate Maps (F]RM), panels 080205-13]5B and 080205-
<br />1705B of Garfield County, Colorado. BMP is focused on those drainageways
<br />~ -"~-~"""""'lIi~-""-___'.._e'..-"",=__",...,..__"",
<br />or portions thereof within their PU)). property limits, These drainageways
<br />-~ ......- .-...--.....,.".,.....". - ~ ,.''"'.....~'"'.~--Q-..-..''.7 _",__
<br />are outlined on Figure ].
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<br />Figure ] shows the extent of the IOD-year floodplains for the drainageways,
<br />as delineated in the ]986 F]RM, BMP's PUD boundary, and the naming nomen-
<br />clature developed by Wright Water Engineers (WWE) , The FIRMs delineate I
<br />>'ipproximately 24.5 miles of 100-fool: wide "Zone A" 100-year floodplain, (vv,/I\/
<br />'\ " ,,- _~I_" l,..f.J,(-~.,'
<br />The drainageways are shown on the USGS topography in Figure 2, Figure 3
<br />schematically represents the naming nomenclature d~I(~ped_~L_~ for
<br />reference,
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<br />The designation and delineation of
<br />done using approximate methol~,
<br />factors were not determined.
<br />
<br />the IOD-year floodplains by FEMA was
<br />Base flood elevations and flood hazard
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<br />Hydrology
<br />Drawing I shows the basin and subbasin delineations for the drainageways,
<br />the channel reaches, and design points used in conjunction with the HEC-l
<br />computer model. The HEC-I computer model was used to compute the runoff
<br />hydrographs and, thus, peak IfIows for Basins ] and E, the two larger
<br />basins. The subbasin characteristics and channel reach characteristics are
<br />given on Tables ] and 2, respectively The Snyder Unit Hydrograph method
<br />was used in conjunction with the Soil Conservation Service (SCS) soil Joss
<br />method to compute the runoff hydrographs. ) \' \. . :_' (. /
<br />(", '\ l!:::,,~., \" (:r ':;J T\) \~::' 1
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<br />The percent imperviousness of the subbasins under future development condi-
<br />tions was determined by the weighted average of 2 percent for open space
<br />land and 50 percent for mixed residential land use. Drawing 2 outlines the
<br />two land use categories. ]n general temls, only land below elevation 6,000
<br />feet is designated as mixed residential land use:, The land above 6,000
<br />feet is designated as open space land.
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