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Cross sections for Cottonwood Creek below Woodman Road, Monu~ent Creek above the U.S. Air Force Academy, Kettle Creek, Pine Creek, Peterson Field Drainage, Spring Creek, and Templeton Gap Floodway were obtained from aerial topographic mapping prepared by Landmark Mapping, Ltd., between 1981 and 1983 (Reference 24). Cross section data for Monument Creek Tributary and the upper reaches of Monument Creek in the vicinity of Palmer Lake were obtained from aerial photographs compiled by Hogan and Olhausen (Reference 27) using photogrammetric techniques. All bridges and culverts were surveyed to obtain elevation data and structural geometry. Supercritical and critical flow conditions predominate in the Upper Monument Creek reach and the Monument Creek Tributary due to steep channels. Water-surface elevations at cross ~ections in these reaches are based on critical depth. Starting water-survace eleva- tions are based on critical depth or the corresponding water-surface elevations at the confluence of two streams (Reference 3). A split flow occurs on Pine Creek at the Colorado State Highway 83 crossing due to the limited capacity of the culvert. Because the roadway embankment is sufficiently high to divert flows above 1,200 cfs to the south, all recurrence i~tervals coincide with the 100- year flood on the Pine Creek Overflow profile. Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments for w~ich a floodway was computed (Section 4.2), selected cross section locations are also shown on the Flood Ins~rance Rate Map (Exhibit 2). Channel roughness factors (Manning's "nil) used in the hydraulic computations were chosen using engineering judgment based on field observations o~ the streams and flood plains. Roughness values for the detailed-study streams ranged from 0.015 to 0.065 in the channels with values rangi~g from 0.020 to 0.080 in the overbank areas. These values correspond to concrete c~annels o~ the low end and de~sely vegetated overbanks on the tigh end of the scale. Photographs also aided in the documentation of channel a~j overbank roughness coefficients. Starting water-s~rface elevations were either based on coincident condition elevations, the slope-area method, or elevations of an acjacent st~dy. The hydraulic analyses for this study were based on u~obstructed f:ow. The flood elevations shown on the profiles are th~s con- sidered valid only if hydraulic structures re~ain unobs~r~cted, operate properly, a~d do not fail. 18