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curves computed from the gaging records discussed in paragraph 4. The MITCAT model was calibrated with the Golden gage, while SWMM was calibrated with the Derby gage. Studies were made to reconstitute the computed dis- charge probability values in the 10 to 25-year range since this is the level where rainfall-runoff events apparently begin to dominate the dis- charge array. Calibration studies at Golden using the MITCAT model were made by varying the SCS curve numbers used in the loss routine of the program. The calibrated discharge was 4,700 cubic feet per second at about the 20-year level. An additional check was made at the 100-year level with Technical Manual No. 1 published by the Colorado Water Conservation Board in 1976. Using the criteria directly without reference to the record at the Golden gage a 100-year discharge of 12,400 was obtained which compares with the MITCAT results of 12,200 cubic feet per second. At the Derby gage ca1ibra- tion studies of the SWMM model were made by varying the detention storage. Comparison runs at the 100- and 10-year levels with urbanization removed from the model produced a discharge frequency relationship that crosses the computed curve at about the 50-year level. The model results ref1ect- ing the effect of existing development is shown on attachment 3. 6. DISCHARGE-PROBABILITY PROFILES. a. General. The discharge-probability profiles for the 500-, 100-, 50- and 10-year events shown on attachments 4 and 5 were developed for Clear Creek beginning at the Jefferson-Clear Creek County line and extending to the mouth. These profiles were developed for existing and fully urbanized conditions. The scenario for fully urbanized conditions was based on typical 7 i I I