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full weight was given to the observed flood-frequency relation because the syn- thetic flood-frequency relation was too low in comparison with relations for other stations; in fact, the synthetic 100-year flood was exceeded in 1965 by a flood recorded at a site about 1 mile downstream (see table 7, Gray Creek near Trini- dad), Similarly, full weight was given to the synthetic flood-frequency relation for stations 07125050 and 07153450 because the observed 100-year flood was less than the synthetic 10-year flood. Independent Variables . The following independent variables or basin and climatic characteristics were defined for each basin and used in the multiple-regression analysis: , J 1. Total drainage area, A, in square miles--the total topographic drainage area of the basin. Effective drainage area, AE' in square miles--the contributing drainage area for more frequent (less than Q25) floods (that is, the total area less the drainage areas for all flood-detention res- ervoi rs in the basi n) . Elevation; E, in feet--the elevation above sea level of the gage site or point of interest. Maximum relief, RM' in feet--the elevation difference between the highest point in me basin and the gage site or point of interest. Mainstem length, L, in mi les--the length of the main channel from the study site to the basin divide, Streambed slope, SS' in feet per mile--the slope of the main chan- nel from the study site to a point about 10-channel widths up- stream. Channel slope, S , in feet per mile--the average slope of the main channel computecf by the 85 percent! 10 percent method described by Benson (1962). 2. 3. 4, 5. 6. 7. Basin slope, SB ' in feet per mile--the average slope of the effec- tive drainage area (AE) obtained by measuring the lengths of all 100-ft contour lines in the basin, multiplying by 100, and dividing by the effective drainage area, 9. Channel width at maximum depths of 1 ft or 5 ft, WDJ, and WDs' in feet--the average width obtained by measuring the channel width 1 ft or 5 ft above the thalweg at 10 locations at the gage or study site, each spaced about one channel width apart. 10. Precipitation intensity for l-hour 100-year, 6-hour 100-yea~, a.nd 24-hour 100-year storms, I"lOO, ISolOO , and I24ol00, In In- ches--the average basin precipitation intensities for the indicated duration and recurrance interval as given by Miller, Frederick, and Tracey (1973). 8, For each of the 15 stations in the multiple-regression analysis, the values of all independent variables are shown in table 8. 19