<br />GLOSSARY RH The ratio of a specified recurrence-interval flood to
<br /> the 2-year recurrence-interval flood. (Harley,
<br />A The contnbuting drainage area, in square miles. In 1978).
<br /> urban areas, drainage systems sometimes cross RIlOO Rainfall intensity, in inches, for the 2-hour lOO-year
<br /> topographic divides. Such drainage changes occurrence. Determined from Weather Bureau
<br /> should be accounted for when computing A. (1961) or Miller and others (1973).
<br />BDF The basin development factor, an index of the prev- R12 Rainfall intensity, in inches, for the 2-hour 2.year
<br /> aIence of the drainage aspects of (a) stonn sew- occurrence. Determined from Weather Bureau
<br /> ers, (b) channel improvements, (c) impervious (1961) or Miller and others (1973).
<br /> channel linings, and (d) curb-and-gutter
<br /> streets. The range ofBDF is 0-12. A value of RQx The peak discharge, in cubic feet per second (ft'/s),
<br /> zero for BDF indicates the above drainage as- for an equivalent rural drainage basin in the
<br /> peets are Dot prevalent, but does not necessar- same hydrologic area as the urban basin, and
<br /> ily mean the basin is nonurban. A value of 12 for recurrence intetval x. For this study equiva-
<br /> indicates full development of the drainage as- lent rural discharges were computed from ap-
<br /> peets throughout the basin. See text for details plicable Geological Survey regional flood-
<br /> of computing BDF. frequency reports, as indicated in table I.
<br />CN A soil-cover-<:omplex curve number as described by S The logarithmic standard deviation of annual peak
<br /> the Soil Conservation Service (]97S). discharges for a gaging station.
<br />E An index of local runoff volume, in inches, for the SCSS An index of potential infiltration, in inches, com-
<br /> 2-hour 2S-year rainfall, computed by proce- puted by the equation SCSS = (],OOO/CN) - ]0
<br /> dures described by the Soil Conservation Ser- (Soil Conservation Service, 1975).
<br /> vice (]97S). SL The main channel slope, in feet per mile (ft/mi),
<br />Gs The logjuithmic skew coeffICient of t!te annual peak measured berween points which are 10 percent
<br /> discharges for a gaging station. and 8S percent of the main channel length up-
<br />IA The percentage of the drainage basin occupied by stream from the study site. For sites where SL
<br /> impervious surfaces, such as houses, buildings, is greater than 70 ft/mi, 70 ft/mi is used in the
<br /> streets, and parking lots. equations.
<br />K An index of impervious area, computed by the
<br /> equation K=I +O.OlS'IA (Carter, 1961). ST Basin storage, the percentage of the drainage basin
<br />L The basin length. in miles, measured on topographic occupied by lakes, reservoirs, swamps, and
<br /> maps along the main channel from the gaging wetlands. In.channel storage of a temporary
<br /> station to the basin divide. nature, resulting from detention ponds or
<br />LT Lagtime, in hours, for the urban watershed, com. roadway embankments, is not included in the
<br /> puted as the time from center-of-mass of rain- computation of ST.
<br /> fall excess to the center-of-mass of the corre- UQx The peak discharge, in cubic feet per second (fl'/s),
<br /> sponding runoff. Computed only for stations for the urban watershed for recurrence interval
<br /> having continuous rainfall and runoff data. x. That is, UQ2 = 2-year urban peak discharge,
<br />R' Coefficient of determination, a measure of the pro- UQS = S-year urban peak discharge, and so
<br /> portion of the total variance of the dependent forth.
<br /> variable that is accounted for by the indepen- X The logarithmic mean of annual peak discharges for
<br /> dent variables in a regression analysis. a gaging station.
<br />
<br />VI Glos....,.
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