FLOOD02408

• County: Statewide
• Community: Nationwide
• Basin: Statewide
• Title: Design Hydrographs for Very Small Wathersheds from Rainfall
• Date: 7/1/1962
• Prepared By: USDA Hydrograph Laboratory, Civil Engineering Section Colorado State University
• Floodplain - Doc Type: Educational/Technical/Reference Information

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T1
4<12

4<13
T4
4<15

4<16
T7
Ta
4<19

*D
1

*D
5

Table 2. Symbols and definitions of independent variables for stepwise
multiple regression analyses.

1. Topographic Parameters
Watershed area, acres.

Length of the longest collector from the gaging station
carried out to the watershed perimeter, L feet.

Length along the main stream from the gaging station to the
point nearest the mass center of area, L feet.
c
Fall over watershed, H feet.

Average main-channel slope, S feet/foot, is the slope of
c
a straight line drBlm through the gaging point on the
longitudinal section of the longest collector such that the
area between it and the horizontal axis equals the area
below the longitudinal section.

Average land slope, percentage.

L/ -.;s:- .
c
Drainage density, in feet of mapped. channel per acre.

Time of concentration, computed from the Soil Conservation
Service nomograph involving H and L, in hours.

D6

II. Design Indices Depicting Land Use and Soils

Infiltration capacity after one hour of continuous rainfall
according to A.S.C.R. (21) tables of soil and coven inches/hour.

S.C.S.'s intermediate runoff curve number (14).

D7

S.C.S.'s curve number after correction for antecedent rainfall (14).

D2

Runoff volume expected from S.C.S. relationship with rainfall and
corrected curve number, inches.

D4

Watershed lag from Mockus' nomogram (22) which includes 5.&.5.
curve number, hours.

Cook's III from runoff producing characteristics (23) such as
soils, land use and topography.

Da Turner's C (24) for use in Q a CIA.

* Denotes parameters which were used in the final regression equations.