FLOOD00425

• County: Statewide
• Title: HYDPAR- users manual
• Date: 11/1/1978
• Prepared For: US
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

Header Record. The final page of output represents the first record of
Tape 20 and includes information taken from the previous T4 and J2 cards (2l).
An explanation of the various field values is also shown on the sample output
(page lO of Exhibit 3-1).

Snyder's Lag Technique

The option in the UYDPAR program which permits the user to compute Snyder's

basin lag according to equation 3-3 and the percentage of impervious surface

within a subbasin is detailed below. Several pages of output relating to

this computational procedure are included in Exhibit 3-2. As in the previous

exa~ple, the numbers in parenthesis in the text refer to particular parts of

the sample output.

Equation. The equation that is utilized in this procedure is given (22)
along with definitions of the different variables.

Percent Impervious Summary. A card image of each LU card is provided
(23). A table of user-provided values is displayed showing the percent mrn-
perviousness for each land use category .(24).

Subbasin Parameter Cards. Card images of the SB card input are included
in the output. This display provides an opportunity to verify the input
values of the subbasin data (25).

Subbasin Summary Table. For each subbasin under analysis, the stream

length (miles), length to the centroid of the area (miles), stream slope

(feet per mile), and HEC-l station values are given (26). HEC-l stations are

required only when the results of the job are saved for automated interfacing

with the HEC-l program through ATODTA.

Specific Subbasin Data. Specific subbasin data is tabulated (27). For

each land use category in the subbasin, values are output for percent im-

perviousness, surface slope (not required for Snyder's technique), area,

3-l3