The program ONLINE_S_HYDROGRAPH changes the duration of an input unit hydrograph using the S-hydrograph method.

1. The duration of the input unit hydrograph can be either 1 hr, 2 hr, or 3 hr. The input unit hydrograph must be defined at 1-hr time intervals.

2. The program calculates the unit hydrographs for the other two durations. For example, if the input duration is 2 hr, the program will calculate the unit hydrographs for 1-hr and 3-hr durations.

3. The computational procedure is explained in Table 5-9 of the text.

4. Some unit hydrographs may be ill-posed, and this may lead to errors in the S-hydrograph transformation to other durations. The results should be taken with caution if the ordinate sum at the bottom of the output table is not the same for all three hydrographs.