TR55GRAPH will calculate peak discharge using the SCS TR-55
Graphical Method (Ponce, V.M., 1989. Engineering Hydrology, Principles and Practices, Prentice Hall).
The program will prompt you
to enter catchment area A, rainfall depth D, return period T, curve number CN,
storm type, time of concentration tc, and percentage
of pond and swamp areas P.
Click the YES radio button if you are using SI units;
click NO if you are using U.S. customary units.
In SI units, use catchment area in km2 and rainfall depth in cm;
in U.S. customary units, use catchment area A in mi2 and rainfall depth D
in inches.
The return period T (yr) should be in the range 1-100.
The curve number CN should be in the range 1-100.
A more practical range is 45-95.
Select appropriate storm type:
Type I, Type IA, Type II, or Type III.
In the TR-55 graphical method,
the time of concentration tc is restricted in the range 0.1-10 hr.
In the TR-55 graphical method, the
percentage (%) of pond and swamp areas P
is restricted in the range 0-5.
The program reports peak discharge (in m3/sec for SI units;
in cfs for U. S. customary units) for the specified return period.