STEP A: First, input and store values for K:
Enter value for S
Square root of S
Times constant of 1.486
Calculate and invert denominator
Times value for n
= STO or M+
Store constant K
STEP B: To calculate R for various values of V:
RCL or MRC
Times value for velocity
Raise product to 3/2 power
Displays value for R
NOTE: RCL stands for recall memory and MRC stands for clear memory.
STEP C: Repeat Step B for different V values until you reach an acceptable R and Q.
Find Hydraulic Radius in Ditch Table
STEP 6. Select the appropriate hydraulic radius from the appendix.
Use the ditch table, table 4-3, page 4-14. There are four types of tables; V symmetrical, V nonsymmetrical,
trapezoidal symmetrical, and trapezoidal nonsymmetrical, listed in FM 5-430-00-1/AFPAM 32-8013, Volume 1.
For this problem, use table 4-2, page 4-7.
Locate the columns representing the side slopes of the ditch being designed, for example, 3:1.
Locate the R values that fall above and below, or the one that is exactly equal to the R value found from the
nomograph of Manning's Equation. In the example, the values are 0.85 and 0.90. USE THE LOWER VALUE!
For example, use 0.85.
Table 4-7. Selected appendix radius