Length (\( L = \frac{1000}{(I - A)WS} \)):

Where:

• \( L \) is the safe length of the furrow, in feet (ft).
• \( I \) is the rainfall intensity, in inches per hour (in/hr).
• \( A \) is the absorption or infiltration rate of the soil, in inches per hour (in/hr).
• \( W \) is the furrow spacing, in feet (ft).
• \( S \) is the slope or gradient of the furrow, in percent (%).