Hydrology and Runoff

In the SCS-CN method, the standard assumption for initial abstraction $I_a$ in terms of potential retention $S$ is:

Options:

• (A) $I_a = 0.2 S$
• (B) $I_a = 0.5 S$
• (C) $I_a = 0.05 S$
• (D) $I_a = 0.1 S$