The runoff coefficient (C) is defined as the ratio of the peak runoff rate to the rainfall intensity. The runoff coefficient mathematically indicates for a watershed whether the runoff is likely to be high or low. The value of C depends on the type and characteristics of the watershed. If the watershed is composed of very tight soil, steep slopes, or cultivated land (or all three of these), the runoff rate will be high. If the soil is sandy, with flat slopes, and covered with good vegetation, the runoff will be low.
The runoff coefficient for watersheds with various topographic, soil, and cover conditions can be estimated by using the values given in Table 17.1.
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