Answer:
The right answer is "5.105×10⁸ m³/sec".
Step-by-step explanation:
The given values are:
Catchment area,
A = 3 km²
Length to watershed,
L = 1100 m
Average watershed slope,
S = 0.9% i.e., 0.009
Curve number,
CN = 60
Rainfall duration,
D = 20 min
Let,
- Time form beginning of the rainfall will be "
". - Lag time will be "
".
Now,
⇒

On substituting the values, we get
⇒

⇒

then,
⇒

⇒

⇒

⇒

⇒

hence,
The peak flow will be:
⇒

⇒

⇒

⇒

or,
⇒