Section 4: Soil and Water Conservation Engineering
Watershed Management
Subtopic: Watershed characterization and land use capability classification
Question Statement:
A drainage basin has a total catchment area of $A = 45.0\text{ km}^2$ and an axial basin length of $L = 10.0\text{ km}$ measured along the main stream path from mouth to basin divide. The dimensionless form factor ($R_f = A / L^2$) of the watershed is ________ (round off to two decimal places).
Answer Key:
0.45
Step-by-Step Solution & Explanation
1. Horton's Form Factor ($R_f$):
$R_f = \frac{A}{L^2}$
Where:
- Catchment area $A = 45.0\text{ km}^2$
- Basin length $L = 10.0\text{ km}$
$R_f = \frac{45.0}{(10.0)^2} = \frac{45.0}{100.0} = 0.45$
(A lower form factor indicates an elongated basin with lower, flatter flood peaks).