Section 4: Soil and Water Conservation Engineering
Watershed Management
Subtopic: Watershed characterization and land use capability classification
Question Statement:
A drainage watershed of area $A = 28.0\text{ km}^2$ has a total blue-line stream length of $L_{total} = 84.0\text{ km}$ across all stream orders. The drainage density ($D_d$) of the watershed in $\text{km/km}^2$ is ________ (answer in integer).
Answer Key:
3
Step-by-Step Solution & Explanation
1. By Horton's definition, drainage density $D_d$ is the total length of streams of all orders per unit drainage area:
$D_d = \frac{\sum L}{A}$
Where:
- $\sum L = 84.0\text{ km}$
- $A = 28.0\text{ km}^2$
$D_d = \frac{84.0\text{ km}}{28.0\text{ km}^2} = 3.0\text{ km/km}^2$
(Expressed as integer: 3).