Q.60 The ratio of the total length of streams of all orders within a basin to its area is called
- Astream order
- Bstream density
- Ccatchment density
- Ddrainage densityCorrect
Solution
Concept
Drainage density is the total length of all streams divided by the basin area.
Formula
Dd = ΣL / A
Step-by-step solution
1. Add the lengths of streams of all orders in the basin: ΣL. 2. Divide this total by the basin area A. 3. Dd = ΣL / A, with unit km/km². 4. This ratio is called the drainage density.
Explanation
Drainage density shows how well a basin is drained by its streams. A high value means many streams and fast runoff. A low value means poor drainage and more infiltration.
Why the other options are wrong
A: Stream order is the rank of a stream in the network (Strahler method), not a ratio. B: Stream density (stream frequency) is the number of streams per unit area, not their length. C: 'Catchment density' is not a standard hydrology term.
Shortcut
Length / Area = Drainage density; Number / Area = Stream density.
Common mistake
Mixing up stream density (count per area) with drainage density (length per area).
Correct answer: D) drainage density