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Difficulty: MediumDrainage Patterns and River Basin Analysis

A topographic map extract reveals a drainage network where major streams flow parallel to each other along elongated valleys, while short tributary streams join them at approximately right angles across alternating belts of resistant and non-resistant rock strata. Which drainage pattern is depicted, and what geological structure primarily controls its development?

  1. Trellis pattern, controlled by folded sedimentary rocks with alternating hard and soft strataAnswer
  2. B
    Radial pattern, controlled by central volcanic domes or isolated conical peaks
  3. C
    Dendritic pattern, controlled by flat-lying rocks of uniform regional resistance
  4. D
    Centripetal pattern, controlled by central structural depressions or interior basins

Answer

Trellis pattern, controlled by folded sedimentary rocks with alternating hard and soft strata
The trellis drainage pattern is characterized by parallel main channels flowing along soft-rock valleys formed by folded rock strata (synclines/anticlines), with short tributary streams cutting across resistant ridges to join the main channels at right angles.

Step-by-Step Solution

1
Analyze the spatial arrangement of the main streams and tributaries described in the scenario
Main channels are aligned in parallel valleys, and smaller tributaries join them at right angles across alternating rock belts.
Geological controls such as differential erosion of inclined or folded strata determine the pattern of river networks.
2
Match the geometric characteristics to the appropriate drainage pattern class
Parallel main streams with right-angled tributary junctions define a trellis drainage pattern.
Trellis drainage typically forms in ridge-and-valley landscapes produced by folded rock structures.

Key Concept

Trellis Drainage Pattern and Geological Structure
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Topics

Drainage Patterns and River Basin Analysis

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