Dendritic Drainage: The Tree-Like Network of Rills, Creeks & Streams

A dendritic drainage pattern is the most common river network geometry—resembling a tree's branching structure.

Formation Conditions

• Uniform rock resistance – Homogeneous lithology (shale, sandstone, granite).
• Gentle, regular slopes – No structural control (faults, folds, joints).
• Isotropic erosion – Water cuts equally in all directions.

Anatomy

• Trunk: Main river (highest order).
• Branches: Tributaries (progressively lower order).
• Twigs: Creeks, runs, kills.
• Rootlets: Rills, gullies, ephemeral channels.

Horton-Strahler Ordering

• 1st order = no tributaries (rills).
• 2nd order = two 1st-order join.
• n-th order = two (n-1)th join.
• Amazon = 12th order; Mississippi = 10th.

Contrast Patterns

• Trellis – Folded strata (ridges/valleys).
• Radial – Volcanoes, domes.
• Rectangular – Fault/joint control.
• Deranged – Glacial debris, karst.

Why It Dominates

Most crust is gently dipping, homogeneous sedimentary/crystalline rock. Water follows gravity's path of least resistance → statistically optimal branching (minimum energy dissipation).

Dendritic isn't just pretty—it's physics' default plumbing.