Fluvial geomorphology of erosional environments

V-shaped valleys with interlocking spurs
1. typical of upland mountain streams as high flow velocities that follow intense precipitation cause intense vertical erosion with this high potential energy thus, producing V-shaped valleys.
  1. Upland mountain streams - intense rainfall, vertical erosion = V-shaped valleys.
2. Steepness may vary with climate, vegetation and geology
  1. Climate - precipitation affects river discharge and mass movements on valley sides.
  2. Vegetation - Roots bind soil together stabilising slope.
  3. Geology - Impermeable rocks produce steeper valleys E.g. streams in carboniferous limestone cut canyon like valleys
3. Interlocking spurs = stream forced to wind a sinuous course around the protrusions of the surrounding highland, spurs appear to interlock blocking the view of the valley.
4. Headward erosion/spring sapping - at source where it appears to migrate upslope into its watershed. Undercutting, rock, soil and veg.
Waterfalls
1. Form when flowing rivers cross into less resistant rock E.g. Great Whin Sill UK
2. Form when rivers flow over the edge of a plateau E.g. South America and Africa
3. No friction at the brink of the fall so velocity increases.
4. Descending water erodes the underlying rock, forming a deep plunge pool.
  1. Overtime, harder rock may become unstable and undercut retreating the waterfall upstream leaving a steep-sided gorge E.g. until stabilised Rainbow Gorge at Niagara Falls was retreating by 1m per year.
Rapids
1. Form where gradient of river increases without a break in the slope (otherwise it would become a waterfall)
2. Forms where the river flows over dipping bands of more resistant rock.
3. Rapids increase turbulence and thus, erosive power of the river.

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Fluvial geomorphology of erosional environments

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