Fluvial geomorphology of erosional environments

Sharondeep
Mind Map by , created over 5 years ago

Undergraduate Physical Geography (Hydrosphere) Mind Map on Fluvial geomorphology of erosional environments, created by Sharondeep on 04/02/2014.

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Sharondeep
Created by Sharondeep over 5 years ago
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Fluvial geomorphology of erosional environments
1 V-shaped valleys with interlocking spurs
1.1 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.
1.1.1 Upland mountain streams - intense rainfall, vertical erosion = V-shaped valleys.
1.2 Steepness may vary with climate, vegetation and geology
1.2.1 Climate - precipitation affects river discharge and mass movements on valley sides.
1.2.2 Vegetation - Roots bind soil together stabilising slope.
1.2.3 Geology - Impermeable rocks produce steeper valleys E.g. streams in carboniferous limestone cut canyon like valleys
1.3 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.
1.4 Headward erosion/spring sapping - at source where it appears to migrate upslope into its watershed. Undercutting, rock, soil and veg.
2 Waterfalls
2.1 Form when flowing rivers cross into less resistant rock E.g. Great Whin Sill UK
2.2 Form when rivers flow over the edge of a plateau E.g. South America and Africa
2.3 No friction at the brink of the fall so velocity increases.
2.4 Descending water erodes the underlying rock, forming a deep plunge pool.
2.4.1 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.
3 Rapids
3.1 Form where gradient of river increases without a break in the slope (otherwise it would become a waterfall)
3.2 Forms where the river flows over dipping bands of more resistant rock.
3.3 Rapids increase turbulence and thus, erosive power of the river.

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