Fluvial Landforms Flashcards
Three mechanisms that could create terraces
glacial outwash climate change rise in base level tectonic uplift vegetation
What is the overall process of terrace formation
changing balance between water and sediment coming into the river and its ability to transport the water/sediment rapidly. Or, simply, a change in base level or change in gradient
What is a strath terrace
terrace formed on bedrock from abraded material
what is an alluvial terrace
a terrace formed from sediment
What is a destructive delta
a delta that erodes sediments faster than they are deposited. Tend to be flatter and low relief
What is a constructive delta
deltas that deposit sediments faster than erosive rates. Tend to be more lobate and elongate
Why do alluvial fans commonly have segmented convex profiles
deposition happens when river leaves the confines of its channel. deposition shifts laterally across fan and outward from mountain.
How is energy expended in a river
friction against bedding
carrying sediment
internal friction (eddies, turbulence, viscosity)
What causes External Resistance
Internal friction: particle size bedforms vegetation channel irregularities human made structures
What causes Internal Resistance
amount of sediment being carried by the water.
more sediment in suspension = more viscous water which mixes less easily
Explain terraces created by an Aggrading River
a terrace due to the river not being able to re-work floodplain sediments / floodplain is no longer active
Explain terraces created by Degrading River
river incises and prevents flooding into the floodplain
What is an erosional terrace
a terrace because the channel/river incises down
What is a depositional terrace
vertical accretion and river cannot flood
