Fluvial Geomorphology Flashcards
Whats a meandering river?
Clear cut off points and ox bow lakes
Whats a braided river?
Lots of fine sediment, multithread
Whats a anabranching river?
Multithread systems that fall between braided systeams and meandering
Whats a anastomosing river?
Composed of two or more interconnected channels that enclose floodbasins
Sediment flux depends on two things:
The energy or force exerted by the flow
The amount of sediment available for transport
Controls on bedload transport
Sediment size and arrangement on the bed (Resistance to movement).
Force exerted by water flowing over the bed.
Upstream supply of sediment.
Connectivity to upstream sediment supply.
Flume experiments (e.g. Schumm and Khan, 1973) indicate that…
The straight meandering braided platform transition is associated with increased slope (energy) and increased sediment supply.
Bed load
Describes particles in a flowing fluid (usually water) that are transported along the bed.
Suspended load
The amount of sediment that is suspended within the water column.
Wash load
The overland flow thats flowed across the earth surface, collecting fine sediment.
Bed material load
The portion of the sediment that is transported by a stream that contains material derived from the bed.
There are four main processes of transportation. These are:
suspension
solution
saltation
traction.
Nine Degrees of Freedom” for alluvial rivers
- Cross section categories:
- Width (W)
- Depth (d)
- Maximumdepth (dm)
- Velocity (V)
Nine Degrees of Freedom” for alluvial rivers
- Plan form:
- Slope (S)
- Sinuosity (p)
- Meander Arc length (z)
Nine Degrees of Freedom” for alluvial rivers
- Long profile:
- Bedform amplitude(a)
9. Bedform wavelength
Channel adjustment to climate change
Warm Phases:
Rainfall dominated events
Vegetation cover
Reduced weathering rates
Incision into valley fill
Styles of channel adjustment I: Meandering Channels
Rivers flow through the least energetic points in a landscape as quickly as they can.
Enhanced erosion on outside of bend and deposition on inside- leads to meanders.
Styles of channel adjustment II: Braided channels
Braided rivers are built up of confluence: difluence channels and braid bars.
These influence adjustment.
Types of change
Deliberate interventions
Have the specific intention of altering hydrological characteristics
Effects can often be specified exactly
Types of change
Inadvertent interventions
An action can have unintended or “unimportant” effects on streamflow
Effects can be difficult to specify