Fluvial Geomorphology Flashcards
Why are rivers important?
Freshwater is integral to virtually all economic, environmental and societal processes:
- underpins the economy
- human health
- food production
- industrial processes and energy generation
- ecological functioning
Wide range of psychological functions:
- recreational activities
- aesthetic values
- religious and cultural functions
Rivers are the arteries of much of terrestrial Life on Earth
What is a Hypsometric Curve?
- A hypsometric curve is essentially a graph that shows the proportion of land area that exists at various elevations by plotting relative area against relative height.
What is the first basic fluvial concept?
- The energy of a stream can accomplish geomorphic work, this depends on a number of factors, including gradient, base level, and volume of flow (discharge).
What is the second basic fluvial concept?
- The gradient (slope) of a stream is defined as the drop in elevation per unit distance. Characteristically, a river has a steeper slope nearer the headwaters and a more gradual slope downstream.
What is the third basic fluvial concept?
- The level below which a stream cannot erode its valley is base level. In general, the ultimate base level is sea level.
- Base level associated with sea level is a primary control on global hypsometric curve
Study the diagram for base level
https://docs.google.com/document/d/11SlS_6djE3BGAezT2-FeVRTdxG1P1jVyj-u3X2L5qDo/edit?usp=sharing
What are the Idealised Drainage Basin – Process zones
- Source Zone
- Transfer Zone
- Sink Zone
What happens in the Source Zone?
- This is where water comes from the mountains or just the place where the river starts at the headwaters
- Where most of the sediment that the river carries come from, also where mass movements such as debris flows and landslides occur
What happens at the Transfer and Sink zones?
- Transfer zone is where some of the sediment from the source zone is deposited and where weathering such as sheet erosion and rill erosion occur
- Sink Zone is where most of the sediment is deposited and where gully erosion, bank erosion and floodplain storage occur
What happens when we have rainfall in a catchment area?
- Precipitation is converted to runoff via infiltration and overland flow
- Runoff amount is determined largely by basin characteristics (lithology, soils, drainage basin size, shape, density) and climate + HUMANS
What is a Hydrograph?
- A time variation of water discharge in a river at a point
Study the diagram of a Hydrograph
- google doc
What is the equation for discharge?
- Discharge is the volume of water at any one point in the landscape
- Discharge (Q) = W (width) x D (depth) x V (velocity)
- Units = m^3/s (cumecs)
What is planform roughness?
- The friction created as the flow of water goes around meanders in the river
What is Spill resistance (hydraulic roughness)?
- resistance created as water goes over little steps or rocks in the river (water rapids)
What is Skin resistance?
- Skin resistance referse to the bed and banks of the river and how much friction they cause as the water flows past them. They include:
- Bed roughness
- Bed form roughness
- Vegetation roughness
What is bed roughness?
- The gravel size of the sediment composing the bed of the river
What is bed form roughness?
- The river shapes the bed into different shapes, elevations and corrugations, the roughness of this may cause friction was the water flows past and hence creates flow resistance
What is vegetation roughness?
- The vegetation growing on the banks of the river and the dead plants on the banks of the river
