Chapter 15 Flashcards
Surface water (41 cards)
Hydrosphere
Water at and near the surface of the Earth.
Reservoirs (%)
- Ocean (97.5%) for millennia
- Ice (1.8%) for millennia
- Groundwater (0.63%)
- Lakes and Rivers (0.016%) for months
- Atmosphere (0.001%)
Streams
Body of flowing water confined to a channel with a concave longitudinal profile
Stream gradient
Slope of a stream, ratio of elevation to distance.
Discharge
Volumetric measure of water that flows through a stream or river. The product of cross-section and average velocity.
Head/headwater
Where the stream starts
Drainage basin/watershed
Region from which water is collected. All flowing surface water converges to a single point, normally the ocean.
Mouth
Where a stream empties into another water body
Bed
Base of a stream
Banks
Confines of a stream during normal flow
Floodplain
Region covered during a flood where sediment is deposited
Sediment loads in a stream (3)
Dissolved (chemical sediment), suspended (mechanical sediment), bed (saltation, rolling, sliding, mechanical sediment)
Erosion in Graded streams
As the gradient decreases, the ability to erode decreases and the rate of sedimentation increases. The size of sediment particles decreases downstream.
Rock that is more resistant to erosion can change profile with a local base level (EX: Waterfalls)
Graded streams reach equilibrium with gradient and velocity varying together.
Base level
The lowest level to which a stream can erode. (EX: The ocean or a lake (local)). Changes in sea level cause changes in base level and changes to the longitudinal profile of a stream.
Capacity
The maximum load of solid particles that a stream can transport
Competence
The maximum particle size that a stream can transport, proportional to velocity squared.
Sorting of sediment in a stream
Sediment too big to be transported will be dropped in sequence (boulders, gravel, sand, silt, clay)
V-shaped stream valley
A river cuts down and the sides undergo weathering.
Erosion transports material to the river through gravity and rainfall. Steepness of slopes depends on strength of rock.
Wide stream valley
The stream gradient decreases as a stream reaches base level and there is less down-cutting and more widening of the valley. Side-to-side migration of channel produces an erosional floodplain.
Meandering streams
Deviation of a slow stream from a straight line is enhanced through positive feedback. As meanders are cut through oxbows lakes are left behind as the river cuts itself off.
Point Bar
Inside edge of a meandering stream. Sediment deposited makes flow faster and causes erosion.
Cut bank
Inside edge of a meandering stream. More erosion makes bends.
Braided streams
High energy streams with high sediment load that is deposited and partially blocks channels.
Anastomosing streams
Low energy stream with multiple channels separated by stable islands that are often vegetated