Week 7 - Overview

Question 1

Relate variations in energy levels of water and wind flows to erosion, transport and deposition processes, and the resultant fluvial and/or aeolian landforms

Answer 1

Most of worlds landforms created by running water, fluvial landforms are either erosional or depositional.
Erosion happens via 4 processes, hydraulic action (exertion of water force on cavities), abrasion (flow causes sediments to collide with riverbanks and bed creating cavities), attrition (sediments to each other creating smaller ones) and corrosion (acidic water dissolves sediment).
Sediment is transported where there is sufficient energy in waterflow (volume and velocity). Transported as dissolved, suspended or bed load. Deposited when there is insufficient energy.
Fluvial activity:
Aggradation = increased deposition, reduced energy and increased sediment supply
Degradation=streambed sediment erosion, reduced sediment & increased flow energy
We get stream degradation (upper, middle, lower)

Question 2

Explain typical fluvial features at upper, middle and lower courses of a river long profile

Answer 2

Upper course - lots of kinetic energy = lots of erosion = v shaped channels
E.g. rapids, waterfalls, lakes, ponds,
Middle course - decrease in gradient = transfer (change in direction of erosion=more lateral erosion)
E.g. Lakes, streams
Low course - very flat, not much velocity, lots of deposit of sediment (alluvium deposited), floodplain strip widens developing alluvial meanders
E.g. floodplains

Question 3

Explain how river energy levels can vary with tectonic or eustatic changes, and the resultant landforms

Answer 3

Faulting and folding can change the landscape therefore changing the river channel, stream degradation, this means with less kinetic energy or more we can see a difference in flow energy and water volume available

Rejuvination:

• increasing the potential energy between high and low points due to processes causing:
• Uplift of land surface (e.g. tectonic processes such as folding togive anticlines; thrust faulting)
• Lowering of sea level (e.g. increased sea-ice, glaciation)

Question 4

Predict and explain the expected changes in fluvial energies, processes and landforms when a dam is built on a river

Answer 4

Dams

• Effects natural flow regimes
• Many locations downstream is also effected, ecology effected

How do dams effect hydrology?

• Normally there is a high change of discharge throughout the year
• Natural variation, wet vs dry season
• Reduces discharge

Question 5

Explain how wave action and the factors that affect them, lead to the development of erosional and depositional coastal features

Question 6

Describe how sea-level changes in the past can help to explain some landforms observed in the present, including their implications on fluvial processes

Question 7

Explain the processes of eluviation and illuviation

Answer 7

Eluviation - Removal of dissolved or suspended material from a layer or layers of the soil by the movement of water when rainfall exceeds evaporation. Such loss of material in solution is often referred to as leaching. The process of eluviation influences soil composition.

Illuviation - Illuviation, Accumulation of dissolved or suspended soil materials in one area or layer as a result of leaching (percolation) from another. Usually clay, iron, or humus wash out and form a line with a different consistency and color. These lines are important for studying the composition and ages of rock strata

Question 8

Discuss the value of knowledge of soils to human activities such as agriculture, building and construction, and land use planning