ENVS10001 Lecture Notes - Lecture 14: Stream Energy, Landform, Yarra River
26 May 2018
School
Department
Course
Professor
ENVS10001 – Putri Shafira 2018
188
Wednesday, April 18th 2018
From Lecture 14: Fluvial processes and landforms by Alexis Pang
How hydrological processes or Fluvial processes help to form the landscape, since almost all of
the landscape (for the site visit task) has been affected by fluvial processes.
Prior knowledge:
1. Initial landscapes: tectonic and volcanic
2. Sequential landscape:
- Aeolian by wind
- Glacial by ice
- Fluvial by water
- Groundwater (Karst) à helps form karst landforms in limestone landscapes
- Marina/ Coastal
3. Weathering & Mass movement
4. Earth materials
5. Geological and Topographic Maps à fluvial processes very much integral part of
landscape formation.
Introduction
1. Most of the world’s land surface has been sculpted by running water across time and
some various most last extent;
2. Most landforms have been formed by running water as it erodes, transports, and deposits
sediment
3. Fluvial landforms can be classified as:
- Erosional à carved by water
- Depositional à alluvial forms
4. These landforms are the result of fluvial processes, largely as:
- Overland flow (hillslope processes)
- Stramflow (river processes) à major/ most visible outputs off catchment
Scope
1. Erosion, transportation and depositional processes in streams à How streams actually
work
2. The hjulstrom diagram à To model and predict how sediment will be eroded, transported
and deposited with river’s stream energy/ flow energy
ENVS10001 – Putri Shafira 2018
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3. River long profile and cross-section
4. River plan-forms
5. River rejuvenation
6. Rivers and humans à natural resources
How does a stream erode, transport, and deposits?
There are 4 main processes that occurred in the streams to erode:
1. Hydraulic action à due to the force of flowing water
Water flow exerts forces onto cavities in river bank causing instability and collapse; also
picks up sediments from river bank and bed.
2. Abrasion à collision of sediments with the river banks
Water flow causes sediments to collide with river banks and bed, causing cavities to be
formed
3. Attrition à between the sediments; as they’re entrain/ in the flow of the stream, they
colliding against on another
Sediments collide and chip against with one another, giving smaller, rounded sediments.
4. Corrosion à chemical characteristics of rain water and stream water
Acidic stream water dissolves rocks and sediments such as limestone. Stream water tends
to be acidic because it comes supplied through rain and also move through the hillslope,
soils & rocks, which decomposing organic materials make it acidic, dissolve rocks and
sediments (e.g. limestone & calcareous materials).
Transport of sediment occurs when it is entrained in the water flow which has sufficient energy
(flow volume and velocity).
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Sediment load
Streams carry their load as dissolvent suspended, and bed load.
A. Dissolved matter (stuff in solutions) is transported invisibly in the form of chemical
ions (e.g. salts, sodium chlorides get carried in solutions – stuff that actually can’t be
seen but carried in the water quality testing). All streams carry some dissolved ions
created by mineral alteration.
B. Sand, gravel and larger particles move as bed load, rolling or sliding close to the
channel floor. à Bed load, depending on the size of sediments in interactions with
streams energy material will be transported differently (large materials may not be
carried up into the flow because it is pretty heavy, therefore it moves as bed loads –
slides/ rows on the channels)
C. Clay and silt are carried in suspension – that is they are held within the water by
turbulent eddies in the stream. à if the river has a very high energy, then it can have
some sand in suspension for a bit of time (but mostly, in suspension in normal flow, it
has light materials which are clay and silt being carried in the suspension, and therefore
they can be transported in a long distance).
How soil are forms in the involve in the action of rivers à Rivers are integral to the formation
of soil as well when there is a lot of Fluvial material.
Streams deposit sediment when there is insufficient energy to transport sediments.
Document Summary
From lecture 14: fluvial processes and landforms by alexis pang. How hydrological processes or fluvial processes help to form the landscape, since almost all of the landscape (for the site visit task) has been affected by fluvial processes. Prior knowledge: initial landscapes: tectonic and volcanic, sequential landscape: Groundwater (karst) helps form karst landforms in limestone landscapes. Marina/ coastal: weathering & mass movement, earth materials, geological and topographic maps fluvial processes very much integral part of landscape formation. Depositional alluvial forms: these landforms are the result of fluvial processes, largely as: Stramflow (river processes) major/ most visible outputs off catchment. Scope: erosion, transportation and depositional processes in streams how streams actually work, the hjulstrom diagram to model and predict how sediment will be eroded, transported and deposited with river"s stream energy/ flow energy. Envs10001 putri shafira 2018: river long profile and cross-section, river plan-forms, river rejuvenation, rivers and humans natural resources.
