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Questions and Answers
Which of the following are fluvial landforms found in the lower course of a river?
Which of the following are fluvial landforms found in the lower course of a river?
River capture only occurs in the upper course of a river.
River capture only occurs in the upper course of a river.
False
What type of fluvial landform is created by a river's decrease in energy when it reaches a floodplain?
What type of fluvial landform is created by a river's decrease in energy when it reaches a floodplain?
delta
Knickpoints mark sharp changes in __________ of a river.
Knickpoints mark sharp changes in __________ of a river.
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Which term describes the process of a more energetic river capturing a less energetic river?
Which term describes the process of a more energetic river capturing a less energetic river?
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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Which of the following best describes superimposed rivers?
Which of the following best describes superimposed rivers?
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Antecedent rivers maintain their course after high-lying areas are formed.
Antecedent rivers maintain their course after high-lying areas are formed.
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Undergraded rivers have excess energy and erode their channels.
Undergraded rivers have excess energy and erode their channels.
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What role do wetlands play in drainage basins?
What role do wetlands play in drainage basins?
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What is a primary result of river rejuvenation?
What is a primary result of river rejuvenation?
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The _____ River is noted as an example of a threatened river system.
The _____ River is noted as an example of a threatened river system.
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Which aspect is NOT important in catchment and drainage basin management?
Which aspect is NOT important in catchment and drainage basin management?
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People have no impact on the volume and flow of water in a drainage basin.
People have no impact on the volume and flow of water in a drainage basin.
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Name one way human activities can detrimentally affect river ecosystems.
Name one way human activities can detrimentally affect river ecosystems.
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Which drainage pattern appears tree-like?
Which drainage pattern appears tree-like?
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Draining density is only influenced by the hardness of rocks.
Draining density is only influenced by the hardness of rocks.
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What is the term for the amount of water flowing in a river channel measured in cubic metres per second?
What is the term for the amount of water flowing in a river channel measured in cubic metres per second?
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The cross-profile of a river in the lower course will have a ________ shape.
The cross-profile of a river in the lower course will have a ________ shape.
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Match the following stream orders with their descriptions:
Match the following stream orders with their descriptions:
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What type of flow describes water moving over a smooth surface?
What type of flow describes water moving over a smooth surface?
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The upper course of a river has a gentle gradient.
The upper course of a river has a gentle gradient.
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Drainage density can be categorized as low, medium, high, or ________.
Drainage density can be categorized as low, medium, high, or ________.
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Study Notes
Fluvial Landforms
- Rapids are created by fast flowing water over rocky riverbeds.
- Waterfalls mark a sharp drop in a riverbed, often found where hard rock meets softer rock.
- Meanders are bends in a river channel, formed by erosion on the outer banks.
- Alluvial fans are cone-shaped deposits of sediment at the base of mountains.
- Levees are natural embankments formed by deposited sediment on either side of a river.
- Braided streams are networks of intertwined channels, forming where a river has a high sediment load.
- Oxbow lakes form when a meander is cut off from the main river channel.
- Flood plains are flat areas of land on either side of a river channel, formed by sediment deposition during floods.
- Deltas are triangular areas of land at the mouth of a river, formed by deposited sediment.
River Grading
- Graded rivers have a balance between their gradient, volume and channel shape, allowing them to flow efficiently.
- Overgraded rivers have excess energy and erode their channels.
- Undergraded rivers do not have enough energy to flow and deposit their load.
Rejuvenation of Rivers
- River rejuvenation occurs when the river's energy level increases due to factors such as isostatic uplift, sea level drop, increased runoff, or water addition.
- Knickpoints are sharp changes in gradient, often marked by waterfalls or rapids.
- River terraces are remnants of old valley floors, indicating past river levels.
- Valley within a valley forms when a rejuvenated river erodes a new valley within an old one.
- Entrenched meanders are meanders carved into steep valley sides by rejuvenated rivers.
- Ingrown meanders are meanders that erode sideways, creating overhangs above the stream.
River Capture
- River capture occurs when a more energetic river erodes headward and captures the water of a less energetic river, creating distinctive landforms.
- Captor stream is the more energetic river that captures the other river.
- Captive stream is the less energetic river that is captured.
- Misfit or beheaded stream is the section of the river that lost its headwaters.
- Elbow of capture is the point where the capture occurred.
- Wind gap is the dry valley segment between the elbow and misfit stream reflecting the original river course.
- Knickpoint waterfall is the sharp change in gradient where the higher-lying captive stream flows into the captor stream.
- Abstraction is the process of the watershed becoming lower and shifting its position.
Superimposed and Antecedent Rivers
- Superimposed rivers have patterns that don't reflect the underlying geology, suggesting they formed on a previous landscape before erosion exposed the current bedrock.
- Antecedent rivers formed before the uplift of the surrounding land and maintained their course as the land rose.
Importance of Managing Drainage Basins
- Drainage basins are essential for collecting and storing precipitation, providing fresh water for people and the environment.
- Wetlands are crucial for water storage, stream flow regulation, and water filtration.
Human Impacts on Drainage Basins
- Human activities significantly impact drainage basins and their functions, including:
- Deforestation reduces water infiltration and increases runoff.
- Agriculture can introduce fertilizers and pesticides into watercourses.
- Urbanization leads to increased impermeable surfaces, causing runoff and flooding.
- Mining can pollute watercourses with heavy metals and other toxic substances.
- Pollution from industrial and agricultural activities can degrade water quality.
- Dam construction alters river flow regimes and can impact downstream ecosystems.
- Recreation can contribute to erosion and pollution if poorly managed.
Catchment Management Strategies
- Catchment and drainage basin management focuses on preserving healthy drainage basins, rivers, and wetlands, using strategies such as:
- Legislation to control water use, pollution, and discharges.
- Maintaining riparian vegetation for erosion control and water quality improvement.
- Careful investigations before building dams.
- Managing alien tree planting to prevent ecological damage.
- Controlling development on flood plains and river channels.
- Promoting sustainable farming practices.
- Public education about water resource conservation.
Marico River Case Study
- The Marico River in South Africa exemplifies a threatened river system.
- Mining activities in the catchment area pose potential risks to the river's ecosystem, water quality, and communities that rely on it.
Drainage Patterns
- Dendritic drainage patterns resemble a tree, forming in areas with uniform rock hardness and gradient.
- Parallel drainage patterns develop where the land slopes uniformly, with rivers and tributaries flowing nearly parallel.
- Deranged drainage patterns lack a discernible organization, often found in areas with disrupted topography or glaciated landscapes.
Drainage Density
- Drainage density is the total length of streams per unit area in a drainage basin.
- Factors influencing drainage density include evaporation rates, rainfall, infiltration, and rock hardness.
- It can be categorized as low, medium, high, or very high.
Topographic Maps and Stream Order
- Topographic maps are useful for identifying stream order and drainage density.
- First-order streams are the smallest and have no tributaries.
- Higher-order streams are formed when two streams of the same order merge.
River Discharge and Flow Types
- Discharge is the volume of water flowing through a river channel at a particular time.
- It is measured in cubic meters per second (cumecs).
- Laminar flow is smooth and relatively fast, occurring on smooth surfaces.
- Turbulent flow is chaotic and slower, characterized by eddies and internal friction.
River Profiles
- Longitudinal profile depicts the river's gradient along its length.
- The upper course is the steeper upstream section near the source.
- The middle course is downstream, where the gradient is gentler.
- The lower course is the flatter, final segment near sea level.
- Transverse profile is a cross-section of the river valley.
- The upper course has a deep, narrow V-shape.
- The middle course has a more open V-shape.
- The lower course has a very wide, open V-shape.
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Description
Explore the fascinating world of fluvial landforms including rapids, waterfalls, and meanders. This quiz will also cover concepts like graded rivers and their efficient flow characteristics. Test your understanding of how water shapes the landscape around us.
