Rivers: Hydrology, Processes & Management

A set of fill-in-the-blank flashcards covering key concepts on rivers, hydrology, fluvial processes, flooding, and management strategies.

The Water Cycle System

A closed system, meaning it has no inputs or outputs.

Drainage Basin System

An open system with both inputs and outputs.

Drainage Basin Boundary (Watershed)

A watershed is the boundary separating one drainage basin from another.

Cause of Downhill River Flow

Gravity causes water to flow downhill in a river system.

High Drainage Density

Drainage basins with many tributaries exhibit high drainage density.

Permeable Rocks and Drainage Density

Permeable rocks allow more infiltration, leading to lower drainage density.

Hydrograph Impact of Increased Surface Run-off

Increased surface run-off creates a hydrograph with a short lag time and a steep rising limb.

Peak Discharge on a Storm Hydrograph

On a storm hydrograph, peak discharge is the maximum amount of water held in the channel.

Gentle Hydrograph and Flood Risk

A gentle hydrograph indicates a low risk of flooding.

Freeze-Thaw Weathering

Weathering caused by repeated freezing and thawing of water in cracks is called freeze-thaw weathering.

Abrasion in Rivers

Abrasion is the wearing away of river bed and banks by the load carried.

Traction in River Transport

Large boulders rolled along the river bed are transported by traction.

When River Deposition Occurs

Deposition occurs when the river's energy drops and it can no longer carry its load.

Steepest Section of a River Course

The upper course is the steepest section of a river.

Meander Formation (Erosion Type)

Lateral erosion dominates in the formation of meanders in the middle and lower courses.

Oxbow Lake Formation

When a meander loop is cut off from the main channel, it forms an oxbow lake.

Levees (Natural Embankments)

Levees are natural embankments formed after repeated flooding and deposition.

Delta Formation at River Mouth

At a river mouth where deposition exceeds removal, a delta may form.

River Contamination from Urban Sewage

Urban areas often discharge untreated sewage, introducing pathogens and nutrients that contaminate rivers.

Eutrophication Cause

Fertilizer runoff can cause eutrophication, leading to algal blooms.

Overuse of Water Resources

Excessive irrigation that removes more water than is replenished is an example of overuse of water resources.

Impact of Sparse Vegetation on Water Run-off

Sparse vegetation leads to less interception and more surface run-off.

Impact of Impermeable Urban Surfaces

Impermeable surfaces in cities reduce infiltration and increase surface runoff.

Function of Dams

Dams store water in a reservoir and can regulate river discharge.

Environmental Drawback of Dams (Sediment)

One environmental drawback of dams is that trapped sediment can degrade farmland downstream.

Afforestation for Flood Management

Afforestation helps flood management because tree roots bind soil and increase interception.

Impact of Straightening River Channels

Straightening a river channel typically increases the speed of flow, potentially increasing flooding downstream.

Erosion on Meander Bends

On a meander, erosion occurs on the outer bank, forming a river cliff.

Deposition on Meander Bends

Deposition on the inside of a meander bend creates a slip-off slope.

Waterfall Retreat Mechanism

A waterfall retreats upstream as the soft rock is undercut faster than the hard rock.

Lag Time on a Hydrograph

Lag time is the time between peak rainfall and peak discharge on a hydrograph.

Conditions for High Drainage Density

High drainage density occurs in climates with more rainfall and less infiltration.

Throughflow

Throughflow describes the movement of water through the soil.

Groundwater Flow

Groundwater flow is the movement of water through the rocks.

Aquifers

Aquifers are permeable rocks that hold water.

Interception (Water Cycle)

Interception is the process by which precipitation is caught on leaves and branches.

Effect of Snow and Ice on Hydrological Cycle

Snow and ice acting as water stores reduce the speed of the hydrological cycle.

Flashy Hydrograph

Surface run-off reaching the river quickly produces a hydrograph described as flashy.

Salt Crystallisation Weathering

Salt crystallisation is a type of physical weathering in which salt growth widens cracks.

Biological Weathering (Tree Roots)

Tree roots widening cracks in rocks is an example of biological weathering.

When River Load Deposition Occurs

Deposition of load occurs when river energy cannot overcome friction with the bed and banks.

Suspended Load Characteristics

Suspended load consists of light materials carried without touching the bed.

Valley Shape in Upper River Course

In the upper course, vertical erosion combined with mass movement creates V-shaped valleys.

Thalweg

The thalweg is the fastest flow line within a river channel.

Factors Contributing to Higher Discharge Peak

In storm conditions, impermeable rock, high drainage density, and urban land use all contribute to a higher discharge peak.

Impact of Lake Reclamation on Flood Risk

Reclamation of lakes reduces their ability to store excess water, increasing flood risk.

Benefit of Flood Monitoring Systems

Monitoring and early warning systems reduce flood damage by allowing timely evacuation.

Concrete Flood Walls (Protection and Drawback)

Concrete flood walls mainly protect against minor floods and may cause visual pollution.

Attrition (River Erosion)

Attrition is erosion that wears down the transported load itself.

Alternative Name for Hydraulic Cycle

The hydraulic cycle is also known as the water cycle.