1. Hydrology and Fluvial Morphology Key Terms Flashcards
9696 - Cambridge AS Geography
Drainage Basin System
An area of land defined by a ridge line (watershed) that channels all surface water to a single collection point, like a river mouth, lake, or ocean.
Outputs
Water that leaves the drainage basin system.
Evaporation
The process where liquid water changes into a gas and enters the atmosphere.
Evapotranspiration
The combined process of evaporation (from the soil and water surfaces) and transpiration (release of water vapor from plants).
River Discharge
The volume of water flowing past a specific point in a river at a given time.
Stores
Locations within the drainage basin system where water is temporarily held.
Interception
Water caught by vegetation leaves and branches, which evaporates back into the atmosphere.
Soil Water
Water held in the spaces between soil particles.
Surface Water
Water visible on the Earth’s surface, like in streams, lakes, and oceans.
Groundwater
Water stored underground in saturated rock and soil layers.
Channel Storage
Water temporarily held within the channel of a river or stream.
Flows
The movement of water within the drainage basin system.
Throughfall
Precipitation that drips through the canopy of vegetation and reaches the ground.
Stemflow
Precipitation that runs down the stems of plants and reaches the ground.
Overland Flow
Water that flows over the land surface because infiltration cannot keep up with precipitation.
Channel Flow
Water moving within the channel of a river or stream.
Infiltration
The process of water soaking into the ground.
Percolation
The downward movement of infiltrated water through soil and rock layers.
Throughflow
Water that moves laterally through soil layers above the water table.
Baseflow
Groundwater that slowly discharges into streams and rivers, contributing to their flow even during dry periods.
Water Table
The upper boundary of the saturated zone in an aquifer.
Groundwater Recharge
The process by which water infiltrates the ground and replenishes the groundwater table.
Springs
Places where groundwater naturally flows out of the ground.
Discharge Relationships
How the volume of water flowing out of a drainage basin (discharge) changes over time in response to various factors.
Hydrograph
A graph showing the discharge of water from a drainage basin over a period of time.
Storm Hydrograph
A hydrograph that shows the rapid rise and fall of discharge in response to a specific precipitation event (storm).
Annual Hydrograph
A hydrograph that shows the variation in discharge throughout a whole year, reflecting seasonal changes in precipitation and other factors.
Influences on Hydrographs
Factors that affect the shape and characteristics of a hydrograph.
Precipitation Type and Intensity
The form (rain, snow, hail) and amount of precipitation that falls within the drainage basin.
Temperature
Air temperature affects rates of evaporation, transpiration, and infiltration.
Evaporation
The process where liquid water changes into a gas and enters the atmosphere.
Transpiration
The release of water vapor from plants.
Evapotranspiration
The combined process of evaporation and transpiration.
Antecedent Moisture
The amount of water already stored in the soil and groundwater before a precipitation event.
Drainage Basin Characteristics
Physical properties of the drainage basin that influence water flow.
Size and Shape
Larger and more circular basins tend to have slower and more sustained discharge.
Drainage Density
The total length of streams per unit area of land within the basin. Higher density indicates faster drainage.
Porosity and Permeability of Soils
Porosity is the space between soil particles; permeability is how easily water can flow through those spaces. Both influence infiltration and runoff.
Rock Type
Different rock types have varying permeability and storage capacity for water.
Slopes
Steeper slopes promote faster overland flow and less infiltration.
Vegetation Type
Vegetation can intercept precipitation, influence infiltration rates, and affect evapotranspiration.
Land Use
Urbanization with paved surfaces increases runoff and reduces infiltration.
River Channel Processes
The physical processes that shape a river channel, including erosion, transportation, and deposition of sediment.
Channel Processes
Specific mechanisms by which rivers erode, transport, and deposit sediment.
Erosion
The wearing away of rock and soil by flowing water.
Abrasion/Corrasion
Erosion caused by rocks and pebbles grinding against the river bed and banks.
Solution
Chemical dissolving of rock minerals by water.
Cavitation
Erosion caused by the rapid formation and collapse of bubbles in the water.
Hydraulic Action
The force of flowing water physically breaking apart rock and soil.
Load Transport
The ways that rivers carry sediment downstream.
Traction
Rolling and sliding of large, heavy particles along the river bed.
Saltation
Bouncing movement of medium-sized particles along the river bed.
Suspension
Finer particles carried within the flowing water column.
Solution
Dissolved minerals transported in the water itself.
Deposition and Sedimentation
The settling out of sediment from the river channel.
Hjulström Curve
A graph that shows the relationship between water velocity and particle size, indicating which processes (traction, saltation, suspension) dominate for different sized particles.
River Flow
The movement of water within a river channel.
Velocity
The speed of water flow at a particular point in the river.
Discharge
The volume of water flowing past a specific point in a river at a given time.
Laminar Flow
Smooth, streamlined flow where water layers move parallel to each other (rare in rivers).
Turbulent Flow
Most common flow pattern in rivers, with swirling eddies and mixing of water layers.
Helicoidal Flow
A corkscrew-shaped flow pattern in meandering rivers, with faster water on the outside of bends.
Thalweg
The deepest part of a river channel, often located along the line of fastest flow.
Channel Types
Different morphologies of river channels based on flow patterns and deposition.
Straight Channel
Relatively uncommon, with a straight course and minimal erosion or deposition.
Braided Channel
A network of channels separated by islands of deposited sediment, common in wide, high-gradient rivers with abundant sediment load.
Meandering Channel
A sinuous channel with bends (meanders) that migrate over time, leaving behind features like oxbow lakes.
Landforms
Features created by river channel processes.
Meander
A bend in a river channel.
River Cliffs
Steep banks formed by erosion on the outside of meanders.
Point Bars
Areas of sediment deposition on the inside of meanders.
Oxbow Lakes
Horseshoe-shaped lakes formed when a meander neck is breached, cutting off a loop of the old river channel.
Riffle and Pool Sequences
Alternating sections of shallow, fast-flowing water (riffles) and deeper, slower-flowing water (pools).
Waterfalls
A steep drop in the river bed where water plunges vertically.
Gorges
Deep valleys with steep sides eroded by a river.
Bluffs
High, steep banks along a river channel.
Floodplains
Flat, low-lying areas adjacent to a river channel that are periodically flooded.
Levees
Natural ridges of sediment deposited along the banks of a river channel during floods.
Deltas
Triangular landforms deposited where a river enters a body of standing water (lake or ocean).
Birdfoot Delta
A fan-shaped delta with multiple distributaries spreading out like a bird’s foot.
Arcuate Delta
A crescent-shaped delta with convex facing the source of incoming sediment.
Estuarine Delta
A delta formed in a sheltered environment where fine sediment mixes with seawater, creating a partially enclosed estuary.
Human Impact
The ways in which human activities affect river systems.
Modifications to Catchment Flows and Stores
Changes to the movement and storage of water within a drainage basin due to human activities.
Deforestation
Removal of trees, which can increase surface runoff and decrease infiltration, leading to faster and more intense floods.
Afforestation
Planting trees, which can increase interception, infiltration, and slow down runoff, leading to less intense floods.
Urbanization
Conversion of land to urban uses (buildings, roads) increases paved surfaces, reducing infiltration and increasing runoff.
Abstraction
The removal of water from a river or groundwater source for human use (drinking, irrigation).
Water Storage
Construction of reservoirs to store river water for later use.
Modifications to Channel Flows
Changes to the way water flows within a river channel due to human activities.
Hard Engineering
Structural measures to control river behavior, often with environmental drawbacks.
Floods
The overflowing of a river channel onto adjacent land, causing damage and disruption.
Causes of Floods
Heavy precipitation, rapid snowmelt, catchment modifications (reduced infiltration), and blockage of channels.
Impacts of Floods
Loss of life, property damage, infrastructure disruption, contamination of water supplies, and ecological damage.
Flood Risk Prediction
Estimating the likelihood and severity of future floods.
Recurrence Interval
The average time period between floods of a certain magnitude.
Flood Prevention and Amelioration
Strategies to reduce flood risk and lessen the impact of floods that do occur.
Forecasts and Warnings
Providing timely information to communities about potential floods.
Dams
Large structures that control river flow and store water, but can disrupt natural sediment transport and ecosystems.
Straightening
Removing meanders from a river channel to increase flow velocity and reduce flood risk, but can also increase erosion downstream.
Levees
Artificial raised banks along a river to contain floodwater, but can lead to a false sense of security and encourage development in floodplains.
Diversion Spillways
Channels that divert excess water from a river during floods, but can have environmental impacts downstream.
Soft Engineering
Techniques that work with natural processes to manage flood risk.
Floodplain Management
Restricting development in floodplains to minimize damage from floods.
Drainage Basin Management
Practices like afforestation and soil conservation to reduce runoff and increase infiltration.
Wetland and Riverbank Conservation
Protecting wetlands and natural vegetation along rivers to enhance water storage and reduce erosion.
River Restoration
Restoring natural meanders, reconnecting the river with its floodplain, and improving habitat for aquatic life.
2020 Yangtze River Flood
A major flood event that occurred in the middle and lower reaches of the Yangtze River basin in China during July and August 2020. Affected areas included Hubei, Jiangxi, Anhui, Jiangsu, and Jiangxi provinces.
Heavy Rainfall cause of 2020 flood
Persistent and intense rainfall over a long duration, exceeding the capacity of the river channel and exceeding historical records. The heaviest rainfall occurred in the provinces of Jiangxi and Anhui, with some areas receiving over 400 mm of rain in just five days.
Climate Change causes of 2020 flood
While not definitively proven in this case, some experts suggest climate change may be increasing the frequency and intensity of extreme precipitation events.
Reduced Infiltration cause of 2020 flood
Land-use changes, like urbanization, may have reduced the ability of the catchment to absorb rainfall, leading to higher surface runoff. The extent to which this was a factor is still being investigated.
Loss of Life from 2020 floods
Though not as severe as some past Yangtze River floods, some casualties were reported. At least 141 people died as a result of the floods.
Displacement from 2020 floods
Millions of people were evacuated from their homes due to rising floodwaters. An estimated 6.3 million people were displaced from their homes.
Property Damage from 2020 floods
Homes, businesses, and infrastructure suffered significant damage from flooding. Over 28,000 homes were destroyed, and economic losses were estimated at 82.23 billion yuan (11.76 billion USD).
Economic Disruption from 2020 floods
The floods caused widespread disruption to transportation, agriculture, and other economic activities. Disruptions to transportation and agriculture had a significant impact on the national economy.
Habitat Destruction
Floodwaters inundated natural habitats, potentially harming aquatic and riparian ecosystems.
Water Pollution
Increased erosion and runoff can lead to contamination of water supplies with sediment and pollutants.
Disruption of Natural Processes
Floods can disrupt natural processes like sediment transport and nutrient cycling.
Reservoir Management
Utilizing the cascade reservoir system along the Yangtze River to regulate water flow and reduce peak discharge. The Three Gorges Dam played a significant role in managing floodwaters, though it did experience record inflow levels.
Flood Forecasting and Warning Systems
Issuing timely warnings to communities about potential floods, allowing for evacuation and preparation. Flood warnings were crucial in enabling evacuations and reducing casualties.
Sustainable Land-Use Management
Practices like afforestation and soil conservation to improve infiltration and reduce runoff. Long-term planning to address potential impacts of climate change is ongoing.
Floodplain Management
Restricting development in floodplains and exploring flood-resilient building practices. Re-evaluating floodplain development and implementing stricter regulations are being considered.
Climate Change Mitigation
Efforts to reduce greenhouse gas emissions to minimize future increases in extreme weather events. China has committed to ambitious climate change mitigation goals.
