Water on the Land Flashcards
(27 cards)
What is discharge and what’s it measured in?
The amount of water in a river measured in cubic metres per second (m^3/sec).
What 6 factors affect the amount of discharge?
Rainfall (type/amount), temperature, previous weather (wet/dry), relief (steep/gentle), rock type (permeable/impermeable), land use (rural/urban).
Why does discharge usually increase from source to mouth?
Tributaries add water to the main channel so the width and depth increases.
What is velocity and what’s it measured in?
The speed of the river measured in m/s.
Why does river velocity increase form source to mouth?
As discharge increases, there’s less frictions from the bed and banks. Water can flow faster (even though gradient becomes gentler).
What are the 4 erosion processes of rivers?
Hydraulic action, abrasion, attrition, corrosion.
What are the 4 ways a rivers load can be transported?
Traction, saltation, suspension, solution.
Deposition occurs when the river slows down and energy is lost. When are the 3 times this happens?
On the inside bends of meanders, where the channel widens and at the mouth.
Is the heaviest material (boulders) deposited last and the lightest (clay) last? Also, wha happens to the solution?
Yes.
Minerals in solution becomes salt in the sea.
What is a long profile and what’s it divided into?
A cross-section of a river from its source to mouth.
Divided into upper, middle and lower courses.
Describe a rivers usual gradient.
Decreasing gradually downstream.
Long profiles are usually concave, but what can make gem irregular?
Different rock types.
Describe the upper, middle and lower course of the cross-profile.
Upper: River erodes vertically to form narrow steep-sided V-Shaped valley. Bedload is angular boulders.
Middle: Begins to erode laterally. Valley widens w/ gentler slopes. Bedload is round pebbles.
Lower: Lateral erosion. Deposition forms wide valley w/ flat valley floor. Bedload is sand, silt, clay.
What is drainage basin?
Area of land drained by a river and its tributaries.
What is a watershed?
An area of high land separating 2 drainage basins.
What is a tributary and confluence?
Tributary is a smaller river joining a larger one. Confluence is the place where the 2 join.
Define waterfall, where do they occur and what is its formation?
It’s a place where water flows vertically usually occurring in the upper course where different rocks are.
Soft rock erodes quicker>undercuts hard rock so it overhangs>overhang collapses into plunge pool>water runs over.
Describe the formation of an ox-bow lakes and what happens after.
Narrow neck of land within a meander erodes when there’s high flow>meander loop gets bigger and more circular>river breaks the loop off so the water follows the main flow.
Over time lake becomes a marsh then dries up.
What’s a flood plain and where are they formed?
An area of flat land either side of a river. Formed in lower course where valley is widest.
Describe leeves and their formation.
Raised banks of sediment either side of river channel.
Over years of flooding, the thinner load deposits on outer parts of flood plain while largest sediment deposits at channel edges. This builds up.
Name the 3 physical causes or fiver floods and 2 human.
Phys: prolonged rain=short heavy rainstorm, snow melt, steep slopes w/ narrow valleys.
Hum: deforestation, construction of urban areas.
Describe a hard engineering method of flood management and 2 soft engineering methods.
Hard: Dams - Built in upper valley to create reservoir so water flow is controlled.
Soft: Flood-plain zoning - Restrict building in areas at risk of floods.
Flood warnings - Gives time to flood-proof houses, move possessions upstairs, evacuate.
Outline the Kielder Water reservoir case study.
UK 1982, 12km long, 50m deep, £170mill to build.
Benefits: hydro-elec. power station using water from reservoir, unique plants & animals, water shortages, millions of trees>forest employs hundreds, flood prevention, tourism.
Probs: changes landscape, affects habitat, potential for erosion downstream, re-housing, thousands of acres lost, monoculture trees.
Outline the 3 Gorges dam case study.
East China, built to provide electricity, 30+ tributaries.
Positives: Social (reduced flood risk, hydro-elec. energy to millions), Environmental (replaces coal power stations that pollute & help climate change), Economic (saves money for electricity).
Negatives: Social (millions re-housed, damaged homes), Environmental (increase downstream erosion, landslides), Economic (most expensive dam, dredging needed for sediment accumulation).
