1.3 River Landscapes Flashcards
Define Ribbon Lake
Large, narrow lake, occupying a v-shaped valley
Define V-Shaped Valley
A valley formed where a glacier used to be
Define Meltwater
River which form when glaciers melt
Define Moraine
A mass of rocks/ sediment carried and deposited by a glacier
Define Hydraulic Action
Water is forced into cracks in the rock and air is forced out explosively, breaking off pieces of the banks
Define Abrasion
This is when pebbles grind along a rock platform, much like sandpaper. Over time the rock becomes smooth.
Define Attrition
This is when rocks that the sea is carrying knock against each other. They break apart to become smaller and more rounded.
Define Corrosion
When acid rain causes chemical weathering
Define Chemical Weathering
Acids in seawater slowly dissolve rocks
Define Biological Weathering
Roots of growing plants and burrowing animals or nesting birds can cause rocks to weather
Define Mechanical Weathering
Caused by repeated freezing and thawing of water in a crack or hole in the rock.
What is deposition?
When sediment, usually carried by waves is laid down or deposited
When does deposition occur?
When their is not enough energy to carry sediment any further
Define Source
The beginning of the river
Define Confluence
Where 2 rivers meet
Define Watershed
An area of highland between two drainage basins
Define Mouth
Where a river flows into a lake or the sea
Define Tributary
A small river/ stream that flows into a larger river
Drainage Basin
The area drained by a river and its tributaries
How does the channels shape change through the course of a river?
The channel becomes larger the further down the river it is.
How does the gradient change through a river course?
Decreases. The gradient starts very steep but the steepness evens out as it reaches the lower course.
How does the discharge change through a river course?
It increases as it goes down the river.
How does the velocity change through a river course?
It increases due to less friction.
How does the sediment size change through a river course?
The sediments erode one another getting smaller through the river course.
Describe how a plunge-pool forms
When hard rockets on top of soft rock, the waves erode at the soft rock creating an undercut. Hydraulic action and abrasion then deepen this into a plunge-pool.
What is likely to occur if you have an overhang?
The overhang is likely to collapse
On which side of a bend does water travel faster?
Outside
What forms on the outside bends of rivers?
River Cliffs
What forms on the inside bends of rivers?
Point Bar (Slip-off Slope)
Describe levees
A natural (or artificial) wall that increases the height of a river bank to prevent flooding.
Describe Channelisation
Widening or deepening the river to increase the discharge
Describe Flood Relief Channels
Channels made to relieve a river from high discharge
Describe Dams and Reservoirs
Large (usually artificial) lakes used to collect water and store it.
Describe Washlands
Areas of land near a river allowed to flood to take stress of off other areas
Describe River Restoration
The process of restoring a river to improve natural process
Describe Floodplain Zoning
This involves placing restrictions on land usage in the areas surrounding a river.
Describe Vertical Erosion
Erosion of the bed
Describe Lateral Erosion
Erosion of the sides
Describe the formation of Oxbow Lakes
As a Meander becomes deeper and deeper, the river may meet itself and then find another path, this leaves an oxbow lake
Describe Meanders
As river rushes around bends, the outside is eroded more than the inside, this causes bends called meander
What is the Tees-Exe line?
A line which separates highland and lowland Britain
Describe a River Profile
Altitude decreases as the river gets further from the source
How does depth change down the river?
Gets deeper down the river
How does valley profile change down a river?
In the upper course it is narrow and steep, it gets wider and the banks slope more further down the river
What is the shape and size of sediment in the upper course?
Angular Boulders
What is the shape and size of sediment in the middle course?
Rounded Rocks
What is the shape and size of sediment in the lower course?
Smooth, Round Pebbles
What are the three sections a river can be broken down into?
Upper Course
Middle Course
Lower Course
What features are present in the upper course?
Waterfalls
Gorges
Interlocking Spurs
V-shaped valley
What features are present in the middle course?
Meanders
Floodplain
Gentle Slopes
What features are present in the lower course?
Meanders Floodplain Estuary Levees Ox-bow Lake
What features are present in the mouth of a river?
Deltas
What model shows us how features of a river change across the profile?
Bradshaw Model
Define Irrigation
A method in which a controlled amount of water is supplied to plants at regular intervals for agriculture
Define Saturated
Holding as much water or moisture as can be absorbed
What are 6 physical causes of flooding in the UK?
Impermeable Rock Steep Valley Sides Hot, Dry Weather Ploughing Slopes Deforestation Dams Burst
How do impermeable rocks contribute to flooding?
Water does not soak into the ground, causing more surface run-off
How do steep valley sides contribute to flooding?
More water runs down to the river, increasing discharge so that less is needed to cause the flood
How does hot, dry weather contribute to flooding?
Means that the soil becomes hard and water cannot soak in
How do dam bursts contribute to flooding?
Greatly increases discharge and water in the area
How does deforestation contribute to flooding?
Water is not soaked up by roots and therefore the soil is more quickly saturated, once soil is saturated, there is greater surface run-off
How does ploughing contribute to flooding?
Soil can hold less water
What do hydrographs show?
How a river responds to a storm event
They show the relationship between rainfall and river discharge
Define the rising limb on a hydrograph
Line representing the rapid rise in water after a period of intense rainfall
Define the falling limb on a hydrograph
Represents the reduction in the amount of rainfall reaching the river channel
What is lag time? (Hydrographs)
The difference between the heaviest rainfall and the point at which the river contains the largest amount of water
What factors influence lag time?
Size of a drainage basin
Vegetation
Velley side steepness
Soil Type
