Enquiry Question 4 Flashcards
Where is the River Wharfe
The River Wharfe starts in the Yorkshire Dales and runs North East of Leeds. It runs into the River Ouse. Source is 310m above sea level and mouth is 5m above sea level.
Waterfall
Linton Falls
A waterfall occurs when more resistant rock is over a layer of less resistant rock
The less resistant rock erodes more easily by abrasion and hydraulic action creating an over hang
Eventually the overhang of more resistant rock collapses and results in further erosion of less resistant rock
The rivers bedload swirls at the foot of the waterfall, eroding the river bed to form a plunge pool
V-Shaped valleys and spurs in the upper course
A rivers discharge is low in the upper course and so it only has enough energy to erode downwards - vertical erosion
The valleys sides are slowly broken down through weathering
The weathered material is transported by gravity towards the river channel, steepening the valley sides
The steep sided and narrow valley shape is then created
Interlocking spurs form where there are more resistant bands of rock, which the river cannot erode
What is a Spur
A piece of land jutting into a river descending from a mountain into a valley
Soil creep
Individual particles of soil move slowly down a slope under the force of gravity. They collect at the bottom of The Valley sides, the river may erode this material.
Slumping
Happens when the bottom of a valley side is eroded by the river. The slop becomes steeper and the material above slides downwards.
Discharge
The volume of water flowing in a river measured in metres cubed per second
Increases downstream because of multiple tributaries joining and the river has become larger
Long profile
Showing the gradient of the river and how this changes with distance from Source
Channel cross profile
Shape of the river channel
Valley cross profile
Shape of the land next to the river
Channel width
Increases downstream as erosion has caused River to widen
Channel depth
Increases downstream as there is more water to erode surrounding material
Velocity
Increases downstream as there is more discharge and the river bed is smoother so less friction occurs. Also less proportion of river is touching rock
Sediment load volume
Increases downstream as the cross sectional area increases so more sediment can be held in the river
Sediment particle size
Decreases downstream because of more attrition having occurred so sediment is smaller and smoother
Channel bed roughness
Decreases downstream as more erosion occurs
Slope angle (gradient)
Decreases downstream as erosion in upper course is more vertical creating more v shaped valleys. In lower course erosion is more horizontal.
Meanders
When rivers enter their middle and lower stages they begin to erode sideways
The rivers erode on the outside of the bend where the current flows strongest and fastest
This washes away the river bank creating a river cliff
On the inside of the bend where the flow is weakest, it deposits material forming a slip off slope
When the river meander reaches the sides of The Valley it erodes them widening The Valley floor and floodplain
Oxbow lakes
Erosion cause the outside bends of a meander to get closer together until only a small bit of land is left between (the neck)
The river breaks through this land, usually during a flood, and the river flows along the shortest course
Deposition eventually cuts off the meander forming an oxbow Lake
Peak rainfall
When heaviest rainfall occurred
Peak discharge
The time with the highest river discharge
Lag time
The time taken between the peak rainfall and peak discharge
Rising limb
The river level is rising
Falling limb
The river level is falling
Flashy hydrograph
A hydrograph that responds quickly to rain with a high peak discharge, steep rising limb and short lag time
Interception
Water is stored on vegetation
Infiltration
Downward movement of water into the soil from the ground
River channel flow
Movement of water in the river channel
Groundwater storage
Water is stored within rock deep down
Soil moisture storage
Where water is stored within the soil
Surface run off
Water flowing horizontally on top of the ground
Percolation
Downward movement of water deeper below the surface into the rock
Groundwater flow
Water moves through the cracks and joints of rock towards river
Surface storage
Water is stored on the surface
Throughflow
Water moves horizontally through the soil towards the river
Subdued hydrograph
Lower peak discharge, not a steep rising limb and long lag time
How does deforestation affect storm hydrographs
No vegetation to absorb water
Soil becomes saturated
Less infiltration
More surface runoff
How does steep relief affect storm hydrographs
Runoff happens quicker
How does urbanisation affect storm hydrographs
Ground impermeable
No infiltration
More surface runoff
How does saturated soils affect storm hydrographs
Less infiltration
More surface run off
How does impermeable rock affect storm hydrographs
No infiltration
More surface runoff
How does land use change affect storm hydrographs
Farming:
More vegetation
More infiltration
Less surface runoff
Cattle:
Less vegetation
Less infiltration
More surface runoff
Levee
When a river floods it deposits heaviest particles first
They form the levee, a natural embankment
Delta
When a river reaches another body of water is loses velocity and deposits sediment
If river deposits sediment faster than coastal processes remove it then sediment builds up in layers in a fan shaped delta
Where is Sheffield
South Yorkshire, east of Liverpool and Manchester
7 hills in it
East of Peak District
Top 2 human factors for flooding in Sheffield
Lack of river defences in what was described as a 1 in 1000 event
Issue with drainage - they weren’t large enough to hold all the rain
Top 2 physical factors for Sheffield flooding
Sheffield lies at confluence of 3 rivers
Antecedent rainfall: recently had a lot of rainfall, ground was already very saturated
