the changes downstream in a river valley in a river valley river studies
TRANSCRIPT
The Changes downstreamThe Changes downstream
in a river valleyin a river valleyRIVER RIVER STUDIESSTUDIES
The Hydrologic CycleThe Hydrologic Cycle
Infiltration = Groundwater SystemInfiltration = Groundwater System
Runoff = Surface Water SystemRunoff = Surface Water System
Satellite view of river Satellite view of river drainage, Middle Eastdrainage, Middle East
What is this features?
Upper valley Upper valley characteristicscharacteristics
Upper valley Upper valley characteristicscharacteristics
Upper valley Upper valley characteristicscharacteristics
“V”shape valley, vertical erosion dominant
Upper valley Upper valley characteristicscharacteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Upper valley Upper valley characteristicscharacteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hill slopes
Upper valley Upper valley characteristicscharacteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hill slopes
Narrow, shallow channel, low velocity and discharge
Upper valley Upper valley characteristicscharacteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hill slopes
Narrow, shallow channel, low velocity and discharge
Large bed load derived from upstream and from valley sides
Interlocking spurs, Interlocking spurs, Robinson, Lake DistrictRobinson, Lake District
A typical upper course valley with interlocking spurs, steep valley sides and active slope processes
River load in upper River load in upper coursecourse
Boulders are large and semi-rounded, due to attrition within the load and abrasion with the stream bed and banks
Why are they rounded?
Rapids in the Upper Tees Rapids in the Upper Tees ValleyValley WHAT IS A RAPID?WHAT IS A RAPID?
High Force waterfall, R. High Force waterfall, R. TeesTees
WHAT IS A WATERFALL?
High Force waterfall, R. High Force waterfall, R. TeesTees
Plunge pool
What is this feature called?
Waterfall creates gorge as it recedes upstream by eroding the base and neck
HOW IS A GORGE FORMED?
HOW IS A GORGE FORMED?
Waterfall formationWaterfall formationLook at the diagram, How is a waterfall formed?
High Force Waterfall R. High Force Waterfall R. TeesTees
Close-up of potholesClose-up of potholesHow are these formed?
Potholes, human scale!!Potholes, human scale!!
Erosion ProcessesErosion Processes
is when the river is loaded with material in suspension is when the river is loaded with material in suspension and scours away at the river banks. (Sandpaper and scours away at the river banks. (Sandpaper effect)effect)
is the shear force of the river impacting on the sides of is the shear force of the river impacting on the sides of the river banks.the river banks.
is substances carried in solution such as acids. They is substances carried in solution such as acids. They dissolve rocks away over long periods of time.dissolve rocks away over long periods of time.
is when bed load collides into each other with the is when bed load collides into each other with the current flow and breaks down into smaller particles.current flow and breaks down into smaller particles.
Abrasion (Corrasion)Abrasion (Corrasion) - - Hydraulic ActionHydraulic Action --
CorrosionCorrosion - -
AttritionAttrition --
Middle course, R. TeesMiddle course, R. TeesMiddle course, R. TeesMiddle course, R. TeesHOW DOES THIS DIFFER FROM THE UPPER SECTION?HOW DOES THIS DIFFER FROM THE UPPER SECTION?
Middle course, R. TeesMiddle course, R. Tees
Valley opens out, more gentle slopes, wider valley bottom
First signs of meanders
River channel wider, deeper, greater velocity and discharge
WHAT DO YOU THINK THE ARROWS POINT TO?WHAT DO YOU THINK THE ARROWS POINT TO?
Meandering RiversMeandering Rivers
WHAT IS A MEANDER?
Formation of MeandersFormation of Meanders
Point bar deposits
Point Bar DepositsPoint Bar Deposits
Point bar deposits grows laterally through time
Meander, R. Lavant, Meander, R. Lavant, ChichesterChichester
Meander, R. Lavant, Meander, R. Lavant, ChichesterChichester
Floodplain
Point bar deposits on the inner meander bend where there is low energy
River Cliff Slip-Off Slope
WHAT DO THE ARROWS POINT TO?WHAT DO THE ARROWS POINT TO?WHICH WAY IS THIS
MEANDER MOVING?WHICH WAY IS THIS MEANDER MOVING?
Cut bank erosion (River Cliff)
Point bar deposits }Meander
loop
WHERE IS EROSION TAKING PLACE?WHERE IS EROSION TAKING PLACE?
WHERE IS DEPOSTION TAKING PLACE?WHERE IS DEPOSTION TAKING PLACE?
A
B
C
D
E
F
Meander on the R. Meander on the R. ColoradoColorado
WHY IS DEPOSITION OCCURING HERE?WHY IS DEPOSITION OCCURING HERE?
How did these
meanders form?
REVISION: What River features do you get here?
Migrating meanders, R. Migrating meanders, R. Gongola, NigeriaGongola, Nigeria
WHY ARE THEY MIGRATING?WHY ARE THEY MIGRATING?
What happens to the river What happens to the river when it moves to the when it moves to the middles coursemiddles course
Gradient becomes less steepGradient becomes less steep River continues to erode vertically but River continues to erode vertically but
LATERAL erosion now occurs in LATERAL erosion now occurs in MEANDERSMEANDERS
What is MEANDER MIGRATION ?What is MEANDER MIGRATION ? Name three effects it have on the valley?Name three effects it have on the valley? What factors effect how much load is What factors effect how much load is
being carried?being carried?
TransportationTransportation
What are the four methods of transportation?What are the four methods of transportation? TractionTraction - is when large particles roll along the river - is when large particles roll along the river
bedbed
SaltationSaltation - - is when smaller particles bounce and is when smaller particles bounce and collide in a leapfrog manner across the river bed.collide in a leapfrog manner across the river bed.
SuspensionSuspension - is when the river holds even smaller - is when the river holds even smaller particles and carries them in its current. This is when particles and carries them in its current. This is when the river appears to be murky.the river appears to be murky.
SolutionSolution - is when dissolved material is carried. - is when dissolved material is carried.
Lower Course: Severn Lower Course: Severn ValleyValley
Lower Severn ValleyLower Severn Valley
Well developed meanders with bars in the channel indicating high sediment load
Very gentle valley side gradients
HOW DOES IT DIFFER FROM THE MIDDLE COURSE?
Very wide floodplain
Flood PlainsFlood Plains
The entire floodplain can become covered with water during floods.
HOW DO YOU THINK THE TERRACES WERE FORMED?
Ox Bow Lake FormationOx Bow Lake FormationLOOK AT THE DIAGRAM & EXPLAIN THERE FORMATIONLOOK AT THE DIAGRAM & EXPLAIN THERE FORMATION
Formation of an Oxbow
Ox Bow lake on Ox Bow lake on MississippiMississippi
LevLevee formationee formation
LeveesLeveesWHAT DO YOU THING HUMANS MIGHT HAVE DONE TO THIS LEVEE?WHAT DO YOU THING HUMANS MIGHT HAVE DONE TO THIS LEVEE?
Delta Formation
WHAT IS A DELTA?WHAT IS A DELTA?
DEPOSITON OF MATERIAL BY THE RIVER WHEN IT ENTERS THE SEADEPOSITON OF MATERIAL BY THE RIVER WHEN IT ENTERS THE SEA
WHY DOES IT DROP ITS SEDIMENTWHY DOES IT DROP ITS SEDIMENT
Mississippi Delta from Mississippi Delta from Space Space
MISSISSIPPI
The Nile Delta from spaceThe Nile Delta from space
River NileRiver Nile
Estuary FormationEstuary Formation
The Lower Course of a river valley has been DROWNED by a rise in sea level or a fall in the land level.
HOW DOES THIS DIFFER FROM A DELTA?HOW DOES THIS DIFFER FROM A DELTA?
RAISED VALLEY SIDESRAISED VALLEY SIDES
USING YOUR ATLASFIND AN ESTUARY (LOOK AT THE RIVER THAMES)
USING YOUR ATLASFIND AN ESTUARY (LOOK AT THE RIVER THAMES)
USING YOU ATLASLOCATE THE RHONE DELTA
USING YOU ATLASLOCATE THE RHONE DELTA
The Rhone DeltaThe Rhone Delta
The Rhone Delta S. The Rhone Delta S. FranceFranceLook at p39 and identify the
KEY FEATURES CAN YOU SEE IN THE SATELLITE PHOTO?
Look at p39 and identify the KEY FEATURES CAN YOU SEE IN THE SATELLITE PHOTO?
The Rhone DeltaThe Rhone Delta
WHY HAS A DELTA FORMED HERE? LOOK AT P 39 WHY HAS A DELTA FORMED HERE? LOOK AT P 39
Summary of valley Summary of valley characteristicscharacteristics
Upper Interlocking spurs “V” shaped valley Waterfall Gorge
Middle Wider valley Gentler valley sides
Meanders
Lower Widest part of valley
Floodplain Terraces Ox Bow & Levees Delta, Estuary
The River TeesThe River Tees
TRY AND FIND THE RIVER TEESIN YOUR ATLAS
HINT LOOK AT THE MAP
TRY AND FIND THE RIVER TEESIN YOUR ATLAS
HINT LOOK AT THE MAP
Land Use in Drainage Basin Land Use in Drainage Basin of River Teesof River Tees
WHAT IS THE AREA IN EACH BOX?WHAT IS THE AREA IN EACH BOX?
Upper TeesUpper Tees
WHAT HUMAN INFLUENCES EXIST IN THE MAPS?WHAT HUMAN INFLUENCES EXIST IN THE MAPS?
COW GREEN RESERVOIRCOW GREEN RESERVOIR
The Upper Tees Cronkley The Upper Tees Cronkley ScarScar
WHAT LAND USES CAN YOU SEE IN THE PHOTO?WHAT LAND USES CAN YOU SEE IN THE PHOTO?
WHAT ARE THE KEY GEOGRAPHCIAL FEATURES YOU CAN SEE IN THE PHOTOGRAPHWHAT ARE THE KEY GEOGRAPHCIAL FEATURES YOU CAN SEE IN THE PHOTOGRAPH
MOORLANDMOORLAND
STEEP VALLEY
SLOPE DEBRISSLOPE DEBRIS
TURBULENT RIVER
CHANNEL
TURBULENT RIVER
CHANNEL
Upper TeesUpper Tees
WHAT IS THE NAME OF THE WATERFALL?WHAT IS THE NAME OF THE WATERFALL?
The Lower Course TeesThe Lower Course TeesThe Lower Course TeesThe Lower Course Tees
HOW HAS THE RIVER AND LAND USE CHANGED?HOW HAS THE RIVER AND LAND USE CHANGED?
FLAT VALLEY FLOORFLAT VALLEY FLOOR
WIDE MEANDERSWIDE MEANDERS
URBAN SETTLEMENTURBAN SETTLEMENT
WHAT LAND USE CAN YOU SEE IN THE PHOTOGRAPH?WHAT LAND USE CAN YOU SEE IN THE PHOTOGRAPH?
The Lower TeesThe Lower TeesTEESMOUTH ESTUARYTEESMOUTH ESTUARY
The River meets the SeaThe River meets the Sea
LOOK AT P42WHAT DO YOU THINK THE PHOTOS SHOW?
LOOK AT P42WHAT DO YOU THINK THE PHOTOS SHOW?
WHAT IS THE FUNCTIONOF THE BARRAGE?WHAT IS THE FUNCTIONOF THE BARRAGE?
River ManagementRiver Management
Formation of the Formation of the Mississippi River DeltaMississippi River Delta
Early delta
More recent delta sediments Modern
delta
Causes of FloodsCauses of Floods
A Flood can occur when a river exceeds its bank full stage A Flood can occur when a river exceeds its bank full stage and water will subsequently inundate the adjacent and water will subsequently inundate the adjacent surrounding area.surrounding area.
Heavy rainfallHeavy rainfall - long periods of heavy rainfall will lead to an - long periods of heavy rainfall will lead to an increase in surface runoff and increase in river level.increase in surface runoff and increase in river level.
Snow melt and heavy rainfallSnow melt and heavy rainfall - water in storage may be freed by - water in storage may be freed by Spring melts increasing surface runoff. Spring melts increasing surface runoff.
DeforestationDeforestation - cutting down of trees leads to a reduction in - cutting down of trees leads to a reduction in interception rates and an increase in surface runoff. This may interception rates and an increase in surface runoff. This may also lead to rapid erosion rates due to a lack of stability in the soil also lead to rapid erosion rates due to a lack of stability in the soil subsurface.subsurface.
UrbanisationUrbanisation - tarmac and concrete surfaces are impermeable - tarmac and concrete surfaces are impermeable and lead to an increase in surface runoff.and lead to an increase in surface runoff.
Flood Control and Flood Control and ManagementManagement
There are a number of ways managing floods:There are a number of ways managing floods: 1. 1. Afforestation Afforestation - planting trees increases interception rates and reduces - planting trees increases interception rates and reduces
surface runoff.surface runoff. 2. 2. Dams and ReservoirsDams and Reservoirs - these hold back and regulate the flow of river - these hold back and regulate the flow of river
water. Can be used as fresh water supply and generation of HEP.water. Can be used as fresh water supply and generation of HEP. 3. 3. Diversion ChannelsDiversion Channels - overflow channels which take surplus water out of a - overflow channels which take surplus water out of a
river in times of flood.river in times of flood. 4. 4. Channel Straitening and DredgingChannel Straitening and Dredging - smoothens the channel to increase - smoothens the channel to increase
the speed (velocity) of the river and get water out of the drainage basin as the speed (velocity) of the river and get water out of the drainage basin as quickly as possible.quickly as possible.
5. 5. Artificial LeveesArtificial Levees - makes river banks higher therefore holding more water. - makes river banks higher therefore holding more water. 66. Culverts. Culverts - semi circular, smooth channels increase velocity and gets - semi circular, smooth channels increase velocity and gets
water away from urban areas as quickly as possible.water away from urban areas as quickly as possible. 7. 7. Revetments and Channel WallsRevetments and Channel Walls - strengthen river banks from erosion. - strengthen river banks from erosion.