Post on 07-Jan-2016
description
Learning objectives
1. To understand the long profile changes of a river as it moves downstream
2. To understand the cross profile changes of a river as it moves downstream
60 second challengeWe have learnt lots of new words
associated with the Hydrological cycle and rivers.
How many can you remember in 60
seconds?
A River’s journey…..from source to the mouth
Where a river begins= SOURCEWhere the river flows into the sea= MOUTH
What does this
show?
Today we are going to study how these profiles change as the river moves
from its SOURCE to the MOUTH
A rivers journey…
A rivers journey…
A rivers journey…
A rivers journey….
Watch this!!!
1. Valley Long Profiles
• The gradient of the land is the cause of the changes in the characteristics of a river from source to mouth
• At the source of the river there are high mountains with a steep gradient.
• As the river reaches the lowlands the gradient becomes gentler.
• However the river is determined by its environment - it also shapes the environment too!
• It does this through erosion.• The river is in balance with its
environment creating a graded profile.
1. Valley Long Profiles
The graded profile
Concave shape
In reality the shape of a profile is never this smooth. e.g. rocky
outcrops of resistant rock that are difficult to erode.
Distance downstream
alt
itude
Upper valley characteristics
Upper valley characteristics
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hillslopes
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hillslopes
Terracettes formed by soil creep
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hillslopes
Narrow, shallow channel, low velocity and discharge
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hillslopes
Terracettes formed by soil creep
Narrow, shallow channel, low velocity and discharge
Large bedload derived from upstream and from valley sides
Interlocking spurs, Robinson, Lake District
A typical upper course valley with interlocking spurs, steep valley sides and active slope processes
River load in upper course
Load is dumped in summer due to the low discharge unable to carry the c________ and c__________ of load at higher flow levels
River load in upper course
Load is dumped in summer due to the low discharge unable to carry the capacity and competence of load at higher flow levels
River load in upper course
Load is dumped in summer due to the low discharge unable to carry the capacity and competence of load at higher flow levels
River load in upper course
Boulders are large and semi-rounded, due to attrition within the load and abrasion with the stream bed and banks
Load is dumped in summer due to the low discharge unable to carry the capacity and competence of load at higher flow levels
Middle course, R. Tees
Middle course, R. Tees
Valley opens out, more gentle slopes, wider valley bottom
First signs of meanders
Middle course, R. Tees
Valley opens out, more gentle slopes, wider valley bottom
First signs of meanders
Floodplain
Middle course, R. Tees
Valley opens out, more gentle slopes, wider valley bottom
First signs of meanders
Floodplain
River channel wider, deeper, greater velocity and discharge
Lower Severn Valley
Lower Severn Valley
Well developed meanders with bars in the channel indicating high sediment load
Very wide floodplain
Very gentle valley side gradients