River Dee Case Study
Long Profile:
Upper course:
Source is 460m above sea level – rainfall >3000mm
V shaped valley with steep upland slopes – runoff is high
Geology: Hard igneous rocks – resistant to erosion
Narrow/shallow channel full of angular stones – friction slows down the river
Vertical erosion
Middle course:
Wider and flatter valley (floodplains) – gradient decreases
Smaller and rounder sediments
Lateral erosion
Discharge and velocity increase as more tributaries join
Lower course:
Rainfall <750mm
Geology: softer rocks e.g. sandstone
Wide flat valley
Lateral erosion
Wide and deep channel
Velocity is greatest due to less friction
Increased discharge as more tributaries join
High sediment load – muddy water
Catchment
94% is rural (forestry and farming)
Important source of water for 3m people
Famous for commercial and recreational fishing
Supports large areas of habitats including rare species such as the otter and water vole
Changes to the river
Building of reservoirs
Growing demand in 1960s – reservoirs built to store water during winter
Llyn Brenig collects 800k cubic metres of water a day and can hole 60m cubic metres in total
Discharge downstream reduced – reduces flood risk
Building of flood defences
Long Profile:
Upper course:
Source is 460m above sea level – rainfall >3000mm
V shaped valley with steep upland slopes – runoff is high
Geology: Hard igneous rocks – resistant to erosion
Narrow/shallow channel full of angular stones – friction slows down the river
Vertical erosion
Middle course:
Wider and flatter valley (floodplains) – gradient decreases
Smaller and rounder sediments
Lateral erosion
Discharge and velocity increase as more tributaries join
Lower course:
Rainfall <750mm
Geology: softer rocks e.g. sandstone
Wide flat valley
Lateral erosion
Wide and deep channel
Velocity is greatest due to less friction
Increased discharge as more tributaries join
High sediment load – muddy water
Catchment
94% is rural (forestry and farming)
Important source of water for 3m people
Famous for commercial and recreational fishing
Supports large areas of habitats including rare species such as the otter and water vole
Changes to the river
Building of reservoirs
Growing demand in 1960s – reservoirs built to store water during winter
Llyn Brenig collects 800k cubic metres of water a day and can hole 60m cubic metres in total
Discharge downstream reduced – reduces flood risk
Building of flood defences
