DL: The River Wye Flashcards
Describe the course of the River Wye
- (Source) Plynlimon, Rhayader, Builth Wells, Hay-on-Wye, Hereford, Ross-on-Wye, Symonds Yat, Monmouth, Tintern, Chepstow (mouth)
Where is the source of the River Wye?
- Plynlimon - Plynlimon Hills in Cambrian Mountains
- 690m above sea level
Describe the geology at the source (Plynlimon)
- Gritstone, mudstone and shales - sedimentary rock which is easy for the river to erode vertically
- Thin soils
- Impermeable surfaces leads to more surface runoff
Describe the climate at the source (Plynlimon)
- 2650mm rainfall a year
- Heavy rainfall due to relief rainfall = surface runoff
- Cold temps due to altitude = freeze thaw weathering
How does the climate and geology work together at the source?
- More rain means more erosion creating V-shaped valleys
- Mass movement on the valley sides contributes material to the river
- More sediment in the river means more abrasion
Describe what happens at Rhayader
- 219m above sea level
- Rapids form here due to alternation bands of less and more resistant rock
Describe what happens at Bulith Wells
- 130m above sea level
- Valley begins to widen as the Wye begin to migrate across the floodplain and form meanders
- Lateral erosion is more important
Describe what happens at Hay-on-Wye
- 97m above sea level
- River enters its middle course, meanders move across a wider floodplain and creates an ox-bow lake as they migrate
Describe the geology at the middle course (Hay-on-Wye)
- Sandstone, more easily eroded allowing the river to erode laterally (side by side)
- Horse-shoe bend is an oxbow lake
Describe what happens at Hereford
- Biggest settlement on the River Wye
- Downstream of Hereford the floodplain starts getting wider as the valley floor is flatter
- The river Lugg joins the Wye as a tributary, bringing more discharge
Describe what happens at Ross-on-Wye
- As the floodplain as developed at Ross-on-Wye, levees have formed. Over time the levees become vegetated
Describe what happens at Symonds Yat
- The meanders of the Wye are deeply incised forming a gorge as the river is unable to erode more resistant outcrops of limestone
- Important tourist feature
At Chepstow the Wye and Severn have their confluence. At this point both the Severn and Wye are tidal and suspended sediment can be seen in the rivers.
- In the past, humans have altered the Wye’s course and drainage basin in ways that have exaggerated flooding
- Deforestation, poor soil management and building on the floodplain have changed the landscape through which the Wye flows
- People have responded in the past using hard defences to prevent floodwater from reaching properties
Natural flood management
- Increasing infiltration Into the soils - better soil management techniques
- Slowing the flow of water - creating features which obstruct flow across the river channel or floodplain
- Storing water upstream - water can be stored within the upstream catchment and released slowly
Trackery improvement
In channel water retention
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Infield water retention
- Allows strips of land upstream along the river to flood, resorting the natural flood plain
- Allow surface flow to collect and soak away
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Afforestation
- New trees are planted or seeds are sown in an area where there were no trees, creating a new forest
- More infiltration
Soil improvment
- Aerate soils to increase infiltration rates
Overwinter cover
