The River Severn And It's Estuary- Case Study Flashcards
Where is the River Severn located?
South West UK, Wales.
Where is its mouth/estuary?
The Bristol Channel
What is the River Severn’s tidal range?
15 metres
How wide is its estuary?
3.2km wide
Describe the Severn’s tidal bore
- Travels as far as Gloucester on high spring tides
- Large bores occur 25 days a year
- Travel 8-21 km per hour
- Get faster upstream
- Cause damage to the river banks and vegetation
What are the characteristics of an estuary?
- High tidal range
- Very wide
- Mudflats that are visible at low tide
- Salt marshes
- Tidal bores (huge waves which funnel up the river)
How is an estuary formed?
1) A large river, such as the River Severn, entered the sea at a narrow mouth.
2) After the Ice Age, melting ice caused a rise in sea levels. Low lying valley sides became flooded.
3) The original channel of the ricer is now on the estuary floor where it provides a deep channel for shipping
What direction is the river flowing in?
From East to West.
What are important points to notice (3)?
- The salinity (saltiness) increases towards the sea
- There are two sources of sediment (river and sea)
- The estuary is tidal so fluvial and marine processes operate.
Where do estuary mudflats form?
In sheltered areas where tidal water flows slowly.
How are estuary mudflats formed?
1) As a river transports alluvium down to the sea, an incoming tide transports sand and marine silt up the estuary.
2) Just downstream of the tidal limit, fresh water mixes with salt water. Here, velocity is reduced which causes deposition.
3) Deposition causes build up of mud layers called mud flats. These are covered at high tide but exposed at low tide.
What might happen to mudflats after a while?
They may become colonised by salt marsh vegetation such as cordgrass.
