590km^2, including Betws-y-Coed and Llanwrst. 40,000 live in the catchment and 3200 properties are at risk
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Physical causes: tributaries
3 tributaries merge at Betws-y-Coed, before passing through a narrow valley, made worse by tidal locking
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Gradient
Steep upper catchment in Snowdonia National Park, with mountains up to 600m. 1700mm catchment average, 3000m at highest due to orographic uplift
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Geology
Meigneint Moors - impermeable volcanic rocks, steep valley sides + peat plateaus with waterlogged soils
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Human causes: agriculture
Drainage for intensive agriculture
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When?
31st Jan 2004
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What happened?
417mm in the upper catchment in 6 days
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Properties
86 properties flooded
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Services
2 hospitals, 12 schools and 59 gas/electric substations flooded
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Economic
£5 million damage to railway line, £6.6 million total
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Roads
15 tonnes of landslide material blocked the A4086 near Capel Curig
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Event: National Trust
In the upper course, the National Trust Ysbyty Estate is restoring 20,000 acres of blanket bogs, blocking 350km of drainage ditches, and replanting wet woodlands. Gwydir Forest now covers 72.5km^2
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Lake
Lyn Conwy is the biggest lake on Meigneint Moors and has a sluice gate to increase storage
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Llanwrst
£7 million on defences in 2010. The artificial flood culvert, 720m long, 1.8m wide cost £2 million
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Dutch dams
cost £750,000
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Vulnerability: Monitoring
River monitoring from gauging stations - feeds into EA response centre who update the website every 15 mins
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Other cards in this set
Card 2
Front
Physical causes: tributaries
Back
3 tributaries merge at Betws-y-Coed, before passing through a narrow valley, made worse by tidal locking
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