River Quaggy (C.S)

River Quaggy (C.S)

1. Background

   • Small river in London, UK
   • 17km long
   • Source: Locksbottom, Farnborough
   • Lower area it becomes an urban river
     • Flows in-between houses
   • Upstream it is more natural and not urbanised
   • One of the Thames smaller tributries
   • The mouth of the river meets at River Ravensbourne
   • Part of the Ravensbourne catchment area

2. Regime of River Quaggy

   • Changes in the discharge over a period of time at a particular point
   • V responsive regime
     • When it heavily rains the discharge in the river quickly increases
   • No significant artificial influences
     • No dams etc
   • 1995: significantly high flow all year round
   • 2005: lower annual discharge, peak flow in Nov
   • Average daily flow has fallen since 1995

3. Flood Event

   • Worst event was Christmas Eve 2014
   • Was London's worst winter flood event
   • Quaggy burst its banks , inundating 22 homes
     • Another 20 homes had flooded gardens
     • Allotments and sports ground flooded
   • A month's worth of rain in 24hrs
     • 50mm in 25hrs
   • High winds blew branches and trees into the river causing to block the trash gate ∴ it bursts its banks

4. Flood control (Mitigation)

   • Attempts in the past to mitigate flood events
   • Between 2003+2006, Environmental Agency (EA) installed trash gate as part of £11.8 Mil flood mitigation scheme to stop debris collecting @ culvert's entrance
   • EA built two small reservoirs to collect flood water + protect homes

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