River Misbourne

The River Misbourne rises in a field on the outskirts of Great Missenden in Buckinghamshire, passing through Little Missenden, Old Amersham, Chalfont St Giles, Chalfont St Peter and under the Chiltern railway line and the M25 motorway to its confluence with the River Colne just north of where the Colne is crossed by the A40 Western Avenue.

River Misbourne
River Misbourne near Chalfont St Giles
Location
CountryEngland
Physical characteristics
Source 
 ⁃ locationnr Great Missenden
Mouth 
 ⁃ location
River Colne near Denham
Basin features
River systemThames

History
River Misbourne was diverted via culverts under M25 motorway. This is the downstream portal of the culvert. The railway viaduct is visible over the trees in the background.

In 1906 the Great Western Railway (GWR) constructed the Chalfont Viaduct to carry trains between London and High Wycombe across the river. In the mid-1980s, when the M25 was being constructed, the Misbourne was diverted under the motorway via underground concrete culverts. The route of the motorway was then aligned to pass through the arches of the Chalfont Viaduct.[1][2]

Flow

The river is a 'perch' stream, flowing over a bed of impermeable material on top of a porous substrate. This state is only quasi-stable since in periods of low rainfall the water table drops below the level of the impermeable layer. If groundworks are then carried out which damage this layer, the river can sink into the porous substrate and disappear.

The Misbourne has had intermittently reduced or stopped-flow due to abstraction for domestic supply from the aquifers feeding it. This has caused its course to be neglected to lead to partial obstruction. When the water company undertook remedial measures to restore the flow, there were episodes of flooding in both Chalfont St Peter and Chalfont St Giles. Subsequent work has restored the integrity of the course. The upper part of the river was dry for over 3 years starting in November 2003 but re-appeared in February 2007 following several months of above-average rainfall which raised the water table.[3]

References
  1. Kelly, Alison (2009). "Chalfont Viaduct Buckinghamshire - Historic Building Recording" (PDF). Oxford Archaeology. Archived (PDF) from the original on 20 September 2018. Retrieved 20 September 2018.CS1 maint: ref=harv (link)
  2. Hamilton, Ray (2015). M25: A Circular Tour of the London Orbital. Summersdale Publishers Limited. ISBN 9781783726561. Retrieved 20 September 2018.
  3. Misbourne starts flowing again (Bucks Free Press article)

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