River Misbourne

The River Misbourne is a chalk river that begins in a field on the edge of Great Missenden in Buckinghamshire. It winds through several villages including Little Missenden, Old Amersham and Chalfont St Giles before passing under the Chiltern railway line and the M25 motorway. The river descends about ninety-four metres over its seventeen-kilometre length as it flows towards its meeting with the River Colne. Its name first appears in records from the early 15th century as Misseburne, with the second part coming from the Old English word for stream. Scholars have suggested the first part may refer to water plants like water arum or to an old personal name, though the exact origin remains uncertain. The river’s history includes the 1906 Chalfont Viaduct built by the Great Western Railway to carry trains between London and High Wycombe. In the mid-1980s the Misbourne was rerouted through concrete culverts beneath the new M25, and the motorway was later aligned to run through the viaduct’s arches. The river’s flow depends on rainfall because it sits above porous chalk that drains water away when levels are low. During dry spells the upper reaches have dried completely, most recently for over three years from late 2003 until early 2007. Visitors walking the valley can follow paths that cross the river at several points between Great Missenden and Chalfont St Peter. The chalk stream supports wildlife typical of clear-water habitats, and the surrounding villages retain old bridges and mill sites linked to the river’s past use. The Chalfont Viaduct remains a prominent landmark where trains still cross above the valley. The river’s intermittent flow and the engineering works along its course tell a story of how water has shaped both landscape and settlement over time.