The Bulbourne flows in the Chiltern Hills, part of a system of chalk downlands throughout eastern and southern England, which formed between 84 and 100 million years ago in the Cretaceous Period when the area was a chalk-depositing marine environment.

[5] The valley is at the southernmost limit of the Pleistocene glaciation ice erosion of the Chiltern scarp, giving it a smooth, rounded appearance.

It also fed the three moats of the large Norman (Motte and Bailey) Berkhamsted Castle, that stands close to the centre of the town.

The river created a marsh environment (at times referred to as an 'unhealthy swamp') in the centre of the valley, which added to the defences of the castle.

Ensuring a constant supply of water in a region of permeable chalk was an engineering challenge which required the building of reservoirs, pumps and boreholes.

After the Pre-Roman Road and the canal, the next major transport route to carve its way along the Bulbourne valley was Sparrows Herne Turnpike founded in 1762, followed by the London to Birmingham railway, in 1834.

In 1883, the Berkhamsted Times congratulated a Mr Bedford on having converted the remaining "dirty ditches and offensive marshes" into watercress beds.

[18] Thus the River Bulbourne was reduced by centuries of increased drinking needs, dredging, milling and agriculture, as well as by the London to Birmingham Canal.

[20] Another small tributary was 60 feet (20 yd) at St Johns Well Lane (in Berkhamsted); it dried up in the 1930s due to increased local water-pumping needs.