The Eastern branch rises on Ditchling Common, and flows through Haywards Heath and Burgess Hill.

Below the junction, the combined stream flows for 10.8 miles (17.4 km) to reach the English Channel at the port of Shoreham-by-Sea.

2. c. cxvii),[2] the river was improved, to aid both navigation and drainage, and barges could reach Bines Bridge on the Western Adur.

[1] In 1824, the civil engineer May Upton produced a plan for extending the navigation northwards to West Grinstead, at a cost of just under £6,000.

Seven men were named as proprietors, including Lord Selsey and Sir Charles Merrick Burrell, and they were empowered to raise £6,000 by issuing shares, and an additional £3,000 by mortgages if required.