The River East Stour is one of the tributaries of the Great Stour in Kent. The East Stour, 10.3 miles (16.5 km) long ) rises on the Greensand ridge at Postling north of Hythe as a number of small streams. It then flows under the M20 motorway to continue in a westward direction: the river meanders across the Low Weald plain, passing Mersham on the way.