From the NMR:
River navigation originally from Canterbury to Richborough Port, there being 2 flash locks above Fordwich. Now navigable to Fordwich. 19 miles long, there are no locks on the navigable section. The earliest act to improve the navigation was 1514, with a second in 1825.

Between Upstreet and Sarre a canal provides a shortcut. This is shown on mapping of the late 18th century and 19th and 20th century OS mapping, where it is labelled as the Mile Cut. It appears to have fallen from use and been filled in the second half of the 20th century.

A dredged channel extended from Richborough Military Port out into Pegwell Bay. (1)

<1> Robert Holden, 2012, Supporting documentation of possible ancient Wreck high up in Sandwich Bay close to Ebbsfleet (Unpublished document). SKE17979.