They want to replace it with a 16km one between Southend-on-Sea and Sheerness.

(blue marker is where the Thames Barrier currently is)

Released in 2005, a study by four academics contained a proposal to supersede the Thames Barrier with a more ambitious 16 km (10 mi) long barrier across the Thames Estuary from Sheerness in Kent to Southend-on-Sea in Essex.[26]

In November 2011, a new Thames Barrier, further downstream at Lower Hope between East Tilbury in Essex and Cliffe in Kent, was proposed as part of the Thames Hub integrated infrastructure vision. The barrier would incorporate turbines to generate renewable energy and include road and rail tunnels, providing connections from Essex to a major new Thames Estuary Airport on the Isle of Grain.[27]