Relative Sea-Level (RSL) change since the mid-1st century AD places limits on the locations of Roman ports on the River Exe. Supplies from Northern Gaul, destined for the Neronian legionary fortress at Exeter and its dependent civilian sites, may be demonstrated to have been unloaded downriver from the fortress at Exeter. Utilising a combination of available historical and archaeological data, glacial isostatic adjustment and estimated RSL over the past 2000 years, confirms that Roman sea-transports or river barges could not have reached the Exeter fortress on the tide. Furthermore, on the basis of the estimated tidal reach and depth of the River Exe in the mid-1st century AD, limitations may be placed on the location of both sea-port and barge-quay facilities, thus allowing the areas of search for these installations to be narrowed.