Up to 300 HGVs could be temporarily “stacked” at the former ferry port as they wait to take goods to Northern Ireland, under a plan drawn up by ministers to mitigate any disruption.
Authorities fear that new border checks introduced following a no-deal Brexit will slow down traffic through the nearby port of Cairnryan, leading to long queues.
The number of lorries using the Scottish port may also increase dramatically as the Holyhead to Dublin crossing becomes less attractive due to the extra checks needed to enter the EU.
The plan is among a range of measures being put in place by the Scottish Government to prepare for the possibility of the UK leaving the EU without a deal at the end of the month.
Ministers are also setting up a £7 million “rapid poverty mitigation fund” to help the nation's poorest communities cope with any financial shocks caused by Brexit.
Administered by local councils, the money could be used to help people pay their rent, cover their fuel bills or buy food, with some prices expected to rise after the UK's exit.
Pharmaceutical companies have also been asked to stockpile an additional six weeks' supply of medicines to cope with any shortages, with a dedicated group set up to monitor the situation daily.
The Scottish NHS is also maintaining higher than usual stocks of medical devices and other supplies in case of difficulties obtaining replacements.
In a statement at the Scottish Parliament, Deputy First Minister John Swinney said the scenario could "generate a significant economic shock which could tip the Scottish economy into recession".
Warning the effects on people's living standards could be severe, he said a rise in prices of only 5 per cent would be enough to "push an additional 130,000 people into poverty".
He told MSPs: "There is no amount of preparations that could ever make us ready, in any real sense, for the needless and significant impact of a no-deal outcome."
Conservative MSP Donald Cameron stressed his party was "committed to leaving the EU with a deal as the best way avoid a no-deal exit".
He said: "We continue to believe that securing a deal is best for protecting our economy and that is where our efforts should be concentrated."
Labour's Alex Rowley warned of the "severe and unnecessary harm" a no-deal Brexit would bring, and insisted it would be the Tories who would be responsible for "such grim consequences".