Pulrose Bridge in Douglas is set to close for 12 months from March 2021.
It's whilst a £3.4m project is underway to replace the bridge - designed to reduce the risk of flooding and protect 'vital infrastructure connections'.
The current structure was built in 1931, the DOI says it's no longer practical nor economically justifiable to extend its life further.
As witnessed in 2015, the River Douglas is susceptible to flooding - the department says new reinforced concrete and steel beam structures will significantly reduce this risk.
The bridge will also feature cycle lanes on both sides, linking Peel Road with the Heritage Trail and Nunnery cycle routes.
Pedestrian access between Peel Road and Pulrose will be maintained, while traffic will be diverted.
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