A multi-million pound Belfast underpass submerged under six metres of water only a month after opening remains vulnerable to further flooding episodes, an inquiry team found today.
Motorists were forced to abandon their vehicles in the M1 underpass on the outskirts of Belfast when a nearby river overflowed and swamped the newly completed section of the £104 million (€124 million) city bypass upgrade.
An independent team of experts commissioned to investigate the incident in August at Broadway has warned it could be repeated if changes to the flood defence system are not made.
Amey Consulting said though the scale of the downpour that fell on the city had not been experienced since 1914, the underpass should have coped. The culvert diverting the Clowney Water around the motorway was designed to withstand a one-in-100 years scale of flood.
The August storm was not as severe as that and rated at a level between a one-in-50 year and one-in-70 year flood.
The consultants have recommended that a £40,000 research project is now undertaken to establish what changes can be made to the drainage system.
"There remains a potential for further flooding of the underpass until the hydraulic efficiency of the system has been checked and any required changes and other mitigation measure are in place," the report concluded.
As well as the modelling exercise to examine the drainage system, the consultants have recommended the raising of the banks, the introduction of a more robust early warning system with more liaison with the Met office and more regular inspections of the culverts.
The banks have already been raised to the 500mm level and a new monitoring process has been introduced.
PA