Environment Southland and KiwiRail have held “high level discussions’’ about raising the height of the railway bridge crossing the Mataura River at Gore, as the bridge has been identified as being at risk during a large flood.

However, KiwiRail says the bridge meets its current operating standards, and raising the height of the bridge would be a major project.

During the February 2020 floods, the swollen Mataura River lapped the bottom of the bridge.

An email released under the Official Information Act, written by an Environment Southland staff member [whose name was withheld by the council] dated May 19, 2020, says ‘’work has been done to increase the efficiency of the river channel and now the road and rail bridges represent the main constraint to flow in the channel.’’

READ MORE: * Environment Southland independent planners supports consent be granted for proposed Gore bridge * Coronavirus: Regional council applies for $18m for stopbank funding * $19.7 million worth of insurance claims paid out for Southland floods * New Pyramid Bridge stood up to Southland floods

“It is understood that the flow capacity under the rail bridge is around 2400 сumecs (roughly equivalent to a one in 70 year storm). At greater flows it is expected that the water would be above the level of the bottom flange of the spans. The rail level and the top of the stop banks are at approximately the same height, so the girders supporting the rail would be at risk during elevated river levels,’’ the email says.

The regional council’s climate resilience (shovel-ready) projects involve upgrading and raising the stop banks that protect Gore from Mataura River flooding.

Environment Southland catchment operations manager Ramon Strong said the rail bridge had been identified for some time as a concern for flood flow in an extreme flood event, particularly the potential for flood flow in the river to be partly obstructed by the bridge, exacerbated by a build-up in debris against the bridge.

Staff have discussed the matter with KiwiRail on several occasions, and understand the complexities with raising the bridge, he said.

“As part of our planning to improve the flood protection system, we are taking into consideration the impact that the rail bridge has on flood levels immediately upstream of the bridge,’’ Strong said.

KiwiRail general manager South Island operations Mark Heissenbuttel said KiwiRail and Environment Southland staff have held high level discussions about the bridge but no feasibility report or cost estimates to raise the bridge have been undertaken.

“At this stage no major works are planned for the bridge in the short or long term as the bridge meets our operating standards,’’ he said.

“Raising the height of the rail bridge over Mataura River would be a major project with the potential to require significant changes to the current road layout in Gore where existing roads intersect with the rail line.

“If the bridge was to be raised, the rail track would also need to be raised along the approaches to the bridge and the existing level crossings on Ontario Rd and River St would need to be moved to accommodate this raised track. Four other level crossings would also potentially need to be changed.’’