Whakatāne District Council has found boulders stopping the McAlister Street flood gates from opening were responsible for recent surface flooding in the area.

In a media statement, infrastructure general manager Bevan Gray said investigations into surface flooding of Peace Street, Apanui Avenue, McGarvey Road and Brabant Street on November 3 had involved specialist divers inspecting the McAlister Street pump station and the flood gates within Whakatāne River.

"We found two large boulders had been intentionally placed in front of these gates to stop them from opening and operating as usual. This meant the water that had built up within the town network couldn't get out to the river when the tides were low and exacerbated the flooding issue."

About 100mm of rain fell in a short period of time last Thursday.

Mr Gray said the McAlister Street pump station was built to manage a one in 10 year event and the intensity of rain had been greater than that.

He said the event had been the ultimate test of the recent stormwater enhancement works.

"The new stormwater system in the Peace Street neighbourhood is engineered to direct water to the lowest point on the road, away from properties.

"Despite the significant volume of water, the system has operated as intended with no report of damage to physical property, which previously may have occurred in such an event.

During periods of heavy rain, temporary road closures could be required.

“The system relies on the co-ordinated functioning of multiple components, and any failure in flood gates or pumps can impede its performance."

To reduce the risk of reoccurrence the council would conduct regular maintenance checks on all flood gates and pump stations, remove any obstructions promptly, and enhance monitoring systems to detect issues swiftly.

“However, in weather events with a greater return period than one in 10 years, we are likely to see surface flooding issues.”

LDR is local body journalism co-funded by RNZ and NZ On Air.