After the August 2022 severe weather event Nelson City Council committed to building back better, increasing our infrastructure’s resilience to flooding and heavy rain.
Rainfall last week closely tracked August 2022 levels, but fortunately did not last as long. Despite that stroke of luck, many of the post-2022 improvements were put to the test last week.
Nelson Mayor Nick Smith says he is encouraged by how well the repaired infrastructure performed during the weather event last week.
“Last week’s rainfall was not as intense as the August 2022 event, but this was still a significant test for our infrastructure, and I’m pleased to say it came up trumps. This was a real-life endorsement of Council’s build back better strategy.”
During severe weather events there is always a risk that the Maitai River will flood. This event was no different with water flow in Maitai reaching 100 cubic metres per second (cumec), a 1-in-5-year flood event, compared to the 2022 levels of 500 cumecs.
In the 2022 weather event, the two footbridges at Waahi Taakaro Golf Course were washed away. In January 2024, Council opened a new bridge, recently named Te Arawhiti o Rangiriri and designed to withstand a flooding event, allowing the Maitai to flow underneath.
“The river acted as we expected, and the bridge met expectations. Even when the flow was at its highest we were fully confident that the bridge would not be affected. The rock armoring under the bridge also protected the river bank which contains important infrastructure,” says Group Manager Infrastructure Alec Louverdis.
Further down the Maitai is the newly installed Sunday Hole Boardwalk, which was completed in July 2024.
“A lot of the damage to infrastructure occurs when debris travelling down the Maitai River gets stuck and then causes more debris to pile up. The handrails on the boardwalk were designed to essentially break away when under pressure, allowing the river, and debris to continue to flow down the river. Photos show the boardwalk entirely underwater, but the boardwalk came out unscathed, including the handrails.”
Following the 2022 weather event, Council identified two high-priority stormwater intakes and fitted them with cameras and level sensors.
“The level sensors monitor the flow of water at the intake and will alert us if the level is rising due to a blockage,” says Alec.
“This allows us to monitor the intake remotely without needing the maintenance contractor to be physically present on site.
“We received multiple alarm notifications during the recent weather event and as a result the duty officer mobilised a team to clear the blockage and water continued to flow through the intake rather than flooding and damaging the streets.”
