Whanganui has had a history of repeated flooding in low-lying areas, particularly in areas adjacent to the Whanganui River.
The inlet of the Whanganui River is subject to tidal influence with high silt content and has caused flooding and damage to the nearby properties and roads. Climate change modelling indicated that heavier and more frequent downpours had the potential to cause more localised or large-scale flooding in this part of the country, so a solution needed to be found.
One of the causes of flooding in Whanganui was river water flowing back through the stormwater outfall system. To prevent this backflow, WaStop Inline Check Valves were installed on the outlets of DN1350 and DN450 concrete pipes. The DN1350 pipe was a new line draining an industrial subdivision catchment, the existing DN450 line had a valve installed at the same time.
With the newly installed WaStop Valves in place, backflow into these pipelines had been eliminated. The stormwater system is better able to cope with periods of high rainfall coinciding with high river levels as there is now capacity for attenuation in the system.
This solution has provided peace of mind for Whanganui residents and property owners by protecting their properties from future flood damage.