Piha, the Westcoast Beach community experienced two major floods this year; one on the 3rd of February which claimed the lives of two teenagers and another on the 28th of April. In response, members of the community and the Auckland Council are searching for ways to prevent further destruction in the event of future floods.
On the 29th of August, the Auckland Council released a report titled The Piha Community Resilience Project. The report recognises that Piha is “particularly at risk of natural hazards” and so the project aims to develop a “new Community Resilience Plan to increase community preparedness, which incorporates a plan for how first responders will work with this isolated community.”
A separate council report titled Piha Stream (Glenesk Road) Flooding Assesment focuses exclusively on Glenesk Road as it is especially vulnerable to floods. This road tracks the floor of Piha Valley and, from end to end, the Piha Stream runs alongside it. The floods on Glenesk Road are the result of the stream overflowing. The report analysed the extent of damage caused by the February and April floods and it also uses scientific models to forecast the frequency and magnitude of future floods. In addition, the report outlines possible solutions to mitigate damage in the future.
According to the Piha Stream Flooding Assessment report, the floods in February and April caused inundation of 24 properties and a “length of Glenesk Road from number 12 through to number 30 was inundated up to depths of 2 metres”. Additionally, the report shows that 12 rainfall events, which saw rainfall levels of 25mm or more within 90 minutes, have occurred over the last 11 years.
The forecasts in the report suggest that a one in 10-year flooding event could inundate all houses on the north side of the Piha stream as well as two campgrounds

The report raises possible solutions to mitigate future damage. The first suggestion mentioned is to engineer work “to divert or convey storm flows away from property and people at risk.” This option will require an operation that will widen the stream from the Seaview Road Bridge to 105 Glenesk Road. However, the operation will also require the “acquisition of approximately 13 residential land parcels” and there is a high likelihood that such an operation will not gain consent under RMA regulations.
Another possible solution is to raise all vulnerable buildings above the forecasted one in 100-year flood level.
Both suggestions will be relatively expensive and so, for the time being, they remain suggestions and the council “has no legal obligation to implement any of the options”.
Finally, the report discusses the promotion of new forecasting and communicative technologies. One caveat to this option is that it is not realistic to expect an alarm system to alert the public early enough to avoid all possible danger as the stream rises too quickly.
Local Park Ranger Geoff Calvert thinks that the Council is “doing the minimum necessary to avoid liability”. He says “they put up signs that say ‘Flooding Risk Area’, but really it’s common sense.”
However, Calvert is also unsure of any viable solutions to the problem. “Glenesk Road is in a Valley, so it was carved out by the stream, so naturally it’s going to flood and there’s not much you can do.”
It is true that the Piha Valley is prone to floods. A prominent theory amongst locals is that the congestion of the stream which leads to overflowing was largely man-made. In the early 20th century large shipments of soil and sand were placed around the stream as a foundation for development. According to this theory, the land moving in the area “has damaged the natural ability of the floodplain of the Piha valley to absorb and slow water during storm events.” If this is true, it may be too late and costly to restore the valley to its original state.
For Calvert, the most optimal solution, currently, is to promote a “general level of awareness” to the community and visitors. He believes that once people are used to the idea that the Piha Stream will flood from time to time, the community will respond in a more “measured and organised way.”
Sources
Geoff Calvert – Park Ranger
Smedley, R. (2018). Piha Stream (Glenesk Road) Flooding Assesment.


