When I was at intermediate school in 1992 we had a day off at the end of term due to a large low pressure system coughing up a heavy snow event. Aside from causing a complete province wide shut down, the tail end of the storm brought a massive southeasterly swell that battered the gently sloping sandy beaches of Pegasus Bay and cut away metres of slope. Over the coming months and maybe years, long shore drift moved the sediment back into place. But there was a lesson for any coastal management planner and physical geographer in this: protect your coastal communities or pay the price.
Decades later and having watched another battery of New Zealand beaches, this time caused by a sub tropical depression turning into a deep low that drove huge waves ashore along the eastern coast line of New Zealand, I cannot help but wonder if we have learnt anything?
If we look at the damage left behind and the grief that even 2 days after it began to move away, it caused those local communities, I would guess the answer to the question is: no. Despite the seas having been across the roads before, despite previous erosion problems, it seemed to escape peoples minds that these were not such big storms.
The coastal geographers have been warning New Zealanders for decades. Way back when I was in high school there was a section of the community in Christchurch who wanted to remove the sand dunes in Christchurch because they were affecting property prices. No one wanted to know about the potential for storm surge during large southerly storms or sub-tropical lows. Nor did they want to know about the tsunami risk posed by earthquakes both near field and far field. To them, these were things that happened elsewhere.
Few will forget the appalling video clips from Japan showing the sea sweeping all before it during the huge tsunami that followed the magnitude 9.0 11 March 2011 earthquake. Watching entire coastal communities succumb to the ferocious power unleashed by these waves is not an easy watch. And now there is no doubt among coastal communities that we have to be prepared for tsunami. But what about the storm surge from weather events that pass through every few years or so? Especially when they virtually demolish coastal roads and flood whole communities?
Christchurch seems to have headed the warnings to leave natural coastal protection alone. Whilst plans for revitalizing New Brighton continue talking about the residents, and making it a more attractive area for tourists, few now seem to have the appetite that existed in the late 1990’s for removing the dunes.
But with potential climate change and change in local marine topography over time, the behaviour of the sea will change. The tide that used to stop two metres down the beach might now be lapping the upper edge of the beach. Wave energy on the coast helps to determine the type of beach one gets – will it be gently sloping like New Brighton with its dunes or a high energy environment where no one can safely swim, such as Birdlings Flat? Are you right at sea level on the coast, or do you have a couple of metres altitude to protect you from coastal flooding?
One might have ignored those questions in the past, but can you ignore them in the future?