Living in Christchurch, I was always vaguely aware of a park in the north-east of the city called “The Groynes”. It seemed an odd, and rather un-illustrious name for a park (given its homonymity with that particular part of the body), but I never took the time to find out what its origin was.
Had I had the curiosity to investigate, I would have found out that “The Groynes” derives its name from large blocks, made from concrete filled woolsacks, which were placed in the Otukaikino Creek in the 1930’s to separate it from the main branch of the Waimakariri River. (Though why this was done is still a mystery to me – the otherwise helpful Christchurch City website was silent on that point.)
Also somewhat mysterious, is the etymology of the term “groyne”. It’s first recorded use was in the 1580s, when it was used in the sense of “strong, low sea wall”, and was perhaps derived from the old French word for “pig’s snout” (groin) because the wall looked like one. This doesn’t seem all that convincing to me, but that is what the dictionary suggests.
Thankfully, where the story gets a little more convincing is how it all relates to environmental history. When Europeans first settled in the Manawatu (and other previously forest-covered districts), the rivers followed a relatively defined course. However, as milling and burning of forest progressed, the bush that had once densely covered the river banks was destroyed. Erosion of river banks ensued, and this led in turn to the land adjacent become increasingly eroded as the river ate into it. This was the case in the town of Palmerston North, which lost an estimated 30 hectares of land from the Hokowhitu/Fitzroy area alone between 1882 and 1907. (Though sometimes this had an up-side, see: Prehistoric revelations of a Manawatu flood)
Realising something would need to be done to keep erosion in check, the settlers and local bodies tried using groynes, the first appearing downstream from the Fitzherbert Bridge in 1882. But what exactly are groynes?
Groynes are structures built out from the riverbank (or seashore), which push water away from the bank edge. They can be made of rock, concrete, or fallen trees with the butt end anchored into the bank. Groynes help prevent erosion and trap silt, which in turn helps build up eroded areas.
Unfortunately, these early groyne efforts were not overly successful, and settlers and local bodies soon turned to other methods, such as planting willow and poplar boughs along the side of the bank. This appeared to work well, but eventually many of these trees became a flood hazard in themselves, owing to their propensity to break off and take root in dense huddles in unwanted places on the river. The irony of planting exotic trees along the banks that had only recently been denuded of indigenous vegetation did appear to go unnoticed, however.
Groynes are still used today in the Manawatu River and elsewhere. When you next spot some, perhaps you can decide for yourself whether you see any resemblance to a pig snout. I remain unconvinced.
Further reading: Roche, M. M. (2000). “Taming the land”. In B. G. R. Saunders (ed.) The South of the North: Manawatu and its neighbours.
Photo top: Modern-day groynes in the Manawatu River. Photo by Margaret Riordan (Kiwi Nomad’s Wanderings); Above right: the groynes at “The Groynes”, Christchurch. Photo by Christchurch City Council.