Are the sand dunes just a big sand pit for anyone to play in? No, sand dunes are a dynamic and ever-changing ecosystem that has the prime function of protecting the hinterland from the sea. You may have seen dramatic pictures of buildings disappearing over a cliff or the garden wall into a raging sea during a big storm - an example of people not understanding our coast is a volatile place and that the dunes and foreshore can come and go. When the sea is whipped up by storms it has no special respect for man-made structures.
Out at Castlecliff we have a rather different situation with our dunes. The man-made moles on each side of the Whanganui River, protrude out into the sea and act rather like arms outstretched - they slow down the southerly flowing currents and sand is deposited on the shoreline. It is estimated the beach currently increases by about half a metre a year. That explains why "Seafront Rd" is now so far from the beach.
If you take the time to drive north up Karaka St, and park opposite number 164, you can walk out to the cliff edge on the Beacon Reserve, and look down at the triangle of sand that has built up since the moles were built in the 1880s.
This dune area is very "new" and thus fragile. When its vegetation cover is damaged the wind soon whips up the sand, creating huge blowouts and dunes of fresh sand that relentlessly creep across the landscape in an easterly direction, due to the prevailing westerly winds.
Unfortunately, despite signs banning them, motorbikes are frequently ridden through the fore-dunes, destroying areas of natural spinifex meadows and pingao and releasing the sand, which is then blown on to the carparks and into buildings. Removing vehicles and horses, and encouraging people to walk only on the agreed walkways as is done in other parts of New Zealand, would reduce the damage and the amount of windborne sand released.
