Eroded beach face, Spirits Bay, Aupouri Peninsula, Northland
One of the most beautiful aspects of a sandy beach is the way its character always changes, constantly being rearranged with every tide depending on the weather and the state of the sea. As such, the character of a beach is a direct reflection of the nature of the waves, currents and tides that have shaped it, and looking at a beach one can therefore often get a feeling for whats happened there over the last few days.
When I took this photograph at Spirits Bay the moon had been close to full the previous night, meaning that the tides had been getting gradually higher as spring tides approached a couple of days away. This was clearly evident from the eroded nature of the beach too, where successively higher tides were slowly eroding away the sand that had been piled up by smaller tides earlier that same week. This kind of erosion causes a beach to be flattened out during spring tides, only to be gradually piled up again during the smaller neap tides that follow.
The same cycle can happen with changing weather and sea conditions: calm weather and low swells allow sand to be moved onshore to build up a steep beach face, while storms cause rapid and widespread beach erosion, shifting huge volumes of sand back offshore to flatten out the entire beach until the next calm spell sees the sand move onshore again. In some regions this cycle may be seasonal, relating to winter storminess and summer calm.
These natural cycles of replenishment and erosion have frequently been overlooked by overzealous coastal developers, who often view the dunes next to a beach as prime real estate rather than a natural store of sand that is occasionally reclaimed by the sea during storms to be replenished during calm spells.