Saturday, November 22, 2008
We have been filming the seawall. This wall runs along the edge of the western side of the island - almost along its entire length. In the Google Earth image you can just make out the canoes anchored a few meters offshore. There is almost no current here - the water is very still (In this season the wind blows from the east sheltering this side. Soon the season will change, the wind will blow from the north west reversing the current past Nukutoa). In the photo the darkness in the water is seagrass, underwater this stuff looks a lot like long AstroTurf. If you look carefully at the image you will see blotches of coral further out. At this point the water becomes deep enough never to dry out at low tide.
The seawall was first built many years ago but needs constant attention and maintenance. The nets that hold the stones wear out and need to be replaced frequently. The wall was built because apparently when the north west winds came they would whip up the waves pushing the water into the houses on the foreshore during the high tide. Building a wall keeps the waves off the land but the sand of the beach gets pulled out into the lagoon by the reflected wave where it gets trapped in the seagrass.
Rubbish on the island is buried behind the seawall to build up the level of the backyards of the houses on the foreshore and further prevent incursions by the sea.
The result in the western shore of the island is that what once was a beach is now slippery rocks and what once was deep water off the beach is now shallow sandy water covered with seagrass with the occasional bit of rubbish washed from broken sections of seawall.
There is also a seawall along the north shore of the island. This wall doesn't look as bad possibly because new sand made on the reef is deposited here by the strong current. Sometimes, however, it seems that the current pulls sand off the shore faster than it can be deposited. This sand ends up in the seagrass and doesn't come back.
Scott and John have begun surveying the island and surrounding reef and are learning more daily about how erosion affects this island. Soon we should start building up a clearer picture of what is going on here.