Slope Stabilisation

We stabilise our slope to prevent our regeneration work slipping away.

Pom Pom Island has a steep slope from the reef crest to the deep water dropoff at a depth of around 50m. All this slope has been seriously blasted in the past by bomb fishermen. All that is left of the original reef are the rubble fragments on a seriously sloping reef. The structures we build are difficult to stabilise.

Step reef with spikes to hold it into place. It is easy to see how steep the rubble slope is.

Our coral growth techniques which work well on flat areas of seabed were modified to create step reefs aimed to create small reefs on the steep slopes. These look great initially but too many of them are unstable and deteriorate rapidly. While the corals grow and the fish live on the step reefs we create, unfortunately the slope continues to win and a beautiful series of steps fixed solidly to the seabed becomes a tumbled mess after turtles scratch and fish dig.

After much trial and error, we are gradually refining a coral rubble reef conservation system that seems to be stable. We are stabilising the rubble with soft coral nets, which slows the rubble movement and which the turtles do not destroy. We then plant soft corals and sponges on the nets to hold the rubble together.

We also build rubble cages at the top of the slope, which are wire baskets attached to the ground. We fill these with coral rubble and like the nets, plants sponges and corals over the basket to help hold the rubble to the sea floor.

Netting planted with soft corals and sponges to hold the rubble above the interlocking step reefs.