Hi All,
Thanks for your previous response. We have considered the sources and information provided from this response and have aligned it with our research. Upon doing this, we have pulled together some ideas to consider for Design Area 5.2, Coastal Erosion Protection on Saibai Island, and were wondering if we could receive some feedback on the feasibility of our ideas. Specifically, we are wondering if any of these have been trialled before? Whether a combination of these ideas might contribute to a solution? And what materials, machinery, or manpower is available on the island to support these projects?
Project 1- Tetra Pots: A large, heavy, tetrapod-shaped biodegradable pot to plant the mangroves within to allow them to establish as the pot degrades. This solution utilises local materials in the construction of the pots by using a coral aggregate concrete mix including organic materials. Issues around this solution are the pots being so heavy, weighing approximately 1t, and from our research Saibai seems to only have the 1 tractor on the island to be utilised. Another disadvantage is that it requires a slower, more expensive process to construct, pour and allow the pot to cure before use, with limited moulds available and a large working area is required.
Project 2 – Temporary Sea wall: Throughout the planting process, spoil earth materials from construction around the island could be utilised to construct a small sea wall around high current areas allowing mangroves to establish. The main issues identified for this solution are the area required for protection, the limited material available, and the high risk to the environment and cultural heritage sites.
Project 3 – Coconut husk Wave Breaker: A floating coconut curtain or net which reduces the impact and power of current and waves. This product hangs down the required depth to reduce the waves and current enough to maintain the integrity of the mangrove seedlings. The issues presented with this solution include the size of the protected area required, the wave breaker being of insufficient length, and the integrity of the wave breaker after exposure to weather and strong currents effecting longevity.
Project 4- Planting bag with natural fibre: Planting mangrove seedlings within a natural fibre bag to stabilise the soil while the plants establish. This solution may need to be used in low current areas or in conjunction with another project to ensure effectiveness. This can be made to out of a range of materials, including palm leaves, and can be made to a range of different sizes to suit species and application of mangroves. The area and amount of mangrove restoration required presents an issue given that several holes need to be excavated, as well as back fill for planting with minimal access to machinery. Another challenge is meeting the mass production needs of the fibre bags with limited resources and manpower on the Island.
Project 5 – Stakes: By placing extended stakes several metres into the soil it assures that the mangrove seedlings are supported, and the plants cannot be washed away by the rapid currents. These stakes may be timber, steel, or any material available, and can be recycled for multiple seedlings. The number of stakes required to restore the mangroves, as well as the availability of manpower or machinery to drive the stakes into the ground as well as remove them once mangroves are established, present some surmountable challenges.
Project 6 – Implementation of a mangrove Nursery: Growing mangroves on site within a protected area until they are established enough that they can be planted on the coast and exposed to these intense natural elements. Utilising an onsite nursery to develop the mangroves provides an economic boost for the island. However, the area required for the nursery, transportation, maintenance, and planting present some challenges.
Project 7 – Bamboo/timber Break wall: Constructing a break wall out of bamboo or timber piles, driven into the soil surrounding the desired planting area, to reduce the impacts of the rapid currents and waves. The issues associated with this solution are the area required for protection, the number of posts required, as well as limited machines and manpower to drive and remove the posts.
Any feedback or suggestions are appreciated,
Thanks, Online Group 2
Andrew McGlashan