5.2 Mangroves

To whom it may concern,

We are completing ENEG11007 at CQU. We have chosen to investigate Design Area 5.2, coastal erosion protection on Saibai Island, for our project. Considering the broad scope identified in the EWB Challenge Brief, we would like to ask if you could provide some more clarity about the specific scope of this design area.
We have taken into consideration the considerably slow growth of mangroves and would like some more details so that we can refine our project scope, schedule and risk assessment.

To refine these areas, is there further details you can provide around:

-Is the mangrove growth or erosion a seasonal issue?
-What local resources are already available on Saibai Island?

-What current community engagement strategies are available on the Island?

-Does the community need a permanent or temporary solution (for example, an artificial reef to wait for mangrove growth)?

-Are there any time restrictions to establish mangroves or stop erosion?

-What current controls or measures are currently in place or available?

-What is the extent or area of erosion/mangrove restoration?

-What’s at risk? Industry, housing, foreshore or other?

-Are we correct in assuming that it is preferable to produce a low-maintenance solution, that the community can monitor?

-What are the safety and risks of erosion/mangrove loss (environmental, personal, industry)?

-What industries are active on the island? It would be great to have some understanding of the context. What happens on the island, population, jobs, etc?

-Is the desired objective or result just erosion control, or does the community have other desired benefits in mind?

Thanks! Your clarification is appreciated,

Online Group 2.

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

Hello,

I am curious regarding to a previous response to an answer about the depth level and I am wondering if it is still the same and is the measurement mts or a typo.

Thank you for your response

Hi Jean,

Thank you for your responses thus far.

To assist in completing the assessment of our options we require a few specific pieces of information:

1. Is it possible to provide some specific space requirements for the project as we have approaches that are better suited to larger areas and approaches that are better suited to smaller scale projects.

2. Is there a culture, custom or practice of weaving from natural materials in the local community that could be utilized for the weaving of baskets and bags for coastal rehabilitation?

3. Is there capacity for initial harvesting of bamboo, poles for stakes, and leaves for weaving, and for the cultivation of bamboo for an ongoing supply for future projects and maintenance?

4. Is there capacity for coconut harvesting to be used in an environmental restoration project or are they harvested for commercial purposes?

5. Is there capacity for local labour to participate in the harvesting of bamboo, construction of bags and baskets from natural materials and the erection of support stakes or bamboo breakwater walls?

Thanks
Online Group 2

• This reply was modified 3 months ago by Bryan Wells.

Hello,

I am curious how long would it take to establish an artifical reef in Saibai Island and the distance it would cover to combat coastal erosion.

Thank you

• This reply was modified 2 months ago by Henry Han.