Rubble stabilisation

Coral growing over 3D frames in Indonesia

Coral growing over 3D frames in Indonesia, photo: Jordan Hollarsmith, UC

The RRAP Rubble Stabilisation R&D Subprogram is investigating methods to stabilise damaged reef surfaces where dead or degraded corals have become loose and unconsolidated rubble, preventing or slowing reef recovery.

Natural and man-made disturbances (for example, cyclones, ship groundings, crown-of-thorns starfish outbreaks or coral bleaching) can reduce functional and diverse coral reefs to fields of rubble, with an unstable and mobile surface. The lack of stability and frequent motion inhibits recruitment (settlement and regrowth) of young corals back onto reefs and hampers recovery.

Rubble stabilisation, as a reef restoration technique, is in its infancy. 

It is also important to be able to identify coral reefs that can most benefit from restoration strategies: those most vulnerable to rubble formation, and those where prevailing wave regimes can make mobile rubble persist and hinder recovery.

The Rubble Stabilisation Subprogram aims to:

  1. Estimate the current and future scale of rubble generation on the Great Barrier Reef to determine the extent of the problem and future threat
  2. Create Reef-wide risk assessment maps to highlight areas most vulnerable to rubble generation, and areas where rubble is likely to become a persistent constraint on reef recovery, for use in planned management activities after disturbances
  3. Deliver a range of guidance tools to help prioritise the range of possible rubble stabilisation interventions
  4. Demonstrate the efficacy of an existing rubble stabilisation method and conduct experimental trials of biogeochemical bonding methods that can be more environmentally friendly and have a greater opportunity to deploy at larger scales.

Coral rubble, photo: Peter Mumby.

Scope and expected outcomes

The initial four-year program has the following objectives:

A. Understand where rubble is going to be a problem on the Great Barrier Reef.

Of interest is identifying reefs where rubble is most likely to be generated through cyclone disturbance, crown-of-thorns starfish outbreaks and/or bleaching events, each of which can generate different rubble volumes and characteristics. In addition, we will identify where the hydrodynamic conditions can maintain or continue to mobilise rubble, preventing stabilisation and thus coral settlement and recovery.

B. Test the efficacy of existing approaches to rubble stabilisation and explore new biogeochemical-binding methods.

Evidence will be drawn from existing reef restoration activities to assess the effectiveness of rubble stabilisation on ecosystem recovery. While some of this information will be available from other trials, we will run an evaluation of the efficacy of at least one existing methodology under a range of physical conditions. We will also begin innovative research to explore the potential of biogeochemical binding methods as a future prospect for rubble stabilisation at larger scales than currently economically feasible.

C. Create a rubble intervention tool.

Drawing on the above outcomes, a dedicated package of rubble stabilisation guidance tools will be produced (such as manuals, maps, and standing operating protocols) to assist reef managers to prioritise assessment of rubble stabilisation interventions and allow users to decide where stabilisation activities are likely to be both useful and feasible.

The data and outcomes of this subprogram will also be utilised by the RRAP Modelling and Decision-Support Subprograms to be integrated alongside a broader suite of ecological dynamics and alternative restoration strategies.

Subprogram leaders:

Subprogram team members:

Partners

Supported by the Queensland State Government Small Business Innovation Research Program.