Step 5: Produce detailed design

Once the mix of management interventions that address the objectives have been identified it is necessary to develop, document and cost a detailed design plan. Designs are needed for all management interventions, not just engineered solutions. Maintenance, monitoring and engagement activities for the life of the project also need to be designed. Legal and safety requirements as well as timelines for approvals need to be considered. The detailed design needs to be guided by suitably qualified experts (e.g. a fluvial geomorphologist can design the work but it may need to be signed off by a registered engineer), and include local knowledge and input. Once finalised, a review of the design plan (including ground-truthing), will assist with determining the feasibility of the proposed management interventions (i.e. can it be implemented at the intended locations, at the appropriate scale, in the sequence necessary and within the available budget?).

Designing for a mix of interventions

Depending on the mix of management interventions selected to achieve the objective, the design may need to incorporate more than one site and/or more than one intervention.

In simple cases there may be a single site requiring rehabilitation and a clear intervention. Often rehabilitation designs are restricted to a single landholder’s property or a reach that is a few kilometres in length.

In complex cases, multiple sites may need to be rehabilitated to produce the desired outcomes. In these situations, the design must consider all the sites and the range of interventions required. Examples include:

• rehabilitation of incision in a river: may require multiple grade control structures to address the change in slope after incision.
• reducing water temperature: may require applied research followed by active revegetation of several sites.
• erosion of coastal areas: may require research and monitoring to understand source of sand supply and community engagement and education.
• weed management: in addition to active weed management, community education, participation and awareness may be required.

Approvals and legal obligations

Ensure that the actions do not cause environmental harm or break the law. Federal, State and local legislation and policy and planning need to be considered in any rehabilitation and management. These approvals can be lengthy and expensive and need to be factored in early in the design process. They may include approvals for planning, species permits, earth works, sediment and erosion control. Relevant occupational health and safety policies and requirements need to be observed.

Staging of interventions

Staging of management interventions needs to be considered in the detailed design for both simple and complex rehabilitation projects. For example, if active revegetation is the intervention option selected, a stock exclusion fence may need to be constructed before vegetation is planted.

Designing for soil requirements, ground cover and earthworks

• Consider safety issues including the slope of any earthworks.
• Identify potential contaminated land and / or acid sulfate soils. Acid sulfate soils are safe and harmless when undisturbed. If acid sulfate soils are dug up or drained they come into contact with oxygen. The pyrite in the soil reacts with the oxygen and oxidises. This process turns pyrite into sulfuric acid, which can cause damage to the environment and to buildings, roads and other structures. The acid also attacks soil minerals, releasing metals like aluminium and iron. Rainfall can then wash the acid and metals from the disturbed soil into the surrounding environment.
• Plan timing of works in accordance with seasonal conditions. For example, undertake earthworks in the dry season to mitigate risk from storm damage and flooding, which would then line up with planting in autumn, ready for rain.
• Consider spoil and soil balances for cutting and filling. Where is the soil going to or coming from?
• In Great Barrier Reef catchments make use of the Reef Trust Gully and Streambank Toolbox for investigating and/or targeting intervention sites and possible interventions for reducing sediment yields and associated nutrients into the Great Barrier Reef.

Designing for plant selection and placement

• Plan the layout of plants. Planting in rows may be efficient where large areas are being planted. Although some trees may be lost in the longer-term, the closer the trees are planted, the quicker they will grow and provide shade, which may be important for some sites.
• Plan for the range of plants to be used, the number of each required, the source of the plants and how they will be watered.
• After determining what local plants that should be used it makes sense to develop a table including preferred hydrology, soil type and bank position, wind, drought and temperature tolerances and more.
• Click on thumbnail for example plant list.
• The plant list is an important step and will guide which plants are purchased and where the plants are placed.
• When selecting species for revegetation, select a diverse range of vegetation forms suitable for planting in the different zones of the system e.g. sedges etc. in lower areas, trees in upper areas. Find out more in the Plant selection for WSUD: WSUD design guidelines for Mackay, Wetland plants of the Townsville—Burdekin floodplain, Wetland Plants of the Wet Tropics and the Rehabilitation Guidelines for the Great Barrier Reef catchment
• Don't forget the importance of some form of ground cover, such as mulch. It will protect the soil and once well-watered-in, reduce the amount of maintenance required.
• Plan for the timing and sequence of planting including ensuring that any plant removal required does not result in further damage to the ecosystem (e.g. removal of woody weeds which are stabilising a stream bank may need to be slowly removed and replaced with native vegetation).
• Some birds and animals may dig around and uproot new plants, so netting or interlocking plant grids may be required to protect young plants. The placement of logs, branches and rocks will also help deter some fauna.
• Consider how weeds will be managed in the establishment phase and in the longer-term including the use of mulch, shading, and herbicides.

Designing for fauna

• It is important to consider what species of fauna inhabit the area and which species are to be attracted. Consider how those species would normally use the area. Some birds need long clear areas to feel safe and be able to land and take off, others need thick cover. Be aware that not all species habitat needs are compatible. If the rehabilitation goal is to protect a rare, native bird, having large open areas with little understorey may not be suitable. If the site is large enough it may be possible to provide for multiple species.
• It may be necessary to provide additional habitat for wildlife e.g. nest boxes, hollow logs, wood, dead trees and snags within the ecosystem to provide cover for fish and encourage breeding. Do the species need an island for breeding and protection from predators? Which plants will attract the right species and create the right habitat?
• If removing weeds, plan around the breeding cycles of the species that already live there.
• Consider undertaking the work in stages to ensure areas for resident fauna are available to retreat to while the new plants have a chance to establish and provide cover.
• Ensure that any works occur that do not interfere with critical breeding, feeding, roosting or movement/migration times.
• Spend some time during both the day and night observing how wildlife use the area, particularly if there are plans to change the access to the area such as via fencing.
• When selecting the type of fencing ensure that native species still have access to the site when installed (e.g. chain mesh fencing may prevent turtles moving in and out of the site).

Designing for maintenance

To ensure the project is resilient to current and future pressures and the investment in the rehabilitation is realised, interventions need to be designed and constructed to allow for future maintenance, considering the frequency, duration, access and cost. An example is the design of small curb-side litter traps (openings in road curbs that allow sediment and debris to collect, minimising the blockages of gutters and lowering the amount of possibly contaminated sediment entering rivers through the stormwater system). To trap sediment and debris they need to have a rough surface with an uneven bed and protruding rocks. However, this design means that maintenance crews cannot get shovels in efficiently to remove the accumulated litter. The result is that the structure could quickly become ineffective. A repositioning of the rough area so that maintenance can occur would make the initial design more effective.

Grass swales can act as water quality improvement systems. However, they can become boggy and difficult to access and maintain if they are not constructed with vehicle access in mind.

Weed management interventions need to consider long-term maintenance. Many weed management activities can result in short-term ecosystem improvement but without maintenance can revert to previous conditions. Weed management needs to consider the broader catchment and landscape.

Interventions can require ongoing maintenance, or get to a point where they are self-sustaining[1]. The former are often engineered, while the latter are frequently vegetation driven solutions.

The maintenance frequency can be categorised into the following three types[1]:

1. routine, such as weeding, or the removal of debris on structures
2. disturbance related, such as checking fencing after flooding
3. lifecycle maintenance, such as structures that need their condition and effectiveness evaluated periodically.

Routine maintenance can often be more efficient than irregular checks. For example, invasive weeds can regrow and establish quickly. Where fencing has been installed, routine maintenance is essential to ensure fauna such as turtles are not trapped, or that the effects of feral pests such as pigs do not get worse if they can get inside the fence.

Monitoring design

When planning for the rehabilitation of aquatic ecosystems, it is important to make decisions based on the best available knowledge at several scales. Scale can be spatial (i.e. site, catchment, and broader system-scales) and temporal (i.e. specific climatic seasons and the suitability of rehabilitation during these times).

The CAMP can be built from existing documents, such as funding applications and project plans. Information that is already available in the funding application, project plan, Aquatic Ecosystem Rehabilitation Plans (AERP) or similar planning documents can be referenced, rather than re-writing, for the purposes of the CAMP. The purpose of the CAMP is to record the logic and reasoning for the assessment/monitoring of changes in the condition in a wetland after an event or resulting from management interventions. The CAMP sets out the decisions, the reasoning (rationale) behind those decisions, and what changes are expected against each of the selected indicators.

A suggested outline for the CAMP is as follows:

• introduction to the region and the wetland
• summary project information
• short summary of what the project is trying to achieve (services to be provided to beneficiaries)
• approach and rationale for determining sites, and the location of the sites
• approach and rationale for determining timing and frequency for assessments/monitoring
• indicate rationale for choice of metrics/assessment approaches for scoring indicators
• expectations at end of project for condition indicators
• expectations for pressure/threat indicators
• other expectations not captured through indicators
• review of monitoring and management regime.

Having a CAMP, allows for an assessment of both the immediate response to project intervention and long-term trends of condition indicators during and following intervention and event recovery. An important aspect of the CAMP is that it distinguishes the expected change in condition due to management intervention within the context of background variability (i.e., threats in the wetland surrounding area and at the landscape scale as well as background variability from weather, biological and chemical processes). A CAMP should document the frequency and timing of monitoring and the site location.

Costing and review of the design plan

The final design needs to be properly costed and care must be taken to ensure that the costing is for the life of the project, including any long-term objectives. Costings need to include site monitoring and maintenance as well as ongoing stakeholder communication and information sharing.

In cases where there are multiple intervention options the detailed design enables them to be compared based on variables such as cost, the amount of disturbance at the site, or the greatest community support.

A final review of the design plan allows for refinement based on the funds available and the timing of actions. This may result in an amendment of the interventions used or staging of the project.

Things to think about

• Have the legal, planning and health and safety requirements for the rehabilitation work been identified and are they achievable?
• What timeframes will be associated with relevant approval processes?
• Have the implications of future pressures (e.g. climate change and development) been considered?
• Have the relevant experts been engaged? Are engineer approved drawings required?
• How will stakeholders and beneficiaries be included in the design process?
• What is the location and spatial extent of the design?
• What is the land status, and who owns and/or manages the land? Determine this for the intervention site as well as any site access points.
• Has a Condition Assessment Monitoring Plan been developed to ensure that the design is based on an understanding of the range of conditions at the site and that ongoing monitoring has been planned?
• What resources and materials (type and amount) are required?
• How will materials be transported to and stored on site?
• What maintenance will be required, who will do it, how often and for how long?
• Have public safety considerations been included in the design, (e.g. can people trip or fall off structures?)
• Has signage been considered for safety and educational purposes?
• How will the management actions be evaluated, monitored and shared?
• What is the timespan of the management intervention?
• What is the sequence/staging and timing of the intervention?
• What is the funding source and budget? Have three quotes been obtained for every service or material required? What are the costs of the whole project including maintenance?
• What site preparation is required before any works commence?
• Will there be a need to dispose of any waste from the site?
• Has the detailed design been ground-truthed via a site visit?
• Where will the plan and design be stored so that it can be accessed and understood in the future?

Two simple example action lists can be seen by clicking on the thumbnails below.

Additional information

• The Riparian Zone Estimator Tool (RipZET)
• Wetland Rehabilitation Guidelines for Great Barrier Reef Catchment
• Reef Trust Gully and Streambank Toolbox

References

1. ^ a b Moore, HE & Rutherfurd, ID (November 2017), 'Lack of maintenance is a major challenge for stream restoration projects', River Research and Applications. [online], vol. 33, no. 9, pp. 1387-1399. Available at: https://onlinelibrary.wiley.com/doi/10.1002/rra.3188 [Accessed 27 May 2022].

Last updated: 30 June 2022