The action plan

Actions and priorities should be based on the site information, the desired wetland values and services, as well as the resources available (as outlined in Step 3). A list of prioritised actions together with time-line and equipment list should be developed. For example if erosion and sediment comes up as a threat to the values of the wetland then the plan will need address both short and long term sediment control e.g. short term - sediment fencing; long term: adding vegetated filter strips and or buffer zones or the placement of boulders and logs may be necessary for stabilisation.

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

Setting priorities

Prioritising actions is important for a variety of reasons e.g. limited resources and seasonal considerations, breeding times, wet and dry periods, resource constraints and people availability? Does the timing of one action impact on another? For example there is no use planting new trees if the animals that ate the original plants still have access.

Site preparation

Site preparation is an important part of the rehabilitation process. The site preparation will vary depending on the site and the extent of the work (cleared site vs. site with established flora) e.g. soil improvement, weed removal, plant removal, storage and replacement, access to water, fencing, provision of ground cover, sediment fencing. Consider, if the site is contaminated and needs re-mediation before rehabilitation starts or will waste disposal be required?

Hydrology

The hydrology affects most wetland processes, such as sediment and soil processes, nutrient treatment, weed and native seed movement and, in coastal wetlands, salinity levels. These processes come together to determine the type of flora and fauna that develop in the wetland. Hydrologic conditions are extremely important for the maintenance of a wetland’s structure and the way it functions. A wetland’s water regime is one of the most important determinants of the establishment and maintenance of specific types of wetlands and wetland processes[1]. The hydrological features that affect the wetland do not only involve the amount of water entering the wetland but also the time when it arrives, and the retention period. For example too much water entering a wetland (farm runoff or irrigation tail-water) may be detrimental to that wetland type and change the values of the wetland; similarly, restricting water from entering a wetland (irrigation drawdown or diversion) may also be detrimental to values of the wetland. Hydrological conditions also affect nutrient cycling, with wetlands that have water flowing through them or in pulses having the highest rate of nutrient cycling[1]. Many wetlands have been impacted by barriers and changes to drainage features which has altered the hydrology and may need to be remediated by removal, modification or the installation of fauna movement devices e.g. fishways.

The main types of inflows to a wetland are: rainfall, flooding from rivers, surface flows (e.g. farm runoff and irrigation tail-water), groundwater and tidal influences.

The main types of outflows from a wetland are: seepage to groundwater (aquifer recharge), evaporation from standing or running water, water released to the atmosphere by plants (evapotranspiration) and overland or channel flows.

It is important to know the wetlands seasonal variations e.g. high flows / flooding and low flow periods and they will also impact other aspects of the wetland e.g. flora and fauna. It is these extreme events that will have the most impact on shaping the wetland.

 

Soil, ground cover and earthworks

If the soil is not in good condition, you may need to condition it (e.g. adding leaf matter) or, use wetland plant species that can tolerate the soil type. Adding weed free compost or mulch is one way of improving the soil and may bring in good insects and bacteria that will help with continuing soil improvement. The mulch will also help protect the top layer of soil from wind and water erosion and help hold in moisture. If the soil is compacted, due to use, digging up the soil around where the plant is going in and adding mulch will also help the plant establish.

But, don't put the mulch in the waterway or in areas where it can wash out and cause problems downstream and don't forget to check the legislation to see what the rules are as bark and woodchips may be listed as a water contaminant. It is worth doing research as there are many ways to ensure good ground cover depending on the weeds and the site e.g. rocks, geotextiles, planting into current weeds shading them out over time. Much research has been undertaken into the best approaches to the removal of particular weeds species e.g. various pesticides work differently on different species or plant types (monocots vs. dicots).

Modifications to the any hard structures e.g. bedrock need to be very seriously considered as they can have major impacts both upstream and downstream.

It is important to identify potential contaminated land and / or acid sulphate soils. As the pyrite in Acid sulphate soils, when dug up or drained and comes into contact with oxygen, turns into sulphuric 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. Read more on acid sulfate soils.

Flora

Revegetation might only be needed when the natural return of plant species is unlikely e.g. in some cases controlling access, hydrology, weeds or pests is all that is needed. Plants can undertake a number of roles and be planted for a number of reasons. After determining what local plants that should inhabit the area 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 ). The plant list is an important step and will guide which plants you purchase and where the plants are placed.

The location and function of vegetation on stream banks is important to ensure structural integrity and protection of the banks, particularly in high rainfall and flood prone areas. When selecting species for revegetation, select a diverse range of vegetation forms suitable for planting in the different zones of the bank 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

Fauna

It is also important to consider what species of fauna inhabit the area and which species to attract. You need to 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 wren then having large open areas with little understory may not be suitable. If the site is large enough you may be able to provide for both by having some thickly planted areas going to the water. Habitat requirement research needs to be undertaken to ensure the required results.

Will you provide additional habitat or extras for wildlife e.g. nest boxes, hollow logs, wood, dead trees and snags within the waterway (to provide cover for fish and encourage breeding)? Do the species you are trying to attract need an island for breeding and protection from predators? Which plants will attract the right species and create the right habitat?

Land use and surface roughness

The roughness of the landscape influences the speed of water movement across it. This applies to all types of flow including runoff, overland, and channel flows. Complex habitats such as rainforests, with a high density of trees and a developed under-story will significantly reduce flow speed; simple habitats, such as open grassland, or open forests with a cleared under-story will provide little resistance to flows. Consequently, rougher surfaces will increase the height of local floods, whilst smoother surfaces will increase the speed at which water drains from the land, potentially increasing flood sizes downstream. This is important to consider within the context of the larger catchment (e.g. how the flows will impact the wetland) and locally (e.g. how you can reduce flow and hold water).

Additional information

• The Riparian Zone Estimator Tool (RipZET)

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References

1. ^ a b Mitch, W & Gosselink, J (2015), Wetlands Fith Edition, John Wiley & Sons Inc, Hoboken, New Jersey.

Last updated: 10 September 2018