In order to assist in the selection of an appropriate management option, the table below provides (by way of an example) a list of the possible causes of saltmarsh loss or degradation, the likely consequential effect and possible management solutions. However, it is essential that these are defined on a case by case basis, dependant on the objectives for the intervention, the nature (and quality) of the baseline environment and the cause of the change.
Cause |
Effect |
Potential Management Solution |
Grazing pressure
|
Change in floral diversity |
Change the grazing regime.
Monitor species diversity particularly if any rare or scarce species are belived to be present. Fence off any areas of particular sensitivity. |
| Grazing pressure |
Localised erosion, generally in the upper/mid marsh |
Fence off eroded areas, as once erosion starts it could increase rapidly if not managed. Allow for natural recolonisation but ensure that relief is suitable for vegetation establishment, particularly on creek edges. If planting is necessary, only plant species that are present in the adjacent area. |
Change in tidal flows due to coastal development |
Increase in scour and erosion |
Sedimentation fences (potentially in conjunction with intertidal recharge) could be used to reduce the flow of water reaching the saltmarsh edge. In some cases, planting could be adopted. However, only native species should be used and ensure that they are used within the correct tidal zone. Note that it is only worth planting if there is enough sediment available to feed the saltmarsh. |
Channel dredging |
Slumping of intertidal area fronting saltmarsh |
Sediment recharge into the estuarine system or onto intertidal area. Use of this technique, and the type of material to be used, will depend on the nature conservation/fisheries interest of the site and the ability of the system to ‘hold’ the sediment once it is placed. In some cases, this may require planting of saltmarsh vegetation, but only species already present on the site should be used, to ensure the sites’ ecological integrity, and the marsh should be sufficiently stable to allow for growth of the leading edge. This will depend on the extent and rate of slumping.
Some form of stabilisation may also be necessary, such as sedimentation fences. Revetments should only be used as a last resort, as they will prevent the movement of material to the site and not allow for the colonisation of saltmarsh vegetation. |
Loss of natural wave break offshore (e.g. removal of sandbank due to natural movement or dredging; change in the orientation of a tidal inlet) |
Increased wave exposure causing erosion of the seaward edge of the marsh |
Nearshore rock sill/offshore breakwater; dependent on the nature of the receiving environment and the objective of the saltmarsh management (e.g. if the erosion is occurring within an estuary that is important for shellfish or as a fish nursery, it is essential to determine the effect of placing a sill/breakwater both on the species concerned and on the water exchange rates and movement of sediment); needs to ensure that sediment is still available to feed the saltmarsh. |
| Sea level rise |
Creek lengthening and widening |
If allowing the natural roll back of the saltmarsh is not a viable option, then it is likely that the only option is to accept the loss of the saltmarsh. Recharge of sediment to raise saltmarsh levels may provide some additional time and reinstate diversity.
Managed realignment should be investigated as an option to allow the creation of saltmarsh or allow natural roll back. (CIRIA, 2004) |
| Decrease in species diversity as saltmarsh squeeze occurs |
| Ship wash |
Erosion of the seaward edge of saltmarsh and creek walls |
Reduce the speed of vessels to a speed that reduces the wash caused by the vessel. If possible, change direction of approach of the vessel, to alter wave direction.
In extreme cases, the use of sedimentation fences can reduce the flow of water reaching the saltmarsh. |
| Recreational pressure |
Change in floral diversity |
Prevent pressure through interpretation boards. Restrict and/or control access through the use of boardwalks over the saltmarsh.
In some cases planting could be used to recolonise degraded areas, in order to prevent further erosion. However, only use species present in marsh already to maintain biodiversity |
| Localised erosion, generally in the upper marsh |
| Change in freshwater/ seawater input |
Change in floral diversity |
Dependent on the management objective of the site, manage the freshwater input to the site via sluices. In some instances changes to salinity could increase diversity within the overall site. Large scale changes (e.g. due to an increase in freshwater input), however, could lead to the loss of saltmarsh vegetation as halophytic plants are displaced from the site. |
| Potential for improvement of drainage to facilitate flushing of water. |
| Pollution |
Change in floral diversity |
Preventative measures are necessary to stop pollution from entering the site source control. |
| Extreme events, such as oil spills, should be dealt with on a case-by-case basis, but oil should generally be left to degrade naturally. |
| Loss in plant vigour |
Potential for improvement of drainage to facilitate the flushing of water. This is dependent on the nature of the pollutant and the period of exposure. |
| Disease |
Loss in plant vigour |
Potential for improvement of drainage to facilitate flushing of water. However, this will be dependent on the nature of the disease.
Also potential for planting, but ensure that chemical conditions are suitable prior to planting as certain diseases can render the soil conditions unsuitable for colonization. Certain plant diseases may be species specific, so consider the use of alternative species within areas subject to die-back due to disease. |
| Localised erosion |
