An essential component of the development of a management scheme to address saltmarsh loss, improve coastal defence value and/or enhance ecological status is to monitor the state of the physical and biological systems. A suitable monitoring strategy, therefore, needs to document and, where possible, quantify the physical and biological change associated with a scheme to refine predictions and to determine the need for any further management measures. Any monitoring strategy should incorporate sound data management, including (at a minimum) metadata (i.e. information) about the data gathered.

Crucially, the monitoring strategy needs to be sufficiently focused to ensure that useful results are derived. Therefore, the selection (and level of detail) of the parameters to be monitored should relate, as closely as possible, to the objectives for which the scheme was developed (e.g. if for ecological purposes, then the monitoring should provide detailed and objective measures of biological parameters and sufficient physical parameters to help explain any changes). The CIRIA Managed Realignment guide (Leggett et al., 2004) includes some useful information on monitoring techniques for physical parameters in saltmarsh environments and the CIRIA guide on Maximising the use and exchange of coastal data (Millard & Sayers, 2000) provides sound guidance on data management issues.

Whatever monitoring techniques are adopted, it is important to remember that saltmarshes are dynamic systems. It should be understood that change can be natural and, in many cases, is an essential feature of the habitat and how it functions. As discussed throughout this manual, factors influencing change include:

• Sediment availability (size and quantity).
• Sea level (absolute and relative changes).
• Tidal range and water levels (magnitude and frequency and in relation to saltmarsh level).
• Wave climate (magnitude and frequency).
• Location.
• Ecological processes (e.g. succession and colonisation).
• Human action (e.g. enclosure, grazing).
• Grazing (natural such as geese).
• Pollution and pollutants (impacting upon and stored by the saltmarsh).

Measuring change (e.g. knowing that a saltmarsh is eroding or accreting or that a species is disappearing), however, does not of itself provide the knowledge necessary to determine policy or agree management action. For example, although sea level rise may be occurring in a location with saltmarsh loss, the saltmarsh may actually be responding to (adapting and keeping pace with) sea level rise and the loss related to vegetation die-back.

Many other factors are likely to have an influence. Tides and tidal range, sediment availability and the nature of the coast all influence the development of saltmarsh. Local weather conditions, including rainfall, discharge rates of rivers and the state of the tide, also contribute to the pressure put on saltmarsh stability; and erosion rates will depend on the strength of the feature being affected by the erosive force. In addition, changes in sea level per se (eustacy) are the result of global forces associated with the atmospheric temperature, whether due to human influences or not. Where the land level is stable or sinking (isostacy) the coast will be inundated. Given all of these factors, it may be difficult to determine the precise reasons for the loss of saltmarsh without expert guidance.

Despite this, the fact remains that in some areas (especially south east England) the overall area of saltmarsh is diminishing and, as a consequence, coastal defences are being undermined and land threatened with flooding. The measurement of change in saltmarsh, therefore, can provide a very powerful indication that an adverse effect is occurring, which needs to be addressed.

Click on the links above for further information on the Survey and Monitoring of Saltmarshes.