Managed realignment (bank)

Description of measure

Bank Realignment involves the deliberate removal of existing seawalls or embankments in order to allow the waters of adjacent coasts or estuaries to inundate the land behind.

Application

Implementing the mitigation measure of Managed Realignment using the technique of Bank Realignment is well suited to schemes where the primary purpose of the works is the creation of lower lying intertidal habitat, such as mud flat or sand flat, for ecological benefit.

By removing the entire bank, greater wave action influences the site, reducing the amount of sedimentation and keeping levels more conducive to tidal flat, rather than salt marsh, development.  In addition, more naturally functioning interactions occur between the existing intertidal area and the newly-inundated area. 

Bank Realignment has been practiced within the UK and Europe as a means of implementing Managed Realignment.  The online managed realignment guide (ABPmer, 2009) provides details on three schemes for Bank Realignment in the UK.

The main constraints specifically to Bank Realignment are related to; increased costs due to removal of the entire length of wall, rather than just breaching defined sections; potential loss of footpaths (as many run along the crest of sea embankments); and considerable volumes of waste are created which need to be disposed of.

Managed realignment (bank) at RSPB Wallasea Island Wild Coast Project, Essex

Benefits for the Water Framework Directive (WFD)

Bank Realignment shares the general benefits for the WFD relating to the overall mitigation measure of Managed Realignment. Bank Realignment results in:

  • Reduced sedimentation rates compared with Breach Realignment due to greater wave activity on the site.
  • More conducive conditions for mudflat formation and has potentially greater benefits for the benthic/macro invertebrates Biological Quality Element (BQE).
  • Creation of a wide intertidal area, which may be subject to regular wave action and this may be beneficial for ridge development, although it may also limit the rate of sedimentation of fine sediments.
  • Greater connectivity between the existing intertidal and the newly inundated area than Breach Realignment or Regulated Tidal Exchange techniques, hence increasing the likelihood of creating a self-sustaining intertidal system at the site.

Bank Realignment can be suitable for the creation of habitats that exist at lower levels, such as mudflat or pioneer saltmarsh and can provide a wider intertidal sandflat to feed sand dunes or beaches. The wide intertidal mudflat created can also provide a suitable feeding area for water birds and fish.

To read more about the effectiveness of the measure within academic literature please click here: Effectiveness for Biological Quality Elements

prev   1  2  3  4   next