Soils and ‘managed retreat’ in South East England

Abstract

Much of the low-lying farmland around the coastline of south-east England was once inter-tidal salt marsh, which was subsequently reclaimed from the sea and converted to farmland. It is becoming increasingly uneconomic to maintain the embankments which protect this land from the sea.Managed retreat' involves relocating the embankments further inland and recreating inter-tidal habitat in front of them. Salt marsh not only provides a protective buffer for these sea walls by dissipating wave energy, but is also important as a habitat for birds and as a source of organic matter for ®sh and inter-tidal fauna.When`managed retreat' takes place, the creation of inter-tidal habitat occurs on soils that have undergone physical and chemical changes, some of which are irreversible. However, the indications are that rapid sedimentation creates conditions in which salt marsh plants germinate and become established; soil salinity rises quickly to a level which restricts competition from terrestrial plants, and deposited sediment is relatively rich in available phosphorus. The physical properties of the old agricultural soil in¯uence the subsequent development of creeks.Soils and`managed retreat' in south east England

Centuries of Human-Driven Change in Salt Marsh Ecosystems

“…Managed retreat, as this goal is known in England, reverts reclaimed land to intertidal marsh and mudflat by moving dikes or seawalls inland to create a more natural coastal flood buffer (Hazelden & Boorman 2001). In 2002, approximately 200 ha of salt marsh in England were restored in experimental tests of managed retreat (Pethick 2002).…”

Surface elevation change in natural and re-created intertidal habitats, eastern England, UK, with particular reference to Freiston Shore

“…Also, the persistence of a compacted soil surface beneath the post-breaching deposits inside the realignment may have inhibited vertical tidal flushing, nutrient transfer and contaminant removal, as has been described elsewhere in eastern England (e.g. Hazelden and Boorman 2001;Spencer et al 2008). All these factors potentially limit the degree of subsidence and dewatering within the realignment site compared to natural intertidal deposits over comparable time periods and may explain some of the variability of surface elevation change, surface accretion rate variability, and the changing relations between these two measures, within the realignment.…”

“…In the areas remote from the breaches (SET9, SET11), the inter-relations over time between surface elevation change and surface accretion were highly variable. Reclaimed agricultural soils differ from intertidal substrates as they have a lower organic matter content (Ellis and Atherton 2003) and different organic matter composition (Santin et al 2009), lower nutrient content, lower water content, decreased porosity and increased density (Hazelden and Boorman 2001). Root biomass may also make significant contributions to near-surface accretion in saltmarsh soils and is clearly related to surface vegetation community dynamics (e.g.…”

Agricultural fingerprints in salt-marsh sediments and adaptation to sea-level rise in the eastern Cantabrian coast (N. Spain)

“…Once sufficient elevation is reached in relation to the tidal frame, recolonisation by vegetation occurs and enhances sediment trapping (Friedrichs and Perry, 2001). The regenerated saltmarshcontinues to develop under lower sedimentation rates, although full restoration of natural functions often takes longer (Hazelden and Boorman, 2001).…”