Remote sensing of geomorphological and ecological change in response to saltmarsh managed realignment, The Wash, UK

An integrated remote sensing approach quantified saltmarsh dynamics in response to a sudden change in surface elevation due to a saltmarsh restoration scheme. The biogeomorphological relationship between surface elevation and saltmarsh presence occurs over the long-term so can be difficult to observe, though the ‘managed realignment’ of coastal defences provides a unique experimental opportunity to study this relationship. Realignment at Freiston Shore, Lincolnshire, UK in August 2002 caused a sudden and high-magnitude sediment input into the local coastal system, significantly increasing the intertidal surface elevation. The resulting impacts on the external, fronting saltmarsh were quantified by aerial photography and airborne multispectral imagery. Algal and pioneer saltmarsh boundary positions were calculated from 1984 to 2006, with the latter zone migrating slowly seaward pre-realignment (3.8 m a−1), but advancing significantly post-realignment (21.3 m a−1). Classification of five-year multispectral imagery accurately showed subtle changes in vegetation community composition within these boundaries. The realignment site was also colonized rapidly compared to other restoration sites, due to its high starting surface elevation. This study shows how, with sufficient sediment input and accommodation space, coastal management decisions can release intertidal surfaces from physical constraints to saltmarsh colonization.

[1]  J. S. Rodwell,et al.  British Plant Communities: Volume 5, Maritime Communities and Vegetation of Open Habitats , 2000 .

[2]  Peter Rothery,et al.  Managed realignment at Tollesbury , 2008 .

[3]  K. Kiehl,et al.  Impact of different sheep grazing intensities on salt marsh vegetation in northern Germany , 1996 .

[4]  Tom Spencer,et al.  Assessing seasonal vegetation change in coastal wetlands with airborne remote sensing: an outline methodology , 1998 .

[5]  P. W. French,et al.  The changing nature of, and approaches to, UK coastal management at the start of the twenty-first century , 2004 .

[6]  S. Silvestri,et al.  Mapping salt-marsh vegetation by multispectral and hyperspectral remote sensing , 2006 .

[7]  Kai Jensen,et al.  Plant Species Responses to an Elevational Gradient in German North Sea Salt Marshes , 2010, Wetlands.

[8]  A. Hastings,et al.  Mapping marshland vegetation of San Francisco Bay, California, using hyperspectral data , 2005 .

[9]  Richard A. Wadsworth,et al.  Airborne remote sensing of intertidal biotopes : BIOTA I , 1999 .

[10]  John Robert Lawrence Allen,et al.  Morphodynamics of Holocene salt marshes: a review sketch from the Atlantic and Southern North Sea coasts of Europe , 2000 .

[11]  Richard Bingley,et al.  Trends in Uk Mean Sea Level Revisited , 2008 .

[12]  Alfred C. Redfield,et al.  Development of a New England Salt Marsh , 1972 .

[13]  J. French,et al.  Numerical simulation of vertical marsh growth and adjustment to accelerated sea‐level rise, North Norfolk, U.K. , 1993 .

[14]  Jon P. Mills,et al.  Detection, measurement and prediction of shoreline recession in Accra, Ghana , 2008 .

[15]  P. W. French.  Managed realignment The developing story of a comparatively new approach to soft engineering , 2006 .

[16]  Richard J. S. Whitehouse,et al.  Observations of the morphodynamic behaviour of an intertidal mudflat at different timescales , 1998, Geological Society Special Publication.

[17]  Jon French,et al.  Tidal marsh sedimentation and resilience to environmental change: Exploratory modelling of tidal, sea-level and sediment supply forcing in predominantly allochthonous systems , 2006 .

[18]  Michael Collins,et al.  The establishment and degeneration of a temporary creek system in response to managed coastal realignment: The Wash, UK , 2007 .

[19]  R. Nicholls.  Coastal flooding and wetland loss in the 21st century: changes under the SRES climate and socio-economic scenarios , 2004 .

[20]  E. L. Hunter,et al.  An assessment of two classification methods for mapping Thames Estuary intertidal habitats using CASI data , 2002 .

[21]  P. Rothery,et al.  Monitoring the development of intertidal habitats on former agricultural land after the managed realignment of coastal defences at Tollesbury, Essex, UK. , 2006, Marine pollution bulletin.

[22]  Jennie Graham,et al.  Ecological re-engineering of a freshwater impoundment for salt marsh restoration in a hypertidal system. , 2010 .

[23]  Cédric Bacher,et al.  Characterization of intertidal flat hydrodynamics , 2000 .

[24]  Michael B. Collins,et al.  SEDIMENT DYNAMICS ASSOCIATED WITH MANAGED REALIGNMENT; FREISTON SHORE, THE WASH, UK , 2005 .

[25]  Richard A. Wadsworth,et al.  Short-term vegetation succession and erosion identified by airborne remote sensing of Westerschelde salt marshes, The Netherlands , 2004 .

[26]  M. B. Machmuller,et al.  Forecasting the effects of accelerated sea‐level rise on tidal marsh ecosystem services , 2009 .

[27]  J. Zedler,et al.  Wetland resources : Status, trends, ecosystem services, and restorability , 2005 .

[28]  Philip B. Williams,et al.  Physical Evolution of Restored Breached Levee Salt Marshes in the San Francisco Bay Estuary , 2002 .

[29]  H. Brumsack,et al.  The impact of tidal inundation on salt marsh vegetation after de-embankment on Langeoog Island, Germany—six years time series of permanent plots , 2009 .

[30]  Ian L Turner,et al.  Shoreline Definition and Detection: A Review , 2005 .

[31]  Jan Bakker,et al.  Plant colonization after managed realignment: the relative importance of diaspore dispersal , 2005 .

[32]  J. S. Rodwell,et al.  British Plant Communities: British Plant Communities , 2000 .

[33]  D. Friess,et al.  Are all intertidal wetlands naturally created equal? Bottlenecks, thresholds and knowledge gaps to mangrove and saltmarsh ecosystems , 2012, Biological reviews of the Cambridge Philosophical Society.

[34]  Donald R. Cahoon,et al.  A Method for Measuring Vertical Accretion, Elevation, and Compaction of Soft, Shallow-Water Sediments: RESEARCH METHODS PAPERS , 2000 .

[35]  M. B. Collins,et al.  Short-term changes in sedimentological and hydrographic characteristics over a sandy intertidal zone, the Wash, U. K. , 1982 .

[36]  Daniel Friess.  Impacts of managed realignment on low-lying coasts , 2009 .

[37]  Richard A. Wadsworth,et al.  The use of airborne remote sensing for extensive mapping of intertidal sediments and saltmarshes in eastern England , 2003 .

[38]  Jennifer M. Brown,et al.  Looking for evidence of climate change impacts in the eastern Irish Sea , 2011 .

[39]  Marvin E. Bauer,et al.  Integrating Contextual Information with per-Pixel Classification for Improved Land Cover Classification , 2000 .

[40]  E. Robert Thieler,et al.  The Digital Shoreline Analysis System (DSAS) version 3.0, an ArcGIS extension for calculating historic shoreline cange , 2005 .

[41]  D. J. de Jong,et al.  Restoration of salt marshes in the Netherlands , 2002 .

[42]  Anthony J. Davy,et al.  Drainage and Elevation as Factors in the Restoration of Salt Marsh in Britain , 2002 .

[43]  M. Dixon,et al.  Managed realignment–lessons from Wallasea, UK , 2008 .

[44]  P. W. French.  Managed retreat: a natural analogue from the Medway estuary, UK , 1999 .

[45]  Johan van de Koppel,et al.  Self‐Organization and Vegetation Collapse in Salt Marsh Ecosystems , 2004, The American Naturalist.

[46]  Richard F. Ambrose,et al.  A Comparison of Remote Sensing and Ground‐Based Methods for Monitoring Wetland Restoration Success , 2003 .

[47]  Bart A. Kornman,et al.  Restoration of the Sieperda Tidal Marsh in the Scheldt Estuary, The Netherlands , 2002 .

[48]  R. G. Hughes,et al.  Successional development of saltmarsh in two managed realignment areas in SE England, and prospects for saltmarsh restoration , 2009 .

[49]  A. Jensen,et al.  The effect of cattle and sheep grazing on salt-marsh vegetation at Skallingen, Denmark , 1985, Vegetatio.