Sediment transport on the Freiston Shore managed realignment site: An investigation using environmental magnetism Robin Rotman a, ⁎ , Larissa Naylor a,b,c , Rachael McDonnell a , Conall MacNiocaill d a Oxford University Centre for the Environment, South Parks Road, Oxford OX1 3QY, UK b Department of Geography, University of Exeter, Cornwall Campus, Penryn, Cornwall, TR10 9EZ, UK c Environment Agency, Block 1, Government Buildings, Westbury on Trym, Bristol, BS10 6BF, UK d Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, UK Received 1 February 2007; received in revised form 23 December 2007; accepted 28 December 2007 Available online 3 January 2008 Abstract This paper presents the first attempt to use environmental magnetism to quantify sediment provenance on a managed realignment (MR) site. MR is one technique for creating/restoring intertidal habitats and improving the standard of coastal flood protection. Monitoring of MR sites is essential for determining how successful they are at achieving these aims, and normally includes measurement of sedimentation rates through the use of accretion plates and sediment erosion tables (SETs). One limitation of this technique is that the provenance of sediment accreting on realigned surfaces cannot readily be quantified. Our results demonstrate that magnetics-based fingerprinting can successfully apportion sediment source contributions to created/restored coastal saltmarshes with an efficiency similar to that of existing un-mixing models applied to other habitats (82.87%). Analysis of mineral magnetic properties (χ FD , IRM soft and SIRM) demonstrated that the majority of sediment accreting on the Freiston Shore MR Site (Lincolnshire, UK) is derived from established saltmarshes seaward of the breached embankment. This indicates that the MR site may be growing at the expense of neighbouring saltmarshes—thereby undermining the habitat-creation objectives used to justify MR. It is recommended that future MR monitoring programmes consider the provenance of post-breach deposits to help identify any adverse impacts that wetland creation/restoration may have on existing habitats. Further testing of environmental magnetism in coastal saltmarshes and MR sites is necessary to validate wider use of the technique. © 2008 Elsevier B.V. All rights reserved. Keywords: Saltmarsh; Managed realignment; Sediment fingerprinting; Environmental magnetism; Wetland creation 1. Introduction Since Roman times, large tracts of saltmarsh have been claimed from the sea through the construction of embankments (Pethick, 2002). This has resulted in the degradation of coastal halophytic communities, particularly in Europe and North America (Wolters et al., 2005). Only in recent decades has the environmental value of saltmarshes been realised, and with this realisation have come increasing efforts to conserve these areas. Marshes provide numerous environmental functions including wildlife habitat, fisheries protection, carbon sequestration, water quality improvement, social/recreational opportunities and coastal flood protection (King and Lester, 1995; Costanza et al., 1997; Möller et al., 1999; Shepherd et al., 2005). By attenuating wave height and dissipating wave energy, saltmarshes reduce the cost of sea wall maintenance and lessen flood risks for the hinterland (King and Lester, 1995). In light of these ecosystem functions, and in consideration of various national and international conservation directives (such as the European Habitats Directive: 92/43/EEC), efforts are now in place to preserve existing intertidal areas and to create and restore additional saltmarsh habitat in many parts of the world. Several creation and restoration techniques have been used, both in isolation and in tandem, such as polders, wavebreaks, sediment Available online at www.sciencedirect.com Geomorphology 100 (2008) 241 – 255 www.elsevier.com/locate/geomorph ⁎ Corresponding author. P.O. Box 207305, New Haven, CT 06520, USA. Tel.: +1 203 479 2692; fax: +1 847 295 8694. E-mail address: robin.rotman@yale.edu (R. Rotman). 0169-555X/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.geomorph.2007.12.006