Abstract

Salt marshes and, to a lesser extent, tidal flats, attenuate incoming hydrodynamic energy, thus reducing flood and erosion risk in the coastal hinterland. However, marshes are declining both globally and regionally (the Northwest European region). Salt marsh resistance to incoming hydrodynamic forcing depends on marsh biological, geochemical and geotechnical properties. However, there currently exists no systematic study of marsh geotechnical properties and how these may impact both marsh edge and marsh surface erosion processes (e.g. surface removal, cliff undercutting, gravitational slumping). This has led to poor parameterization of marsh evolution models. Here, we present a systematic study of salt marsh and tidal flat geotechnical properties (shear strength, bulk density, compressibility, plasticity and particle size) at Tillingham, Essex, UK.

Highlights

  • Salt marshes and tidal flats attenuate incoming waves, tidal and storm surge-induced currents

  • While many studies have assessed the hydrodynamic forces acting on salt marshes (e.g. Möller & Spencer, 2002; Fagherazzi et al 2006; Callaghan et al 2010; Tonelli et al 2010), and some have assessed the role of biological properties in stabilizing salt marsh substrates (e.g. Turner et al 2001; Morris et al 2002; Le Hir et al 2007), very few have looked at substrate properties and how these might affect marsh stability

  • The few studies which do characterise salt marsh and tidal flat substrate properties rarely measure these properties in the context of known erosion mechanisms and do not enhance our knowledge of how substrate properties relate to marsh stability

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Summary

Introduction

Background Salt marshes and tidal flats attenuate incoming waves, tidal and storm surge-induced currents. Marsh stability is defined as the ability of marsh substrates to resist the erosive forces induced by waves, tides and storm surges, while accreting at a rate which keeps pace with sea-level rise (Reed, 1995). This stability is in part dependent upon the hydrodynamic force acting on the marsh and the resistance of both the marsh platform and margin to erosion. Models simulating salt marsh change under different future climate forcing scenarios generally include an erodibility coefficient (e.g. Mariotti & Carr, 2014), but, due to a lack of data, these coefficients are rarely related to measured geotechnical and sedimentological properties

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