Impacts of Climate Change on Estuarine Habitats in the UK: Critical Evaluation of the Saltmarshes and Sea-Level Rise Model (SLAMM)

Estuarine wetland environments are at risk of significant transformation and loss due to sea-level rise and there is an increasing need to model such impacts. In a UK context, the relatively small size and morphological complexity of many estuaries necessitates a high spatial resolution but models must also be capable of efficient application over time scales of decades to centuries that correspond to widely used IPCC climate change scenarios. Little previous work of this kind has been carried out to date in the UK. An exception is the EU-funded BRANCH project, which simulated the drowning of intertidal topography, due to sea-level rise, and potential mudflat and saltmarsh responses to a change in inundation regime. However, this approach neglects the interplay of sea-level rise and sedimentation. Accordingly, this study investigates the potential of a more dynamic spatial landscape model to represent meso-scale impacts of sea-level rise on UK estuary environments. It takes as a starting point the Sea Level Affecting Marshes Model (SLAMM), which has been widely used in the USA. This is built around the US National Wetlands Inventory classification and adapting it to suit the tidal sedimentary environments and habitats typical of the UK requires changes to the source code. This paper presents results obtained from the application of an appropriately modified SLAMM code to contrasting estuarine environments in eastern England. The aim is to evaluate the ability of SLAMM to produce plausible projections of intertidal habitat change. The estuaries studied are covered by high-resolution altimetry data, and an extensive literature on their physical process regime allows the parameterisation of the various sub-models in SLAMM. A Matlab-based shell is used to perform an initial sensitivity analysis to better understand the nature of the modelled sea-level rise effects. This shell also provides a framework for Monte Carlo simulations forced by a set of UKCP09 sea-level rise scenarios.