The development of a tool for examining the morphological evolution of managed realignment sites

Abstract

This paper describes the development of a model for prediction of local changes in morphodynamics resulting from managed realignment, undertaken as part of a UK project funded by Defra. The methodology builds on the conceptual modelling approach to habitat development employed successfully by Di Silvio (1989, 1998), Di Silvio and Gambolati (1990) and others for lagoon environments. The overall approach can be described as hybrid – combining bottom-up (process-based) and top-down (simplified and/or empirical) predictive techniques – to describe the essential inlet functioning. The model described in this paper is used to predict the evolution of a managed realignment site under the action of tides and waves and sediment supply. Validation of the managed realignment model is undertaken using the available survey data from before the realignment and from several years afterwards. The performance of the model is promising in this respect, producing the right magnitude and the main qualitative features of bathymetric change. Longer simulations are used to see how the growth of saltmarsh itself affects the evolution of the setback field and how sea level rise would affect the development of saltmarsh.