Hindcasting and forecasting marsh ecomorphodynamics by integration of model with stratigraphic record

Abstract

Marsh morphodynamics models are usually calibrated using sparse short-term measurements. Hence, their ability to predict long-term trajectories (centuries to millennia) is highly uncertain. Here I improved an existing model for marsh ecomorphodynamics and used it to hindcast the whole morphodynamic trajectory (2500 years) of an actual salt marsh in New England (USA). The model includes enough processes – among which tidal currents and waves, sand and mud transport, and vegetation population dynamics – to simulate a realistic marsh analogue that closely matches the modern topobathymetry and stratigraphy. Marsh trajectory is highly sensitive to initial bathymetry, mud supply from the nearshore, wave erosion processes, and vegetation dynamics. Each one of these factors is important yet difficult to calibrate on its own. Matching the long-term evolution with the stratigraphic record provides a global constraint for the processes and parameters in the model, increasing the confidence in future long-term predictions. This type of comparison complements those made at short times scales, and it should be used more routinely.