Application of lidar digital terrain modelling to predict intertidal habitat development at a managed retreat site: Abbotts Hall, Essex, UK

A key question in designing any managed retreat site concerns the nature of the habitats which will be created, and their likely long-term sustainability and development. Studies of historical sea wall failures in Essex have shown that former reclaimed areas may respond to renewed tidal flooding in different ways depending on a number of factors, most importantly the elevation of the land at the time of breach, which governs the frequency and duration of tidal flooding. This paper demonstrates how digital terrain modelling using airborne lidar data can be used to calculate the elevation of the land behind a breach and to predict the likely habitats which will be created. When combined with data from sites of historical sea wall failure, predictions can also be made about the likely geomorphological and biological evolution of the created habitats in the longer term. At Abbotts Hall on the northern side of Salcott Creek, Essex, where a managed retreat scheme was activated in October 2002, the highest areas above 2.35 m OD were predicted to develop stable saltmarsh, intermediate areas between 2.1 and 2.34 m OD to develop potentially unstable saltmarsh which is likely undergo internal dissection, and the lowest areas below 2.1 m OD to remain as mudflat or lagoon. Approximately 38 per cent of the site was predicted to develop stable saltmarsh, and nearly 50 per cent to remain as lagoon or mudflat. Monitoring is now being undertaken but it will be several years before the accuracy of the predictions can be assessed. Copyright (C) 2004 John Wiley Sons, Ltd.