Short-term vegetation succession and erosion identified by airborne remote sensing of Westerschelde salt marshes, The Netherlands

Abstract

The Westerschelde estuary is the only major uncontrolled estuary in the south of The Netherlands. More than 15 000 ships per year use it to access the Belgian port of Antwerp. A major dredging operation along the Westerschelde in the late 1990s has changed the tidal regime and increased tidal inundation of the salt marshes at high tide. Airborne remote sensing (CASI) has been acquired in 1998 and 2000 for three salt marsh sites in the Westerschelde estuary. An additional dataset exists for one site for 1993. The CASI data have been classified into maps of salt marsh vegetation. These provide an input for GIS-based modelling of sediment erosion/accretion. Maps of Normalized Difference Vegetation Index (NDVI) values allow change detection: successional change of salt marsh vegetation is clearly demonstrated. The 1993, 1998 and 2000 data show a successional trend between 1993 and 1998 that is, in part, reversing between 1998 and 2000. Data also showed significant erosion of the salt marsh edge. Data are being used to extrapolate field measurements and help produce sediment budgets for the individual salt marshes.

Acknowledgments

We are grateful for the assistance and co-operation of the other participants in ISLED, especially the co-ordinator T. Cappenberg and other staff of NIOO-CEMO, Yerseke, The Netherlands. R Jordans and other staff of the Survey Department, Rijkswaterstaat, Delft, The Netherlands provided essential data (including the 1993 CASI dataset) and advice. We acknowledge help and advice from staff of the Section for Earth Observation, CEH Monks Wood, UK, the Natural Environment Research Council (NERC) Airborne Remote Sensing Facility, Swindon, UK and the NERC Geophysical Equipment Pool, Edinburgh, UK. H. Balzter of the Section for Earth Observation, CEH Monks Wood provided software for calculating Kappa coefficients.