Mapping Coastal Mediterranean Wetlands using Sub-pixel Spectral Signatures and Multi-temporal Landsat Data
Reschke, Julia1; Hüttich, Christian2
1University of Wuerzburg, GERMANY; 2Friedrich Schiller University, Jena, GERMANY

Wetland ecosystems are affected by short periodic changes in vegetation dynamics and hydrological patterns. Moreover, Mediterranean wetlands are affected by distinct land use pressures in recent decades caused by agriculture intensification, urban growth, and increasing tourism infrastructure. Biotope inventory requires mapping at scales that fit to the character and dimension of the ecosystem. Satellite-based wetland mapping still bears the most uncertainties compared to other land cover types. Image classification techniques have to better adapt to specific wetland characteristics, such as spatial heterogeneity, seasonal dynamics and fuzzy transition between different land cover classes. For this purpose, a pixelbased method for wetland delineation based on multi-temporal Landsat data in West Turkey was developed and analyzed. In addition to common vegetation indices and texture measures, the usefulness of seasonal indices was tested. Multi-temporal Landsat imagery was combined with high resolution satellite data to extract sub-pixel information of RAMSAR wetland land classes based on a random forest regression algorithm. The classification achieved an overall accuracy of 79.02 %. In addition to the crisp wetland classification the mapping framework provides a map of fractional cover information of different wetland classes including information about fuzzy spatial transitions of highly heterogeneous distribution patterns of wetland habitats and related intra-annual seasonal dynamics. Mapping spatio-temporal wetland dynamics at continuous field scales increases the applicability of Landsat-derived maps for local-scale ecosystem monitoring and management on habitat level, and also supports future reporting mechanisms, e.g. in the framework of the RAMSAR Convention on Wetlands and NATURA2000.

Figure. Regression layers of wetland classes: (a) mudflats, (b) marshland, (c) water bodies and (d) rivers/channels.