###### Abstract
Since the launch of TerraSAR-X in 2007, followed by TanDEM-X (both X-band), the COSMO-SkyMed satellite constellation (X-band), and Radarsat-2 (C-band), these satellites provide SAR data with resolutions in the scale of meters [8]. The radar satellite Sentinel-1 with a slightly lower resolution (5 m in stripmap mode) has been available since 2014 with open data policy. With the technical improvements not only offered by the SAR sensors, but also with increasing spatial and/or spectral resolution of electro-optical systems (e.g., Landsat-8, RapidEye, SPOT-4, World-View, or currently, Sentinel-2), the use of satellite data for the protection and management of coastal areas such as the Wadden Sea is becoming increasingly realistic. Against this background, a number of German research projects such as OFEW (2005-2007), DeMarine-1-Environment TP4 (2008-2011), DeMarine-2 SAMOWatt (2012-2015), and WIMO (2011-2015) was conducted to apply high-resolution satellite data for the requirements of monitoring and long-term ecological research in the Wadden Sea; for overviews, see [9; 10; 11; 12; 13]. Various authors have demonstrated the value of state-of-the-art satellite data for the exploration of tidal areas [10; 14; 15; 16; 17; 18; 19; 20]. The further development of image classification methods designed for the tidal area has gained pace, for example, regarding the exploitation of polarimetric information from SAR data, whose potential has already been documented by, e.g., Refs. [21; 22; 23]. The aim of the present study is to determine the potential of the high-resolution intensity images acquired by TerraSAR-X to identify the distribution and development of the main geomorphological structures and habitats in a whole tidal basin and their dynamics which are of utmost importance for monitoring and long term ecological research but also for the management of the area. In order to recognize as many different surface structures as possible, this study focuses on visual image interpretation, which takes into account backscatter intensity and contrast as well as shapes, patterns, and textures of surface features reflected by the SAR data, but also their configuration or surrounding context. This is of particular importance because the Wadden Sea, characterized by a flat topography, a very dynamic variability, the variety of gradients, transitional zones, and surface structures under the influence of constantly changing water levels and weather conditions, poses great challenges to classification of intertidal surfaces. In this context, visual analysis should provide technically unsophisticated access to as much of the information contained in the SAR data as possible. Previous knowledge and experience play an important role in the visual interpretation process, with recognition and interpretation running through an iterative process, where both steps heavily rely on one another [24]. That is, context information, such as environmental conditions (acquisition time related to tidal cycle, water level, weather conditions) and processes, field experience, and in situ data, which is difficult to quantify automatically, are essential components flowing into the analysis. Therefore, in this study, extended field observations partly synchronous to the satellite acquisition are carried out throughout the period of the investigations to validate the image interpretation results. An initial basis of the terrain knowledge was laid during the comprehensive mapping of the main study area as part of the DeMarine-1 project. TerraSAR-X spotlights and high resolution spotlights proved most suitable to investigate typical intertidal surface structures and habitats such as mussel beds, shell-detritus, gully systems, mud fields, and bedforms which are clearly reproduced and can be drawn from the intensity images by visual analysis.