The terms of reference for a monitoring tool were defined in close cooperation with the end-users which in first instance consisted of the team responsible for floodplain vegetation management and the state forestry agency, one of the bigger landowners in the floodplains. We had ample discussion on the requirements of the end-users, such as ‘the tool must be usable in the field e.g. using a tablet with GPS functioning’, ‘the tool must allow for quick analysis per cadastral plot’ and ‘information must be downloadable for further processing in GIS if needed’. The basic terms of reference were:
The added value of year-maps was only later recognized as there was a need for a map with the highest possible accuracy that could be used in communication with all stakeholders, and would be less affected by inaccuracies in single image classifications as a result of e.g. atmospheric disturbances. The on-the-fly single date-maps gave a good up-to-date insight, but different stakeholders could confront each other with different day-maps. Also, for reference in communication, a more stable year-map was thus preferred. Also, time series were added to allow for a better understanding of the development of vegetation through the years and have a better approach for areas where changes in vegetation type fluctuated through the years, due to the management of the area.
The overall technical classification workflow is visualized in Figure 3. For data-retrieval, pre-processing and classification is carried out on the Google Earth Engine (GEE; Basic remotely sensed data consisted of Sentinel-2 MSI (Level-1C) data and the Dutch LiDAR based AHN (0.5m raw samples), both are available through GEE. Including Lidar-based data in the classification improves results for floodplain vegetation