Water Surface Level Monitoring of the Axios River Wetlands, Greece, Using Airborne and Space-Borne Earth Observation Data

This case study demonstrated how modern remote sensing data can contribute to the monitoring of flooding events. The study was carried out in an area of high environmental interest, the Axios river wetlands, Greece. The spatial resolution of satellite-image-based standardised metrics was increased with the use of UAV-obtained aerial images, equipped with an RGB camera. A strong relation
$(\mathrm{R}^{2}=0.85)$
was observed between the NDWI and a linear combination of RGB intensities of the aerial image, after averaging within the lower-resolution satellite-image pixels. Application of the derived model directly on a separate aerial image taken on the same day over a nearby location was highly successful in separating land from sea, in high-resolution. A more extensive evaluation is needed, with simultaneous in-situ observations, to assess the suitability of the method for flooded versus dry ground segmentation.