Fig. 5

Representative example of the extraction of features related to the historical hydrological networks. In these images it is possible to identify the old Beas dry course (1), which is drawn in the historical SoI maps and is still visible in RS imagery (1: B–H). Three other paleochannels (2, 3 and 4), are also drawn on the SoI map (2–4: C), but are not visible in nowadays aerial imagery (2–4: B). Finally, a large trace of a disconnected oxbow was not drawn on the SoI maps (5: C) and is not visible in the aerial imagery (5: B). Those features are present and detectable in modern topography, and local relief-based visualization techniques such as MSRM (D) are very useful in rendering them visible. These features can be also intuited examining vegetation indices, but they are much more subtle and difficult to interpret. In the study area the longer series of Landsat 5 images (E) have been more useful than Sentinel 2 (F), even with the difference in resolution. In the latter case, Spectral Decomposition techniques (PCA) based on the wet periods is giving slightly better results (G, H)