GIS and remote sensing for tracking morphological changes and vegetation coverage at the reach scale: the Po River case study

With the increasing availability of freely accessible satellite images and Geographical Information Systems (GIS), the use of remotely sensed information for monitoring riverine hydro-morpho-biodynamics is spreading, providing new evidence at multiple scales. In the present work, Landsat 4,5,7,8 images spanning the period 1986-2017 were processed via GIS for evaluating the morphological changes and the vegetation cover of a lowland 40-km reach of the Po River, in Italy. Two indices were analysed: the Normalized Difference Vegetation Index (NDVI) to evaluate the vegetation coverage and the Modified Normalized Difference Water Index (MNDWI) for monitoring the planar evolution of the channel. Aiming to consider the maximum growing period of the local vegetation, only images acquired in July were taken into account, and compared with the water discharge measured just upstream of the study site. The observed trends pointed out a tendency of the river towards an oversimplified morphology, characterized by a single main channel, relatively deep, with partially or fully vegetated banks. Such evolution was correlated with the local hydrology, highlighting that the reduction of flooding events can foster this oversimplification process