High resolution DEMs for the analysis of fluvial and ancient anthropogenic landforms in the alluvial plain of Padua (Italy)

The alluvial plain around Padua results from the sedimentary activity of the Brenta and the Bacchiglione rivers since the last glaciation to the modern times. The inner and oldest part of the city developed on the banks of a former meander of the Brenta River, later occupied by a minor course, the Bacchiglione. Early archaeological evidence dates back to the final Bronze Age and the first urban settlement started in the Iron Age. The underground of the city centre consists of alluvial sediments overlaid by Iron Age, Roman, and Medieval archaeological deposits. A comparison of high-resolution DEMs, built from different datasets (CTR, CTR-n, CTC maps; LiDAR), is presented. This comparison shows how the accuracy and density of spot heights influence the derived geomorphological interpretations. LiDAR data have the potential to generate a very accurate DEM, even if it is very sensitive to local topographic anomalies and the specific conditions of acquisition. Only the CTC DEM can really be compared to LiDAR in terms of resolution: whereas the CTR DEM provides a good approximation of the mean surface of the alluvial plain, it also tends to «over-smooth» both natural and ancient anthropogenic landforms. The CTR-n DEM has higher resolution than the CTR but it is less suitable for geomorphological analysis. The LiDAR and the CTC DEMs, integrated with remote sensing data, provided new insights on the geometry of fluvial landforms at different scales, from single levees and bars to large alluvial ridges and interfluves. Moreover, these allowed for a high detailed investigation of the morphology of the archaeological mound in the city centre for geoarchaeological purposes.