Geomorphological mapping in urban area: changes in stream network of Genoa historical city (Liguria, Italy)

All over the centuries the expansion of residential, industrial and harbour settlements of Genoa city have impacted on geomorphological processes along the narrow coastal plains and surrounding slopes. Mostly the drainage network has been strongly modified by rectification, diversion and culvert interventions, causing critical flow section reductions (Limoncelli & Marini, 1971; Brandolini & Sbardella, 2001). These morphological changes resulted in increasing geo-hydrological hazard and, consequently, Genoa municipality has been affected by even more recurrent floods (Brandolini et al., 2012; Faccini et al., 2015). This research focuses the attention of Genoa Old Port and surrounding area - where historically town developed - with the aim to reconstruct the former stream network, culverted since Middle Ages and currently almost totally underground. The final goal is to perform a G.I.S. based geomorphological map applying the proposal of legend in testing progress within AIGeo. The study is based on comparison among ancient and recent maps, aerial photointerpretation, historic archives data, geotechnical investigations conducted for engineering purposes and field survey.The area, with an extent of about 8.5 km2, is characterized by several catchments, from W to E: San Bartolomeo (0.49 km2), San Lazzaro (1.33 km2), San Teodoro (0.54 km2), Lagaccio (2.36 km2), Sant’Ugo (0.8 km2), Carbonara (1.1 km2), Sant'Anna (0.72 km2) and Torbido (1.17 km2). These watercourses, modified over time in channels and nowadays with a man-made hydraulic network catchments, flow culverted under the streets of the old town (Bixio et al., 2015). A more detailed knowledge of these underground streams could contribute to a better evaluation of geo-hydrological hazards and planning of risk mitigation measures for supporting Basin Master Plan of Genoa metropolitan area