Does anthropogenic morphogenesis contribute to geomorphodiversity in urban environments?

Urban geomorphology studies the landscape in cities, and changes induced by human activities to the natural landscape. Cities have different geological-geomorphological substrates, and humans as "geomorphic agents" have been operating within them in different times since the Paleolithic, threatening the Earth-surface heterogeneity and ecological sustainability, especially in urban areas. Urban geomorphology helps understanding natural and historical landscape evolution, changes to natural morphologies, and the effects of the development of cities on natural geomorphological processes. Quantitative geomorphodiversity describes the variety of landforms and morphological processes characterizing the landscape. Geomorphodiversity maps can be prepared using heterogeneous spatial data, at different geographical scales. Here, we adopt the land surface diversity index of Italy, which approximates field-based geomorphological maps. One relevant example of the latter, in Italy, is the geomorphological survey carried out in Rome, which integrates field surveys, historical maps, aerial photographs, archaeological and geomorphological literature. In this work, we compare the land surface diversity index, obtained with a simple and objective approach, with comprehensive geomorphological maps of locations describing the rural-urban gradient within the Rome urban area. We aim at understanding the representativeness of the geomorphodiversity index at the local scale, and its advantages and limitations, in urban areas. We describe a simple approach to compare the geomorphodiversity index and the geomorphological dataset. The method pins down to a common ground the five diversity classes, in the raster index, and the number of landforms mapped in the field, in the geomorphological map. Most notably, the latter distinguishes natural and anthropogenic landforms, allowing us a different assessment for these substantially different geomorphological elements. Results highlight that both natural and anthropogenic processes contribute to geomorphodiversity in urban environment, and in areas having different urbanization level. They are relevant to understand the anthropogenic morphogenesis impact on geomorphodiversity in urban environment.