Temporal evolution and interactions of landslides and urban areas revealed by air-photointerpretation and morphometric analysis

Based on multi-temporal mapping from air-photointerpretation, this contribution shows that the urban expansion of two Italian villages in the second half of the last century was substantially driven by the proximity to the pre-existing historic center, regardless of the presence of landslides (Zumpano et al., 2020). This is due both to a better accessibility to pre-existing services and sub-services, and to the lack of adequate knowledge - or the general underestimation - of the landslide hazard conditions adjacent to historic centres.  In both vilages, this circumstance led to building on portions of pre-existing landslides - evidently not known, or considered stabilized - which were subsequently reactivated, posing serious risk conditions. These areas were investigated by deriving multi-temporal DEMs from the historical aerial photos (Santangelo et al., 2022) previously interpreted and using the Geomorphodiversity Index (GmI) (Burnelli et al., 2023) as a proxy for the morphometric modifications introduced by progressive urbanisation. Results demonstrate that in both cases investigated, the anthropic modifications of naturally achieved equilibrium conditions - measured by high differences in GmI before and after urbanization - were the most probable cause predisposing the partial reactivations of dormant landslides. This opens at the possibility of using GmI variability as a measure of the onset of potential geomorphological critical issues associated with new urbanizations, and possibly, computing the expected GmI variabilty already at the design phase, benefiting an adequate territorial planning. Overall, this study suggests caution in the urbanization of areas exposed to landslide hazards, even if landslides are considered dormant, and related hazard is only potential.

 

References:

Zumpano, V., Ardizzone, F., Bucci, F., Cardinali, M., Fiorucci, F., Parise, M., Pisano L., Reichenbach, P., Santaloia, F., Santangelo, M., Wasowski, J., Lollino, P. (2020). The relation of spatio-temporal distribution of landslides to urban development (a case study from the Apulia region, Southern Italy). Journal of Maps, 17(4), 133–140. https://doi.org/10.1080/17445647.2020.1746417

Burnelli, M., Melelli, L., Alvioli, M. (2023). Land surface diversity: a geomorphodiversity index of Italy. Earth Surface Processes and Landforms., 48(15), 3025–3040. Available from: https://doi.org/10.1002/esp.5679

Santangelo, M., Zhang, L., Rupnik, E., Deseilligny, M. P., and Cardinali, M. (2022). Landslide evolution pattern revealed by multi-temporal DSMS obtained from historical aerial images, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLIII-B2-2022, 1085–1092, https://doi.org/10.5194/isprs-archives-XLIII-B2-2022-1085-2022, 2022