ALBERT

Description: Tsunamis are one of several processes that contribute to coastal remodeling. This research interpreted geomorphic features over time to better understand if a relationship exists between the flash remodeling of coasts, expressed by bidimensional-fractal dimensions, and known tsunami energy. Fractal geometry analysis, through the box-counting and correlation integral methods, was applied to the physiography of four oceanic coastlands: three in Sumatra, Indonesia, and one in Japan, hit by tsunamis in the last 14 years. Their shoreline fractal dimensions before and after the events and the present-day ones were calculated and compared. Results highlighted any difference or convergence of calculated fractal dimensions. Significant numerical variations of fractal dimensions of the shores before and after each tsunami were registered, and those values gradually decreased post-tsunami. These shorelines, considered stable before tsunamis, increased in physiographic irregularity up to 5–11% immediately after the phenomena; this slowly diminished to 2–5% about 8 to 15 years later; and finally to 3–6% present-day, compared to the pre-event shorelines. Considering these changes of the fractal dimension and the hydrodynamic energy of the tsunami, responsible for the abrupt coastal remodeling, a simple empirical expression and evaluation of the residual resilience is proposed. As a first step, a real physical meaning, in terms of energy, is attributed to the (dimensionless) fractal dimension.

Description: Urban-geomorphology studies in historical cities provide a significant contribution towards the broad definition of the Anthropocene, perhaps even including its consideration as a new unit of geological time. Specific methodological approaches to recognize and map landforms in urban environments, where human-induced geomorphic processes have often overcome the natural ones, are proposed. This paper reports the results from, and comparison of, studies conducted in coastal historical cities facing the core of the Mediterranean Sea – that is, Genoa, Rome, Naples, Palermo (Italy) and Patras (Greece). Their settlements were facilitated by similar climatic and geographical contexts, with high grounds functional for defence, as well as by the availability of rocks useful as construction materials, which were excavated both in opencast and underground quarries. Over centuries, urbanization has also required the levelling of relief, which was performed by the excavation of heights, filling of depressions and by slope terracing. Consequently, highly modified hydrographic networks, whose streams were dammed, diverted, modified in a culvert or simply buried, characterize the selected cities. Their urban growth, which has been driven by maritime commercial activities, has determined anthropogenic coastal progradation through port and defence or waterfront works. Aggradation of artificial ground has also occurred as a consequence of repeated destruction because of both human and natural events, and subsequent reconstruction even over ruins, buried depressions and shallow cavities. As a result, the selected cities represent anthropogenic landscapes that have been predominately shaped by several human-driven processes, sometimes over centuries. Each landform represents the current result, often from multiple activities with opposing geomorphic effects. Beyond academic progress, we believe that detecting and mapping these landforms and processes should be compulsory, even in risk-assessment urban planning, because of the increase of both hazards and vulnerability as a result of climate-change-induced extreme events and extensive urbanization, respectively.