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Sviluppo ed analisi di proposte di ICZM-MSP in aree specifiche: costa emiliano-romagnola. Volume 1: Quadro conoscitivo di riferimento e sua analisi ai fini della pianificazione dello spazio marittimoICM-MSP nella Regione Adriatico Ionica

open 8 no Multiple processes contributing to natural land subsidence in a shallow coastal aquifer near Ravenna (Italy) were identified by analysing the relationships among different data set time series (water table level, rainfall, land reclamation drainage, sea level, etc.) and establishing the correlations with vertical ground motion observed at a high-resolution settlement gauge. Our study highlights the presence of three deformation components related to different processes controlling land subsidence: elastic, delayed-elastic, and irreversible (plastic) components. The elastic and delayed-elastic components are closely related to water table fluctuations that change the effective stress in two portions of the coastal aquifer at a daily (in the sandy unconfined portion) and seasonal time scales (in the layered clay-rich semi-confined prodelta portion), respectively. The irreversible component represents the trend in the land subsidence time series and is due to primary consolidation (pore pressure dissipation) of the fine-grained prodelta levels above where the settlement gauge is located. The amplitudes of the elastic component can be up to 0.2–0.3 mm whereas the amplitude of the delayed-elastic component reaches 0.89 mm. The primary consolidation rate of deformation is 0.9 mm yr−1 and constrains the likely age of prodelta sediments deposition to 1300–2800 years before present. The delayed-elastic subsidence rate has similar magnitude to that due to primary consolidation and is connected to poroelastic effects in the prodelta sequence following seasonal variations in water table. Our findings are important for planning land subsidence management and monitoring strategies especially where the surface aquifer structure is heterogeneous due to different depositional settings. The natural land subsidence rate in the Holocene sediments of the shallow coastal aquifer of Ravenna (North eastern Italy) that we measured in this study accounts for 10 %–20 % of the total current land subsidence rate observed in this portion of Ravenna coastal area (10–20 mm yr−1). open Antonellini, Marco; Giambastiani, Beatrice Maria Sole; Greggio, Nicolas; Bonzi, Luciana; Calabrese, Lorenzo; Luciani, Paolo; Perini, Luisa; Severi, Paolo Antonellini, Marco; Giambastiani, Beatrice Maria Sole; Greggio, Nicolas; Bonzi, Luciana; Calabrese, Lorenzo; Luciani, Paolo; Perini, Luisa; Severi, Paolo

As a consequence of climate change and land subsidence, coastal zones are directly impacted by sea-level rise. In some particular areas, the effects on the ecosystem and urbanisation are particularly enhanced. We focus on the Emilia-Romagna (E-R) coastal plain in Northern Italy, bounded by the Po river mouth to the north and by the Apennines to the south. The plain is ∼ 130 km long and is characterised by wide areas below mean sea level, in part made up of reclaimed wetlands. In this context, several morphodynamic factors make the shore and back shore unstable. During next decades, the combined effects of land subsidence and of the sea-level rise as a result of climate change are expected to enhance the shoreline instability, leading to further retreat. The consequent loss of beaches would impact the economy of the region, which is tightly connected with tourism infrastructures. Furthermore, the loss of wetlands and dunes would threaten the ecosystem, which is crucial for the preservation of life and the environment. These specific conditions show the importance of a precise definition of the possible local impacts of the ongoing and future climate variations. The aim of this work is the characterisation of vulnerability in different sectors of the coastal plain and the recognition of the areas in which human intervention is urgently required. The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) sea-level scenarios are merged with new high-resolution terrain models, current data for local subsidence and predictions of the flooding model in_CoastFlood in order to develop different scenarios for the impact of sea-level rise projected to year 2100. First, the potential land loss due to the combined effect of subsidence and sea-level rise is extrapolated. Second, the increase in floodable areas as a result of storm surges is quantitatively determined. The results are expected to support the regional mitigation and adaptation strategies designed in response to climate change.