Extreme rainfall causing floods and great damage occurred in many areas of central-east Sardinia in the period 6–11 December 2004. A total of approximately 700 mm of rain was measured during this extreme event, with a maximum reaching 510 mm of rainfall in 1 day at the rain gauge of Villagrande (Ogliastra). During and immediately after the event all fluviokarstic canyons were activated for at least 1 week, reaching the highest water levels in at least 50 years and reversing great quantities of sediment-loaded water onto the coast and with important geomorphical modifications. There was public fear that serious damage to the natural resources would occur, such as the famous Cala Luna beach that was almost completely destroyed by the flooding of the Codula Ilune River and by the coinciding sea storm. The river, in fact, eroded the longshore bar (beach) and destroyed the small backshore lagoon. A monitoring study has been initiated in order to analyse the natural evolution of this littoral system and to define the resilience of this interesting geomorphosite. The observations have shown that the flood, albeit impacting negatively in the moments immediately after the disaster, almost completely restored the natural equilibrium of this coastal karst geo-ecosystem within a season.

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The stability of embankment dams without an impermeable core depends on the characteristics of the face slab that prevents internal erosion, piping and eventual collapse of the structure. Under a Mediterranean climate, the impermeable asphaltic face slab is subjected to high solar radiation and consequent temperature changes, which can generate the creation of cracks and joints. The Medau Zirimilis dam, located in the Casteddu River (Sardinia), is an embankment dam that has undergone seepage and continuous repairs in its asphalt face slab. These reparations have been conducted because of the occurrence of cracks and relative movement of different segments of the slab. To evaluate if seepage endangers the integrity of the dam, GPR was used, with different antennas (100, 250 and 500 MHz), along its crest and upstream and downstream faces, and the data were integrated with infrared thermographic images. Although geophysical data do not show structural changes affecting the main dam structure, deformation structures at shallow levels and in particular in the upstream face and along the crest of the dam have been identified. Such deformation affect s the road atop the crest, the face slab and underlying levels, resulting in landslides that include material from several meters below the surface. The analysis permitted the identification of the origin of surficial cracks and their effects on the face slab. These sectors, independent of current

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