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Sea Level Rise, causes, consequences, and environmentally friendly techniques aimed at coastal protection: online educational and informative resources - Part 1

摘要


A rise of 0.6 m in sea level is a likely figure for 2100, this is mainly consequent to land ice melting and thermal expansion; this latter is expected to continue for centuries even if climate forcing is stabilized. The change in sea level is regionally different as a consequence of several factors, such as currents and gravitational weakening. While, for instance, east of the Philippines the sea is rising three times faster than the average, around Greenland the level is decreasing. Here, the huge ice loss is weakening the local gravity which implies a lower attraction for oceanic water and, despite the factors that increase the sea level, this latter is decreasing. Coastal subsidence can be much quicker and threatening than sea level rise. This happens in particular in mega deltas that undergo, e.g. natural compaction of sediments, deforestation, interruption of sediments inside embanked areas, groundwater and hydrocarbons withdrawal. The vulnerability of the coasts is intensified by the trend of human development in coastal areas that amplifies the challenges for coastal management. The paper and the documents that it presents deal with environmentally friendly techniques aimed at mitigating coastal erosion and subsidence. The loss of mangrove forests and the loss of sediments trapped in the dams may contribute to amplify problems of subsidence and coastal erosion. Extensive mangrove areas, and the important ecosystem services that they provide, have been lost during past decades. In order to help mangroves to grow again in those areas, protection against the waves and restoring the presence of sediment are the necessary steps. Mangrove soil surface has already exhibited the possibility to undergo elevation, thus keeping pace with sea level rise and persisting even over thousands of years. The sediments that typically accumulate in reservoirs, besides reducing the functions of a dam, deprive the environment of materials that prove crucial, e.g. in facing coastal erosion. This is why they are considered "resources out of place". For these reasons the prevention or the minimization of the sedimentation in a reservoir should be always incorporated in both design and management of a dam. Some of the documents quoted herewith describe methods that can be used to keep or even to restore the original volume of a reservoir. Nowadays the current global rate of net storage loss consequent to sedimentation exceeds the rate of new storage construction.

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