Submerged breakwaters3/18/2023 Therefore, it is recommended to carry out artificial nourishment operations rarely enough to let the environment recover after a disturbance. In addition, ecologists claim that interventions in the sea bottom, associated both with dredging and beach fills, are harmful to the benthic ecosystem. Similarly to the other means of shore protection, the artificial nourishment is accompanied by a number of problems and constraints related, for instance, to the availability of sediment borrow areas with sand of appropriate quality. It can be applied as the sole shore protection measure or as a supplementary method, supporting the existence of “hard” engineering defense in the form of groins, breakwaters or revetments. In case of intensive erosion and significant deficit of sediments, the artificial shore nourishment is most effective. These criteria can be met by applying the artificial shore nourishment or construction of submerged breakwaters. Nowadays, there is a clear preference to implement the shore protection methods which are environmentally friendly and invisible to tourists, whenever possible. It should be pointed out that many of the currently occurring groin systems were built a long time ago and therefore, the technical condition of some groins is inferior, presumably causing their lesser effectiveness. Such a length of groins is favorable to recovery of the natural nearshore sea bed profile, improves the shore stability, prolongs the nourishment duration and raises the effectiveness of the groin system. (2004), the groin tip should reach the first underwater bar, particularly if the shore is artificially nourished. Thus, the meaning and efficiency of groins strictly depend on both the availability of appropriate sand and structural issues. The supply of sandy material can be natural (longshore sediment transport) or artificial (shore nourishment). In particular, the coastal sea bed profile together with the nearshore resources of sandy sediments and the resulting morphodynamic processes play an important role. Groins, especially in the form of timber palisades, are relatively cheap and easy to build, but their effectiveness largely depends on the technical condition, as well as local environmental factors, mostly parameters of hydrodynamic and lithodynamic processes. In the previous decades, revetments and groins were the most popular coastal protection structures ( Pilarczyk & Zeidler 1996 Kunz 1996). The protection activities are preceded by decisions on technical measures to be applied. As coastal regions are densely populated and additionally attractive for tourists in the summer season, the shore protection against erosion and flooding is necessary. As a result, many seashores, mostly the sandy ones, are gradually but permanently retreating. Recently, coastal changes hae become increasingly intensive. The coastal zone is subject to continuous evolution due to the influence of waves and currents.
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