Shore protection is vital for the sustainable development of coastal zones. The later are indeed unique and valuable areas in the sense that they are favoured as habitats by humans and wild life alike. Worldwide, over 65 % of the large cities with more than 2.5 million inhabitants are located in coastal areas, deltas and estu¬aries, and almost 40 % of the population of our planet are living within a 100 km wide coastal strip. Moreover, each coastal zone represents a unique ecological and morphological environment which has been developed through millennia without great human inference such as industry, transportation, tourism, etc. Though coastal zone represent only 6 % of the total planet surface, the coastal ecosystems provide almost 40 % of the value of the services of all ecosystems of our planet (Oumeraci, 2000). Therefore, the basic dilemma primarily consists in the dramatically increasing pressure (urbanization, tourism, industry, etc) on coastal zones and the necessity to protect both human lives and assets against natural hazards, and on the other hand in the necessity to preserve the valuable coastal ecosystems. Methods and techniques to overcome this dilemma are therefore urgently needed. One of the solutions is the use of so-called “soft” shore protection such as geotextile structures which can more equally fulfill both socio-economic and environmental development criteria than the commonly used hard coastal structures worldwide. However, to increase the acceptance of such soft structures more research is urgently needed.With this background my research in the frame of the DBU scholarship consists of two working packages (WP1 & WP2):(i) WP1 concentrates on long-term durability of geo-synthetics, which includes the analysis of all related processes and mechanisms. Among them are the ones closely connected to the marine environment, such as chemistry and biology of the seawater, abrasion caused by the sediment laden flow, fatigue caused by the action of the waves. Moreover, the relative importance of other effects is also being analyzed, with a particular focus put on the UV radiation. Further, WP1 will also include the analysis of the available tools and techniques to assess the long term durability of geotextile structures applied for shore protection. This analysis will lead to a development of a conceptual framework and methodology to predict the lifetime of such constructions which will contribute substantially to a sustainable shore protection. (ii) WP2 deals with the susceptibility of geo-synthetics to marine growth. A rapid development of marine organisms on the surface of geotextile was observed in most of the built marine structures, especially in Australia. The amount and type of the developing organisms depends on the type of geotextile material and the local environmental conditions. The most commonly observed organisms are for instance barnacles, red algae, ascidians, crabs, annelids, polychaetes, sponges and shrimps. However, a systematic study summarizing all these observations which were gained from isolated case studies is still lacking. Moreover, an additional layer of marine organisms developed on the surface of the geotextile material is expected to improve the durability of the structure, for example by protecting it from the UV radiation, but it is still not clear how the other engineering properties of the geotextile will be affected by the organisms. WP2 will therefore focus first on analyzing the data from worldwide available surveys, which will result in recommendations on the effect of geo-synthetics on marine ecosystems as well as on the effect of the ecosystems on the engineering properties of the geo-synthetic material. Overall, WP1 & WP2 will provide a consistent package of knowledge on the interaction of coastal structures made of geotextile and the marine environment, including a conceptual framework for sustainable shore protection using geotextiles. Moreover, the knowledge gaps will also be more clearly identified. The results are therefore expected to have a substantial impact worldwide on the applications of geo-synthetics for various classes of structures in the marine environment, but also on future research directed towards filling the identified knowledge gaps as well as towards the full practical implementation of the proposed conceptual framework.
01.03.2011 - 31.12.2011
Technische Universität Braunschweig
Leichtweiß-Institut für Wasserbau
Abteilung Hydromechanik und Küsteningenieurwesen
Prof. Dr. Hocine Oumeraci
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