An environmental and economic analysis for geotube coastal structures retaining dredge material

Abstract This paper investigates the environmental and economic sensitivity of coastal structures for two different construction methods; a traditional rubble mound structure and a geotube coastal structure using dredged material. The analysis is undertaken for two projects: a small scale coastal protection project using a revetment and a medium size capital harbour expansion using a breakwater. This work provides further insight into previously published work by Sheehan et al. (2009) on the economic aspects of geotube technology and identifies the optimum method of construction for each type of coastal structure. An economic sensitivity analysis is undertaken on the key logistical parameters involved in the construction of these coastal structures. An environmental sensitivity analysis focuses on the CO 2 emissions produced from the construction of the coastal structures for both construction methods. These sensitivity analyses are undertaken using a decision support software program (DMMAP), developed to assist users at the planning stages of a project to achieve sustainable dredge material management. The key logistical parameters are analysed to generate environmental and economic ranking tables. The analyses highlight that the size of the structure and the distance to the source of the quarry material are crucial factors in determining the optimum construction method. This work shows that geotubes are a viable alternative to traditional rubble mound coastal structures. It also shows that traditional construction methods may be more economical than geotube structures when considering small coastal structures. In general, the larger the scale of the project the greater the potential savings in CO 2 emissions and cost that can be achieved through the use of geotube technology. Geotubes, with the use of dredge material, may provide a sustainable beneficial use for dredge material and offer a serious economic and environmental alternative to traditional rubble mound structures.