Ingleses - Brazil: Solutions to urban problems due to coastal morphology

Abstract

Master project report. This report describes the research done by the authors to the erosion and dune migration problems in the town Ingleses. Ingleses is located in the north of Ilha Santa Catarina in Brazil. This report describes a follow-up research on the research in 2007 of project group CF71 from Delft University of Technology. The beach erosion in the embayed beach threatens the buildings at the southern stretch of the beach. Furthermore, a large dune field, Moçambique Dune, is migrating towards the north and encroaches houses in the southern part of Ingleses. The aim off this report is to give better insight in the problem and present a solution. Research has been done to investigate the migration speed of the dune and the erosion rate of the beach. This is done by a photo analysis. Aerial photographs from several years and a Geographical Information System are used for this purpose. The average migration speed since 1938 of Moçambique Dune is a little more than three meters per year. In the southern part of Ingleses, the beach erodes one to two meters per year since 1960. The zero-solution is also a part of this research. Using the migration speed of the dune, the damage is quantified in case no measures are taken. Also the damage at the coast is quantified with the use of the erosion rates. Especially the damage at the coast will be significant. This zero-solution is a reference situation for the solution presented in this report and gives insight in the scale of the problems. A maximum loss of 1,5 million euro’s per year is expected in case no actions are taken. The solution presented in this report is a beach nourishment. For the nourishment, sand will be used from Moçambique Dune. This way, two problems are solved at the same time. For the design fill a beach width of 38 meter will be constructed. Also an advanced fill is calculated for a design lifetime of 10 years. The design fill is calculated with the erosion rates calculated with the photo analysis. The fill sand from the dune is coarser then the sand from the native beach. For this reason the beach will be steeper after the nourishment. In the report the construction method for the nourishment is also considered. Two construction methods are elaborated, the use of trucks and the use of pumps and pipelines. For both methods an estimation is made for the construction time and the construction costs. Both construction methods are compared in a Multi Criteria Analysis (MCA). In this comparison the pipelines turned out to be the better method. However, this method is more expensive. The zero-solution and the nourishment are also compared in a MCA. In this comparison the nourishment turned out to be the better solution. The nourishment is also the cheaper solution. Another aim of this project is the improvement of the numerical model made in 2007. Some scenarios are modelled in this research. The first scenario is the situation from 1938 when the sand from Moçambique Dune was an input of the system. Other scenarios are investigated to analyze the bypass at the northern headland. Finally, the scenario with the designed nourishment is modelled. The numerical model appeared to still be extremely sensitive to several parameters that still are not well-known like the wave characteristics and sediment bypass. Further extensive research to these parameters is necessary in order to obtain a reliable model. During this research a lot of additional data about the coastal system around Ingleses is collected and analyzed. Assumptions are verified and a better insight in several important parameters is given. It is concluded that a nourishment is a suitable and feasible solution for the erosion problems. The sand from the Moçambique Dune can be used for this nourishment which is a suitable solution for the encroachment problems as well.Hydraulic EngineeringCivil Engineering and Geoscience