Recife

Abstract

Over the past decades the north-eastern coast of Brazil has been degrading due to erosion. This degradation has both natural- and men-made causes. Brazil has no specific laws and acts which relate to coastal protection and management up to this date. Beaches in the metropolitan area of Recife show variety in beach width according to the seasons. However the local factors play such a significant role in this, that it is not possible to establish a direct link between the seasons and beach width. Since the beginning of the 20th century, men has built structures all along this coast without proper guidelines. Wrong implementation of the structures has ,most probable, made matters worse. Another aspect is that men built structures (1970) on the backshore creating less back buffer which resulted in relative erosion. This paper entails the study of the coast of metropolitan Recife which is 45 km long. The goal of this study is to assess the area: to create solutions for their problems. The paper consist of two parts, part A and part B. Part A consists of a study of the entire coast of metropolitan Recife. Part B focuses on Boa Viagem, an area of 2.78 km within the metropolitan area of Recife. In order to assess the entire area more suffiecient, the area has been split up into 7 parts, from north to south: Janga, Casa Caiada, Bairro Novo, Fortim, Boa Viagem, Piedade and Candeias. All these areas have been studied in order to find the cause of erosion, and possible solution. This has been done by preliminary assessment, where the current structures are observed; a problem assessment, this study emphasizes each area’s problem and probable causes; and finally a solution assessment where possible solutions are represented. The total area of the coast of metropolitan Recife consists of men-made hard structures such as groynes, breakwaters and revetment. But has also natural breakwaters such as reefs. The presence of the latter makes study of this coast highly complex. The area has one major and one minor source of sediment. The major is the sediment that is transported in the littoral drift. The minor source is sediment being discharged by the rivers in the area. The sediment is fine to medium size sand. The current level of “protection” is highly ineffective and has made matters worse in many cases such as Casa Caiada. The level of protection can be classified as poor. Initially, the area was thought be a flood risk, however, closer inspection has revealed that coastal flooding is a non-issue in the metropolitan area of Recife. The amount of erosion cannot be limited but only displaced if hard measures are deployed. If sediment is trapped in one area, another area will be adversely affected. The only solution to sediment deficiency is introducing additional sediment in the area. Part B focusses on Boa Viagem, an area of 2.78 km long with probably the most economic value. The coast of Boa Viagem has healthy beaches but also shows signs of erosion. The area consist mostly of reefs, but also has revetments and a harbor. Different solutions for Boa Viagem have been presented, via a Multi Criteria Analysis one has concluded that a solution of only nourishment will be applied. The nourishment will be dredged by a hopper, 10 km off the coast. The hopper transports the sand with the aid of a pumping system through a 2.5 km piping system to the beach. The nourishment will be spread by a bulldozer and a scraper. In order to maintain the beach, re-nourishment will be done every 5 years. The total amount of initial nourishment is 1.2 million m³ sand. And for re-nourishment 0.5 million m³ sand has been calculated. The whole operation cost R$ 143 mln ( € 60 mln ) during a period of 50 years, this includes: initial nourishment, re-nourishments and interest etc.