Shoreline Changes in Tuban District in East Java Caused by Sea Level Rise Using Bruun Rule and Hennecke Methods

Abstract

Changes in the shoreline setback is a major threat of coastal areas dominated by sandy beaches and coastal lowlands. The impacts of sea level rise itself will be greatly felt by coastal regions in the island nations, such as Indonesia. Tuban is one of northern coastal areas in East Java, which includes the areas where the condition of beaches damaged. Thus, it is necessary to investigate the characteristics of beaches in Tuban, and how much the sea level rise occurs in Tuban district as well as the extent of its influence on the shorelines of Tuban. The calculation of sea level rise was predicted using the Least Square Method with tidal data of Semarang city in 1985-2014 which was later adopted as the tidal of Tuban, and the sea level rise at the beaches in Tuban, which was estimated at 0,024 meter annually by implementing the equation of y = 0.002x + 0.751. In the year of 2050 and 2100, the rise of the sea level reaches 2.55 m and 3.54 m respectively. The most appropriate method used is the Hennecke method, with the error value of 0.27%. The error value of Hennecke method is smaller than the error value of Bruun Rule method, which reaches 0.38%. Using Hennecke method, the prediction of the shoreline changes in Tuban with the starting point of the year of 2008 shows that the average shoreline retreat in the year of 2050 is about 94.71 meters and in 2100 is about 234.2 m. However, by using the method of Bruun Rule, the average shoreline retreat in the year of 2050 is about 161.27 m, and in the year of 2100 is about 349.16 m. The adaptation strategies that can be conducted to minimize the impacts are (i) protective pattern, (ii) accommodative pattern, and it is better to have a Strategic Area Construction Plan.