Implementation of Building with Nature (BwN) as Adaptive Concept to Prevent Coastal Erosion in Demak Regency, Central Java, Indonesia

Abstract

North Java, Indonesia's Shoreline degradation has become a severe problem along its coast. The gradually vanishing of the mangrove greenbelt indicates starting of coastal erosion. To overcome that problem, the adaptive concept using Building with Nature (BwN) is expected to become a part of the solution by enhancing the natural process. Construction of permeable structures was started in 2013. Its implementation was modeled using Delft3D. A coupling between Delft3DFlow and Delft3DWave is proposed. The model is conducted in two scenarios, coastal areas without and with permeable structures. Both were simulated in wet and dry seasons. It is analyzed on three years morphological scale. 10 observation points were determined in the front and back of structures. Those are utilized as control points to check the height of sediment trapped. Accumulation of sediment trapped in wet and dry seasons, and the coverage area was a dry season without structures. By adding a permeable structure, the maximum amount of sediment trapped in the wet season reaches 1.52 m in three years of simulation. It can be concluded that permeable structures constructed along the coast can trap the sediment. The placement, length, and number of structures should be considered to produce a wider coverage area. In the future, the sustainability of this adaptive concept is expected to enhance the coastal restoration in Demak coastal area.