Coastal setback: providing resilience against coastal disasters

Coastal setback: providing resilience against coastal disasters

In recent decades, human activities have increasingly become the primary cause of beach erosion due to, amongst others, sand mining and erecting structures too close to the waterline. Some researchers even stated that the major threats to the world’s beaches actually is not nature, but us: humans! It is scientifically agreed that climate change and rising sea levels will result in more frequent and intensity of natural disasters leading to more erosion. However, left to its natural condition, the shape of beach is considered to be in a dynamic equilibrium, i.e. its profile will recover roughly to its initial shape, at least seasonally. Sand replenishment on an eroded beach is dependent on sand availability in the nearshore and dune areas. Any hard engineering structure placed in these areas will inhibit the natural cycle of sand/sediment exchange on the beach, blocking sandy beaches from getting their sand supplies for replenishment. Hence, the creation of permanent coastlines at coastal developments takes away the natural ability of the beaches to ‘recover’ from erosion.

One of the sustainable ways to deal with coastal disasters are to provide an inundation area for protection in times of storm surges, leaving the area free of human settlement and/or infrastructure. A range of coastal sensitivity factors, such as the local topography, hydro-oceanography characteristics, the coastal ecosystem and the related socio-economics of the coastal communities, is used to determine how wide the area should be. Since the coastal area is often located across several administrative areas, this method/approach is best to be included in coastal zone planning regulations, both at the local and the central government level. The recommendation commonly used worldwide to address this regulation is called the coastal setback line determination.

The coastal setback line is defined as the distance from the shoreline within which hard construction is prohibited. Exceptions are often made for coastal defence constructions, preferably in the form of soft-engineering solutions. This expanse preferably also contains a buffer area protecting the landward area from any possible and predicted coastal disasters for that specific site. The coastal buffer zone is a vegetation area adjoining the coastal shoreline that can help to stabilise the coastline and to moderate the impact of storm surge floods. Basically, coastal setbacks are used in the framework of coastal hazard mapping and coastal adaptation to any future events, protecting coastal communities and infrastructure from natural disasters, as well as preserving coastal habitats and ecosystems. There are two types of coastal setbacks, i.e. the elevation setback, which is intended to overcome coastal flooding, and the lateral setback, that serves to deal with coastal erosion.

The coastal area is usually a narrow strip of land with high economic value where activities, such as tourism or property development often threaten the fragile environment. The Coastal zone also attracts more migration into the area when the economic sector flourishes there. Hence, the implementation of a coastal setback requires trade-offs between human safety and strategic economic sectors.

As the biggest archipelagic country in the world, laying on the ring of fire and near the faults occurring where the Eurasian and Pacific plates meet, Indonesia should be more thoughtful in implementing coastal setbacks regulations. The 2014 Presidential Decree and the related Ministerial Regulation on Coastal and Small Island Management stated that the area within a 100m landward distance from the highest tide line is deemed as the coastal setback area. According to the regulation, this area can be used for a single purpose or a combination of purposes, such as conservation, education, recreation and/or coastal defence zone. Each local government is expected to implement this regulation in its local land use planning. Some local government areas have accomplished better results than others, and, let’s face it, there are areas where this regulation is simply ignored. The implementation of a coastal setback line is inherently intended to protect public and private properties in case of coastal disasters, which is not a matter of if, but when it will happen. Seven years after introduction of the Ministerial Regulation, the question is: has it been applied correctly and who is in charge nationally, regionally and locally for regular and frequent oversight?