Coastal erosion is a significant hazard that causes heavy loss of land and damage to structures in coastal areas globally. To mitigate this problem, coastal engineers worldwide are focusing on sustainable coastal development practices. To this end, many countries are using natural protective methods, including vegetation such as mangroves. However, this practice is not without challenges; to ensure that mangroves could grow strongly required at least two years. A natural coastal protection system is the proposed solution, which combines mangrove vegetation as the main structure and geo-bag-dykes as temporary structures to solve this problem. The role of geo-bag-dykes is needed until mangrove plants mature. So, the length of time for geo-bags to degrade naturally is vital to get considered because otherwise, it will become hazardous coastal debris. Today, commonly used geo-bags are made from synthetic fibers that take a long time to degrade. Thus, this study tested alternative materials made from natural fibers, such as lyocell, kenaf, cotton, and rayon. The objective is to determine whether these alternative materials can be used as sustainable geo-bag materials or not in terms of biodegradation. Based on the soil burial test results contained in ISO 11721-1, these alternative materials degrade much faster when compared to commonly used geo-bag materials.

The natural coastal protection system is a proposed solution to the coastal erosion problem, including in Indonesia’s coastal areas, which combines primary natural protection (vegetation such as mangroves) and temporary artificial structures as sustainable coastal development practices. The geo-bag-dike was chosen as a possible temporary structure to protect the growth of mangrove seedlings from sea waves for about two to five years before they are strong enough to prevent erosion. In today’s practice, the geo-bag-dike is made of polymeric synthetic fibers (nonwoven geo-bag), which take a relatively long time to degrade naturally. Thus, this study focused on finding sustainable alternative materials from natural fibers, such as lyocell (Tencel), kenaf, cotton, and rayon, that can be applied as the primary material of geo-bag-dikes by comparing their material properties to nonwoven geo-bag. The results of the laboratory testing method show that kenaf textile has the highest values of tensile and tearing strength, but not higher than nonwoven geo-bags (768 N, 1080 N, and 2140 N for the tensile strength of kenaf, local nonwoven geo-bag, and imported nonwoven geo-bag, respectively). Therefore, kenaf textiles have the potential as a sustainable alternative material. By extrapolating, it is necessary to increase the layer number of kenaf textiles to at least three layers of fabric to resemble the tensile strength of nonwoven geo-bags.