Yuanita, N.; Kurniawan, A.; Setiawan, H.; Hasan, F., and Khasanah, M., 2019. Physical model of natural coastal protection system: Wave transmission over mangrove seedling trees. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 176-180. Coconut Creek (Florida), ISSN 0749-0208.

Erosion is one of main problem in coastal area. In order to solve erosion problem, currently natural coastal protection using vegetation such as mangrove is preferable in many places in the world. However, there are challenges in development of this natural coastal protection, e.g. mangrove-seedling-trees have been damaged by the waves or current, before they are growth strongly which required at least 2 years of plantation. To solve this problem, a natural coastal protection system consists of combination of main natural protection and temporary manmade structures is proposed. The study aimed to quantify the wave height reduction with various mangrove densities as well as the influence of mangrove seedling trees arrangements on wave reduction. The laboratory experiments were conducted in a narrow wave flume using model of mangrove as main natural protection and geotextile-geobag models as temporary manmade structure. Various wave conditions were generated during this laboratory test. This paper focus on the experiment results of wave transmission over mangrove seedling trees in order to determine the most effective configuration of mangrove trees plantation against wave. The results showed that the wave height reduction in area with mangroves was about two times larger compared to that in bare land. The wave reduction difference between tandem and staggered arrangements of trees was less than 20 %. It is also found that the temporary structure is significantly reduce wave height and protect mangrove seeds grow from waves attack.