Geomorphological and hydro-oceanographic analysis related to the characteristics of marine debris on the south coast of Yogyakarta, Indonesia

Abstract

Bantul Regency in Yogyakarta has a shoreline of 16.85 km and is famous for its beach attractions, including Baru and Samas beaches. In Bantul, the Progo river is also recorded in the top 20 rivers globally, contributing to plastic waste pollution in coastal areas. Therefore, the problem of marine debris in Bantul is a serious matter because it can impact the environment and the tourism sector. However, marine debris characteristics in Bantul are still poorly understood. This research aims to determine the characteristics of meso- and macro-sized marine debris, its source and transportation, and the geomorphic and hydro-oceanographic processes that may affect it. A combination of geospatial analysis of high-resolution aerial photographs, field surveys with the transect method, and GIS approaches are used to achieve those objectives. Research shows that the marine debris found at Baru and Samas beaches in Yogyakarta is 149 pieces and 95 pieces, respectively. Macro-sized marine debris was dominantly found in Samas (80%), and meso-sized marine debris was dominantly found in Baru (67%). The total mass of marine debris in Baru and Samas beaches is 129 g and 1722 g, respectively. The vast amount of marine debris and smaller size in Baru is thought to have originated from land and was carried away by fluvial processes in the wider (2462.08 km2) and more elongated (Rb: 0.355) Progo watershed. Meanwhile, the larger mass of marine debris at Samas may be caused by the reflective beach typology (ε: 52.86), which can carry a higher abundance of marine debris.