Identification of Rip Current Hazards Using Fluorescent Dye And Unmanned Aerial Vehicle (A Case Study Of Drini Beach, Gunungkidul, Indonesia)

Abstract

Abstract. Coastal tourism is a leading sector substantially contributing to the regional income of Gunungkidul Regency, Indonesia. However, with more tourists visiting the beach, more lives are threatened by coastal hazards. Rip currents are a channel of powerful, narrow, fast-moving water that can carry floating objects away from the shore, presenting one of the most common coastal hazards to swimmers. Unfortunately, most tourists are unaware of rip currents and their threats and how to avoid them. This study was designed to identify the types and dimensions of rip current in one of the regency’s tourist attractions, Drini Beach. For this purpose, an environmentally friendly fluorescent dye, Uranine, was injected from the shoreline, then the velocity and direction of its movements were observed from aerial video footage captured with a drone. Results showed stationary rip currents with a narrow channel, called a channel rip, with the mean dimensions: 250 m from the shoreline to the head and 10.25 m in width. A break in the reef flat can mostly generate rip currents at Drini Beach. It creates an area that is deeper than the surrounding reef flats through which water and the transported coastal sediments can flow easily offshore. Rip currents identified in this research provide the basis for disaster mitigation measures to reduce fatality.

Coastal hazards mapping using high-resolution UAV image and DEM. A Case study in Siung Beach, Gunungkidul, Indonesia

“…This type of rip current is stationary and persistent, with a specific time occurrence controlled by the tides. Therefore, the mitigation for an accident can be performed by the safeguards by directly prohibiting the swimmers or using markers in the hazard area [26].…”