Cloud computing using Google Earth Engine and Sentinel-1 imageries to detect changes in coastal city water bodies during rainy season
Muhammad Banda Selamat (a), Mahatma Lanuru (a), Muhammad Rijal Idrus (b)

a) Marine Science, Universitas Hasanuddin
Jalan Perintis Kemerdekaan km 10, Makassar - Indonesia
* mbandaselamat[at]unhas.ac.id
b) Climate Change Center, Universitas Hasanuddin
Jalan Perintis Kemerdekaan km 10, Makassar - Indonesia

Abstract

Flooding in low-lying urban coastal areas often occurs during periods of extreme rainfall. Although such floods are temporary, they can cause devastating damage and disrupt transportation and economic activity. As a coastal city, Makassar is faced with extreme tidal phenomena as a result of climate change, which under certain conditions contributes to flooding events. This study aims to spatially detect inundations of water bodies in the rainy season in Makassar City in the 2018, 2019, 2020, 2021 and 2022 periods. A number of Sentinel-1 images that work on microwaves and are available on Google Earth Engine have been deployed and processed using Cloud Computing Technology. Water bodies and land were distinguished by backscattering values of VV polarization using Threshold and Boolean techniques. Water body images were converted from raster to vector and polygon areas were calculated. The largest body of water occurred during the 2021 wet season, at about 1,389 ha (1,787 points), and the lowest at about 986 ha (1,653 points) in 2022. Over the five year period from 2018 to 2022, Manggala, Tamalanrea, Tamalate and Biringkanaya districts have the largest water bodies during the wet season. During this period, the area of water bodies varied between 6% and 8% of Makassar city^s total area, with a trend of decreasing by about 1%.

Keywords: Sentinel-1, radar, water body, Makassar

Topic: Marine and Fisheries Geographic Information System