Pemetaan Dinamika Garis Pantai Kabupaten Indramayu Tahun 2000-2025 Berdasarkan Data Citra Satelit Landsat dengan Pendekatan Digital Shoreline Analysis System (DSAS)
Ovy Salina Aziza, Dr. Ir. Bambang Kun Cahyono, S.T., M.Sc., IPU.
2026 | Skripsi | TEKNIK GEODESI
Kabupaten Indramayu merupakan wilayah pesisir di sebelah utara Jawa Barat dengan garis pantai sepanjang 114 kilometer yang dilalui beberapa muara sungai, sehingga rentan mengalami dinamika abrasi dan akresi secara bersamaan. Berdasarkan data tahun 2015 hingga 2023, tercatat perubahan luas abrasi sebesar 49,51 Ha dan akresi sebesar 93,88 Ha, namun penelitian terdahulu masih terbatas pada rentang waktu pendek dan epok diskrit, sehingga informasi mengenai laju perubahan tahunan serta luas area terdampak secara representatif dalam durasi yang lebih panjang belum tersedia. Penelitian ini bertujuan untuk memetakan dinamika garis pantai wilayah Kabupaten Indramayu tahun 2000–2025 berdasarkan data citra satelit Landsat dengan pendekatan Digital Shoreline Analysis System (DSAS). Penelitian memanfaatkan data citra satelit Landsat 5, 7, dan 8 pada sembilan epok yaitu tahun 2000, 2004, 2007, 2010, 2013, 2016, 2019, 2022, dan 2025 yang dikumpulkan melalui Google Earth Engine (GEE). Setiap epok citra diolah menjadi satu komposit bebas awan menggunakan reducer median, kemudian garis pantai diekstraksi menggunakan algoritma Normalized Difference Water Index (NDWI) melalui thresholding nilai nol, menghasilkan sembilan garis pantai sesaat yang posisinya masih dipengaruhi kondisi pasang surut saat perekaman. Posisi garis pantai pada setiap epok tersebut kemudian dikoreksi terhadap datum Mean Sea Level (MSL) menggunakan hasil analisis harmonik pasang surut serta nilai kemiringan pantai dari data BATNAS. Kesembilan garis pantai terkoreksi dianalisis lajunya menggunakan Digital Shoreline Analysis System (DSAS) dengan metode Linear Regression Rate (LRR) dan Net Shoreline Movement (NSM), kemudian divalidasi dengan data survei lapangan. Hasil penelitian menunjukkan pesisir Kabupaten Indramayu didominasi akresi di sisi utara dan abrasi di sisi barat, akibat kondisi geografis yang berbatasan langsung dengan Laut Jawa serta perbedaan kemiringan pantai antar segmen. Jumlah transek terindikasi abrasi sebanyak 257 garis transek (LRR) dan 231 garis transek (NSM), sedangkan akresi sebanyak 145 garis transek (LRR) dan 171 garis transek (NSM), dengan laju rata-rata tahunan (LRR) sebesar 5,46 m/tahun untuk abrasi dan 9,13 m/tahun untuk akresi, sementara nilai NSM sebesar 116,77 m untuk abrasi dan 242,83 m untuk akresi yang merepresentasikan pergeseran kumulatif 25 tahun, bukan laju tahunan. Luas area terdampak abrasi tercatat 1.061,01 Ha dan akresi 1.288,01 Ha, dengan luas abrasi tertinggi pada periode 2007–2010 sebesar 582,36 Ha dan luas akresi tertinggi pada periode 2013–2016 sebesar 478,26 Ha. Data dilakukan validasi melalui survei lapangan pada 41 titik sampel, menghasilkan RMSE 2,87 meter, MAE 2,32 meter, dan CL95 sebesar 4,96 meter yang memenuhi standar peta skala 1:25.000 dan 1:50.000.
Indramayu Regency is a coastal area on the northern coast of West Java with a coastline stretching 114 kilometers, crossed by several river estuaries, making it prone to simultaneous abrasion and accretion dynamics. Based on data from 2015 to 2023, changes in abrasion area of 49.51 Ha and accretion area of 93.88 Ha were recorded; however, previous studies were still limited to short time spans and discrete epochs, so information on annual rates of change and representative affected areas over a longer duration remained unavailable. This study aims to map the shoreline dynamics of Indramayu Regency from 2000 to 2025 based on Landsat satellite imagery data using the Digital Shoreline Analysis System (DSAS) approach. The study utilized Landsat 5, 7, and 8 satellite imagery data across nine epochs, namely 2000, 2004, 2007, 2010, 2013, 2016, 2019, 2022, and 2025, collected through Google Earth Engine (GEE). Each epoch of imagery was processed into a single cloud-free composite using a median reducer, after which the shoreline was extracted using the Normalized Difference Water Index (NDWI) algorithm through zero-value thresholding, producing nine instantaneous shorelines whose positions were still influenced by tidal conditions at the time of recording. The shoreline position at each epoch was then corrected to the Mean Sea Level (MSL) datum using the results of tidal harmonic analysis as well as beach slope values derived from BATNAS data. The nine corrected shorelines were subsequently analyzed for their rate of change using the Digital Shoreline Analysis System (DSAS) with the Linear Regression Rate (LRR) and Net Shoreline Movement (NSM) methods, then validated using field survey data. The results show that the coast of Indramayu Regency is dominated by accretion on the northern side and abrasion on the western side, attributed to the geographical condition of bordering directly on the Java Sea as well as differences in beach slope between segments. The number of transects indicating abrasion was 257 transects (LRR) and 231 transects (NSM), while those indicating accretion numbered 145 transects (LRR) and 171 transects (NSM), with an average annual rate (LRR) of 5.46 m/year for abrasion and 9.13 m/year for accretion, while the NSM values of 116.77 m for abrasion and 242.83 m for accretion represent the cumulative shift over 25 years, not an annual rate. The area affected by abrasion was recorded at 1,061.01 Ha and by accretion at 1,288.01 Ha, with the highest abrasion area occurring in the 2007–2010 period at 582.36 Ha and the highest accretion area occurring in the 2013–2016 period at 478.26 Ha. The data were validated through a field survey at 41 sample points, yielding an RMSE of 2.87 meters, an MAE of 2.32 meters, and a CL95 accuracy of 4.96 meters, which meets the standard for 1:25,000 and 1:50,000 scale mapping.
Kata Kunci : dinamika garis pantai, DSAS, NDWI, akresi, abrasi.
