Analysis of Shoreline Changes in Ikoli River in Niger Delta Region Yenagoa, Bayelsa State Using Digital Shoreline Analysis System (DSAS)

The use of Digital Shoreline Analysis System was used to determine shoreline changes in Ikoli River, Yenagoa, Bayelsa State. Shoreline data were extracted from satellite imagery over thirty years (1991-2021). The basis of this study is to use Digital Shoreline Analysis System to determine erosion and accretion areas. The result reveals that the average erosion rate in the study area is 1.16 m/year and the accretion rate is 1.62 m/year along the Ikoli River in Ogbogoro Community in Yenagoa, Bayelsa State. The mean shoreline length is 5.24 km with a baseline length of 5.2 km and the area is classified into four zones to delineate properly area of erosion and accretion based on the five class of Linear regression rate, endpoint rate and weighted linear rate of which zone I contain very high erosion and high erosion with an area of landmass 255449.93 m2 of 38%, zone II contain moderate accretion, very high accretion and high accretion with a land area of 1666816.46 m2 with 24%, zone III has very high erosion and high erosion with an area of landmass 241610.85 m2 of 34 % and zone IV contain moderate accretion and high accretion with land area 30888.08 m2 with 4%. Out of the four zones, zone I and II were found to be eroding with 72% and zone II and IV contain accretion with 28%. The result shows that 44% of the area have been eroded. Therefore, coastal engineers, planners, and shoreline zone management authorities can use DSAS to create more appropriate management plans and regulations for coastal zones and other coastal parts of the state with similar geographic features.

Open Digital Shoreline Analysis System: ODSAS v1.0

In this study, we propose a new baseline and transect method, the open-source digital shoreline analysis system (ODSAS), which is specifically designed to deal with very irregular coastlines. We have compared the ODSAS results with those obtained using the digital shoreline analysis system (DSAS). Like DSAS, our proposed method uses a single baseline parallel to the shoreline and offers the user different smoothing and spacing options to generate the transects. Our method differs from DSAS in the way that the transects’ starting points and orientation are delineated by combining raster and vector objects. ODSAS uses SAGA GIS and R, which are both free open-source software programs. In this paper, we delineate the ODSAS workflow, apply it to ten study sites along the very irregular Galician coastline (NW Iberian Peninsula), and compare it with the one obtained using DSAS. We show how ODSAS produces similar values of coastline changes in terms of the most common indicators at the aggregated level (i.e., using all transects), but the values differ when compared at the transect-by-transect level. We argue herein that explicitly requesting the user to define a minimum resolution is important to reduce the subjectivity of the transect and baseline method.

Análise multitemporal da variação da linha de costa no setor centro-sul da Ilha de Santa Catarina, Brasil

O reconhecimento e a quantificação de tendências da variação da linha de costa são de fundamental importância para o entendimento dos processos que moldam os ambientes costeiros, dando suporte à gestão dessas áreas. Este trabalho apresenta os resultados da análise da variação da linha de costa de um período de 78 anos em nove arcos praiais do setor centro-sul da Ilha de Santa Catarina com base em fotografias aéreas de 1938 a 2016. Três modelos espaciais foram gerados no Digital Shoreline Analysis System com a identificação de feições indicadoras de linha de costa: modelo E (limite entre praia-duna), modelo K (limite entre a área seca-molhada) e modelo M (linha de água instantânea). Os resultados mostram heterogeneidade entre os modelos espaciais com a variação média da linha de costa de 0,05 ± 0,12 m/ano para a linha E, 0,12 ± 0,25 m/ano para K e -0,20 ± 0,20 m/ano para M. O modelo E apresenta dispersão de 0,27 m e melhor ajuste às mudanças da linha de costa. O modelo K destaca-se pela alta dispersão (0,35 m) e retrata razoavelmente as mudanças costeiras. O modelo M mostra dispersão de 0,28 m e baixa confiabilidade na representação da variação da linha de costa. O processo de acreção é identificado nos arcos praiais dos Açores-Pântano do Sul e Campeche-Joaquina, sendo responsável pelo aporte contínuo de sedimentos para os sistemas eólicos adjacentes. O processo erosivo é identificado nos arcos praiais da Armação-Caldeirão e do Morro das Pedras-Campeche. Os arcos praiais de Naufragados, Lagoinha do Leste, Matadeiro, Mole e Galheta exibem relativa estabilidade.

Rapid detection of changes in the riverbanks of Laigiang river of the South Central Coast Vietnam: A methodology based on Digital Shoreline Analysis System and Sentinel-2

The research focuses on using Sentinel-2 that can be integrated with the Digital Shoreline Analysis System (DSAS) as an effective tool for the determination of changes in the riverbanks and using linear regression to predict shoreline changes. The research applied the assessment of shoreline changes in the period of 2015- 2020 and forecast to 2025 in Laigiang river of the South Central Coast region of Vietnam. Based on the DSAS tool, parameters such as Shoreline Change Envelope (SCE), Net Shoreline Movement (NSM), End Point Rate (EPR) and Linear Regression Rate (LRR) were determined. The analysis results show that the accretion process in the Laigiang river in the period of 2015-2020 with the accretion area ranges from 81.47 ha. Meanwhile, the area of shoreline erosion only fluctuates around 54.42 ha. The rhythm of evolution is a determinant element for this transitional system.

AVALIAÇÃO DE CURTO PRAZO DA RETRAÇÃO DAS FALÉSIAS DE TIBAU DO SUL-RN

O objetivo desde artigo foi empregar as ferramentas de Geotecnologias, como o Processamento Digital de Imagens (PDI) do satélite de alta resolução espacial QUICKBIRD, a análise espacial em ambientes de Sistemas de Informações Geográficas (SIG) e os módulos estatísticos do Digital Shoreline Analysis System (DSAS) para identificar os setores litorâneos assinalados por falésias marinhas no município de Tibau do Sul/RN, e quantificar as taxas de retração entre os anos de 2003 a 2013. Os resultados demonstraram que cerca de 34% da linha de costa do Município de Tibau do Sul, dominado por falésias, têm sofrido recuos expressivos. As maiores magnitudes de retração da borda das falésias ocorreram nos subsetores N2, C3 e S2, com recuo de 1,5m, 1,71m e 1,9m, respectivamente. O valor da constante LR² esteve mantido em todos os casos e foi maior que 0,75 sugerindo o processo erosivo linear instalado por toda a década avaliada. Deste modo, as ferramentas e métodos empregados servem como subsídios imprescindíveis aos estudos de identificação de processos erosivos costeiros e à construção de instrumentos de controle e gestão ambiental da zona costeira.

Perubahan Garis Pantai pada Musim Timur dan Barat kaitannya dengan Karakteristik Gelombang di Pesisir Kabupaten Takalar, Sulawesi Selatan

Detection of shoreline changes needs to be done to determine changes so that supervision and management planning in a coastal area can be carried out, one of which is on the coast of Takalar Regency, South Sulawesi. This study aims to map changes in the coastline in Takalar Regency in different seasons and to see the effect of the waves on these changes. This study uses Landsat satellite imagery data from 1998-2018, and wave data obtained from Copernicus Marine Environment Monitoring Services (CMEMS). The shoreline data extraction was using the combination of single band and band ratio approach while the shoreline change rate calculation was using the Digital Shoreline Analysis System (DSAS) application. In addition, GeoDa application was used to obtain the regression analysis of the effect of waves on shoreline changes. The results showed that there were similar patterns of shoreline changes between monsoon and west monsoon, although the value were different. Coastal erosion occurs in almost all Takalar coastal area. Some areas that have a high coastal erosion value were the sub-district of South Galesong and Mappakasunggu while the areas that have a high accretion value were the sub-districts of Sanrobone, Mappakasunggu, and Mangarabombang. The waves had a significant influence on changes in shoreline in both the monsoon and west monsoon (P <0.05) with a percentage of 17,2% for the monsoon and 7.3% for the west monsoon which indicated there were other factors that influence shoreline change besides the wave factor on the Takalar Coast. Deteksi perubahan garis pantai perlu dilakukan dalam rangka pengawasan dan perencanaan pengelolaan di suatu kawasan, salah satunya di Pesisir Kabupaten Takalar, Sulawesi Selatan. Penelitian ini bertujuan untuk memetakan perubahan garis pantai di Kabupaten Takalar berdasarkan musim dan melihat pengaruh gelombang terhadap perubahan tersebut. Penelitian ini menggunakan data Citra Satelit Landsat tahun 1998-2018, dan data gelombang yang diperoleh dari Copernicus Marine Environment Monitoring Services (CMEMS). Ekstraksi data garis pantai menggunakan pendekatan perkalian single band dan ratio band sedangkan perhitungan laju perubahan garis pantai menggunakan aplikasi Digital Shoreline Analysis System (DSAS). Analisis regresi untuk melihat pengaruh gelombang terhadap perubahan garis pantai menggunakan aplikasi GeoDa. Hasil penelitian menunjukkan terdapat pola yang hampir sama antara perubahan garis pantai musim timur dan musim barat meskipun dengan besaran yang berbeda. Abrasi terjadi hampir di seluruh Pesisir Takalar. Daerah yang memiliki nilai abrasi yang tinggi yaitu Kecamatan Galesong Selatan dan Mappakasunggu sedangkan daerah yang memiliki nilai akresi tinggi yaitu Kecamatan Sanrobone, Mappakasunggu, dan Mangarabombang. Gelombang memberikan pengaruh yang signifikan terhadap perubahan garis pantai baik pada musim timur maupun barat (P<0,05) dengan persentase 17,2% untuk musim timur dan 7,3% untuk musim barat yang mengindikasikan terdapat faktor lain yang ikut mempengaruhi perubahan garis pantai selain faktor gelombang di Pesisir Takalar.