Indonesian Journal of Geography
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Challenges of Tsunami Risk Reduction on the Serang West Coast
Full text linkThe 2018 Sunda Strait tsunami that was not sourced from tectonics earthquakes hit the west coast of Serang Regency as one of the affected areas. On this account, addressing the tsunami risk in this region shall be done wisely through the Disaster Risk Reduction (DRR) effort. This research aims to firstly examine the DRR that has been implemented after the 2018 tsunami, and secondly identify the internal and external environmental factors, as valuable input in developing the strategies on enhancing the tsunami resilience. This research has a qualitative descriptive study, using primary and secondary data sources. The data collection techniques employ the literature studies, interviews, FGDs, and field observations. Furthermore, this study applies SWOT analysis to identify the internal and external environmental factors. The results indicate the progresses made in tsunami DRR on the west coast of Serang Regency. However, although policies for coastal area planning and management have been established, there is still a need for community socialization, proper implementation, and enforcement of the law. Moreover, both of robust tsunami early warning system and public education on vandalism prevention is also needed. Finally, the results of identifying the internal and external environmental factors show that there are 3 strengths, 3 weaknesses, 3 opportunities and 3 challenges. Accordingly, the results of this identification can be used to formulate advance strategies in increasing the tsunami resilience on the west coast of Serang Regency. Received: 2024-03-20 Revised: 2024-05-03 Accepted: 2025-12-03 Published: 2025-12-0
Estimation of Carbon Dioxide Sequestration and Litter Production in Rehabilitated Mangrove Ecosystems
Full text linkThe ability of mangrove to sequestrate carbon dioxide (CO2) is becoming part of the methods for climate change mitigation due to the ability of plants to absorb and store CO2 from the atmosphere as biomass. Therefore, this research aimed to estimate CO2 sequestration and litter production by Avicennia alba planted in mangrove rehabilitation area. The data collection method was field observation which was used to measure tree parameters and litter on the observation plot. Tree biomass was estimated using the allometric equation and converted to carbon sequestration. Moreover, a one-way Analysis of Variance (ANOVA) test was applied to assess biomass and litter production differences in the observed stations. Regression analysis was also used to diagnose the relationship between tree diameter, biomass, and carbon sequestration. The results showed that the average biomass and carbon storage at tree level were directly proportional to tree diameter and age. At the stand level, biomass and carbon sequestration in the three stations were not significantly different at the 95% confidence level. It was also observed that stem density affected mangrove biomass. The results showed that more mangrove mortality occurred with older ages at the observed stations and this lowered the stem density and biomass. Furthermore, the relationship between diameter, biomass, and carbon sequestration was directly proportional. Litter production also increased directly with tree age and diameter but the trend was insignificant. The leaf part was found to be the most significant contributor to litter production, and the proportion increased with age and diameter. These results were essential information for future sustainable mangrove rehabilitation plans.Received: 2024-04-02 Revised: 2024-06-21 Accepted: 2025-03-07 Published: 2025-04-2
A Spatio-Temporal Analysis of River Channel Migration & Erosion-Depositional Pattern of Lower Part of the Dikrong River of Assam by Using Geo-Spatial Technology
Full text linkRivers often show different morphological changes in different periods and geographical areas; a river's morphology changes due to erosion, deposition & transportation processes to attain the equilibrium state. The activity of erosion & deposition is highest in the alluvial River as a result of the river channel migration, which affects the land cover and the livelihood of the inhabitants. The Dikrang River is the northern sub-tributary of Brahmaputra, which originates in Arunachal Pradesh and flows through the Brahmaputra valley. As a result of the erosion and deposition, both the river channels have migrated, this changes the equilibrium state of the River’s aquatic environment and modifies the land use pattern in the floodplain. The objective of the present study is to identify the River channel migration pattern & the erosion-depositional scenario of the Dikrong River channel from the period of 1973-2022 to identified the responsible factors of the hazard that may helpful for the better management of the River channel. The Survey of India topographical map, LANDSAT satellite images, and geospatial tools have been applied to measure the bank line migration of the Dikrong River. The output of the study represents that the remarkable channel migration occurred in the River due to the vast sedimentation & ongoing erosion activity on both banks of the River. The lower and central parts of the river channel have gradually changed the course of the River both in the direction of the West and East of the Dikrang River channel. The study will be helpful for the planners & geomorphologists in preparing an effective management strategy to solve the problem & proper development of the watershed.Received: 2024-07-27 Revised: 2024-08-20 Accepted: 2025-07-06 Published: 2025-07-3
Spatial-temporal Analysis Distribution of Buildings Martapura River Border in Banjarmasin City
Full text linkThe role of the people of Banjarmasin City has long made the river a center of activity that has a dependence on river culture as a way of life, behavior, and adaptation the river boundary for generations, including the construction of buildings. This activity has an impact on the uncontrollability of buildings. And the function of the river. The study aimed to assess the extent of the distribution and non-conformity of buildings with river boundary regulations stipulated in Banjarmasin City Regional Regulation No. 31/2012 concerning the Determination of Regulation and Utilization of Rivers and Former Rivers. The method used is descriptive quantitative with spatial analysis techniques on visual image interpretation and river area buffering within 15 meters of the left and right banks of the river. Data analysis used an overlay technique to determine the number of buildings within the Martapura River boundary line in Banjarmasin City. The results showed that, over 15 years from 2008 to 2023, the built-up land area changed by an average of 1.30 hectares. Based on the type of built-up land, the most dominant is residential buildings. Non-conforming buildings in 2008 totaled 3,518 buildings, in 2013 totaled 3,365 buildings, in 2018 totaled 3,321 buildings, and in 2023 totaled 3,301 buildings. The decrease in non-conforming buildings occurred periodically in Central Banjarmasin District, and the increase in the number of non-conforming buildings was spread in South Banjarmasin District and North Banjarmasin District.Received: 2024-10-01 Revised: 2025-11-10 Accepted: 2025-12-11 Published: 2025-12-22
Enhancing Accuracy in Detection and Counting of Islands Using Object-Based Image Analysis: A Case Study of Kepulauan Seribu, DKI Jakarta
Full text linkBased on previous observations, a series of steps using digital image processing methods is proposed for the automatic detection and counting of islands to avoid inaccuracies from satellite imagery by leveraging morphological properties of object. The need for accurate spatial data regarding the number of islands in Indonesia is crucial for various developmental purposes. Many small islands known to have beautiful landscapes remain unaccounted for due to the vast territorial waters of the country, posing challenges to manual evaluation of the numbers and distributions. Remote sensing methods offer a viable solution for efficiently counting and inventorying islands. Therefore, this study aimed to detect islands in Kepulauan Seribu, located north of DKI Jakarta, through the thresholding-based segmentation process and count the total number using morphological information. The methodology applied was Object-Based Image Analysis (OBIA), including image gray-scaling, thresholding, morphological operations, connected component labeling, and region-based object counting. The results obtained showed 111 islands, compared to direct observation of image from which 104 were found, with detection accuracy of 93.27%. The discovery not only contributes valuable insights into the specific region but also serves as a basis for potentially applying digital image processing methods on a larger scale to recalculate the number of Indonesian islands. Such recalculations could play a crucial role in informing and guiding future developmental initiatives.
Seasonal Variability of Sea Surface Chlorophyll-a at West Borneo Island
Full text linkThe optimization of marine fisheries activities can be achieved through an understanding of the timing of fishing, access to good information, and knowledge of oceanographic conditions. These conditions often lead to significant nutrient enrichment in the surface layer of the ocean, which in turn increases the sea surface chlorophyll-a (SSC). In the context of the west Borneo Island region, seasonal variability in SSC plays a crucial role in determining potential fishing grounds. The objectives of this study are examining the seasonal variability of SSC, identifying upwelling and downwelling processes through analysis of sea surface wind (SSW), and determining the climatological distribution of Sea Surface Temperature (SST) and sea surface height (SSH) within the water off Labuan Island, Malaysian Borneo, and the Karimata Strait, West Kalimantan, Indonesia. Remote sensing data spanning from 2007 to 2021 were analyzed, encompassing SSC, SST, SSH anomalies, SSW, wind stress curl, and Ekman pumping. Additionally, rainfall and river discharge were examined as supplementary indicators of these oceanographic processes. The findings indicate that SSW plays a pivotal role in driving upwelling and downwelling processes, which in turn influence SSC variability. In Labuan waters, upwelling occurs primarily from November to February, while downwelling predominates from June to September. In contrast, in the Karimata Strait, upwelling is identified from July to September, with downwelling prevalent between March and May. Upwelling events in both regions are characterized by increasing SSC, accompanied by decreasing SST and SSH, while the opposite trends are observed during downwelling events. The peak of rainfall and river discharge in December is noted to potentially enhance SSC variability in the Karimata Strait compared to Labuan Island waters
Three-Dimensional Participatory Mapping for Toponymical Name in Nglanggeran Ancient Volcano of Yogyakarta
Full text linkPlace naming of a local area is closely related to geographic elements. Local names can also be used as a cultural identity and natural condition of a region. Nglanggeran Ancient Volcano (AV) area has local name elements highly influenced by those conditions. It is an interesting study material where a three-dimensional (3D) model can contribute as a medium to collect the place naming traces (toponym) in this area through participatory mapping. Participatory mapping, usually using 2D models in the form of sketches or maps, will be a separate story in interactive 3D media usage resulting from the photogrammetry process. It is expected that the media be able to show the geographical appearance of the Nglanggeran A.V area more clearly, such as geomorphology, geology, vegetation, hydrology, and even local culture, and contribute unexplored information. The results of participatory mapping in toponym collection are expected to be a medium that organizes the place naming of a local area into a complete database, along with the origin of the place names. It is also proposed that the results of participatory mapping through the 3D model be a means of preserving local culture in the Nglanggeran A.V area, making it more familiar to local residents and tourists
The Development of Disaster Risk Map for Semeru Volcano Eruption 2021-2022, East Java, Indonesia
Full text linkThe Semeru Volcano eruption on December 4, 2021 caused damage to social, economic and environmental aspects. The Rejali Watershed (DAS) is one of the areas severely affected due to the eruption. The eruption resulted in 51 deaths, 10,565 displaced people, 1,027 houses damaged, two connecting routes and 43 public facilities damaged. This study mapped the disaster risk areas due to the eruption of Semeru Volcano. This research used Laharz to analyze the lava flow hazard map and weighting for social, economic, physical, environmental, and capacity vulnerability parameters. The results showed that the risk level of Semeru Volcano eruption is divided into three classes: high, medium, and low risk. The high-risk area is 8915.09 Ha (14 %), the medium-risk area is 2174.74 Ha (17 %), and the low-risk area is 1885.60 Ha (69%). The high and medium risks were located on the upper and middle slopes of the Rejali watershed because the upstream area experiences a narrowing of the river flow (bottleneck) due to direct borders with structural land. The Semeru Volcano disaster risk map results can be used as a reference in sustainable risk management efforts in the Rejali watershed to reduce the impact and damage caused by the eruption
Mapping the Impact: Property Crime Trends in Kuching, Sarawak, During and After the COVID-19 Period (2020-2022)
Full text linkThis study aims to explore how COVID-19 and the Movement Control Order (MCO) have influenced the trend of property crimes in Kuching, Sarawak spanning from 2020 until 2022. The lockdown imposed by the government had impacted daily activities in Malaysia, including those in Kuching, Sarawak. The methodology employed in this research involves descriptive analysis and spatial analysis, specifically using the Hot Spot Getis GI* technique, with the support of ArcGIS software. It examines relationships between crime and geography. The trend of property crime cases dropped from 1,144 cases (2020) to 813 cases in 2021 and ended with 683 cases in the year 2022. The value of GiZScore from the lowest of 2.066694 to the highest of 13.365677 is from the year 2021. Property crime in Kuching's urban center was targeted even during MCO beginning March 2020 to November 1, 2021. This indicates a notable decrease in property crime trends during the COVID-19 (2020-2021) pandemic period due to the MCO and lockdown which continue to impact into the subsequent endemic era of 2022. This demonstrates the efficiency of the Royal Malaysia Police, particularly in the context of Kuching, Sarawak