Spatial Analysis of Mangrove Distribution Using Landsat 8 Oli in Badung Regency and Denpasar City, Bali Province, Indonesia

Bali is an island situated among the Indonesian archipelago with huge potential to host mangrove forests. Using remote sensing technology advances, satellite images, such as Landsat images, might be employed to analyse mangrove forest distribution and density. This paper presents an analysis of mangrove distribution in Badung Regency and Denpasar City, Bali, as a basis for the management and conservation of mangrove ecosystems. This study used Landsat 8 OLI images and a vegetation index to analyse the mangrove forest distribution and density in this area. It started by identifying mangrove forests using the RGB 564 band and continued to distinguish between mangrove and non-mangrove objects using unsupervised classification, before analysing mangrove density using the NDVI formula. The results show that the mangrove forest area in 2020 was 1,269.20 ha, with an accuracy rate of 83%. Mangroves were found on the deepest or most curved coastline of the Benoa Bay area, on enclosed waters. This distribution follows the river network in the lower reach, which has thick deposits and is uninfluenced by large currents and waves. Based on the vegetation index analysis results, the mangrove forest area observed mainly had a moderate density, with a total area of 510.85 ha (40%), followed by high density (413.15 ha/ 33%) and low density (340.51 ha/ 27%)

LANDSLIDE RISK MANAGEMENT BY MEANS OF PROPOSED LAND USE IN GINTUNG SUB-WATERSHED, PURWOREJO REGENCY, CENTRAL JAVA PROVINCE, INDONESIA

The research was conducted on Gintung sub-Watershed. Gintung sub-Watershed is located among three districts: Loano District, Purworejo District, and Kaligesing District in Central Java Province. Gintung sub-Watershed is one of areas frequently suffered by landslide hazard. This research is aimed to manage landslide risk in the study area. Land allocation based on risk levels is proposed to provide the management of landslide risk. Three methods were applied in this research. First, statistic-probabilistic method was applied to obtain landslide susceptibility level of the study area. Multivariate statistic was used in this step. Logistic regression model was executed as the statistical approach. Slope, landform, soil, geology, land use, and aspect were the variables which were used in this analysis. Second, questioner survey was done to obtain vulnerability level of the elements at risk in the study area. Settlement and road network were the elements at risk which were analyzed in this step. Stratified-random sampling was applied on vulnerability assessment. Third, risk matrix was applied to obtain the risk level of landslide in the study area. The result of this research showed that 59.4% susceptibility level of landslide in Gintung sub-Watershed is categorized into moderate level. Probability of future landslide in the study area is greater than 0.6 respectively. Logistic regression equation stated that land use is the most controlling factor of landslide in the study area. Vulnerability level of settlement in the study area is categorized into moderate level. Vulnerability level of road network is categorized into high level. Based on the risk matrix, landslide risk level in the study area is categorized into moderate level. As a consequence, according to landslide risk levels in the study area, the proposed land uses are to limit settlement expansion in very steep slope area, to reduce garden uses through changing into dryland agriculture in flat up to undulating area and changing into bush and shrub in slightly steep up to steep slope area

The Ecological Perspective of Landslides at Soils with High Clay Content in the Middle Bogowonto Watershed, Central Java, Indonesia

The clay layers at hilly regions in the study area were very thick. The presence of very thick clay caused several difficulties in terms of environmental management, particularly in reducing georisk due to landslide. However, initial observations proved that areas of active landslides had better vegetation cover. The objective of this study was to find out ecological roles of landslides in livelihood in the Middle Bogowonto Watershed. The ecological roles of landslide were examined through field empirical evidences. Texture, bulk density, permeability, structure, and index plasticity were conducted for analyses of soil physical properties. Stepwise interpretation was made using 1 : 100,000–1 : 25,000 Indonesian topographic maps and remote sensing images of 30 m–<10 m spatial resolution. The results showed that landslides formed three landform zones: residual, erosional, and depositional zones. The area that did not slid, the residual zone, had massive soil structure and very hard consistency. Crops cultivated in this zone did not grow well. In the areas of active landslide, the environmental conditions seemed to be more favorable for living creatures. The landslides resulted in depositional zones with gentle slopes (4° to 15°), higher water availability, and easier soil management. The landslides also acted as the rearrangement process of landforms for better living environment