Abstract:The mapping of soil movement was examined by comparing an extension of the deterministic Soil Stability Index Mapping (SINMAP) method, and an overlay method with trigger parameters of soil movement. The SINMAP model used soil parameters in the form of the cohesion value (c), internal friction angle (φ), and hydraulic conductivity (k s ) for the prediction of soil movement based on the factor of safety (FS), while the indirect method used a literature review and field observations. The weightings of soil movement trigger parameters in assessments were based on natural physical aspects: (1) slope inclination = 30%; (2) rock weathering = 15%; (3) geological structure = 20%; (4) rainfall = 15%; (5) groundwater potential = 7%; (6) seismicity = 3%; and (7) vegetation = 10%. The research area was located in the Buleleng district, in particular in the ancient mountain area of Buyan-Tamblingan, in the Sukasada sub-district. The hazard mapping gave a high and very high hazard scale. The SINMAP model gave a validation accuracy of 14.29%, while the overlay method with seven trigger parameters produced an accuracy of 71.43%. Based on the analysis of the very high and high hazard class and the validation of the landslide occurrence points, the deterministic method using soil parameters and water absorption gave a much lower accuracy than the overlay method with a study of soil motion trigger parameters.

Sukasada and Sawan Subdistricts are areas in Buleleng Regency that are often hit by landslides due to their geological conditions, since they are composed of weathered volcanic rocks, consisting of intersections with faults and rock joints. A rainfall model analysis is carried out in order to determine the probability of precipitation, while WindRose is used to analyze the duration of the dominant rainfall. Furthermore, SoilVision is used to determine the grain size distribution. Meanwhile, the equations proposed by van Genuchten and Fredlund and Xing are used to estimate the Soil-Water Characteristic Curve (SWCC). The Green-Ampt model is also used to calculate infiltration capacity. Slope stability is analyzed using an infinite slope model in order to produce a spatial-temporal prediction map of slope stability in the form of safety factor (SF). The results of the hydrology analysis reveal that rain with an intensity of 87.32-92.27 mm/day, a duration of 6-7 days, and types of soil in each study location in Sukasada and Sawan Subdistricts affects the amount of infiltration and it, in turn, affects slope stability. Extrapolation results for the spatial-temporal map of landslide hazard reveal the classification of safety factor as follows, SF > 2.13 (low/stable), 1.40 < SF < 2.12 (moderate/critical) and SF < 1.39 (high/landslide).

Keruntuhan terjadi sehari setelah hujan ekstrim yang terjadi selama 4 hari mengguyur daerah sekitar Kecamatan Kintamani pada bulan Februari. Tingginya kerusakan yang terjadi perlu dilakukan analisa teknis untuk mengetahui penyebab terjadinya keruntuhan melalui observasi dan pengamatan di lapangan dan data-data terkait laporan dari dinas terkait. Tujuan dari analisa ini adalah agar DPT yang akan dibangun kembali menjadi lebih kokoh untuk menahan beban dan menghindari terulangnya kejadian serupa pada bangunan yang baru. Dari observasi dan fakta lapangan dan analisa numeris pada lereng longsor, keruntuhan DPT disebabkan oleh karena dimensi DPT yang terlalu ramping sehingga tidak mampu menahan tekanan tanah aktif saat jenuh air. Drainase DPT tidak berfungsi dengan baik sehingga tanah gampang jenuh saat hujan. Keruntuhan juga disebabkan oleh tergerusnya pondasi DPT akibat masuknya air pada retakan horisontal pada bahu jalan. Pondasi DPT tidak berada pada lapisan tanah yang stabil. Penanggulangan risiko bencana diawali dengan penilaian dan pemetaan risiko bencana. Pembelajaran terhadap masyarakat didaerah rawan bencana longsor dilakukan secara intensif agar mampu menilai secara visual ancaman terjadi. Upaya mitigasi lebih efektif lainnya dengan investasi pengurangan risiko bencana berupa penerapan system peringatan dini dengan teknologi tepat guna. Kata Kunci : manajemen infrastruktur, dinding penahan tanah, mitigasi bencana, Geo-Slope.

Disaster of soil movement from NDMA (National Disaster Management Authority) of Indonesia mention from 2003-2017 shows the increasing. Investigation of potential ground motion based on sampling data of boring test on slopes along the Denpasar-Singaraja road around Gitgit Village which provides the greatest threat to settlements and public facilities. This research is expected to show the influence of rainfall on slope stability. This research is expected to show the influence of rainfall on slope stability. Furthermore, safety factor analysis based on daily rainfall data and numerical analysis was assisted by SLOPE/W and SEEP/W software tools. The analysis was carried out using a normal, heavy, and very heavy rain model. Safety factor declined after the 3rd day of rain after that the safety factor dropped to the 6th day with a safety factor 1.141 indicating the condition to be critical. The result shows the effect of rainfall decreasing safety factor after the second day of rain and the fourth day of safety factor shows a value of 1.003 where the slope is in a critical condition leading to failure, these results can be used to make early warning system of landslide hazard.

The Mount Batur Geopark area is vulnerable to debris flow triggered by heavy rainfall and weathered rocks that threaten the villages below. The estimation of the potential debris flow inundated area in this study has been determined by using the DFLOWZ model. The Digital Elevation Model (DEM) is the primary requirement data input in the model. Furthermore, the analysis of mean rainfall intensity and the hydrograph flood design have been calculated by the polygon Theissen and Nakayasu synthetic unit hydrograph method, respectively. The observation result has exhibited that basin flow occurs in the valley and river at the elevation ± 1500 m above sea level, which curves in hilly valleys and westward flow direction. The DFLOWZ analysis result depicts the area potentially inundated by a debris flow event as 49,830 m 2 with an inundation height based on the slope of 5-7 m. Furthermore, the peak of discharge debris flow, the debris flow volume, and the debris flow range are 100.15 m 3 /s, 50,072.85 m 3 , and 49.5 meters, respectively. This condition indicates that there is a risk of debris flow in the form of sand, silt, and boulders around the river in the range of 49.5 meters and a sediment thickness of 1-1.5 meters.