See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/337819953 Study Case of Geological Hazard at Eretan Area Based on Morphometry Analysis Conference Paper · November 2019 CITATIONS READS 0 61 5 authors, including: Arthur G.P. Nayoan Sofyan Rahman Universitas Trisakti Universitas Trisakti 2 PUBLICATIONS 0 CITATIONS 4 PUBLICATIONS 4 CITATIONS SEE PROFILE Harry Pramudito Universitas Trisakti 6 PUBLICATIONS 6 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: slope stability View project Jakarta groundwater development View project All content following this page was uploaded by Arthur G.P. Nayoan on 07 December 2019. The user has requested enhancement of the downloaded file. SEE PROFILE PROCEEDINGS JOINT CONVENTION YOGYAKARTA 2019, HAGI – IAGI – IAFMI- IATMI (JCY 2019) Tentrem Hotel, Yogyakarta, November 25th – 28th, 2019 Study Case of Geological Hazard at Eretan Area Based on Morphometry Analysis Rivolino Edison (1), Arthur G.P. Nayoan (1), Rafael H. Daned (1), Sofyan Rachman (2) and Harry Pramudito (2) (1) Student of Geological Engineering Department, Trisakti University (2) Lecturer of Geological Engineering Department, Trisakti University Abstract Lately the topic of disasters is a main topic that is always discussed by the public. Disasters that occur naturally are always related to the geological conditions that exist in some region and regional conditions, such as Indonesia which has a tropical climate so that the lithology of an area becomes easily weathered. One of the areas that the author is currently researching is Eretan and its surroundings, West Java. This time the author research aims to determine and analyze the geological disaster of the research area that is associated with the disaster mitigation. The method used by the author is geological mapping, morphometric analysis, and remote sensing method. Based on the morphometric analysis the author got three geomorpholical units of the study area, the units are structural steep slope hills, denudational sloping hills, and fluvial sloping slightly tilted low hills. Using the remote sensing method the author know about the residential area and the current environmental conditions of the research area. Based on the geological mapping that has been done, the writer knows the geological unit of the research area, namely volcanic breccia, claystone, tuffaceous breccia, and alluvial deposits with weathering levels which are generally high weathering - extreme weathering. The research results of the authors based on the analysis that has been carried out, that the area have potential landslides in the east of the research area that can disrupt and inhibit river water flow in the east of the research area which is assumed to produce floods in the surrounding residential areas. loss of property, damage to facilities & infrastructure, and other public facilities, as well as causing victims of humans and other living things. In this research the writer focused on the type of landslide geological disaster. Generally the controlling factors for landslide disaster including geomorphological conditions/slope, geological conditions, soil conditions or rocks that make up the slopes, conditions of hydrogeology, and land use conditions (Sampurno, 1975). But, in the author’s research area there are two causes that can trigger a landslide disaster. The first cause it is the lithology itself, what type of rock that occur in the area. The last cause is what is the morphological formation that exists in some area. This two causes occur in the author’s research area in the Eretan and it’s surroundings. Keywords : Geological Hazard, Morphometry, Geology, Remote Sensing, and Eretan Area Introduction Until now the public’s understanding about geological hazard in Indonesia is inadequate. Recent disasters like Palu’s earthquake and Banten’s tsunami, have made the community looking up the geological hazard’s topic. The disaster that occur in Indonesia is related to the conditions that existed in Indonesia, where Indonesia itself is traversed by three main plates (Indo-Australia, Eurasia, and Pasific). Then Indonesia is a country that has a tropical climate which bringing many benefits, but also it can bring a negative impact that causes disasters. According to Zakaria (2010) geological hazard is an event caused by geological conditions involving geological aspects and resulting in Figure 1: The landslide disasters classification (Cruden and Varnes, 1996) Data and Method The method that author used in this research is geological mapping, morphometric analysis, and remote sensing method with research aims to determine and analyze the geological disaster of the research area and associated with the disaster mitigation. PROCEEDINGS JOINT CONVENTION YOGYAKARTA 2019, HAGI – IAGI – IAFMI- IATMI (JCY 2019) TBA Hotel, Yogyakarta, November 25th – 28th, 2019 the surrounding community, because there were no village or infrastructure around the area. Geomorphological Analysis and Geological Mapping Figure 3: The appearance of a structural steep slope hills in the research area (Purple Line) Figure 2: The research flowchart Result and Discussion a. Geomorphological Analysis In the geomorphological analysis the author use Van Zuidam (1983) for the morphometric analysis that occur in the research area and also assisted with the Verstappen (1983) geomorphology genetic classification. Based on this analysis the author got three geomorphological units, the units are structural steep slope hills, denudational sloping hills, and fluvial sloping slightly tilted low hills. In denudational sloping hills there are a medium landslides probability. Because based on Van Zuidam (1985) analysis the sloping hills has a condition of easier surface erosion with intensive surface erosion and low-speed mass movement. The landslide vulnerability is also related to structural steep slope hills in the east of denudational sloping hills units. In this unit there’s a high probability landslide can occur, because of the unit’s morphological formation itself and the control of geological structure. The author interpret that the landslide will occur towards the river in the east. The last geomorphological unit fluvial sloping slightly tilted low hils has a very low landslide probability, but there a high possibility of flood can occur. Although the impact of the flood was very large on this geomorphological unit, it did not have a negative effect on Figure 4: The geomorphological map of the research area, where the slope tends to tilt to the east b. Geological Mapping Analysis Apart from morphology, lithology types also have a large impact on landslides occurance. Beside that, the author also focuses on the degree of weathering of rocks based on ISRM (1978) in the study area combined with the lithology data. From the geological mapping the author got four geological units volcanic breccia, claystone, tuffaceous breccia, and alluvial deposits. The alluvial deposits in the study area act as a sign of a fluvial genetic geomorphological unit and there’s no sign of weathering effect in this units. Then in the tuffaceous breccia geological unit in the west of the research area there’s many indication of weathering effect in this geological units with range completely wheatered to extremely wheatered. This indication of 2 PROCEEDINGS JOINT CONVENTION YOGYAKARTA 2019, HAGI – IAGI – IAFMI- IATMI (JCY 2019) TBA Hotel, Yogyakarta, November 25th – 28th, 2019 weathering greatly affect the occurrence of landslides in the research area. Other than that the location of this unit which tends to be higher further strengthens future landslides probability and this unit also in the area of denudational sloping hills geomorphological unit. BD landslide in the research area is high enough on the slope’s cliff west of the river. TL Figure 7: The geological engineering map and the distribution of lithologies in author’s research area Figure 5: The appearance of a tuffaceous breccia geological unit with the indication of highly wheatered in the outcrop Going to the east of tuffaceous breccia unit the author found the clay geological units which there are some indication of medium weathered effect in this geological units. Then in the next of geological units the author found volcanic breccia with weathering indication in range from slightly to medium weathered. But the main problem that the author find the indication of completely weathered to extremely weathered on the slope’s cliff. This make the causes of the slope in west of the river to be more susceptible to occur landslides in the research area. Figure 8: The river flow pattern map that show us the connection about Cimanuk river with the river around the village Figure 6: The appearance of a volcanic breccia geological unit with the indication of medium wheatered in the outcrop of the research area c. Remote Sensing Analysis From the analysis that has been done about the landslide in the research area based on geological mapping and geomorphological analysis. The probability of occurance of Figure 9: The remote sensing map and the location of Kadujaya village east from the research area (Yellow Circle) 3 PROCEEDINGS JOINT CONVENTION YOGYAKARTA 2019, HAGI – IAGI – IAFMI- IATMI (JCY 2019) TBA Hotel, Yogyakarta, November 25th – 28th, 2019 From the remote sensing in can be interpret that if landslide will occur in the future, the movement direction of the landslide will be in accordance with the same of the slope direction. If this landslide occurs, it will hold up of the river (Cimanuk River) flow from the dam (Jatigede Dam). This situation coincides with the location of the Kadujaya village east of the research area, where the direction of the river flow around the village will lead to the larger river (Cimanuk River). Zakaria, Z. 2010. Praktikum Geologi Teknik. Bandung. Universitas Padjajaran. Because the Cimanuk river flow is hold up by the landslide material, it will make inhibition of river flow around the village and make the local flood. Conclusions Based on this research that the author did, the landslide in the research area are closely related to morphological formation and weathering conditions. Generally the range of weathering condition in the research area slightly wheatered to completely wheatered and from the author interpretation this can cause the future landslide in the research area. If the landslide occur in the future, it will hold up the Cimanuk river flow and will hold up the river flow around the village naturally. So from that the author's advice for the local government, must hold learning about local disasters that can occur in the recent area to the local village, so that the local villager will always be vigilant in the event of a disaster such as landslides that the author has interpreted in this research in the research area. References Cruden, D.M., Varnes, D.J. 1996. Landslide Types and Process; Landslides Investigation and Mitigation, Special report 247. Transport Research Board, National Research Council, Editors : K.A.Turner dan R. Schuster, National Academy Press, Washington, DC. ISRM, 1978. Suggested Methods for The Quantitative Description of Discontinuities in Rock Masses. Int. J. Rock Mech. Sci. & Geomech. Abstr., Pergamon Press Ltd, Vol. 15, p. 319 – 368. Sampurno. 1975. Geologi Daerah Longsoran Jawa Barat. Pertemuan Ilmiah Tahunan IV Ikatan Ahli Geologi Indonesia. Van Zuidam. R. A. 1983. Guide to Geomorfhology Ariel Photographic Interpretation and Mapping. ITC Enschede The Nederland. Van Zuidam R. A. 1985, Aerial Photo – Interpretation in Terrain Analysis and Geomorphologic Mapping, Smith Publisher, The Hauge, ITC. Verstappen, H. Th., 1983. Applied Geomorphology Geomorphological Surveys for Environmental Development. New York. El sevier 4 View publication stats
