Academic journal article Geopolitics, History and International Relations

GROUNDWATER TABLE AND LANDSLIDE VULNERABILITY IN VARIOUS LANDFORMS IN THE PRAMBANAN DISTRICT (Bokoharjo, Sumberharjo, Wukirharjo, and Sambirejo Sub Districts)

Academic journal article Geopolitics, History and International Relations

GROUNDWATER TABLE AND LANDSLIDE VULNERABILITY IN VARIOUS LANDFORMS IN THE PRAMBANAN DISTRICT (Bokoharjo, Sumberharjo, Wukirharjo, and Sambirejo Sub Districts)

Article excerpt

ABSTRACT.

The Prambanan District (Bokoharjo, Wukirsari, and Sumberharjo, and Sambirejo Subdistricts) has specific groundwater condition. This area is not only exists andesite and tuff but also stretch fault that give special groundwater behavior characteristics. The aim of this research is to define groundwater table in various landforms in correlation with landslide vulnerability. Field survey measurement was used to define groundwater table in various landforms. Groundwater table sample in various landforms was taken by transect profile or route in each landform. Then, landslide vulnerability in correlation with groundwater table was determined using deterministic approach. Based on the results, it shows that groundwater table is following morphology of landform. Moreover, groundwater in this area gives specific characteristic due to its rock structure. Moreover, landslide vulnerability is low to modest levels due to the condition of groundwater table.

Keywords: groundwater table, landslide, landform

Background

As the major visible destructive phenomena in hilly mountainous terrain (Acharya, et al., 2006), landslides are part of normal landscape development for geomorphic cycles (Wang, et al., 2007). Geomorphology approach can be used to optimal assessing landslide. Landform information as one of geomorphology approaches can be used to identify and classify unstable slope or factor of safety in rapid way (Baum, et al., 2005). Factor of safety can be used to predict landslide occurrence (Liao, et al., 2010). The major cause of landslide is groundwater setting that influences the stability of slope (Gattinoni, 2009). Moreover, a change in groundwater condition is the frequent cause for landslide occurrence (Sabatakakis, et al., 2005).

In Prambanan District particularly Bokoharjo, Sumberharjo, Wukirsari, and Sambirejo has specific characteristic in term of landform. This area is dominated by Structural-Denudational Landform. Morphology and geology conditions in this study area characterize unique groundwater in this area. Bedrock setting in this study area such as breccias, lava flow, and tuff give significant characteristic for groundwater. Fault line lays in this study area can create specific manner to groundwater. Moreover, the thin thickness of soil will influence groundwater table behavior in this area in correlation with groundwater table. The thickness of soil can accelerate landslide occurrence since this study area is relatively hilly area. In addition, low groundwater table due to thin contact of soil to the bedrock can increase the possibility of landslide occurrence. Therefore, this research will review groundwater table and landslide correlation in various landforms. From this point of view, it can explain the correlation of groundwater table with landslide occurrence in heterogeneous landforms in the study area.

Description of the Surveyed Area

The surveyed area was located in four Sub-districts: Bokoharjo, Sambirejo, Wukirharjo and Sumberejo. These sub-districts are included in Prambanan District. Figure 1 shows administrative description of the surveyed area. 5.724 people live in this district (Statistical Center Bureau, 2007). Geological setting in the surveyed area was Undifferentiated Volcanic Rocks, Semilir Formation, Kebobutak Formation and Nglangran Formation. The materials in Undifferentiated Merapi Volcanic Rock consisted of volcanic breccias, lava and tuff. Nglanggran formation consists of volcanic breccias, flow breccias, agglomerate, lava and tuff. Semilir formation includes interbedded tuff breccias, pumize breccias, dacite tuff and andésite tuffs and tuffaceous claystone. Next, Kebobutak formation material is andesitic breccias, tuff, lapili tuff, agglomerate and intercalations of andesitic lava flows. Based on disturbed soil sample in the study area that was taken in December 2010, soil texture in the study area is mostly clay and clay sand. This texture can drive landslide. …

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