Last tsunami in 1994 and 2006 in Java, Indonesia gives huge impact to the loss of property and agricultural production. From an agricultural point of view, the area affected the most by this hazard is the paddy field that is located on the lowland and coastal area. The tsunami hazard caused serious damage included loss of plants, increased plant disease, and delays in harvesting.
Papathoma and Dominey-Howes (2003) has examined the published tsunami risk maps, and generally, those maps indicate that tsunami flood risk is traditionally assumed uniform within the expected flood zone. However, Papadopoulos (2003) has also revealed that the population, infrastructure and land use within a given flood zone are not uniformly at risk. This is because risk is closely related to vulnerability, which measures the potential of loss and damage. Therefore, the vulnerability value is also different for each of element at risk. In term of the agricultural land, which is one of the most vulnerable land use due to the tsunami inundation, estimation of risk can be calculated by determining the type of the agricultural activities (ex., type of crop, etc) in order to have the detail estimation of the loss of production due to tsunami inundation.
Indonesia is considered one of the most tectonically active zones in the world, since this region has very complicated plate-convergences consisting of subduction, collision, and back-arc trusting (see Figure 1). At least some of the coastal areas in Indonesia are subject to tsunami hazard, which is caused by earthquake in a shallow region at subduction and plate boundaries. At least 105 tsunami has occurred throughout the Indonesian coastal areas since 1600, and 90% of this destructive event was generated by earthquake (Hamzah, et al. 2000). Although tsunami hazard, which is considered as the most devastating hazard, occurred frequently and attacked the coastal area of Indonesia, their regional characteristics are not well known. There is still limited study about the tsunami characteristics, hazards and tsunami-risk reduction strategies. One of the important issues pertaining to the risk reduction program is the generating of the hazard map, identification of the element at risk and the estimation of the potential damage due to the hazard.
Due to the changes in density of agricultural land use pattern of the southern coastal area of Central Java, it has recently been suggested that the potential impacts of future tsunami hazard are likely to be much greater than in the past. To what level selected coastal segments of Central Java (Parangtritis coastal area, Bantul regency) are at risk from, and vulnerable to, tsunami inundation and impacts are the most imperative questions to be answered. Estimation model and calculation is therefore considered as an important task to be done in the near in order to give the preliminary assessment of the potential damage due to the scenario of tsunami hazard.
A remotely sensed approach in combination with the Geographic Information System (GIS) might be more useful for establishing the spatial extent of potential hazard inundation (Marfai and King 2008a, Marfai and King 2008b) as well as to calculate the spatial agricultural damage over large areas (Lillesand et al.2004). Nowadays, the technology of the satellites images are increasing rapidly in term of the technology development and technology application. As example, data acquired by satellite sensors for land use determination, especially at coastal agricultural land use, is becoming an increasingly important source of information for precision farming. A Hyperspectral sensor such as IKONOS has dramatically increased spatial, spectral, and temporal frequencies that make them appealing to applications in precision agriculture. However, due to the large synoptic view provided and reasonable spatial resolution, the Landsat and ALOS satellites are also of equal importance in precision farming.
Based on the tsunami vulnerability map (Bakosurtanal 2006) and the experience of the last tsunami disaster in Pangandaran, it is therefore necessary to map and assess into more detail the potential impact due to the future tsunami. Parangtritis coastal segment, which located not so far from Pangandaran area, has potential risk due to tsunami.
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*) Paper presented at the International conference on coastal environment and management-for the future of human lives on the coastal regions-. 23rd – 24th February 2009. Shima, Southern Mie Prefecture, Central Japan. Asia and Africa Science Platform Program, Japan Society for the Promotion of Science Nagoya University, Japan
By: RATIH FITRIA PUTRI (Double Degree Master Programe Watershed & Coastal Management Gadjah Mada University & Remote Sensing Chiba University, Japan)
