The 3rd IMT-GT 2007; Regional Conference on Mathematics, Statistics, and Applications
University Science of Malaysia

Introduction

Karst means terrain, generally underlain by limestone, in which the topography is chiefly formed by the dissolving of rock, and is commonly characterized by closed depressions, underground drainage, and caves. Karst is one of the natural resource which is un-renewable as it melting and sedimentation process take place during thousands and even million years. Among environmental expert, karst area is very sensitive to environmental change, hence the effort is need to protect this karst area which is volatile to environmental disturbance while maintain it function within the whole ecosystem.

Karstic Areas in Naga Umbang Lhok Nga was selected as a study area in Study of Potential Karstic Areas of the West Coast Regions of The Nanggroe Aceh Darussalam. Naga Umbang Regions of Nanggroe Aceh Darussalam at present experiencing rapid resource depletion and environmental deterioration due to social and economic pressures. Moreover, these pressures are particularly made evident because of the fragility of the development and environment: karst landscapes are more prone to demonstrate negative impacts in the short term than other types of terrain.

During the first meeting of the Scientific Evaluation Team in National Cave and Karst Management Symposium 2001, it became quickly apparent that the most effective means of analyzing the complex and multiple data sets for this process would be through Geographic Information Sys­tem (GIS). All of the data were spatial or could be spatially represented in an ordered series of layers that could be combined for presentation was technically effective but also offered a clear and intuitively understandable process to see potential values of this un-renewable resource.

A Geographic Information System (GIS) is a constellation of computer hardware and software that integrates maps and graphics with a database related to a defined geographical space. The geographical data may be spatial or descriptive in nature. A GIS can be defined as an integrated set of tools within an automated system capable of collecting, storing, handling, analyzing, and displaying geographically referenced information. There are essentially two types of data used in a geographical information system: cartographic data and descriptive or attribute data. Cartographic data provide a spatial or geographical reference for an object, whereas attribute information indicates the characteristics of the object.

Methodology

All data were stored and analysed using the Geographical Information System (GIS). Karst Study Team identified two primary scientific layers of spatial data for the GIS. Geologic and non geologic components were the main components to develop a strategy for identifying properties with highest potential values for possible decision approach. Each component comprises spatial data layers weighed according to their significance. Geologic layers were limestone formation, land slope, and caves. Non Geologic layers were biology and sensitivity.

Geologic data layer

Geologic components were limestone formation, land slope, and caves. Limestone formation relates directly to karstification values. This model assembled to select the limestone formation as karstification units for identifying properties of karst classification. Area of porous limestone formation have a high values than compact one, higher altitude from sea level have a higher value for karst feature. Land slope relates directly to groundwater recharge. This model assembled to develop a strategy for identifying properties with highest hydrologic and aquifer for possible acquisition. Areas of higher slope have a greater propensity for runoff than recharge. A digital elevation model for the county was analyzed by Veni (2001), and areas were subdivided and as-signed point values according to Table 1, with higher ratings reflecting greater potential for groundwater recharge.

Table1. Recharge potential ratings for land slopes

Slope                                                    Rating

Greater than 18%                                      1

Greater than 12% and less than 18%        2

Greater than 6% and less than 12%          3

Greater than 2% and less than 6%            4

Less than or equal to 2%                          5

Cave relates directly to endokarst values. Potential cave to karstification unit is greater than 5 in 1 km2. This component assembled to develop a strategy for identifying properties with highest of cave values. The foundation for all layers was Geologic Map prepared by the ESDM, topographic map prepared by Bakosurtanal, and cave survey by Karst Aceh. The maps were digitized and modified for the GIS by adjusting values based on new information and expanding it into the contributing geologic components for identifying properties with highest potential values.

Non Geologic Data Layer

Non Geologic components were biology and sensitivity. Data collect and store by field surveys. The maps were modified for the GIS model by adjusting values based on information and expanding it into the contributing non geologic components for identifying properties with highest potential values.

Key species relates directly to biology with high properties for equilibrium of ecosystem. Bats with all it functions as key species in karst area. Bats are nature’s insecticide. Each little brown bat can eat up to 1,000 mosquito-sized bugs in one hour. Many bat species in eat fruit or nectar. Bats disperse seeds and pollinate the flowers of thousands of kinds of plants, such mangrove and durians. Without bats many plants would become extinct. Guano utilized phosphate as compost of agriculture plants. Indonesia spends 96 trillion IDR per year to required phosphate as fertilizer (BPS, 2001). Mining process relates directly to alteration of karst feature with high potential for illegal logging and waterless condition. Small limestone factory need at least 1 ton wood for operated wood-stove. Cement factory and limestone mining have potential values for waterless condition. Opening land covers and acquired of limestone are transformed ground water and water catchments area.

Results

ArcGIS, which includes a rich set of tools to work with and process geographic information, was selected as the software to process the data. This collection of tools is used to operate on the GIS information objects such as the datasets, attribute fields, and cartographic elements in both components. These tools are the building blocks for assembling multi step operations. Extract, Overlay, Proximity toolsets was use to geoprocessing data. Each tool applies an operation to some existing data to derive new data and used to automate and record numerous geoprocessing tasks in the GIS.

Extract was use to manipulate data into manageable datasets containing only the desired features and attributes. Overlay was use for topological integration of features based on symmetry. Proximity was use to determine spatial relationships among features, with respect to the distance relationships between features.

The GIS analyzed from the layers and output for each components. Limestone formations in Lhok Nga

Table 2. Cave Density potential ratings for Endokarst

Caves in 1 Km2                              Rating

Greater than 5                                   1

Greater than 2 and less than 5          2

Less than or equal to 2                     3

Aceh Besar were divided into four categories: Raba formation, Peugasu Formation, Lhok Nga Formation, and Aluvium formation. The GIS was analyzing Raba formation is the highest categories as karstification unit were recommended for consideration for limestone formation and reduced three lowest categories may not have sufficient as karstification unit. The Land Slopes in Lhok Nga Aceh Besar was divided into two categories: 0-5% and more than 15%. The select by attributes and select by location tools in ArcGIS interactively select land slope more than 15% features as part of a feature layer. GIS Analyzing continued to intersect of limestone formation and land slope coverage. The area common to both coverages will be preserved in the output coverage as the highest karstification unit and highest ground water recharge values.

The buffer distance was given in map units by 1000 m for identify the properties of cave values. The area shown a potential high density of endokarst values and areas were subdivided and as-signed point values according to Table 2, with higher ratings reflecting greater potential for endokarst value. Analyzing all the layers with GIS was creating a new coverage by merging adjacent polygons or regions that have the potential value for geologic components.

Limestone quarry or mining process relates directly to alteration of karst feature with high potential for illegal logging and waterless condition. Manipulate of this sensitivity was constructed by wood requirement and opening land cover as attribute data. Multiple ring buffers were given in map units as average limestone productivity a day (average 5m3 per day (TDMRC, 2007). GIS identify this high potential value around limestone quarry. GIS identify the proximity of this area in distance is less than 1 km (Table 3). According to Department of Mineral and Energi Resource of Indonesia, area with more than 5 caves in 1 km2 is highest potential area as karstification unit and must be clear from limestone quarry.

Team study was creating a buffer around non geologic features by using the buffer command and proximity analyze. The buffer distance of bats as key species was given into position points by home range value (4500m). Buffer zone shown a potential key species, including zone of insecticide and disperse seeds. Coverage of key species area has shown a potential key species through to four sub districts (Darul Kamal, Darul Imarah, Peukan Bada, and Leupung). Analyzing was continued to computes the point-to-point distance between each limestone’s quarries in coverage.

Distance (m)

LQ: Limestone Quarry

Bold: Distance Less than 1 km

Finally, all the layers with GIS were creating to a new coverage by merging adjacent polygons or regions that have the potential value for geologic components and non geologic components. This area will be recommendation as important and potential karst area for possible initial decision approach, including protection and conservation.

Conclusions

Naga Umbang has potential values as important karst area and need specific research with holistic data and experts.

The GIS has proven a valuable and flexible tool in sorting through several complex factors involving a tremendous volume of information to identify properties that offer highest value for acquisition in the identification of the karst feature and its associated resources. Data can be modify and updating for the various data.

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