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GIS for Aquifer Monitoring and Modeling - From Field Surveys to Simulation Models: A case study of Kaluvelly Pondicherry basin, South India
Saied Pirasteh
Remote Sensing and GIS, Faculty of Engineering
Islamic Azad University of Dezful, Dezful Iran
moshaver1380@rediffmail.com
Hasan Ayazi
Remote Sensing and GIS, Faculty of Engineering,
Islamic Azad University of Dezful, Dezful Iran
Ph:+98 641 6060601
Fax: +98 641 6260890
Abstract
A digital elevation model (DEM) is used for hydrological study or watershed management, topography, geology, tectonic geomorphology and morphometric analysis. Geographical information system (GIS) provides a specialized set of tools for the analysis of topography, watersheds and drainage networks that enables to interpret the tectonic activities of an area. The drainage system maps of Zagros Mountains in south west Iran have been produced for two different dates (1950 and 2001) to establish the changes between geomorphic signatures and geomorphic aspect during time and to correlate them with recent neo-tectonics. This paper discusses the role of drainage for interpreting the tectonic processes as one of important signatures. The study shows variation in drainage network derived from topography maps. Thus, changes in drainage pattern, stream length, stream gradient and the number of segment drainage order from 1950 to 2001 indicate that the Zagros Mountain is subjected to recent neo-tectonic processes and it is a newly active zone.
1. Introduction
The Zagros Mountains are parts of Alpine-Himalayan orogenic system. The Zagros Fold Belt (ZFB) is one the best exposed fold-thrust belts in structural and tectonic perspective. Geology of ZFB was studied by Stocklin (1977). Falcon (1974) has divided the orogen into three structural zones, such as (1) An inner crystalline Zone of overthrusting, (2) An Imbricate Belt, and (3) Zone of Folding often referred to the Simply Folded Belt. Later the geology of the Zagros Structural Belt (ZSB) was studied by many other workers such as Berberian (1976), Colman-Sadd (1978), Darvishzadeh (1992), Ali and Pirasteh (2004), Pirasteh (2004). They divided the ZSB into four units which are as follows:
- Sanandaj-Sirjan Zone
- Imbricate Zone
- Zagros Fold Belt
- Molasse Cover Sequence which are characterized by distinct geological and geophysical signatures.
Mountain topography is the result of highly scale-dependent interaction involving tectonic and surface processes. In ZFB, the bulk of the relief in mountainous region has been formed by uplift along thrust faults striking sub parallel to trace of the thrust zones. Therefore, there is an intimate link between uplift rates, material distribution rates, erosion (Ali and Pirasteh, 2003) and topography due to geomorphic processes and the morphology of the area. By quantifying stream length, stream gradient, the number of drainage segment order, drainage texture and pattern of two different dates (1950 and 2001) tectonic processes are inferred.
The evidence of neo-tectonic activities is commonly available through various geomorphic signatures (stream length, stream gradient, number of the stream segment order) and geomorphic aspects (such as stream drainage texture and pattern). Thus, drainage networks can be used as variable to interpret the structural and tectonic behavior of the area. Numerous studies have been made to develop relationships between tectonics and morphology in ZSB ( Mohr,1976; Ahnert, 1976; Almaz, 1988; Arnett, 1971; Bromhead, 1986; Ali and Pirasteh, 2004; Pirasteh 2004). In order to study the tectonic behavior of the ZFB morphometric parameters of the drainage systems such as stream length, stream gradient, number of drainage segment orders and pattern has been taken in consideration. The term of tectonic geomorphology is used to study the variation and changes in drainages during 1950 to 2001. Topography maps of the study area in scale 1:50000 dated 1950 are scanned and then introduced to GIS environment for digitization process. Digital topography maps in scale 1:25000 dated 2001 of the area are also provided by Iranian Survey Organization (ISO). The use of a digital terrain model of the ZFB for both the dates made it possible to calculate a synthetic drainage system in the terrain and drainage network through which the water runs. A gird-based terrain model of the ZFB represents the continuous surface of the terrain. Drainages are in the direction with the lowest elevation. Each cell has eight adjoining cells and eight possible drainage directions. The direction of the drainages based on the cell’s elevation value with the values of the adjoining cells. The drainage networks in the ZFB could be automatically vectorized in GIS environment. The digital terrain model made for the area has become a useful tool for the study of drainage morphometry.
DEM of the area is prepared for two different dates. Spatial analysis in GIS environment is approached to extract the length of the drainages, stream gradient, number of the segment streams order and further interpretation used to define changes in patterns of the drainages from 1950 to 2001. With significant improvement in resolution of available DEM and computing drainage network in ZFB the evaluation of morphotectonic in a GIS environment tends to be quantitative and more precise. Therefore the study could evaluate the changes in drainage network from 1950 to 2001 and correlate it to tectonic evolution.
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