INTERNATIONAL JOURNAL OF GEOMATICS AND GEOSCIENCES Volume 2, No 1, 2011 Copyright 2010 All rights reserved Integrated Publishing services Research article ISSN 0976 4380 Hypsometric Analysis of Varattaru River Basin of Harur Taluk, Dharmapuri Districts, Tamilnadu, India Sivakumar. V 1, Biju. C 1, Benidhar Deshmukh 2 1- Geomatics Solutions Development Group, Centre for Development of Advanced Computing (C-DAC), Pune - 411007, India. 2- Discipline of Geology, School of Sciences, IGNOU, New Delhi, India. vsivakumar@cdac.in ABSTRACT Hypsometric analysis describes the distribution of horizontal cross-sectional area of river morphology with respect to elevation (area-altitude analysis). Morphology of a river basin plays primary role in the dynamics of surface and subsurface water runoff generation. It is also an essential tool to measure and represent the form of a watershed and its evolution. Aim of the paper is to carry out the Hypsometric analysis of Varattaru river basin of Harur taluk, Dharmapuri district, Tamilnadu using remote sensing and GIS technologies. Hypsometric data were derived and analyzed for each of the divided sub zone of Varattaru river basin from the 30 meter ASTER DEM. It was found that high-medium hypsometric integrals/elevationrelief ratios indicating a youthful to mature stage landscape, medium to complex denudational processes, the linear river morphological changes of this river basin and remote sensing data and open source tools it becomes less tedious to make hypsometric integrals and curves. This paper emphasizes the rainwater harvest practices and management for the watershed at suitable locations for controlling further erosion, reducing the runoff and increases the groundwater potential. Keywords: Hypsometric analysis, Geomatics technology, Harur, Varattaru river 1. Introduction Hypsometric analysis (area-altitude analysis) is the study of the distribution of horizontal cross-sectional area of a landmass with respect to elevation (Strahler, 1952). Naturally, hypsometric analysis has been used to differentiate between erosional landforms at different stages during their evolution (Strahler, 1952, Schumm, 1956). The statistical characteristic in the hypsometric analysis includes the hypsometric integral (I), hypsometric curve, hypsometric skewness, etc. (Wei Luo et al, 2003). Hypsometric integrals and hypsometric curve are important indicators of watershed conditions (Ritter et al. 2002). The hypsometric integral is the area beneath the curve, which relates the percentage of total relief to cumulative percent of area and shape of the hypsometric curve, indicates age of the catchment. Hypsometric integrals and curves can be interpreted in terms of degree of basin dissection and relative landform age: Convex-up curves with high integrals are typical for youthful stage, undissected landscapes; smooth, s-shaped curves crossing the center of the diagram characterize mature (equilibrium stage) landscapes, and concave-up with low integrals typify old and deeply dissected landscapes (Strahler, 1952). It was also found by Strahler (1952) that the hypsometric integral is inversely correlated with total relief, slope steepness, drainage density and channel gradients. This provides a measure of the landform distribution of landmass volume remaining beneath or above a basal reference plane. The hypsometric Submitted on September 2011 published on November 2011 241
integral helps in explaining the erosion that had taken place in the watershed during the health of watersheds. There is a lack of hypsometric analysis based studies for small river basin like Varattaru river to analyze the watershed health, which is due to the tedious nature of data acquisition and analysis involved for estimation. However, due to advent of remote sensing data (including derived digital elevation models) and open source GIS tools, the estimation process becomes easier than conventional methods. Considering the above facts, this study was undertaken to highlight the rainwater harvest practices and management for the watershed at suitable locations for controlling further erosion, reducing the runoff, increases the groundwater potential and stages of landform development in the Varattaru river basin. 2. Study Area Varattaru river basin is located in the southeastern part of Harur Taluk, Dharmapuri district, TamilNadu. It is located between Latitudes 11 12 and Longitudes 78 79 (Figure 1). Varattaru river is one of the major tributary of Vaniar river.. This river originates from Chitteri hills and passes through Velimadurai, Keraipatti, Ellapudiampatti and joins the Vaniar river at north east of Harur town. River basin boundary derived from Berkley tophosheet scale 1:25000. The river basin has a total geographical area of 1005 sq km. Varattaru river pass through major geomorphologic units such as valley fills denudation hills, weathered pediplains, etc. Geologically the area broadly consists of Charnockite and Gneissic rock. The important soil types encountered in the area can be broadly categorized into black to mixed loam and red sandy soils. Elevation varies from 330m to 1300m approximately. The yearly average rainfall observed is ~895 mm in the basin. 3. Data and Method Figure 1: Study area map ASTER DEMs were downloaded from USGS via internet and adjacent DEM were mosaicked together because some part of basin span across few quadrangles. Landsat ETM 30m data were downloaded to know the land use land cover pattern of this basin 242
(http://www.landcover.org/index.shtml). Landsat ETM-MSS data of 30m spatial resolution were fused with pan data of 15m spatial resolution to obtain detailed landcover information. ASTER DEMs and Landsat fused imageries were clipped with reference to approximate basin boundary (Figure 2 & 3). Hypsometric cure was derived for Varattaru river basin from the 30m ASTER DEM. Figure 3 shows the DEM that was used for the landscape characterization of the study area as suggested by Kokkas (2008). Calculation of the hypsometric integral (i.e area under the hypsometric curve) was automated in System for Automated Geoscientific Analyses (SAGA), an open source software using the hypsometric function in morphomertric analysis (http://www.saga-gis.org). Integration of the hypsometric curve gives the hypsometric integral (I). Pike and Wilson (1971) proved mathematically that the elevation-relief ratio (E) which is defined as Integration of the hypsometric curve gives the hypsometric integral (I). Pike and Wilson (1971) proved mathematically that the elevation-relief ratio (E), which is defined as E = (mean elevation minimum elevation)/ (maximum elevation minimum elevation) is identical to the hypsometric integral (I) but has the advantage that it is much more easy to obtain numerically (Singh et al. 2008). The output table contains the relative elevation, relative area, absolute elevation and absolute area information. The output data were normalised and generated hypsometric curve. Elevation contour was derived from DEM and overlaid on Landsat ETM (Figure. 4). Slope map was derived from ASTER DEM for understanding the topography relief variation (Figure. 5). Figure 2: PAN-merged Landsat ETM - FCC Satellite imagery of study area. Reddish black color shows vegetation cover including forest cover. Light red green color shows agriculture and scrubs. 243
Figure 3: ASTER DEM of study area (Unit In meter) Figure 4: Elevation contour overlaid on satellite image. 244
4. Results and Discusion Figure 5: Slope map. Figure 6 shows the results of hypsometric analysis for the Varataru river basin. Hypsometric curves show high-medium hypsometric integrals/elevation-relief ratios indicating a youthful to mature stage landscape. Due to run-off there is more kinetic energy, the ground is cut away faster so the curve of elevation versus area falls off more quickly. Sapping is a lower energy process and so its curve appears rather flat at first and then falls off. In the study area, approximately more than 80% of area (or volume) lay at elevations than mean elevation. It was also observed that there was a combination of moderate convex-concave and slightly S shape of the hypsometric curves for the Varattaru river basin. This could be due to the soil erosion from the basin and down slope movement of topsoil and bedrock material, washout of the soil mass and cutting of stream banks. The hydrologic response of the basin has youthful stage, will have high to moderate rate of erosion during peak runoff and need appropriate soil and water conservation measures. The hypsometric curve expresses medium to complex denudational processes and the linear river morphological changes of this river basin. This study suggests that many artificial recharge structures are suggested at many places to increase the groundwater potential and to control the soil erosion. Low hypsometric integral indicates suitable locations for recharge structures (Keripatti, Kilaparai, Ellapudiampatti and near Harur) and moderate values are suitable sites for preventing soil erosion and also runoff. 245
5. Conclusions Figure 6: Hypsometric curve as obtained for river Varattaru. This study highlights the importance of hypsomertic analysis for rainwater harvest practices and management for the river basin at suitable locations for controlling further erosion, reducing the runoff, increasing the groundwater potential and various stages of landform processes in the Varattaru river basin. So with remote sensing data and open source tools it is becomes less tedious to make hypsometric integrals and curves. Though, the available data and the software module has some limitations, it can be considered to be an encouragement for further study. References 1. Kokkas, N.A. and Miliaresis, G., (2008), Geomorphometric Mapping Of Grand Canyon From The 1-Degree USGS DEMs, ISPRS, proceedings, XXXV, www.isprs.org/proceedings/xxxv/congress/comm4/papers/460.pdf, Accessed on 20-Feb-2011. 2. Pike, R.J. and Wilson, S.E. (1971), Elevation-relief ratio, hypsometric integral and geomorphic area-altitude analysis, Geological Soc. Am. Bull., 82:1079-1084. 3. Ritter, D.F., Kochel, R.C. and Miller, I.R. (2002), Process Geomorphology. McGraw Hill, Boston. 4. Strahler, A.N. (1952), Hypsometric (area-altitude) analysis of erosional topography, Geological Soc. Am. Bull., 63, pp 1117-1141. 246
5. Schumm, S.A. (1956), Evolution of drainage systems and slopes in bad-lands at Perth Amboy, New Jersey, Geol. Soc. Am. Bull., 67, pp 597 646. 6. Singh, O., Sarangi, A. and Sharma, M.C. (2008), Hypsometric integral estimation methods and its relevance on erosion status of north-western Lesser Himalayan Watersheds, Water Res. Mgt., 22, pp 1545-1560. 7. Wei Luo and John M. Harlin, (2003), Theoretical Travel Time Based on Watershed Hypsometry, Journal of the American Water Resources Association, pp 785 792. 247