INTERNATIONAL JOURNAL OF GEOMATICS AND ...International Journal of Geomatics and Geosciences Volume 2 Issue 1, 2011 73 morphometric analysis is derived from the pioneer works of Horton,

INTERNATIONAL JOURNAL OF GEOMATICS AND GEOSCIENCES Volume 2, No 1, 2011

© Copyright 2010 All rights reserved Integrated Publishing services Research article ISSN 0976 – 4380

Submitted on July 2011 published on September 2011 71

Quantitative and Spatial Analysis of Fluvial Erosion in relation to Morphometric Attributes of Sarujharna Basin, East Singhbhum,

Jharkhand Sandipan Ghosh

M.Phil. Scholar, PostGraduate Dept. of Geography, The University of Burdwan, Burdwan, West Bengal, India [email protected]

ABSTRACT

Being the southeastern part of famous Chotanagpur Plateau of India, the Sarujharna Basin is deemed to be considered as a small museum of Indian geology and geomorphology. On the tectonically stable and frequently modified Dhanjori Highlands (southwest of Singhbhum Shear Zone, copper belt) rivers like Sankh, Netra, Sarujharna, Jou, Gara etc. crave out several geomorphic architects (youthold phase) which signify the variable intensity of fluvial erosion. Having different magnitude of rock résistance and spatial variability of forest cover, the monsoonal wetdry type of climate plays a crucial role in hillslope erosion and channel erosion. The present article emphasizes on the spatial distribution and quantification of fluvial erosion taking drainage basins and slope facets as an ideal geomorphic unit. Side by side, to realize the pattern of erosion we have focused on surface runoff, length of overland flow, constant of channel maintenance, hillslope erosion model, length and number of 1 st order stream which are the indirect morphometric measurements of normal erosion. Along with it Geographical Information System (GIS) is used to depict the physical appearance of erosion in thematic maps.

Keywords: Morphogenetic region; surface runoff; length of overland flow; constant of channel maintenance; hillslope erosion model; erosion intensity and GIS

1. Introduction

Erosion is a natural process of Earth’s environment. It is the progressive removal of soil or rock particles from the parent mass by a fluid agent (here only water erosion is considered). Variations of slope and relief, drainage networks and typical landforms are the glimpses of erosion and also result of tectonic activity. The whole process of water erosion is divided into two forms of erosion: (1) channel erosion and (2) slope erosion. Denudation of the surface starts from rainbeat and under the force of gravity, on a slope a vector is added to the movement of particles. We know that ‘little of the earth’s topography is older than Tertiary and most of it no older than Pleistocene’. So most of the landscape details have been produced during the current cycle of erosion, but there may exist many planation surfaces. Side by side in the monsoonal wetdry type of climate rainfall and temperature play a significant role in magnitude of geomorphic processes.

Quantitative and Spatial Analysis of fluvial erosion in relation to Morphometric attributes of Sarujharna Basin, East Singhbhum, Jharkhand

Sandipan Ghosh

International Journal of Geomatics and Geosciences Volume 2 Issue 1, 2011

72

Being a store house of rich mineral deposits, Dhanjori Highlands of East Singhbhum has carried out the museum of erosional landforms of Subarnarekha River system. It is very tough to estimate, regionalize and show the patterns of fluvial erosion, but the significant quantitative basin analysis by Horton, Strahler, Schumm, Chorley, Melton etc. assist us in the actual representation of ground reality, taking contours as a major tool. Morphometric measurements and its spatial representation can be considered as indirect tools to realize the different forms of fluvial erosion. The main study is based on the Sarujharna Basin which has highest elevation of 570 m and lowest elevation of 98 m from mean sea level respectively.

2. Objectives of the Study

While the drainage basin is considered as an open system or a combination of numerous subsystems, then a large number of processes operate in this unit. Erosion processes are the basic functions of inputoutput system of a basin. In every geomorphic study always a new fact is come into view from spatiotemporal analysis of fluvial erosion patterns of a basin (from a different angle of view). So it is worthwhile to tell the objectives of this erosional study. These are as follows:

1. Understanding the role of climate to the degree of geomorphic processes; 2. Estimation of primary erosion process, i.e. surface runoff;

3. Analyse the Basin slope and its relation with other parameters; 4. Assess several essential morphometric index and its spatial distribution based on

drainage networks and contours to understand variable magnitude of water erosion;

5. Mapping the spatial distribution of erosion intensity; and 6. Modelling the hillslope erosion to provide a brief view of sediment yield and soil

loss.

3. Method and Techniques

The emphasis of the geomorphic study has been laid on in depth study of contours, field works, recording data, empirical observation, thematic map and statistical interpretation. The whole study is divided into (1) quantitative approach and (2) processform approach. The quantitative approach of geomorphology is focused on the numerical measurement of the geomorphic unit with special emphasis on the linear aspects, because it serves the successful proof of some empirical analysis of fluvial erosion. The processform approach is emphasised on the forms of the earth, slope variations, drainage networks and water erosion (i.e. sheet erosion, slope erosion and channel erosion).

The subbasins of 4th order Sarujharna Basin (e.g. thirty subbasins of 1 st , 2 nd and 3 rd stream orders) and slope facet are taken as ideal geomorphic unit of study. To make successful the analysis, we have used geological map (Geological Survey of India, 2001), toposheets of 73 J/6 and J/7 (Survey of India, 1977), Landsat TM satellite image (2006), SRTM data of 90 m resolution (2008) and numerous literatures. Here all the fluvial


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morphometric analysis is derived from the pioneer works of Horton, Strahler, Schumm, Chorley etc. Most of the statistical works and calculations are done in SPSS 14.0 software. Raw image processing, georeferencing of toposheet, shape file creation of basin boundary, subsetting of satellite and SRTM and contouring are done in ERDAS 9.1 and ArcGis 9.2. After preparing a georeferenced base map, all the thematic maps are prepared in MapInfo 9.0 software.

3.1 Location of Study Area

The Sarujharna Basin is a 4 th order Basin (NWSE orientation and area: 37.77 km 2 ) of the river system of Sankh which itself is a tributary of the Subarnarekha River. The basin is situated in the Musaboni block of East Singhbhum district (Jharkhand). Longitudinal extension of the basin is 88°21’E to 88°28’E and latitudinal extension is 22°28’N to 22°34’N (figure 1 and 2).

Figure 1: Satellite Standard FCC image of Sarujharna Basin (2006)


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Figure 2: Location Map of Study Area

4. Results and Discussion

4.1 Geological Setting

The study of the geology of Singhbhum was done by many scholars like H.C. Jones (1922), Dunn (1929, 1934, 1940), Iyer (1932), Krishnan (1935), Dunn and Dey (1942) etc. According to Jones the region has the glimpse of Dharwar formation. From the Arachean to the recent alluvium, all the formations with their striking individuality are present here. The following sequence of lithology is widely acclaimed (Satpathi, 1965).


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Table 1: Geology of the Southern Singhbhum Region

Tertiary Deposits and recent Alluvium

Kolhan Sediments Singhbhum Granite

Basic Rocks, Lavas and Tuffs

Ironore Stage

Sandstone and Conglomerate Dhanjori Stage Conglomerate Granite Gneiss Granophyres

Felspathic Schists and Phyltite Chaibasa Stage

Mica Schists Source: S. C. Mukhopadhyay, 1980, p.241 and 242

At south of the copper belt zone, the presence of Dhanjori sandstoneconglomerates provides good examples of sedimentation of a geosynclines (Dhanjori basin). On this almost peneplained surface Dhanjori lavas were poured (Satpathi, 1981). During the Tertiary period the peneplained surfaces were uplifted to different elevations during Oligocene, midMiocene, and PliocenePleistocene. On this complex geological platform the rivers like Subarnarekha, Sankh, Garra, Netra, Katra etc. carved out a jumble of variety of landforms. Highest relief is associated with hard gneiss, quartzite, basalt and epidiorite and low relief is associated with micaschist and phyllites. Dhanjori group of rocks (coarse basic tuff, quartzite, schistose rocks and epidirote) occurs as bands aligning more or less along NWSE direction.

4.2 Other Physical Conditions

It is the southeastern part of the Chotanagpur plateau, having a monsoonal climate but according to Koppen’s classification the region experiences Savanna climate (AW). In the summer season (MarchMay) the mean monthly temperature lies between 29 to 35 0 C and in winter season (NovemberFebruary) the mean monthly temperature ranges from 14.6 to 17.8 0 C. The average amount of rainfall (19011950) ranges between 100 to 150 cm. Based on climate at present 50.98% of the total basin area is covered under dry deciduous (Mahua, Asan, Palas etc.) and dry peninsular Sal forest. There is a Murakanjia reserved forest and a Kundaluka protected forest within the Musaboni block. The soils of the region vary from redloamy soil to laterite soil. The presence of iron oxide, morum beds (duricrust) and deep chemical weathering are chief features of pedogenesis.


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4.3 Morphogenetic Processes and Drainage Basin Characteristics

In accordance with the climatic mode of interactions, i.e., the total complex of current exogeneic processes and also according to the typical relief forms actually produced in every climatic zone by the processes, the land surface of the earth can be divided into numerous climatemorphological zones or morphogenetic regions by different geomorphologists.

Budel (1944, 1948) has suggested the existence of the ‘formkreisen’ or what may be called ‘morphogenetic region’. The concept of a morphogenetic region implies that under a certain set if climatic conditions particular geomorphic processes will predominate and give to the landscape characteristics which will set it off from landscapes developed under different climatic conditions (Thornbury, 1969).

The chief features of this typical morphogenetic region are as follows:

1. The region belongs to Moderate to Selva morphogenetic region (Peltier, 1950) and according to Chorley, Schumm and Sugden’s model (1984) the Tropical Wet Dry morphogenetic processes (Savanna, tropical sheetwash zone) are operated here;

2. It has been found that rainsplash, sheetwash, overland flow, chemical weathering and flash floods are the unique pedogeomorphic processes operating in this region. Seasonal water table fluctuations allow a complex capillary migration and leaching of dissolved constituents in the continuous flow zone;

3. The major factor of laterite formation over Granite is ‘climate’. It is generally agreed that alternating conditions of wetdry are needed for sesquioxide precipitation. The higher the temperature of percolating water the more effective it is in decomposing the rocks and lowering the silica content; and

4. Leading geomorphic processes high pluvial erosion rate, Minimum to moderate mechanical weathering, chemical weathering (seasonal maximum, accelerated by water, giving deep weathering and two weathering zones, at the surface and at the weathering front; surface crusts of Al and Fe generated during dry seasons), mass wasting (mod.max.), fluvial processes (mod.max. highly seasonal sheet floods, rill wash and channel flow), wind action (min.mod.), seasonal rainsplash and sheetwash erosion and laterisation.

The fundamental step in quantitative basin analysis is the demarcation of basin area and the stream orders following a system introduced by Strahler (1952). The Sarujharna Basin is subdivided into twenty 1 st order basins, six 2 nd order basins, four 3 rd order basins and final 4 th order main basin. To understand the overall morphometric signatures of the basin (table 2) the following indices are employed mean basin area in km 2 (Au), drainage density (Dd), ruggedness number (Rn), relief ratio (Rh), constant of channel maintenances (C), length of overland flow (Lg), mean channel slope (Sc), mean ground slope (Sg), maximum valley side slope (θmax) and elongation ratio of basin shape (Re).


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Table 2.Mean morphometric properties of subbasins

Basin Au Dd Rn Rh C Lg Sc Sg θmax Re 1st order 0.34 3.25 0.429 0.15 0.35 0.59 6.59 8.38 15.1 0.61 2nd order 1.18 2.91 0.777 0.12 0.35 0.54 3.80 6.78 17.8 0.60 3rd order 4.10 2.71 0.801 0.10 0.37 0.58 3.05 5.93 16.2 0.78 4th order 37.8 2.56 1.210 0.03 0.39 0.35 1.11 7.06 15.2 0.51 Source: computed by authors

4.4 Estimation of Surface Runoff

After the depression storage of precipitation the rest of the precipitation falling on the catchment area, after satisfying the infiltration demand, is temporarily detained on the ground surface and when sufficient depth is built up it travels over the ground surface towards the stream channels in the form of minor rivulets. This is called the ‘overland flow’.

Table 3: Computation of Annual Runoff of Sarujharna Basin (after Khosla, 1949)

YEAR 1951 1955 1960 1965 197

0 1975

198

0 1985

199

0

199

5 1999

Runoff

(RA )

in mm

213.

2

353.

6

452.

7

356.

1

387

.7

661.

2 388

1005

.1

153

.5 0

1113

.8

Total

Rainfa

ll in

mm

1010

.7

1179

.4

1203

.1

1185

.5

116

2

1431

.3

120

8

1859

.2

947

.9

232

.7

1974

.7

Source: Computed by authors

Surface runoff is defined as that part of the total runoff which travels over the ground surface to reach a stream channel and then through the channel to reach the basin outlet (Reddy, 2008). Therefore, estimation of surface runoff is provided an idea of volume of water required for erosion and transportation in a drainage basin. Based on the assumptions that mean temperature can be taken to be a complete measure of all the factors that are responsible for the losses of water, A.N. Khosla proposed the following formula for runoff. The loss in any month Lm is computed from Lm=5. Tm (for Tm>4.5 C), where Tm is the mean temperature in the month m in C. then the runoff for the month m is Rm= Pm Lm (Rm>=0), where Pm is the precipitation in the month m in mm. the annual runoff RA in mm is then given by RA= sum of Rm (Reddy, P.J.R.,2008). From this analysis it is observed that except 1995 the amount of surface runoff was increased,


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which means that it creates acceleration of overland flow, slope erosion and sediment production (figure 3).

SACTTER WITH REGRESSION LINE

y = 0.3237x + 29.641 R 2 = 0.488

0

200

400

600

800

1000

1200

0 1000 2000 3000 4000

p2/P

TOTA

L ANNUAL RUNOFF

IN m

m

Figure 3: With increasing concentration of annual rainfall (p 2 /P), annual runoff is increased (here p is the rainfall in the month with greatest precipitation and P is the mean

annual precipitation)

4.5 Gradient Aspect of Drainage Basin and Channel Networks

The area under study, a drainage basin or any other selected area, will have to be grouped into different elevation zones, for each of which the average slope will have to be determined. The average slope between two contours is measured by ‘HansonLowe method’. Here intercontour angle of Sarujharna Basin can be calculated from the formula: tan θ = contour interval / intercontour distance. Here the Basin is subdivided into elevation zone of 50 m interval (100550 m). The computed mean of tangent of slope is 7.47 0 with standard deviation of 2.66 and variance R 2 of 7.08. The slope frequency distribution of 31 basins (fig 4) is positively skewed (0.367), which mean slopes are erosional origin in this basin (figure 4). It has been observed that a close quantitative relationship of power form (log Sg=0.52+0.47 log Sc) between average channel slope (Sc) and average ground slope (Sg) over Sraujharna Basin having different rock type and relief.


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Figure 4: Surface slope histogram

Figure 5: Average slope map

From the average slope map we have found that upstream segment of the Basin has increasing ground slope (11 to 19 0 ) and downstream segment has decreasing slope (5 0 to 1 0 ). High relief variation within small area produces steep slope which is depicted in the DEM (Digital Elevation Model). It generates high magnitude of surface flow concentration (kinetic energy) in the monsoonal rainfall. Therefore the map shows that northern and western portions of the Basin have more potential to generate fluvial erosion due to high degree of steepness of average ground slope (figure 5 and 6). The


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downstream segment of the Basin shows aggradational slope i.e. the upstream transported materials are deposited towards mouth with increasing thickness of alluvium.

Figure 6: Digital elevation model

‘Ruggedness Index’ (combination of drainage density and relative relief per km 2 , after R.J. Chorley, 1965) of a basin is an indicative of how much the fluvial process dissects the landscape. The high value denotes the high ruggedness of topography having high drainage density and high magnitude of relief (i.e. gorge, spur and valley). The statistical analysis reveals that basin wise maximum valley side slope (after Melton, 1958) controls the ruggedness of the basin (y = 0.0018 x 2.0168 ) i.e. high valley side slope provides high kinetic energy to water erosion and transportation of eroded materials through channels forming dissected profile of the basin (fig 7).


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Relation Between Maximum Valley Side Slope and Ruggedness Index

y = 0.0018x 2.0168

R 2 = 0.8079 Correlation: 0.8469

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 5 10 15 20 25 30

Maximum Valley Side Slope of SubBasin

Rug

gedn

ess Index of Sub

Basin

Figure 7: Relation between valley side slope and Ruggedness index

4.6 Length of Overland Flow

Surface runoff follows a system of downslope flow paths from the drainage divide to the nearest channel. R.E. Horton (1945) defined length of overland flow (Lg) as the length of the flow path, projected to the horizontal of nonchannel flow from a point on the drainage divide to a point on the adjacent stream channel. Lg is approximately half the average distance between stream channels and is therefore approximately equal to half the reciprocal of drainage density: Lg=1/2 Dd. In order to take into account the effect of slope of stream channels and ground, R. E. Horton refined this generalization to read Lg=1/2 Dd √1(Sc / Sg) 2 where Sc is the mean channel slope and Sg is average ground slope.

The spatial analysis of the distribution of Lg (fig 8) reveals the fact that the basins of all orders are more advanced in the cyclic stage because these basins are characterized by higher values of Lg (0.890.33) in respect of channel slope and ground slope ratio (more sheet erosion and overland flow).

In fact the Lg is largely controlled and affected by geological formation, soil characteristics, plant cover, rainfall intensity and infiltration capacity. The upper catchment areas are covered with thick forest and hard rockbasement (gneiss and quartzite). The result is marked reduction in overland flow but central and lower catchment areas have barren land, agricultural land, loose red loamy soil, comparatively soft schist and micaschist rocks, the result is increment in overland and sheet flow in monsoonal rainfall. Overall 1 st order basins have greater length of overland flow (more sheet flow and low channel erosion). Again Lg is positively correlated with circularity ratio (r=+0.87) and elongation ratio (r=+0.83) of the basin shape.


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Figure 8: Length of overland flow map

4.7 Constant of Channel Maintenance

Schumm (1956) used the inverse of drainage density (Dd) as a property termed constant of channel maintenance C. Thus

C =1/Dd=Au/ sum of Lu

This constant, in units of square feet per foot, has the dimension of length and therefore increases in magnitude as the scale of landform units increases. Specifically, the constant C tells the drainage area required to maintain one unit of channel length and it is a measure of watershed erodibility. Regions of resistant rock type, or with a surface of high permeability so that rainfall infiltrates the soil, or with a forest cover should have a high constant of channel maintenance and a low drainage densities ranging from 1.42 to 5.6 (Morisawa, 1962).

The spatial distribution of C reveals (fig 9) that 1 st order, 2 nd order, 3 rd order and 4 th order basins require 0.170.85 km 2 , 0.270.42 km 2 , 0.320.45 km 2 and 0.39 km 2 of surface area respectively to support each linear km of channel in the Sarujharna basin. C is directly negatively correlated with drainage density (r= 0.86) and maximum valley side slope (r= 0.58). High value of C reveals the low magnitude of erodibility of surface topography due to hard geological structure and thick forest cover. Again low value of C denotes high magnitude of erodibility. Therefore, the upper catchment area is more resistant to erosion than lower portion in this particular morphogenetic system.


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Figure 9: Constant of channel maintenance map

4.8 Spatial Distribution of Erosion Intensity

To consider the channel erosion we have taken the number and length of 1 st order streams of Sarujharna Basin. After the discussion of slope and relief variations, now an attempt is made to match the erosion intensity with the average slope. High frequency of 1 st order streams signifies high magnitude of channel or gully erosion on hillslopes. So here the product of number and length of 1 st order streams is taken as a measure of erosion intensity per km 2 (Morgan, 1986). High erosion intensity (6 to12) is observed at the northern portion of the Basin (fig 10). The orientation of isolines has similarity with average slope map which means the regions of steep average slope guide high value of erosion intensity. Also it is found that the region of minimum length of overland flow (<0.4 km) has maximum erosion intensity (>8) which means maximum gully erosion. Though, rock resistance and forest cover play a separate role. We can compare the erosion intensity map with DEM (fig 6) to realize the strength of fluvial erosion on high relief and steep slope in the upstream section of the Basin. Erosion intensity of topography is also available as dissection index and ruggedness index which are highly correlated with average slope (r = 0.69 and 0.64 respectively).


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Figure 10: Erosion intensity map

4.9 Estimation of Hillslope Erosion (sample study)

Free water acquires both rotational and translation energy as it concentrates to form channelized flow. The rotational energy detaches soil by scouring. The energy of translation enables the flowing water to transport the detached material downhill. Since these energies are concentrated and applied to restricted areas of the ground surface, the flowing water carves grooves into the surface soil. In their initial stages and near the crest of slopes, these grooves are known as ‘rills’. As soon as it starts runoff promptly develops diminute rills and that portion of runoff that flows between rills is called ‘sheet’ or ‘interrill erosion’ (Morgan, 1986).

To measure the rill and interrill erosion of hillslope (fig 11) we have taken webbased ‘Hillslope Erosion Model’ which has been developed by United States Department of Agriculture Agricultural Research Service (USDAARS) research scientists. This model


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incorporates the physicallybased model (kinematic wave equations) which includes the laws of conservation of mass and energy. The further information about the ‘Hillslope Erosion Model’ is readily provided at web link:

“http://eisnr.tucson.ars.ag.gov/hillslopeerosionmodel/”

The main used equations of this model are put forward below. Overland flow on a plane is approximated by the kinematic wave equations:

where h is the average, local flow depth (m), t is time (s), q is discharge per unit width (m 2 /s), x is distance in the direction of flow (m), r is rainfall excess rate (m/s) and the depthdischarge coefficient is K.

The sediment continuity equation for overland flow is:

where c is total sediment concentration (kg/m 3 ), E i is interrill erosion (kg/s/m 2 ) and E r is net rill erosion or deposition rate (kg/s/m 2 ).

The sedimentyield equation for a runoff event as:

where Qs is total sediment yield for entire amount of runoff per unit width of the plane (kg/m), Q is the total storm runoff volume per unit width (m 3 /m), Cb is mean sediment concentration over the entire hydrograph (kg/m 3 ) and x is distance in the direction of flow (m).


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Table 3: Prediction of rill and interrill erosion of sample slope segment using Hillslope Erosion Model (USDAARS)

Slope

Segm

ent

length

canop

y

cover 4

groun

d

cover 5 inter

rill rill rill

runof

f total

Segm

ent

number

detachme

nt

detachme

nt

depressio

n

volume 1

sediment

yield 3

slope 2

metr

e

% % % (Kg/m 2 )

(Kg/m 2 ) (Kg/m 2 ) (m 3 /

m) (Kg/m

)

1 10.9 2.5 65 12 1.158 0 0.002 2.292 12.606

2 26.1 4.4 23 15 1.327 0.141 0 5.489 34.916

3 49 10 19 18 1.185 1.095 0

10.30

5 87.128

4 71.1

12.

2 16 22 1.006 1.527 0

14.95

2

143.10

8

5 99

13.

4 9 26 0.873 1.695 0 20.82

214.74

9

6 121.2

12.

2 0 20 1.197 2.891 0

25.48

8

305.50

6

7 151.7

12.

2 0 29 0.798 1.089 0

31.90

3

363.06

5

8 175.2 20 0 25 0.956 6.391 0

36.84

5

535.70

9

9 190.8

13.

4 16 22 1.006 2.694 0

40.12

5

593.43

7

10 201.9 17. 5 11 1.75 18.665 0 42.46 820.04


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87

8 1

11 222.1 6.7 0 11 1.795 0 2.688

46.70

8

801.99

3

Note: 1 Mean annual runoff 210.3 mm for the year 19301960 and soil erodibility of sandy clay loam 0.56; 3 Sediment Yield at the bottom of the hillslope 36.110 T/ha; 2 slope angle was estimated by field survey using abney level; 4 canopy cover and 5 ground cover were recorded through field observations.

From the above analysis it has been found that from 222.1 metre length of slope total sediment yield is derived at a rate of 36.110 ton/ha/year, having 46.78 m 3 /m of runoff volume at the base of slope. The table 3 and figure 11 depict the rill and interrill soil detachment in relation to soil parameters of the sample slope profile. High degree of slope steepness and long length of steep slope enhance the hillslope erosion and sediment yield with increasing runoff.

Figure 11: Hill side soil erosion relationship

5. Conclusion

The Sarujharna Basin has been tectonically active over a long period of time. The last tectonic event represents a stage of resumption movements along the old line of fracture (shear zone), during much later times, ranging between lateTertiary to recent. From the altimetric frequency curve we have found that there are two proper erosion surfaces (150 metre and 400450 metre respectively) which bear the imprints of upliftments. Again skewness gives a positive value (1.015), which signifies those heights are the product of long erosional processes not of aggradations. Hypsometric integral of 40% (erosional integral60%) validates the mature stage of landform evolution. Steep escarpments of


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valley sides (Kalajhor, Sasdih and Lenjobera villages) are the outcome of upstream vertical incision of Sarujharna River due to base level changes. In some parts of the Highlands have patches of laterites (over quartzites, schist and gravel bed) which were formed during Cainozoic era. It also bears the imprints of old erosion surfaces. According to Geological Survey of India (2006) the region has influenced by sheet erosion, gully erosion and deforestation types of natural hazards which contribute in sediment yield. The amount of overland flow is high in the upper and middle portion the Basin due to low permeability of metamorphic rocks and presence of thin soil cover. Implementing Fournier index (1960), it has been established that the sediment yield of the basin varies from 6.13 7.82 tons/km 2 /annum which is directly correlated with the incidence of annual rainfall concentration. Above all relief, hillslope and slope length, canopy cover, drainage density, runoff, length of overland flow, mean ground slope, monsoonal rainfall concentration etc. are the chief determinants of water erosion and sediment yield (erosion of Dhanjori group of rocks) in the Sarujharna Basin.

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INTERNATIONAL JOURNAL OF GEOMATICS AND ...International Journal of Geomatics and Geosciences Volume 2 Issue 1, 2011 73 morphometric analysis is derived from the pioneer works of Horton,