4. Ijmcar - Prominence of Relief and Dissection

8/20/2019 4. Ijmcar - Prominence of Relief and Dissection

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PROMINENCE OF RELIEF AND DISSECTION STUDIES IN

GEOMORPHOMETRIC CHARACTERISATION OF DRAINAGE BASINS

KARTHIKA KRISHNAN

Research Scholar, School of Earth and Atmospheric Sciences, Madurai Kamaraj University, Madurai, Tamil Nadu, India

ABSTRACT

Geomorphometry is an interdisciplinary field that has evolved from mathematics, the earth sciences, and most

recently computer science. This branch of science, which is concerned with the quantitative land surface analysis, is an

important component of geomorphological research. The present article makes an earnest attempt to identify the

significance of quantitative appraisal of two geomorphometric parameters; relative relief and dissection index in

unveiling the terrain morphometry of a river basin in South Western Ghats. The study has been carried out by

integrating mathematics and computer applications in land surface analysis. It has been concluded that he parameters

taken for the work proves to be the best indicators of regional dissection as well as that of vertical erosion of the land

surface.

KEYWORDS: Geomorphometry, Relative Relief, Dissection Index, Terrain, River Basin

Received: Jan 13, 2016; Accepted: Jan 21, 2016; Published: Jan 27, 2016; Paper Id.: IJMCARFEB20164

INTRODUCTION

Geomorphometry is viewed as the science of quantitative analysis of earth surface shape (Pike, 2000).

This branch of science, which is concerned with the quantitative land surface analysis, is an important component

of geomorphological research. It gathers various mathematical, statistical and image processing techniques that

can be used to quantify morphological, hydrological, ecological and other aspects of a land surface. While

geomorphology focuses on the identification, classification and characterization of landforms and land surfaces,

and the processes which create them, geomorphometry is primarily concerned with the characterization and

representation of the land surface itself.

The earliest studies of geomorphometry were minor applications in the fields of exploration, natural

philosophy, and physical geography- especially geomorphology. Today, it is inextricably linked with

geoinformatics, various branches of engineering, and most of the earth and environmental sciences.

Geomorphometry, which is a modern, analytical-cartographic approach, is the science of quantitative land-surface

analysis (Pike, 1995 and 2000; Rasemann et.al, 2004) which attempts to represent bare-earth topography by the

computer manipulation of terrain height (Tobler, 1976 and 2000). Geomorphometry is an interdisciplinary field

that has evolved from mathematics, the earth sciences, and most recently computer science.

Geomorphometry primarily involves computer characterisation and analysis of topography. With the

wider availability of contour maps after the mid 19th century the relief analysis flourished. Relative relief and

Dissection index are among the important properties that have gained significance due to the advancement of

mathematical, statistical and computer applications in relief studies. Relative relief and Dissection index are

Or i gi n al Ar t i c

l e

International Journal of Mathematics and

Computer Applications Research (IJMCAR)

ISSN(P): 2249-6955; ISSN(E): 2249-8060

Vol. 6, Issue 1, Feb 2016, 31- 38

© TJPRC Pvt. Ltd


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32 Karthika Krishnan

Impact Factor (JCC): 4.6257 NAAS Rating: 3.80

geomorphometric parameters that are used for the overall assessment of morphological characteristics of terrains and

degree of dissection of the region associated with drainage basins.

The present article endeavors to identify the significance of the quantitative appraisal of relative relief and

dissection index in unveiling the terrain morphometry of a river basin in South Western Ghats.

AREA OF STUDY

The Tambraparni River Basin (TRB) (with an areal extent of 867.52 km2) located in the south-west of Indian

peninsula (Figure 1) and occupying the western flank of the Sahyadri Ranges is composed of the basins of River Kodayar,

Figure 1

Paraliar and Kuzhithuraiar. The geographic location of the basin is between the north latitudes 8˚10'58"to 8˚34'39"

and the east longitudes of 77˚05'47" to77˚29'31". Geologically, the basin consists of two types of terrains, namely,

sedimentary terrain and, hard rock terrain. Sedimentary rocks, referable to Tertiary and Quaternary ages of Phanerozoic

age are found restricted along the coastal tract and adjoining lowland zone of the basin. The sedimentary rocks of the

coastal belt include younger fluviatile, fluvio-marine sequences, of Quaternary and of Recent age together with a small

occurrence of aeolian sediments and a succession correlated with Cuddalore Sandstone Formation. Crystalline rocks of

Archaean to late Proterozoic age (referable to charnockite and khondalite groups, garnetiferous quartzo-feldspathic gneiss

and, garnet- biotite gneiss) occupy the major portion of TRB and the region of exposure of these rocks constitutes the hard

rock terrain of the basin.

METHODOLOGY ADOPTED

The entire basin of Tambraparni River has been captured from the latest available Survey of India topographic

sheets of 1:25,000 scale and delineated with the help of ArcGIS 9.3 software. In lieu with the ease of understanding the

terrain of the basin, the entire basin has been delineated and divided into four major sub-basins and 18 minor basins (Figure

2). In the subsequent phase of geomorphic study, GIS has been used extensively in the present work.


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Prominence of Relief and Dissection Studies in 33

Geomorphometric Characterisation of Drainage Basins


In the following phase of estimating the relative relief and dissection index, the entire area of TRB is subdivided

into a number of squares with a series of vertical and horizontal gridlines, each spaced at one minute interval. This was

followed by the estimation of R hp and DI for each square of the grid covering the entire drainage basin. The range of

quantified values are next classified into five categories, on the basis of the relative relief and dissection index valuesdetermined for the unit,

Figure 2

Following a classification scheme and finally an isopleths map showing the Rhp and DI of various parts of the

basin was prepared.

RESULTS AND DISCUSSIONS

Relative Relief (Rhp)

The geomorphometric attribute of relative relief has been first brought out by Glock in 1932. . Glock used the

term ‘amplitude of relief’ and defined it as ‘the vertical distance from a horizontal and fairly flat upland down to the initial

grade of the streams’. Melton (1957) suggested a method to calculate the relative relief by dividing the difference of the

height between the highest and lowest points in the basin (H) with basin perimeter (P), and thus


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Relative Relief = H /P,

whereas, J.C. Maxwell (1960) defined the term as the quotient of maximum relief and basin perimeter. However

these two schemes produce only an identical value of relative relief for a given basin. Therefore, isopleth maps of basins

cannot be prepared with the resulting values. In addition, spatial variation of relative relief within the basin cannot be

properly visualized on the basis of the values obtained.

Relative relief is defined by Smith (1950) as the difference in height between the highest and the lowest points in

a unit area in terms of square grid (one grid being a square kilometre square minute). Therefore grid method wherein the

basin is covered with a mesh of grid squares and calculation of relative relief is made on the basis of the difference

between the highest and the lowest elevations, forms the most suitable as well as the more reliable method for the

determination of relative relief of fluvial basins. In the present study the methodology based on Smith’s definition of

relative relief has been followed. The Figure 3 provides the estimated values of relative relief of TRB.

The values of relative relief obtained for each unit, is then generally categorized into six groups based on the

range of values, as shown hereunder (Table 1)

Table 1: Smith’s Scheme of Categorization of Relative Relief

Sl. No Category Range of Relative Relief (in Metre)

1 Extremely low relative relief 0 - 15m

2 Moderately low relative relief 15 - 30m

3 Low relative relief 30 - 60m

4 Moderate relative relief 60 - 120m

5 Moderately high relative relief 120 - 240m

6 High relative relief above 240m

Lower values of relative relief indicate flatter character of the associated topography and relatively lesser degree

dissection and erosion. An isopleth map, prepared on the basis of Smith’s classification of relative relief in table 1, is

shown in Figure 4.

It is significant to note that among the four sub-basins of TRB, the Paraliar basin has the largest share of 89.1 %

(153.068 km2) of basinal area under very high dissected terrain while the remaining area of 20.79 km2 falls under

moderately dissected to highly dissected category. The least dissected terrain of TRB occurs along the coastal belt that

stretches from Marthandamthurai to Tuttur covering an area of 7.866 km2. Except for a narrow patch close to the

northeastern boundary, the remaining portion of Kuzhithuraiar basin is characterized by low to moderately dissected

terrain. In contrast, excluding a portion located in the neighbourhood of Pechiparai and Upper Kodayar dams the remaining

portion of Kodayar basin comprises terrains of very high dissection.

Dissection Index ( DI )

The term dissection is defined as the process of erosion whereby the continuity of a relatively even topographic

surface is gradually sculptured or destroyed by the development of gullies, ravines, canyon or other kinds of valleys;

especially, the work of streams in cutting or dividing the land into hills and ridges, or into flat upland areas, separated by

fairly close networks of valleys. This process is applicable especially to surfaces such as plains and peneplains. Dissection

index is one of the important morphometric properties of drainage basins and it indicates the degree and magnitude of

dissection of a


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520

50

10

10

48

45

50

25

77 6987 90

40150 73

1324520 50 14953 35

56

50 2645 30

40 45

5030 8240

5040 7060

10 10 50 61122 50685040 908010 10 50 40 1225040 90

20

50 47 30

680

60

499

506040

560

50 70

50 70 74 30 115

461

604060 6650

120 7890

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40 5040 40 30 12340

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90

191600 610 890 790886

391 670 320

464

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420 720 200 300260 380

360

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416

50 45

430 460 220 223 140370 472

40 30 410

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350

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40 70 7567 6 1 60330 343

210 190 100 230 360173 15880 90

181 104 295 277161 100240 124

96 165 390478 220754 606 620 550 280838 709590 930

864 860 863634 610471 590

510

900 765 798580 840400 680 690

560 750 756335 660447 580 760

39 359 342 1303 0 1 24282 40 789

568 1027

370 425529 642

460

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440248

790 550560

842

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94 70

140 517 45470 6070 40 500195 122280 180 58060 6070 50

122

50 53 350 601 44970 1101 38 7 1 39890 181290 450

50

10 10

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1191120 752

7851072660

270820 559

425

399

285

183

5 5 21 5

60 60

730

940

550558 720

610

670 789

271 334

57

428 441

162

5

VALUES OF RELATIVE RELIEFOF

TRB(in metre)

Scale1 square grid = 1 minute square

Fig: 3

20

131 261

426

580

580

Figure 3

Terrain. As far back as 1936, Leonids Slaucitajs used real area and projected area between two successive

contours to calculate dissection index between different surfaces of altitude or terrains, adopting the equation;

where Ra = real area between two successive contours and Pa = projected area between the same contours. Later,

de Smet used mean gradient- expressed as a percentage, i.e. 100x tangents (angle), in the numerator to express the index of

dissection (Chorley, 1972). As these two methods are time consuming, tedious and less reliable, Dov Nir (1957) proposed

a relatively easier and reliable method taking into consideration the dynamic potential state of the region concerned, in

which the ratio between relative altitude (relative relief) and the perpendicular distance from the erosion base as the

dissection index. Following is the formula for the computation of dissection index adopted by Dov Nir:

DI = Rhp / H

The values of dissection index, when derived following the method suggested by Dov Nir will vary between 0 and

1(This means that the values can never be more than 1 except in the case of a vertical cliff). Likewise, a DI value of 0

(denoting complete absence of dissection) is possible only in theory (It is also worth noting that the value is occasionally

expressed in terms of percentage). The values of DI obtained is generally categorized into five groups based on the range

of values, as shown hereunder (Table 2)


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Table 2: The Five Categories of Terrains Based on Dissection Index ( DI ) Ranges

Sl. No Category Range of Dissection Index ( DI ) values

1 Extremely low dissection 0.0 - 0.1

3 Low dissection 0.1 - 0.2

4 Moderate dissection 0.2 - 0.35 High dissection 0.3 - 0.4

6 Very high dissection over 4

From figures 5 and 6, it can be found that localities with the lowest values of dissection index are located only in

the neighbourhood of Upper Kodayar Reservoir. This indicates a lower degree of gully and ravine erosion. This can be

correlated with the presence of hard crystalline metamorphic rocks in this region. Localities with higher values of

dissection index are found in the Paraliar basin as well as in the Chittar basin. This indicates greater intensity of fluvial

action and the presence of a relatively closer network of stream channels in the respective localities. In addition, areas

within the coastal belt below 10m contour are also characterized with higher values of dissection index and this indicates

the presence of fluvial and fluvio-marine sedimentary cover which are easily prone to channelization.

0.29

1

1

0.71

1

0.92

1

0.500.79 0.51

0.690.751 1 0.780.91 0.47

1

0.64 0.541 0.71

0.80 0.69

0.620.75 0.620.67

1 0.83 0.550.80 0.500.630.620.80 0.750.891 0.80

0.67

0 .8 2 0 .5 0 0 .8 0

0.88

0.44

0.77

0.620.890.83

0.80

0.86 0.53

0.71 0.87 0.88 0.43 0.69

0.84

0.860.800.86 0.420.83

0.640.62

0.50

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0.89 0.730.91

0.67 0.710.57 0.57 0.75 0.920.80

0.24

0.75

0.180.68 0. 58 0 .5 2 0 .4 4

0.82

0.140.60 0.61 0.64 0.510.63

0.56 0.76 0.19

0.59

0.21

0.81 0.83 0.24 0.220.47 0.75

0.26

0.49 0.43 0.81

0.09

0.62 0.53

0.63 0.65 0.82 0.71 0.530.77 0.65

0.67 0.60

0.62

0.500.79 0.63

0.81

0.80

0.33 0.44 0.890.48 0.600.80 0.81

0.70 0.68 0 .5 3 0 .7 2 0 .8 00.68 0.720.50 0.53

0.64 0.63 0.78 0.750.71 0.630.77 0.76

0.52 0.69 0.780.79 0.710.84 0.88 0.35 0.30 0.150.57 0.420.67 0.65

0.52 0.52 0.520.63 0.550.63 0.64

0.60 0.51 0.520.72 0.680.82 0.73 0.49

0.70 0.51 0.540.74 0.770.83 0.73 0.66

0.36 0.84 0.81 0.590.43 0.670.82 0.44 0.60

0.62 0.62

0.82 0.830.85 0.86

0.79

0.54

0.850.81

0.91 0.570.69

0.89

0.550.84

0.70 0.70

0.64 0.86 0.850.70 0.600.70 0.57 0.850.71 0.600.75 0.69 0.710.66 0.750.70 0.63

0.55

0.50 0.51 0.85 0.86 0.830.64 0.650.73 0.70 0.820.53 0.690.76 0.85

1

1 1

0.80 0.640.76 0.800.56

0.130.79 0.50

0.720.830.71

0.090.63 0.40

0.25

0.17

0.76

0.78

0.44 0.81

0.54 0.54

0.59

0.54

0.840.83 0.65

0.45

0.51 0.48

0.84 0.81

0.84

1

VALUES OF DISSECTION INDEXOF

TRBScale

1 square grid = 1 minute square

1

0.16 0.19

0.56

0.88

0.82

0.79 0.59

Figure 4


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Figure 5

Figure 6

CONCLUSIONS

The present article makes an earnest attempt to identify the significance of quantitative appraisal of relative relief

and dissection index in understanding the terrain morphometry of Tambraparni River Basin. The study has been carried out

with through various morphometric techniques by integrating mathematics and computer applications in earth science. The

parameters taken for the work i.e., relative relief and dissection index proves to be the best indicators of regional dissection


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as well as that of vertical erosion (degradation) of the land surface.

REFERENCES

1. CHORLEY, R.J., 1972. Spatial Analysis in Geomorphology, Methuen and Co Ltd., London, UK.

2. DOV NIR, 1957. Landform analysis of Mt. Karnel, Geographical Review, Vol. 47, pp. 564-569.

3.

GLOCK, W.S., 1932. Available relief as a factor of control in the profile of a landform, Journal of Geology, Vol. 40, pp. 74-83.

4.

MAXWELL, J.C., 1960. Quantitative geomorphology of the San Dimas experimental forest, California, Technical Report- 19,

pp. 1-95, Office of Naval Research, Department of Geology, Columbia University, New York.

5.

MELTON, M.A., 1957. An analysis of the relations among elements of climate, surface properties, and geomorphology,

Department of Geology, Columbia University, Technical Report II, Project NR 389-042, NewYork.

6.

PIKE, R.J., 1995. Geomorphometry- progress, practice, and prospect. Zeitschrift für Geomorphologie Supplementband

Vol.10, pp. 221-238.

7.

PIKE, R.J., 2000. Geomorphometry- diversity in quantitative surface analysis. Progress in Physical Geography, Vol. 24, pp. 1-

20.

8.

RASEMANN, S., SCHIMIDT, J., SCHROTT, L. and DIKAU, R., 2004. Geomorphometry in mountain terrain, In GIS &

Mountain Geomorphology, (ed.) M. P. Bishop and J. F. Shroder, Berlin: Springer, pp. 101-145.

9.

SMITH, K.G., 1950. Standards of grading texture of erosional topography, American Journal of Science, Vol. 248, pp. 655-

668.

10. TOBLER, W.R., 1976. Analytical cartography: The American Cartographer, Vol. 3, No. 1, pp. 21-31.

11.

TOBLER, W.R., 2000. The development of analytical cartography- a personal note, Cartography and Geographic Information

Science Vol. 27, pp. 189-194.

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4. Ijmcar - Prominence of Relief and Dissection