ORIGINAL ARTICLE

Drainage morphometry and its influence on hydrologyin an semi arid region: using SRTM data and GIS

P. D. Sreedevi • P. D. Sreekanth • H. H. Khan •

S. Ahmed

Received: 31 August 2010 / Accepted: 29 November 2012 / Published online: 19 December 2012

� Springer-Verlag Berlin Heidelberg 2012

Abstract An attempt has been made to study drainage

morphometry and its influence on hydrology of Peddavanka

watershed, South India. Drainage networks for the sub-

basins were derived from topographical map (1:50,000) and

Shuttle Radar Topographic Mission (SRTM) Digital Ele-

vation Model (DEM) data used for preparing elevation,

slope and aspects maps. Geographical information system

(GIS) was used in evaluation of linear, areal and relief

aspects of morphometric parameters. The study reveals that

SRTM DEM and GIS-based approach in evaluation of

drainage morphometric parameters and their influence on

hydrological characteristics at watershed level is more

appropriate than the conventional methods. The mean

Bifurcation ratio (Rb) of the entire basin is 3.88 which

indicate that the drainage pattern is not much influenced by

geological structures. VIII sub-basin have high elongation

ratio (Re), basin relief (Bh), Ruggedness number (Rn) and

time of concentration (Tc). It indicates that the erosion and

peak discharges are high in these basins. Therefore, the

construction of the check dams and earth dams will help in

reducing peak discharge on the main channel. These studies

are very useful for implementing rainwater harvesting and

watershed management.

Keywords Drainage morphometry � Geographical

information system � Shuttle Radar topographic mission �Hydrology � Watershed

Introduction

Watershed management studies are important in semi-arid

and arid regions for protecting the limited water resources,

because at most of the places, surface water resources are

scarce and at some places it is totally absent. In these areas,

groundwater recharge depends only on rainfall. For

understanding rainfall recharge mechanism and ground-

water budget estimation in the watersheds level, first we

have to understand the morphometric parameters at the

basin level.

Watershed management requires physiographic infor-

mation such as watershed slope, configuration of channel

network, location of drainage divide, channel length and

geomorphologic parameters viz. relative relief, shape fac-

tor, circulatory ratio, bifurcation ratio and drainage density

for watershed prioritization and implementation of soil and

water conservation measures. Traditionally, these parame-

ters are obtained from topographic maps or field surveys.

Over the past two decades, this information has been

increasingly derived from digital representation of topo-

graphy, generally called the digital elevation models

(DEM) (Moore et al. 1991; Martz and Garbrechet 1992).

The automated derivation of topographic watershed data

from DEM is faster, less subjective and provides more

reproducible measurements than traditional manual tech-

niques applied to topographic maps (Tribe 1992).

The use of DEM through geographical information

system (GIS) is a powerful approach in this matter, since

automatic methods to analyse topographic features are

allowed with both operational and quality advantages,

while using SRTM data with GIS techniques is a speed,

precision, fast and inexpensive way for calculating

morphometric analysis (Sarangi et al. 2003; Obi Reddy

et al. 2004; Sreedevi et al. 2005, 2009; Valeriano et al.

P. D. Sreedevi (&) � H. H. Khan � S. Ahmed

National Geophysical Research Institute (CSIR), Uppal Road,

Hyderabad 500606, A.P., India

e-mail: pd_sreedevi@yahoo.co.in

P. D. Sreekanth

National Academy of Agricultural Research Management

(ICAR), Rajendhra Nagar, Hyderabad 500407, A.P., India

123

Environ Earth Sci (2013) 70:839–848

DOI 10.1007/s12665-012-2172-3

2006; Grohmann et al. 2007; Ozdemir and Bird 2009).

Here, the authors made an attempt to study drainage

morphometry and their influence on hydrological charac-

teristics (runoff, infiltration, etc.) in the study area.

Study area

Peddavanka watershed situated in the drought prone areas

of Rayalaseema Districts of Andhra Pradesh, South India.

The Peddavanka originates in the southern part of Kurnool

District and drains through northeastern part of Anantapur

district and joins the Pennar River near Chitturu, Anantapur

District. The study area falls in the Survey of India To-

posheet no. 57 E/11, 12, 16 and 57 F/9 between latitude

15�310 to 14�930N and longitude 77�570 to 77�760E(Fig. 1). The total area of the basin is 378.25 km2 and

average annual rainfall is 560 mm.

Geology and structures

The terrain is undulating with several denudational ridges

and hills. The area exposes mainly rock types belonging to

the Peninsular Gneissic Complex (PGC) of Achaean age,

granites and other basic and acidic intrusions (Fig. 2).

The PGC is the wider spread and mainly represented by

banded and streaky gneisses and granitoids. The gneisses

comprise Hornblende–Biotite gneisses, Hornblende gneis-

ses, Biotite gneisses. The granitiods in the form of plutons

or dome shaped bodies of varied dimensions are seen

amidst the gneisses. These granitoids which are massive

and foliated comprise granite and granodiorite (GSI 1995,

2004).

The PGC is intruded by K-rich granites of lower Pro-

terozoic age. These granite bodies which are of varied

dimensions are both grey and pink, the latter being

younger.

Fig. 1 Location map of the study area

840 Environ Earth Sci (2013) 70:839–848

123

Quartz veins and Dolerite/gabbro dykes are mark the

last phase of igneous activity and cut across all the above-

mentioned litho units and show various trends. The general

trend of foliation in rocks of PGC and metamorphic is

NNW–SSE with steep to sub-vertical dips. Joints are seen

along NNW–SSE, S–E and N–S trends. The thickness of

the regolith is varying 2–3 m across the watershed.

Methodology

The Peddavanka watershed has been delineated based on

the water divide line concept. The drainage morphometric

analysis of the Peddavanka watershed was prepared based

on the published topographic maps on a 1:50,000 scale and

also on SRTM data. The drainage network of the basin was

scanned and digitized as available on toposheets (1:50,000).

The basin was divided into 10 sub-basins and morphometric

analysis was carried out at sub-basin level in SAGA GIS

(Olaya 2004). Based on the drainage order, the drainage

channels were classified into different orders (Strahler

1964). Basin parameters viz., area, perimeter, cumulative

length of streams and basin length were measured in GIS.

Parameters, such as Ruggedness number (Rn), drainage

density (Dd), bifurcation ratio (Rb), circulatory ratio (Rc),

elongation ratio (Re), constant of channel maintenance

(C) and time of concentrations (Tc) were evaluated with

established mathematical equations (Table 1).

The SRTM DEM was used for delineating slope, relief

and aspects maps in the watershed. Using SRTM is a

fast and inexpensive way for regional geomorphological

analysis. The data were taken from the http://www.srtm.usgs.

gov/data/obtaining.html and then imported to the SAGA

GIS. The evaluated morphometric parameters were

grouped as linear, relief and areal parameters.

Results and discussion

The total drainage area of Peddavanka watershed is

378.25 km2 and it is divided into 10 sub-basins for the

analysis (Fig. 3). The development of drainage networks

depends on geology, precipitation apart from exogenic and

endogenic forces of the area. The drainage pattern of the

basin ranges from dentritic to sub-dentritic at higher ele-

vations and parallel to sub-parallel in the lower elevations.

Based on the drainage orders, the Peddavanka watershed

has been classified as sixth order basin to analyse linear,

areal and relief morphometric parameters.

Linear parameters

Computation of the linear parameters, such as stream order,

stream number for various orders, bifurcation ratio, stream

length for various stream orders and length ratio are

described below.

Stream number (Nu)

It is obvious that the number of streams gradually

decreases as the stream order increases. With the applica-

tion of GIS, the number of streams of each order and the

total number of streams were computed (Fig. 4). Total

number of streams in the watershed is 923, in that 706

streams are 1st order, 167, 39, 8, 2 and 1 are 2nd, 3rd, 4th,

5th and 6th order streams, respectively (Table 2).

Stream order (U)

The designation of stream order is the first step in the

drainage basin analysis. The streams of the Peddavanka

watershed have been ranked according to the Strahler’s

(1964) stream ordering system and the number of stream

of each segment (Nu) of the order (U) is presented in

Table 2. The details of stream characteristics confirm to

Horton’s (1932) ‘‘law of stream numbers’’ which state that

the number of streams of different orders in a given

drainage basin tends closely to approximate an inverse

geometric ratio. It also confirms to Horton’s (1932) the

‘‘laws of stream length’’ which states that the average

length of streams of each of the different orders in a

drainage basin tends closely to approximate a direct

Fig. 2 Geology map

Environ Earth Sci (2013) 70:839–848 841

123

geometric ratio. The variation in order and size of the

tributary basins are largely due to physiographic and

structural conditions of the region. Application of this

ordering procedure through GIS shows that the drainage

network of the study area is of a sixth order basin. Three

sub-basins (II, V and VI) were identified under third order,

three sub-basins (I, III and IV) under fourth order and one

(VIII) sub-basin under fifth order and X sub-basin is under

sixth order (Table 2).

Stream length (Lu)

Stream length is one of the most significant hydrological

features of the basin as it reveals surface runoff

characteristics streams of relatively smaller lengths are

characteristics of areas with larger slopes and finer textures.

Longer lengths of streams are generally indicative of flatter

gradients. Generally, the total length of stream segments is

high in first order streams and decreases as the stream order

increases. The number of streams of various orders in the

basin is counted and their lengths from mouth to drainage

divide are measured with the help of SAGA GIS (Table 2).

Bifurcation ratios (Rb)

The term ‘bifurcation ratio’ (Rb) was introduced by Horton

(1932) to express the ratio of the number of streams of any

given order to the number in the next lower order.

According to Strahler (1964), the ratio of number of

Table 1 Linear, areal and relief morphometric parameters with description

S.

no.

Parameters Formulae Description References

Linear parameters

1 Stream order (U) Hierarchical rank The smallest permanent streams are called ‘‘first order’’. Two first order

streams join to form a larger, second order stream; two second order

streams join to form a third order, and so on. Smaller streams entering a

higher ordered stream do not change its order number

Strahler (1964)

2 Stream length (Lu) Length of the

stream

The average length of streams of each of the different orders in a drainage

basin tends closely to approximate a direct geometric ratio

Horton (1945)

3 Bifurcation ratio

(Rb)Rb ¼ Nu

Nuþ1The ratio of number of streams of a given order (Nu) to the number of

segments of the higher order (Nu ? 1) is termed as the Rb

Strahler (1964)

Areal parameters

4 Drainage density

(Dd)Dd ¼ Lu

AThe length of stream channel per unit area of drainage basin Horton (1945)

5 Drainage texture

(T)

T = Dd 9 Fs The product of Dd and Fs Smith (1950)

6 Stream frequency

(Fs)Fs ¼

PNu

A

The ratio between total number of streams and area of the basin Horton (1945)

7 Elongation ratio

(Re)Re ¼ D

L¼ 1:128

ffiffiffiAp

LThe ratio between the diameter of a circle with the same area as that of the

basin (A) and the maximum length (L) of the basin

Schumn

(1956)

8 Circularity ratio

(Rc)Rc ¼ 4pA

�P2 The ratio of basin area (Au) to the area of a Circle (Ac) having the same

perimeter as the basin

Strahler (1964)

9 Form factor (Ff) Ff ¼ A�L2 The ratio of the basin area to the square of the basin length Horton (1945)

10 Constant of channel

maintenance (C)

C = km2/km The inverse of drainage density Schumn

(1956)

11 Texture ratio (Rt) T = N1(1/P) The ratio between the first order streams and perimeter of the basin Ozdemir and

Bird (2009)

Relief parameters

12 Relief R = H-h The maximum vertical distance between the lowest and the highest points of

a basin

Hadley and

Schumm

(1961)

13 Basin relief (Bh) Bh = hmax - hmin The maximum vertical distance between the lowest and the highest points of

a sub-basin

Ozdemir and

Bird (2009)

14 Ruggedness

number (Rn)

Bh 9 Dd The product of the basin relief and its drainage density Ozdemir and

Bird (2009)

15 Time of

concentrations

(Tc)

Tc = 0.0078

L0.77(L/H)0.385The ratio between length of main stream and basin relief Kirpich (1940)

842 Environ Earth Sci (2013) 70:839–848

123

streams of a given order (Nu) to the number of segments of

the higher order (Nu ? 1) is termed as the Rb.

In the study area mean Rb varies from 2.93 to7.50; the

mean Rb of the entire watershed is 3.88 (Table 2). Usually

these values are common in the areas where geologic

structure does not exercise a dominant influence on the

drainage pattern (Strahler 1964; Chow 1964). Strahler

(1957) demonstrated that bifurcation ratio shows a small

range of variation for different regions or for different

environment dominates. The Rb between first and second

order streams may be considerably higher than the Rb of

higher order streams in areas of active gullies and ravines

(Verstappen 1983). Sub-basins Rb values range from 1 to

10. The higher Rb for few sub-basins is the result of large

variation in frequencies between successive orders and also

indicates the mature topography.

Areal parameters

Area of a basin (A) and perimeter (P) are the important

parameters in quantitative morphology. The area of the

basin was computed by converting the map of the basin

into polygon form. The total area of the basin is found to be

378.25 km2 (Table 3). Perimeter is the length of the

boundary of the basin which can be drawn from topo-

graphical maps. Basin area is hydrologically important

because it directly affects the size of the storm hydrograph

and the magnitudes of peak and mean runoff. It is inter-

esting that the maximum flood discharge per unit area is

inversely related to size (Chorley et al. 1957). The aerial

aspects of the drainage basin such as drainage density (D),

drainage texture (T), stream frequency (Fs), elongation

ratio (Re), circularity ratio (Rc), form factor (Ff), constant

of channel maintenance (C) and texture ratio (Rt) where

calculated and results are given in Table 3.

Drainage density (Dd)

The Dd is the ratio of total channel segment lengths

cumulated for all orders within a basin to the basin area,

which is expressed in terms km/km2. Dd is generally

inversely related to hydraulic conductivity of the underly-

ing soil. For steep slopes, an inverse correlation has been

modeled by Montgomery and Dietrich (1992). Generally,

Dd increases with decreasing infiltration capacity of the

underlying rocks and/or decreasing transmissivity of the

soil.

The Dd for the whole basin is 2.03 km/km2, while those

of the X sub-basins are shown in Table 3. Dd gives an idea

about the physical properties of the underlying rocks in the

study area. Low Dd occurs in the regions of highly resistant

and permeable sub-soil materials with dense vegetated

cover and low relief; whereas high Dd is prevalent in the

region of weak impermeable sub-surface materials which

Fig. 3 Drainage with sub-basins

Fig. 4 Drainage with different stream orders

Environ Earth Sci (2013) 70:839–848 843

123

are sparsely vegetated and show high relief in the study

area.

Drainage texture (T)

The drainage texture (T) depends on a number of natural

factors, such as climate, rainfall, vegetation, rock and soil

type, infiltration capacity, relief and stage of development

(Smith 1950). The soft or weak rocks unprotected by

vegetation produce a fine texture, whereas massive and

resistant rocks cause coarse texture. Sparse vegetation of

arid climate causes finer textures than those developed on

similar rocks in a humid climate. The texture of a rock is

commonly dependent upon vegetation type and climate

(Dornkamp and King 1971). In simple terms T is the

product of Dd and Fs.

The T of the whole basin is 4.96, while those of the X

sub-basins are shown in Table 3. According to Smith

classification, T of the whole basin comes under coarse

texture, as the values are \4.0.

Stream frequency (Fs)

The Fs of a basin may be defined as the number of streams

per unit area (Horton 1945).

The Fs of the whole basin is 2.44 km/km2, while the Fs

for X sub-basins are shown in Table 3. Generally, high

stream frequency is related to impermeable sub-surface

Table 2 Linear parameters of Peddavanka watershed

Sub-basins Basin

length

(L)

Stream orders (U) Total

stream

no.

Stream length (Lu) Total

stream

length

Bifurcation ratio (Rb) Mean

Rb

1 2 3 4 5 6 1 2 3 4 5 6 Rb1 Rb2 Rb3 Rb4 Rb5

I 9.91 32 9 2 1 44 19.45 6.87 8.85 3.81 38.97 3.56 4.50 2.00 3.35

II 8.60 50 10 1 61 20.26 16.22 8.72 45.20 5.00 10.00 7.50

III 7.45 58 17 6 1 82 33.16 11.94 10.27 5.25 60.61 3.41 2.83 6.00 4.08

IV 5.60 23 7 2 1 33 11.80 7.75 4.10 2.47 26.12 3.29 3.50 2.00 2.93

V 7.50 32 6 1 39 14.83 5.63 6.55 27.01 5.33 6.00 5.67

VI 8.42 36 9 1 46 17.63 4.49 7.97 30.09 4.00 9.00 6.50

VII 15.90 134 32 6 1 173 70.35 30.64 12.91 11.21 125.12 4.19 5.33 6.00 5.17

VIII 11.21 96 16 7 1 1 121 57.44 25.23 9.53 13.69 1.05 106.93 6.00 2.29 7.00 1.00 4.07

IX 6.90 39 11 3 1 54 17.12 5.88 3.54 5.55 32.09 3.55 3.67 3.00 3.40

X 41.70 206 50 10 2 1 1 270 140.53 59.78 19.88 10.77 28.62 16.73 276.31 4.12 5.00 5.00 2.00 1.00 3.42

Peddavanka 41.70 706 167 39 8 2 1 923 402.56 174.43 92.30 52.76 29.67 16.73 768.46 4.23 4.28 4.88 4.00 2.00 3.88

Table 3 Areal parameters of Peddavanka watershed

Sub-basin Area

(A)

Perimeter

(P)

Drainage

density (Dd)

km/km2

Drainage

texture

(T)

Stream

frequency

(Fs)

Elongation

ratio (Re)

Circularity

ratio (Rc)

Form

factor

(Ff)

Constant of

channel

maintenance (C)

Texture

ratio

(Rt)

I 119.37 23.33 2.01 4.57 2.27 0.50 0.45 0.20 0.50 1.37

II 22.09 21.55 2.05 5.65 2.76 0.62 0.60 0.30 0.49 2.32

III 28.02 22.22 2.16 6.33 2.93 0.80 0.71 0.50 0.46 2.61

IV 16.80 17.32 1.55 3.05 1.96 0.83 0.70 0.54 0.64 1.33

V 10.40 18.72 2.60 9.74 3.75 0.49 0.37 0.18 0.39 1.71

VI 12.30 20.28 2.45 9.15 3.74 0.47 0.38 0.17 0.41 1.78

VII 54.51 40.80 2.30 7.28 3.17 0.52 0.41 0.22 0.44 3.28

VIII 46.65 37.48 2.29 5.95 2.59 0.69 0.42 0.37 0.44 2.56

IX 10.70 17.91 3.00 15.14 5.05 0.53 0.42 0.22 0.33 2.18

X 157.41 133.91 1.76 3.01 1.72 0.34 0.11 0.09 0.57 1.54

Peddavanka 378.25 119.04 2.03 4.96 2.44 0.53 0.34 0.22 0.49 5.93

844 Environ Earth Sci (2013) 70:839–848

123

material, sparse vegetation, high relief conditions and low

infiltration capacity. It mainly depends on the lithology of

the basin and reflects the texture of the drainage network.

Elongation ratio (Re)

The Re is defined as the ratio between the diameter of a

circle with the same area as that of the basin (A) and

maximum length (L) of the basin Schumn (1956). It is a

very significant index in the analysis of basin shape which

helps to give an idea about the hydrological character of a

drainage basin.

Elongation ratio for the basin is estimated as 0.53, and

the ten sub-basins are shown in Table 3. The variation of

the elongated shapes of the basins is due to the guiding

effect of thrusting and faulting in the basin. High Re values

indicate that the areas are having high infiltration capacity

and low runoff. The sub-basins II, III, IV and VIII are

characterized by high Re, and sub-basins V, VI and X have

low Re, respectively. The sub-basins having low Re values

are susceptible to high erosion and sedimentation load.

Circularity ratio (Rc)

The Rc has been used as an areal aspect ans is expressed as

the ratio of basin area (Au) to the area of a circle (Ac)

having the same perimeter as the basin (Strahler 1964). It is

affected by the lithological character of the basin.

Circularity ratio values approaching 1 indicates that the

basin shapes are like circular and as a result, it gets scope

for uniform infiltration and takes long time to reach excess

water at basin outlet, which further depends on the pre-

valent geology, slope and land cover. The ratio is more

influenced by length, frequency (Fs) and gradient of vari-

ous orders rather than slope conditions and drainage pattern

of the basin. The Rc of the whole basin is 0.34, while those

of the ten sub-basins are shown in Table 3.

Form factor (Ff)

Form factor is defined as the ratio of the basin area to the

square of the basin length. Horton (1945) proposed this

parameter to predict the intensity of a basin of a defined

area. The Ff of the whole basin is 0.22, while the Ff of ten

sub-basins is shown in Table 3.

Form factor reveals that sub-basins having low Ff have

less side flow for shorter duration and high main flow for

longer duration and vice versa. This condition prevails in

sub-basins I, V, VI and X. High Ff exists in sub-basins III

and IV with high side flow for longer duration and low

main flow for shorter duration causing high peak flows in a

shorter duration.

Constant of channel maintenance (C)

Schumn (1956) used the inverse of drainage density as a

property termed as ‘‘Constant of channel maintenance

(C)’’. It depends on the rock type, permeability, climatic

regime, vegetation cover and relief as well as duration of

erosion. It decreases with increasing erodibility (Schumn

1956). Higher values suggest more area is required to

produce surface flow, which implies that part of water may

get lost by evaporation, percolation, etc. lower value

indicates less chances of percolation/infiltration and hence

more surface runoff (Bhagwat et al. 2011). The sub-basins

V and IX have low C values of 0.39 and 0.33, respectively.

It indicates that these sub-basins are under the influence of

high structural disturbance, low permeability; steep to very

Fig. 5 Elevation map

Environ Earth Sci (2013) 70:839–848 845

123

steep slopes and high surface runoff. The sub-basins of IV

and X have highest C values of 0.64 and 0.57, respectively

and are under very less structural disturbances and less

runoff conditions (Table 3).

Texture ratio (Rt)

Texture ratio is defined as the ratio between the first order

streams and perimeter of the basin. Rt is an important factor

in the drainage morphometric analysis which depends on

the underlying geology, infiltration capacity of bedrock and

relief aspects of the sub-basins. VII sub-basin contains

highest Rt value in the watershed (Table 3).

Relief parameters

Elevation

Elevation is defined as the maximum vertical distance

between the lowest and the highest points of a basin. It is

an important factor in understanding the denudational

characteristics of the basin. The DEM map of the study

area reveals that the maximum height of the whole

watershed is 616.36 m above mean sea level (amsl). The

study area is associated with dissected hills in the north-

eastern part of the watershed and lowest minimum

283.57 m amsl near the confluence of the river (Fig. 5).

Basin relief (Bh)

Basin relief is defined as the maximum vertical distance

between the lowest and the highest points of a sub-basin.

Bh aspects of the sub-basins play an important role

in drainage development, surface and sub-surface water

flow, permeability, landforms development and erosion

properties of the terrain. The analysis reveals that the sub-

basins VII, VIII, IX and X have relief more than 150 m

(Table 4). The high Bh values indicates the gravity of water

flow, low infiltration and high runoff conditions.

Ruggedness number (Rn)

Ruggedness number is defined as the product of the basin

relief and its drainage density. Rn indicates the structural

complexity of the terrain. An increased peak discharge is

the result of the network’s improved efficiency due to an

increase in relief and drainage density (Ozdemir and Bird

Table 4 Relief parameters of Peddavanka watershed

Sub-basins Relief Basinrelief(Bh)

Ruggednessnumber (Rn)

Time ofconcentrations(Tc)

Max Min

I 424.56 355.61 68.95 0.10 1.50

II 426.18 367.93 58.25 0.11 1.90

III 532.16 389.43 142.73 0.24 1.89

IV 553.55 439.66 113.89 0.14 0.78

V 539.03 420.99 118.04 0.30 0.80

VI 569.21 413.05 156.16 0.30 0.81

VII 616.36 366.79 249.57 0.45 3.52

VIII 513.15 323.17 189.98 0.36 3.26

IX 543.12 324.36 218.76 0.59 0.77

X 592.88 283.57 309.31 0.49 8.09

Peddavanka 616.36 283.57 332.79 0.68 25.64

Fig. 6 Aspect map

846 Environ Earth Sci (2013) 70:839–848

123

2009). The analysis shows that the Rn value varies between

0.1 and 0.59. Rn value more than 0.5 for IX sub-basin

(Table 4). The basins having high Rn values are highly

susceptible to erosion and therefore susceptible to an

increase peak discharge.

Time of concentration (Tc)

The time of concentration is defined as the ratio between

length of main stream and basin relief. Tc is the time

required for a particle of water to travel from the most

hydrologically remote point (source) in the watershed to

the point of collection (outlet). Tc values varies from 0.77

to 8.09. For whole basin Tc is 25.64 (Table 4). The highest

Tc value represents the greatest length in time for water to

travel from the most distant point of the sub-basin to its

outlet.

Slope

Slope analysis is an important parameter in geomorphic

studies. The slope elements, in turn are controlled by the

climatomorphogenic processes in the area having the rock

of varying resistance. An understanding of slope distribu-

tion is essential as a slope map provides data for planning,

settlement, mechanization of agriculture, deforestation,

planning of engineering structures, morphoconservation

practices, etc. (Sreedevi et al. 2005, 2009). In the study

area, slope map was prepared based on the SRTM data

were converted into slope and aspect grids using SAGA

GIS (Conrad 2006). Aspect grid is identified as ‘‘the down-

slope direction of the maximum rate of change in value

from each to its neighbors’’ (Gorokhovich and Vous-

tianiouk 2006) (Fig. 6). Slope grid is identified as ‘‘the

maximum rate of change in value from each cell to its

neighbors’’, using methodology described in Burrough

(1986). The slope of Peddavanka watershed area varies

from 0.8� to 6.4� with a mean slope of 1.83� and slope

standard deviation 2.53�. A high degree of slope is noticed

in the northern and northeastern parts of the basin (Fig. 7).

Conclusion

The study reveals that SRTM DEM and GIS-based

approach in evaluation of drainage morphometric para-

meters and their influence on hydrological characteristics

at watershed level is more appropriate than the conven-

tional methods. GIS-based approach facilitates to analyze

different morphometric parameters and to explore the

relationship between the drainage morphometry and

hydrological characteristics.

• The variation of the elongated shapes of the basins is

due to the guiding effect of thrusting and faulting in the

basin.

• The Rc of the basins is less than 1. It indicates that the

infiltration rate is varying throughout the basin.

• Sub-basins I, V, VI and X are having low Ff, it

indicates that less side flow for shorter duration and

high main flow for longer duration.

• High Ff in sub-basins II and IV with high side flow for

longer duration and low main flow for shorter duration

causing high peak flows in a shorter duration.

• Sub-basin IV having highest C values; it represents

that very less structural disturbances and less runoff

condition.

Fig. 7 Slope map

Environ Earth Sci (2013) 70:839–848 847

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• Sub-basins I, V, VI and X are having high Bh values,

which indicates that the gravity of water flow, low

infiltration and high runoff conditions are prevailing in

that basins.

• IX sub-basin having high Rn value indicates that it is

highly susceptible to erosion and therefore susceptible

to an increase peak discharge.

• Sub-basins III and IV have high Re and Ff. VIII sub-

basin having high Bh, Rn and Tc. It indicates that the

erosion and peak discharges are high in these basins.

Therefore, the construction of the check dams and earth

dams will help reduce peak discharge on the main

channel.

This study indicates that systematic analysis of mor-

phometric parameters using GIS can provide significant

value in understanding sub-basins hydrological character-

istics for watershed management planning.

Acknowledgments The authors wish to thank the Director NGRI

for permission to publish this paper. The first author gratefully

acknowledges the Department of Science and Technology (DST),

New Delhi, for financial assistance in the form of Fast Track Young

Scientist Project (No.SR/FTP/ES-49/2009).

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