Drainage Basin Morphometry

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CHAPTER 5

Drainage Basin Morphometry

5.1 Introduction

Morphometric analysis is refers as the quantitative evaluation of form characteristics

of the earth surface and any landform unit. This is the most common technique in

basin analysis, as morphometry form an ideal areal unit for interpretation and analysis

of fluvially originated landforms where they exhibits and example of open systems of

operation. The composition of the stream system of a drainage basin in expressed

quantitatively with stream order, drainage density, bifurcation ration and stream length

ratio (Horton, 1945). It incorporates quantitative study of the various components such

as, stream segments, basin length, basin parameters, basin area, altitude, volume,

slope, profiles of the land which indicates the nature of development of the basin.

This modern approach of quantitative analysis of drainage basin morphology was

given inputs by Horton (1945) the first pioneer in this field. Horton's law of stream

lengths suggested that a geometric relationship existed between the numbers of stream

segments in successive stream orders. The law of basin areas indicated that the mean

basin area of successive ordered streams formed a linear relationship when graphed.

Horton’s laws were subsequently modified and developed by several

geomorphologist, most notably by Strahler (1952, 1957, 1958, and 1964), Schumm

(1956), Morisawa (1957, 1958), Scheidegger (1965), Shreve (1967), Gregory (1966,

1968), Gregory and Walling (1973). Subsequently a number of books by Bloom

(2002), Keller and Pinter (1996) have further propagate the Morphometric analysis.

Stream profile analysis and stream gradient index by Hack (1973) is another milestone

in morphometric analysis. Many workers have used the principles developed by these

pioneers to quantitatively study the drainage basin as a tool for landscape analysis

(Sharma, 1987, Raj et. al., 1999, Awasthi and Prakash, 2001, Phukon, 2001, Sinha-

Roy 2002).

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Quantitative measurements of morphometry used as a reconnaissance tools to make

inferences about particular characteristic of an area viz., tectonic activity. Some

geomorphic indices like hypsometric integral, drainage basin asymmetry, stream

length gradient index, mountain front sinuosity etch are used a measure of active

tectonics (Keller and Pinter, 1996; Sinha-Roy, 2002). Landforms are created via

erosional and depositional processes, the geometry of which is controlled by the

processes that shape them. Morphometric analyses require measurement of linear

features, gradient of channel network and contributing ground slopes of the drainage

basin (Nautiyal, 1994). The morphometric analysis for individual sub basins has been

achieved through measurements of linear, aerial and relief aspect of the basin and

slope contribution (Nag and Chakraborty, 2003).

The basin geomorphic characteristics have long been believed to be important indices

of surface processes. These parameters have been used in various studies of

geomorphology and surface-water hydrology, such as flood characteristics, sediment

yield, and evolution of basin morphology (Jolly, 1982; Ogunkoya et al., 1984;

Aryadike and Phil-Eze, 1989; Breinlinger et al., 1993; Jensen, 1991). By including

basin characteristics such as elevation and main channel gradient, predictions of

stream discharge were substantially improved in comparison to using only drainage

area and precipitation (McArthur and Hope, 1993). More recently, terrain

characterization became an important part in modelling surface processes (Nogami,

1995). The detailed analysis of morphometric and morphological character indicate

the role of the neotectonics in shaping the drainage basin (Raj et.al., 1999).

Geographical Information system (GIS) and Remote sensing techniques using

satellite images are used as a convenient tool for Morphometric analysis. Many

workers have carried out morphometric analysis using these new techniques. Digital

Elevation Model (DEM) and Shuttle Radar Topography Mission (SRTM) widely

used in drainage basin analysis. Srivastava, 1997, Nag, 1998, Duarah et al., 2011,

carried out morphometric analysis, while Nag and Chakraborty (2003) deciphered the

influence of rock types and structures in the development of drainage network in hard

rock area.

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As the main objectives of this work was to discover holistic stream properties from the

measurement of various stream attributes, detailed morphometric analysis is carried

out for the 41 fifth-order drainage sub-basins of Jia Bharali River catchment and

discusses their feature and characteristic and also attempt to find out the stages of

geomorphic development with the help of different morphometric parameter viz.,

streams order, streams number, streams length, mean streams length, bifurcation

ratios, elongation factor, circularity index, shape factor, drainage density, stream

frequency, texture ratio, relief ratio, length of overland flow, constant channel

maintenance, infiltration number, hypsometric curve and longitudinal profiles.

Morphological Studies of rivers are very important to study the behaviour of a river,

its aggradations/degradation, shifting of the river course, erosion of river bank etc. and

to plan remedial measure for erosion and other related problems. Most of the streams

appear to be in conformity with the geological and structural setup of the area.

For detail morphometric analysis of the drainage within Jia Bharali River catchment at

first the fifth order sub basins are delineated from the available toposheet after

assigning ‘stream order’ to all the segments following Horton's (1945) method

modified by Strahler’s (1952). In general the entire fifth order sub basins are selected

for the morphometric analysis in following heads:

• Linear Aspects : one dimension • Areal Aspects : two dimensions • Relief Aspects : three dimensions

The prime objective of morphometric analysis is to find out the drainage characteristic

to explain the overall evaluation of the basin. Morphometric analysis comprises a

series of sequential steps. The drainage layer has been converted to digital format

through on-screen digitization from available Survey of India (SoI) topographic maps

using GIS software Arc-Info 9.1, in the scale of 1:50000 and the attributes were

assigned to create the digital database. Toposheet for the total basin catchment is not

available as the area has sensitive political controversy. Some part of the basin fall in

the international boundary of Bhutan and China. All measurements were directly

computed from the vector data that extracted from the topographic maps. The entire

drainage segments were digitized as lines separately for each order (Strahler 1952).

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Fifth order drainage sub-basins are delineated following surface water divide.

Topological polygons were created and the attribute Table generated thus yielded the

basinal areas. In absence of the Survey of India topographic maps for the

northernmost part of the Jia Bharali basin, the surface water divide and was delineated

with the help of satellite imagery and SRTM DEM. Major sub basin boundaries were

also delineated following this method. Thus 41 fifth-order drainage basins were used

as a statistical sample representative for the entire drainage system to compute the

morphometric parameters analysis (Figure 5.1, Table 5.1).

Figure 5.1: Delineated fifth order sub-basins for morphometric analysis

The morphometric parameters for each basin were directly computed from the vector

data extracted from the topographic maps (basic parameters). The data in the first

category includes maximum order of the streams, number of streams in each order,

length, area, perimeter, relief for each of the basins. Those of the second category are

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the bifurcation ratios, elongation factor, circularity index, shape factor, drainage

density, stream frequency, texture ratio, relief ratio, length of overland flow, constant

channel maintenance and infiltration number.

Linear, aerial and relief aspects of the basin were computed in GIS environment

followed by simple linear regression analysis to see the mutual dependency of some

variables viz., i) stream order vs. stream number, ii) stream order vs. stream length

and iii) stream order vs. Mean stream length. For hypsometric analysis the elevation

contour are generated in ArcInfo 9.1 from the SRTM DEM. The contour layer and

the basin boundary are merged in a single layer and converted into polygon. From the

attribute Table of this polygon layer the area the between two contours within the

basin are noted. Maximum height (H) is the difference between the maximum

elevation and the minimum elevation and, which are calculated by extrapolation.

Mean elevation for each basin also calculated by dividing the sum of frequency of

each pixel elevation by the total number of pixel in the basin. Details of the

morphometric parameters are tabulated followed by analysis of the parameters

through bivariate plots.

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Table 5.1: Fifth order sub basin index and basin name used in the study

Basin Index

Basin Name Basin Perimeter (km)

Basin Area (Sq km)

1 Dipota Nadi 85 255 2 Jorasar Nadi 64 91 3 Mansari Nadi 78 165 4 Dibru Nadi 36 59 5 Khari Dikrai Nadi 46 82 6 Upar Dikrai Nadi 41 75 7 Daigurang Nadi 33 37 8 Khaina Nadi 41 71 9 Lengtey Nadi 37 71 10 Diju Nadi 36 45 11 Pakke River 135 328 12 Tributary of Pakke River 22 28 13 Tributary of Kameng River 23 24 14 Pasa Nadi 58 118 15 Pani Nadi 32 49 16 Papu River 43 95 17 Chakrasong Nadi 39 64 18 Tributary of Pacha River 21 22 19 Pacha River 35 65 20 Lengpla Nadi 17 16 21 Phuchao Nadi 29 44 22 Kade Nala 28 42 23 Pakoti Nadi 35 75 24 Hoda Nadi 23 30 25 Huduri Nadi 29 36 26 Kaun or Hukubu Nala 35 48 27 Gayang River 47 102 28 Ki Nala 29 37 29 Miao Nadi 23 22 30 Upstream of Dinang Bru 33 52 31 Dibri Bru 34 51 32 Difya River 24 28 33 Khenda Nadi 20 22 34 Taamchin RI (Sashi Chu) 38 71 35 Meni Nadi 25 34 36 Nimsinggoto River 27 38 37 Dublo Kho 71 163 38 Tribtary of Tenga River 41 72 39 Dogong Kho 28 37 40 Sessa Nadi 31 44 41 Tipi Nala 61 103

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All the fifth order sub basins are grouped into three divisions. The group of the

completed fifth order drainage sub basin (Figure 5.2) are based on the lithotectonic

setup of the area. The basins in Zone-I are predominantly within the alluvium south of

HFT. Zone-II is mainly characterised by the folded Cenozoic/Gondwana sequence

with pertinacious E-W structural lineament spreading into both side of MBT but

within the HFT and the Pronounced NE-SW lineament. The Zone-III is characterised

by dissected crystalline terrain.

Figure 5.2: Showing the assign three Zone for the drainage basin

5.2 Linear aspects

The drainage network transport water and the sediments of a basin through a single

outlet, which is marked as the maximum order of the basin and conventionally the

highest order stream available in the basin considered as the order of the basin. The

size of rivers and basins varies greatly with the order of the basin. Ordering of streams

is the first stage of basin analysis.

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Stream Order (U)

There are four different system of ordering streams that are available Gravelius

(1914), Horton (1945), Strahler (1952) and Schideggar (1970). Strahler’s system,

which is a slightly modified of Hortons system, has been followed because of its

simplicity. Where the smallest, unbranched fingertip streams are designated as 1st

order, the confluence of two 1st order channels give a channel segments of 2nd order,

two 2nd order streams join to form a segment of 3rd order and so on. When two

channel of different order join then the higher order is maintained. The trunk stream is

the stream segment of highest order.

The total Jia Bharali drainage basin boundary and major river system are delineated

from the satellite imagery and SRTM. It is found that Jia Bharali River is an 8th order

stream. The analyses of morphometric parameters are carried out for the entire 41 fifth

order basin.

Stream Number (Nu)

The total number of stream segments present in each order is the stream number (Nu).

Nu is number of streams of order u. In this present study all the 5th basin are counted

and tabulated for the analysis from the attribute Table of the vector layer (appendix-

III). The total number of stream segments is found to decrease as the stream order

increases in all the sub basins. The study reveals that the development of 1st order

streams is maximum in the Himalayan dissected zones and minimum in the alluvial

plains (Table. 5.2). Similarly the numbers of 2nd and 3rd order streams are gradually

high from alluvial to highly dissected hills from south to north.

Stream Length (Lu)

The total length of individual stream segments of each order is the stream length of

that order. Stream length measures the average (or mean) length of a stream in each

orders, and is calculated by dividing the total length of all streams in a particular order

by the number of streams in that order. The stream length in each order increases

exponentially with increasing stream order.

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From the overall drainage of the study area shows the frequency of the drainage

development is less in the alluvial part (0.7 km-2) and high above the MBT (4.5 km-2)

whereas the overall drainage frequency is 3.8 km-2. It reflects the frequency of the

drainage is high in the upper part of MBT. The drainage density also shows that the

development of drainage is higher in the upper part of MBT. The alluvial part has a

drainage density of ~1 km-1 where as the area above the MBT is 2.9 km-1. The overall

drainage density of the area is 2.6 km-1. It clearly reflects that the drainage

development in the upper part of the MBT is high and the area is highly dissected.

Mean Stream Length (Lū)

Mean stream length of a stream channel segment of order ‘u’ is a dimensional

property revealing the characteristic size of components of a drainage network and its

contributing basin surface (Strahler, 1964). The lengths of stream segments of up to

5th order are measured and the total length as well as Mean Stream Length (Lū) of

each order is computed (appendix-III). The mean stream lengths of stream increase

with the increase of the order. But in some basin shows opposite relation, higher order

stream has a small mean length. In Zone-I, Basin 2, in Zone-II, Basin 4, 12, 13, 16 and

in Zone-III, Basin 18, 24, 29, 33, 35 the length of 5th orders stream is extremely short.

These basin shows variable lithology with asymmetry in nature and these basins are

found along the major structural lineament. The basins shows high hypsometric

integral value and high relative upliftment, reveals the tectonic control on these sub

basins.

In order to find the relation between basin area and the total stream length for

respective sub basins a regression line is constructed using a double log graph. It is

observed that the drainage area bears a power function relationship with stream length

(Figure 5.3)

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Figure 5.3 Log-Log plot of Basin Area (Au) vs. Total Stream Length (Lu) shows conformable relation of basin area and total stream length.

Stream Length Ratio (RL)

The Length Ratio (RL), which is the ratio of the mean length of the stream of a given

order (Lu1) to the mean length of the streams of the next lower order (Lu-1), is then

calculated for each pair of the orders. Length ratio is for 1st-2nd and 2nd -3rd order of

the alluvial plain basin are higher than the basin of other two zones. Elongated basins

(Basin index 7, 14, 37, 41) shows high length ration (up to 14.1 in case of Basin41) in

the higher order where as the basin (Basin index 12, 13, 16, 29, 35) with

comparatively high circularity ratio shows the low length ratio (<1). The variation in

length ratio, attributed to variation in slope of topography indicate youth stage of

geomorphic development in the streams of the study area (Singh and Singh, 1997,

Vittala et al., 2004)

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Table 5.2: Summary of drainage basin parameters in the study area

Division Order Stream Number

Bifurcation Ratio

Mean Bifurcation Ratio

Stream Length (km)

Mean Stream Length (km)

Area (sq km)

Drainage Density (km-1)

Drainage Frequency (km-2)

u Nu Lu Lū Au Dd Df South of HFT 1 556 479.5 0.9 1027.0 1.0 0.7

2 134 4.1 213.5 1.6 3 33 4.1 162.5 4.94 9 3.7 3.5 81.9 9.1 5 4 2.3 80.4 20.1

∑Nu=736 ∑Lu=1017.7 HFT-MBT 1 3346 1995.8 0.6 1150.4 2.9 3.7

2 706 4.7 690.9 1.0 3 149 4.7 4.1 307.3 2.1 4 44 3.4 176.8 4.0 5 12 3.7 162.7 13.6

∑Nu=4257 ∑Lu=3333.5 MBT-MCT 1 15624 8763.2 0.6 4426.1 3.0 4.5

2 3418 4.6 2438.2 0.7 3 762 4.5 4.8 1202.1 1.6 4 172 4.4 595.6 3.5 5 30 5.7 269.8 9.0

∑Nu=20006 ∑Lu=13268.9 Above MCT 1 220 129.7 0.6 50.4 3.6 5.7

2 54 4.1 32.2 0.6 3 12 4.5 4.8 13.1 1.1 4 2 6.0 4.5 2.3 5 0

∑Nu=287 ∑Lu=179.5 In total (available drainage)

1 19602 11261.5 0.6 6653.9 2.6 3.82 4256 4.6 3276.3 0.8 3 939 4.5 4.7 1629.2 1.7 4 212 4.4 802.1 3.8 5 41 5.2 402.6 9.8

∑Nu=25050 ∑Lu=17371.7

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Table 5.3: Mean Stream Length for all the order for entire 41 fifth order basin Order Basin

Index Mean Stream Length

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 0.7 0.8 0.9 0.5 0.7 0.6 0.6 0.5 0.5 0.6 0.6 0.5 0.6 0.5 0.6 0.7 0.5 0.6 0.6 0.5 2 1.3 1.3 1.4 0.9 1.2 1.2 0.7 0.7 0.9 0.7 0.8 0.7 0.6 0.6 0.7 1.6 0.7 0.7 0.7 0.6 3 5.2 3.8 4.1 2.4 2.0 2.5 1.7 1.5 1.7 1.5 1.4 1.4 1.0 1.9 1.2 3.0 1.4 1.5 2.7 1.0 4 6.4 13.3 9.9 7.3 7.0 4.9 1.1 2.9 1.1 4.4 4.5 3.0 3.1 2.7 2.0 6.8 4.8 1.5 2.5 0.8 5 29.9 1.0 33.9 0.6 11.2 6.7 12.1 10.5 12.0 7.8 65.0 2.0 0.8 14.8 7.9 0.9 5.4 0.3 4.7 2.7

Order Basin Index

Mean Stream Length 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

1 0.5 0.6 0.6 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.6 0.5 0.6 0.6 0.6 0.5 0.5 0.6 0.6 0.5 0.6 2 0.8 0.8 0.7 0.7 0.6 0.9 0.6 0.5 0.3 0.6 0.6 0.3 0.6 0.9 0.5 0.7 0.8 0.8 0.8 0.7 0.8 3 1.8 1.6 1.3 1.2 1.2 1.1 2.1 1.2 1.3 1.1 1.1 1.0 0.9 1.4 1.0 1.5 1.4 1.6 1.6 0.8 2.0 4 3.5 1.5 3.0 3.9 4.3 4.0 4.3 2.9 3.9 2.8 3.1 1.9 2.3 2.5 4.3 1.5 3.3 4.8 1.5 6.1 2.0 5 3.1 6.8 10.1 1.0 4.9 7.9 8.1 8.0 1.9 7.5 8.5 6.2 1.3 10.1 1.2 5.0 24.9 7.1 6.5 5.2 29.0

Table 5.4: Stream Length Ratio for different order of the entire 41 fifth order basin

Order Ratio

Basin Index

Length Ratio (RL) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

2nd/1st 1.9 1.6 1.6 1.7 1.7 2.1 1.2 1.4 1.9 1.2 1.4 1.4 1.2 1.2 1.1 2.4 1.2 1.1 1.1 1.3 3rd/2nd 4.0 3.0 2.9 2.6 1.6 2.2 2.3 2.0 1.8 2.1 1.8 2.1 1.6 3.0 1.7 1.9 2.1 2.2 4.0 1.5 4th/3rd 1.2 3.5 2.4 3.1 3.5 1.9 0.7 2.0 0.6 3.0 3.3 2.1 3.0 1.4 1.7 2.3 3.4 1.0 0.9 0.8 5th/4th 4.7 0.1 3.4 0.1 1.6 1.4 10.6 3.6 11.4 1.8 14.4 0.7 0.3 5.6 3.9 0.1 1.1 0.2 1.9 3.6

Order Ratio

Basin Index

Length Ratio (RL) 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

2nd/1st 1.4 1.4 1.2 1.4 1.1 1.7 1.2 0.9 0.7 1.3 1.1 0.5 1.0 1.4 0.8 1.2 1.4 1.3 1.3 1.3 1.5 3rd/2nd 2.4 2.0 1.9 1.7 2.0 1.1 3.4 2.5 3.9 1.8 1.7 3.8 1.5 1.6 2.0 2.3 1.8 2.0 2.1 1.1 2.4 4th/3rd 1.9 1.0 2.3 3.4 3.5 3.8 2.1 2.5 3.1 2.7 2.9 1.9 2.5 1.8 4.3 1.0 2.3 3.1 0.9 7.6 1.0 5th/4th 0.9 4.5 3.4 0.3 1.1 2.0 1.9 2.7 0.5 2.6 2.7 3.2 0.6 4.1 0.3 3.4 7.6 1.5 4.3 0.9 14.4

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Bifurcation Ratio (Rb)

The bifurcation ratio is the ratio between the number of streams in one order and in the

next. It is calculated by dividing the number of streams in the lower by the number in

the higher of the two orders; the bifurcation ration of large basins is generally the

average of the bifurcation rations of the stream orders within it.

The bifurcation ratio of the basin of alluvial region is comparatively low than the

Himalayan zone. The bifurcation ratio is range of 3-5 in case of overall drainage system

of the basin. It is seen that the bifurcation ratio of 2nd and 3rd order stream is higher

than the other ratio (Appendix-III and Table 5.2). The sub basins belongs to the Zone-I

shows the bifurcation ratio of 2-4 of different order whereas the mean bifurcation ratio

in between 3.3-4.2. Similarly the Zone-II basins of eastern part of the Kameng River

having origin along the MBT with N-S directional flow and basins origin in the extreme

eastern boundary with a E-W flow have a mean bifurcation ratio of 3-4.6. The

bifurcation ratio of the lower order shows a higher value. This reflects the high

dissection in the upland area. The sub basin 11 and 14 shows a high bifurcation ratio 4-

8 in the higher order. The sub basin 11, Pakke river has an elongated course, it origin

near the eastern margin of the basin and the trunk channel flows along the major

structural control of MBT in the Gondwana sequence in E-W direction. It turns south in

through a transverse lineament, flow across the MBT and it again turns towards east

upto the MBT. It again turns to south along N-S transverse lineament and through

Siwalik it confluence with Dibru N and flow as Bor Dikrai River up to Jia Bharali in the

alluvium. The pattern of the river itself reflects the structural disturbance of the area.

The higher Bifurcation ratio suggests that the area is tectonically active (Som et.al.,

1998).

In case of Pasa Nadi (basin index 14) shows higher bifurcation ratio of 6, this indicates

the structural control. In longitudinal profile also it is also seen that in the river course

there is lithological and structural control. And the drainage between the MBT and

MCT have comparatively higher bifurcation ratio. As per the Horton (1945) bifurcation

ratio having a less value about 2 to 3 is of flat region. The basins of alluvial plain the

ratio higher order is approximately 2 it reflects that the lower part of the basin is flat.

The mean bifurcation ratio is 3.8. Other hand the ration of the lower order is high and as

per Horton these streams or of highly dissected drainage basins.

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The Bifurcation Ratio is of fundamental importance in drainage basin analysis as it is

the foremost parameter to link the hydrological regime of a watershed under topological

and climatic conditions (Raj et. al., 1999). It helps to have an idea about the shape of

the basin as well as in deciphering the run off behavior. The bifurcation ratio will not be

exactly same from one order to the next order because of possibility of the changes in

the watershed geometry and lithology but will tend to be consistent throughout the

series. From the Figure 5.4- i,ii,iii, it is clear that the Zone-III basins have ruggedness

topography as it shows a high variation in the bifurcation ratio. The Zone-II basins are

also comparatively highly rugged topography than the alluvial part basins. The area

under the Zone-II and Zone-III are moderately and highly dissected area and the

drainage development is high.

Mean Bifurcation Ratio ( Rb ) is calculated as the Arithmetic Mean Bifurcation Ratio

and the result is tabulated corresponding to Sub-order basins as shown in the Table

appendix-III. Using Strahler's (1957) method of taking into consideration of actual

number of streams that are involved in the ratio, Mean Bifurcation Ratio of different

sub-basins was calculated. The mean bifurcation ratio is in between 3-5.9. The basin

having index 18 has the lower bifurcation ratio of 3 and the basin 11 has the higher

bifurcation ratio of 5.9. The higher bifurcation ratio indicates there may be some

structural distortion in that basin area. The overall plotting of the mean bifurcation ratio

against the basin area it is seen that higher is the bifurcation ratio as the basin area

increases.

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Figure 5.4: a,b,c, are the plotting of bifurcation ratio and stream order of different basin in the Zone-I, Zone-II, Zone-III

Figure 5.5: a. shows the variation of mean bifurcation ratio. B. shows the trend of mean bifurcation ratio against basin area

a b c

b a

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Basin length (Lb):

Basin length is the longest dimension of a basin to its principal drainage channel. Sub

basin having index 1, 11 has the longest basin length of 33.9 km and 32.5 km

accordingly and the sub basin 20 has the shortest basin length of 5.5km. Basin length

and the basin area of the alluvial river are maximum and in the dissected hill it is

minimum. Basin lengths for the entire basin are tabulated in the given appendix-III.

Regression Analysis

Graphical presentation of i) the stream order and the stream number ii) the stream

order and the stream length iii) the stream order and the mean stream length is

prepared in a semi-log plot as suggested by Strahler (1957). For this regression

analysis number of streams (Nu) of each order and their length (Lu) are noted from

the attribute Table. All these aspects are then entered in an excel sheet and then the

bifurcation ratio (Rb) is calculated. For graphical plot of Stream order Vs Stream

number and Stream order Vs Stream Length we used the Regression Equation, which

is

y= a + bx (1)

Where ‘b’ is the co-efficient of the Regression equation, which can be calculated from

the following formula –

n)x(x

nyxxy

b 22 Σ−Σ

ΣΣ−Σ

=

Again the value of ‘a’ can be calculated from

xbya −=

Where, y =Mean of y

x = Mean of x

By plotting the values of ‘x’, ‘a’ and ‘b’ in the regression equation (1), we get the

value of ‘y’ for corresponding stream number and stream length. Plotting the antilog

values of ‘y’ in the Y axis in logarithmic scale against ‘x’ value (order) in the X axis

in arithmetic scale, the three necessary bivariate plots are made.

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Stream order vs. the stream number

Graphical presentation (Figure 5.6, 5.7 and 5.8) of the total stream length against the

stream order can also be prepared in a semi-log plot as suggested by Strahler (1957).

It is observed that the number of stream segment increases with decreasing stream

order in the entire sub basins i.e. negative regression relation.

Figure 5.6 Stream order Vs Stream number (-ve corrlation) for the Zone-I

Figure 5.7 Stream order Vs Stream number (-ve corrlation) for the Zone-II

Figure 5.8 Stream order Vs Stream number (-ve corrlation) for the Zone-III

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Table 5.5 Showing the Regression equation for Stream order vs. Stream Number

Basin Index

Regression Equation

Basin Index

Regression Equation

1 y=3.07-0.62x 21 y=2.67-0.56x 2 y=2.42-0.51x 22 y=2.57-0.54x 3 y=2.77-0.57x 23 y=3.07-0.61x 4 y=2.81-0.60x 24 y=2.51-0.53x 5 y=2.83-0.60x 25 y=2.67-0.56x 6 y=2.77-0.57x 26 y=2.78-0.58x 7 y=2.56-0.54x 27 y=3.22-0.65x 8 y=2.94-0.59x 28 y=2.71-0.57x 9 y=2.98-0.60x 29 y=2.51-0.53x 10 y=2.72-0.58x 30 y=2.99-0.59x 11 y=3.89-0.76x 31 y=2.90-0.60x 12 y=2.49-0.53x 32 y=2.65-0.54x 13 y=2.28-0.48x 33 y=2.33-0.49x 14 y=3.20-0.62x 34 y=2.89-0.59x 15 y=2.82-0.58x 35 y=2.72-0.57x 16 y=2.83-0.61x 36 y=2.70-0.55x 17 y=2.87-0.59x 37 y=3.51-0.68x 18 y=2.18-0.46x 38 y=2.96-0.60x 19 y=2.80-0.57x 39 y=2.59-0.55x 20 y=2.18-0.46x 40 y=2.74-0.58x 41 y=3.13-0.65x

Stream order vs. the stream length

Generally, the total length of stream segments decreases with stream order. Graphical

representation of the total stream length against stream order was also prepared in a

semi-log plot as suggested by Strahler (1957). The general logarithms of the number

of stream of a given order, when plotted against the order, the points lie on a straight

line (Horton, 1945). Bivariate plot (Figure 5.9, 5.10 and 5.11) between stream order

and total stream length shows negative exponential functions, indicating that the total

stream length decreases with increase in stream order indicating that development of

drainage is higher for the lower order.

133

Figure 5.9: Stream order Vs Stream Length (-ve corrlation) for the Zone-I

Figure 5.10 Stream order Vs Stream Length (-ve corrlation) for the Zone-II

Figure 5.11 Stream order Vs Stream Length (-ve corrlation) for the Zone-III

134

Table 5.6 Showing the Regression equation for Stream order vs. Stream length

Basin Index

Regression Equation

Basin Index

Regression Equation

1 y=4.68-0.96x 21 y=2.93-0.59x 2 y=2.37-0.38x 22 y=3.27-0.72x 3 y=4.51-0.93x 23 y=3.87-0.80x 4 y=2.29-0.38x 24 y=2.12-0.39x 5 y=3.88-0.81x 25 y=3.05-0.62x 6 y=3.52-0.71x 26 y=3.48-0.74x 7 y=3.54-0.80x 27 y=3.89-0.78x 8 y=3.76-0.78x 28 y=3.28-0.70x 9 y=3.97-0.86x 29 y=2.30-0.45x 10 y=3.39-0.71x 30 y=3.54-0.72x 11 y=5.58-1.17x 31 y=3.58-0.76x 12 y=2.47-0.49x 32 y=2.95-0.63x 13 y=1.83-0.33x 33 y=2.13-0.42x 14 y=4.20-0.86x 34 y=3.78-0.80x 15 y=3.55-0.76x 35 y=2.41-0.45x 16 y=2.75-0.50x 36 y=3.18-0.67x 17 y=3.33-0.67x 37 y=4.75-0.98x18 y=1.31-0.21x 38 y=3.63-0.74x 19 y=3.34-0.68x 39 y=3.25-0.71x 20 y=2.32-0.52x 40 y=3.15-0.65x 41 y=4.52-1.00x

Stream order and the Mean stream length

The values of mean stream length are plotted against respective stream order (Figure

5.12, 5.13, 5.14). These shows the positive relationship between mean stream length

and the stream order for each drainage basin. Sub-basin with index 18 shows a

relationship that reveals more or less a straight line regression of negative relation.

Again in some basin it is observed an exception where the mean stream length of

fourth order is much higher than that of the fifth order (basin index 2, 4, 12, 13, 16,

18, 24, 29 33, 35). Deviation from its general behaviour may suggest that the terrain is

characterized by high relief and/or moderately steep slopes, underlain the various

lithology and probable uplift across the basin (Singh and Singh 1997, Vittala et al.,

2004).

135

Figure 5.12 Mean stream length vs. Stream order plotting of Zone-I

Figure5.13 Mean stream length vs. Stream order plotting of Zone-II

Figure 5.14 Mean stream length vs. Stream order plotting Zone-III

136

Table 5.7 Showing the Regression equation for Stream order vs. Mean Stream Length

Basin Index

Regression Equation

Basin Index

Regression Equation

1 y= -0.61+0.40x 21 y= -0.47+0.22x 2 y= -0.03+0.12x 22 y= -0.55+0.24x 3 y= -0.56+0.40x 23 y= -0.70+0.31x 4 y= -0.15+0.10x 24 y= -0.38+0.14x 5 y= -0.51+0.31x 25 y= - 0.65+0.28x 6 y= -0.49+0.28x 26 y= -0.64+0.30x 7 y= -0.64+0.28x 27 y= -0.69+0.32x 8 y= -0.71+0.32x 28 y= -0.78+0.31x 9 y= -0.63+0.28x 29 y= -0.64+0.22x 10 y= -0.67+0.31x 30 y= -0.76+0.31x 11 y= -1.03+0.49x 31 y= -0.71+0.30x 12 y= -0.46+0.19x 32 y= -0.89+0.31x 13 y= -0.31+0.10x 33 y= -0.37+0.13x 14 y= -0.77+0.35x 34 y= -0.62+0.29x 15 y= -0.62+0.27x 35 y= -0.44+0.16x 16 y= -0.02+0.09x 36 y= -0.56+0.23x 17 y= -0.64+0.29x 37 y= -0.86+0.40x 18 y= -0.02-0.03x 38 y= -0.61+0.29x 19 y= -0.48+0.23x 39 y= -0.56+0.24x 20 y= -0.52+0.16x 40 y= -0.67+0.29x 41 y= -0.80+0.38x

5.3 Areal Aspect

The areal aspect is the two dimensional properties of a basin. It is possible to delineate

the area of the basin which contributes water to each stream segment. The watershed

can be traced from where the stream has its confluence with the higher order stream

along hillcrests to pass upslope of the source and return to the junction. This line

separates slopes which feed water towards the streams from those which drain in to

other streams.

The information of hydrologic importance on fluvial morphometry is derived by the

relationship of stream discharge to the area of watershed. The planimetric parameters

directly affect the size of the storm hydrograph and magnitudes of peck and mean

runoff is the basin area. The maximum flood discharge per unit area is inversely

related to the size of the basin (More, 1967)

137

Drainage Area (Au)

The entire area drained by a stream or system of streams such that all streams flow

originating in the area is discharged through a single outlet is termed as the Drainage

Area. Drainage area measures the average drainage area of streams in each order; it

increases exponentially with increasing order.

The total catchment area of Jia Bharali as well as for the 41 fifth order basin was

computed from the topological polygon that are created by delineation basin from the

toposheet following the surface water divide in ArcInfo9.1 The basin with index 1,

i.e., Diputa River in Zone-I has a 255 sq km of basin area, Pakke River, with basin

index 11, has the highest basin area of 328 sq km in Zone-II, which is the biggest

basin among the 41 basin. In Zone-III, Dublo kho, basin index 37 has the highest

basin area of 163 sq km.

Relation between Basin area and Basin length

It is seen area of the basins of alluvial area are maximum than that of other structural

or transitional piedmont zone. In general the basin area and the basin length both are

proportional and they shows almost +ve relation. This reflects that basin area is

maximum when the basin length has a high value.

Figure 5.15: Showing the relationship between Basin Area and Basin Length

138

Drainage Density (Dd)

Drainage density has long been recognised as topographic characteristic of

fundamental significance. This arise from that fact that drainage density is sensitive

parameter which in many ways provides the link between the form attributes of the

basin and the processes operating along stream course (Gregory and Welling, 1973).

It reflects the landuse and affects infiltration and the basin response time between

precipitation and discharge. It is also of geomorphological interest particularly for the

development of slopes. Drainage basin with high Dd indicates that a large proportion

of the precipitation runs off. On the other hand, a low drainage density indicates the

most rainfall infiltrates the ground and few channels are required to carry the runoff

(Roger, 1971). Dd is considered to be an important index; it is expresses as the ratio

of the total sum of all channel segments within a basin to the basin area i.e., the length

of streams per unit of drainage density. It is a dimension inverse of length (Horton,

1932).

Dd is a measure of the texture of the network, and indicates the balance between the

erosive power of overland flow and the resistance of surface soils and rocks. The

factors affecting drainage density include geology and density of vegetation. The

vegetation density influenced drainage density by binding the surface layer and slows

down the rate of overland flow, and stores some of the water for short periods of time.

The effect of lithology on drainage density is marked. Permeable rocks with a high

infiltration rate reduce overland flow, and consequently drainage density is low.

The drainage density is found to increase from south to north of the basin (Figure

5.16). In the south of HFT the drainage density is low about 1.0 km 1− (Table 5.2).

Again it increases to about 2.9 km 1− between HFT and MBT followed by 3.0 km 1− in

between MBT and MCT. And the highest value of 3.6 km 1− attain in the area north of

MCT. The drainage density for individual basin also shows conformable relation. The

sub basin having index 1, Diputa Nadi has the lower density of 1.7km 1− in the alluvial

part. The Basin no.35, Meni Nadi, tributary of Bichom river north of MBT shows the

higher density of about 3.9 km 1− (Table 5.8). As per the zonation of basins, in this

study on the basis of lithotectonic setup of the area, it is observed that the basins of

alluvial part of Zone-I shows low drainage density (1.7-2.0 km 1− ) as this area has a

139

high permeability. The basins of Zone-II, shows comparatively higher value (2.7-3.7

km 1− ). In the piedmont zone basins shows moderate drainage density. The

precipitation in this area is very high whereas this area exhibit high vegetation also.

From the Table 5.2 and the Table 5.8 it is observed that the Dd north of MBT is 3.0

km 1− confined with Bomdila Group of rock. The sub basins in the western part of the

Jia Bharali catchment shows comparatively high drainage density (2.9-3.9 km 1− ) than

the eastern part (2.3-3.3 km 1− ), which suggest the western part is highly dissected

with a impermeable but erodible lithology.

Figure 5.16 Drainage density map of the study area. Drainage density increases from south to north with higher value in the western part of the basin.

140

Drainage (Stream) Frequency (Fs)

Drainage frequency may be directly related to the lithological characteristics. The

number of stream segments per unit area is termed Stream Frequency or Channel

Frequency or Drainage Frequency (Fs) Horton (1945). Table 5.2 reflects the total

drainage frequency of the basins is 3.8 km-2 and the drainage frequency increase from

south to north. In the alluvial part, south of HFT is 0.7 km-2 and increase abruptly 3.7

km-2 in between HFT and MBT again north of MBT in 4.5 km-2.

The drainage frequency of the entire sub basin ranges from 1.5- 7.4 km-2. Sub basin

having index 32 Difya River has the high stream frequency and the sub basin of

alluvial has the low stream frequency (1.5 km-2). The basins of the structural hills

have higher stream frequency, drainage density while the basins of alluvial has

minimum. These higher values indicate that the area is occupied by Siwaliks in the

lower Himalayan part and the western part by the Bomdila Group of rock. Like the

drainage density, stream frequency is a similar measure of stream network of a

drainage basin. Table 5.9 shows close correlation between drainage frequencies with

drainage density indicating the increase in stream population with respect to increase

in drainage density. To evaluate the relationship between drainage density and stream

frequency, a log-log plot of drainage density vs. stream frequency is prepared. The

regression line indicates the existence of direct relationship between the two

parameters (Figure 5.17).

Figure 5.17 Relation between Drainage density and stream frequency showing the

increase of drainage frequency with drainage density

141

Drainage Texture (Rt)

Horton (1945) defined drainage texture is the total number of stream segments of all

order in a basin per perimeter of the basin. It is important to geomorphology which

means that the relative spacing of drainage lines. Drainage texture is on the

underlying lithology, infiltration capacity and relief aspect of the terrain. Smith (1950)

has classified drainage texture into 5 different textures i.e., very coarse (<2), coarse (2

to 4), moderate (4 to 6), fine (6 to 8) and very fine (>8).

The drainage texture of entire 41 sub basins are of coarse to very fine. Alluvial basins

show very coarse to coarse drainage texture and other basins of Himalayan part shows

moderate to very fine texture. Basin north of MBT and western part of Kameng (37,

35, 32, 30, 27, and 23) shows very fine texture (8-11) with higher infiltration number

(14.8-18.3) reflects high drainage development.

More is the texture more will be dissection and leads more erosion. Sub basins in the

eastern part of Jia Bharali shows moderate to fine texture (except basin having index

11 with drainage texture 10) and the western part fine to very fine texture.

142

Table 5.8: Computed Drainage density, frequency and texture of entire sub basins

Basin Index

Basin Name Drainage Density Km-1

Drainage Frequency

Km-2

Drainage Texture

Km-1 1 Dipota Nadi 1.7 1.5 5 2 Jorasar Nadi 1.7 1.5 2 3 Mansari Nadi 2.0 1.5 3 4 Dibru Nadi 3.1 4.5 7 5 Khari Dikrai Nadi 3.0 3.2 6 6 Upar Dikrai Nadi 2.7 3.4 6 7 Daigurang Nadi 3.3 4.5 5 8 Khaina Nadi 3.0 4.5 8 9 Lengtey Nadi 3.2 4.9 9 10 Diju Nadi 3.3 4.9 6 11 Pakke River 3.0 4.3 10 12 Tributary of Pakke River 3.3 5.4 7 13 Tributary of Kameng River 2.8 4.4 5 14 Pasa Nadi 2.8 3.9 8 15 Pani Nadi 3.7 5.2 8 16 Papu River 2.8 3.3 7 17 Chakrasong Nadi 2.9 4.5 7 18 Tributary of Pacha River 3.0 4.4 5 19 Pacha River 2.9 3.9 7 20 Lengpla Nadi 3.3 5.9 6 21 Phuchao Nadi 3.1 4.7 7 22 Kade Nala 2.9 4.1 6 23 Pakoti Nadi 3.3 4.9 11 24 Hoda Nadi 3.2 5.5 7 25 Huduri Nadi 3.5 5.5 7 26 Kaun or Hukubu Nala 3.5 5.0 7 27 Gayang River 3.1 4.8 10 28 Ki Nala 3.4 5.6 7 29 Miao Nadi 3.8 6.9 7 30 Upstream of Dinang Bru 3.8 6.5 10 31 Dibri Bru 3.5 5.3 8 32 Difya River 3.8 7.4 8 33 Khenda Nadi 3.5 5.3 6 34 Taamchin RI (Sashi Chu) 3.1 4.2 8 35 Meni Nadi 3.9 6.2 9 36 Nimsinggoto River 3.6 5.6 8 37 Dublo Kho 3.2 4.8 11 38 Tribtary of Tenga River 3.2 4.5 8 39 Dogong Kho 3.3 4.9 7 40 Sessa Nadi 3.5 5.5 8 41 Tipi Nala 3.1 4.3 7

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Basin shape

The shape of the basin mainly governs the rate at which the water is supplied to the

main channel. The main indices used to analyse basin shape and relief are the

elongation and relief ratios. The elongation ratio is calculated by dividing the

diameter of a circle of the same area as the drainage basin by the maximum length of

the basin, measured from its outlet to its boundary. Three parameters viz. Elongation

Ratio (Re), Circulatory Ratio (Rc) and Form Factor (Rf) are used for characterizing

drainage basin shape, which is an important parameter from hydrological point of

view.

Elongation Ratio (Re)

Schumm’s 1956 used an elongation ratio (Re) defined as the ratio of diameter of a

circle of the same area as the basin to the maximum basin length. The value of Re

varies from 0 (in highly elongated shape) to unity i.e. 1.0 (in the circular shape).Thus

higher the value of elongation ratio more circular shape of the basin and vice-versa.

Values close to 1.0 are typical of regions of very low relief, whereas that of 0.6 to 0.8

are usually associated with high relief and steep ground slope (Strahler, 1964).These

values can be grouped as,

Elongation ratio Shape of basin

<0.7 Elongated 0.8-0.7 Less elongated 0.9-0.8 Oval >0.9 Circular

The elongation ratio values of the different basins are varies between 0.4 and 1 (Table

5.9). The sub basins of the alluvial region shows low values (0.4-0.5) represent the

elongated basin with low relief. More number of sub basins in the north of MBT

shows oval and circular shape. The circular basin is more efficient in run-off

discharge than an elongated basin (Singh and Singh, 1997). The central parts of the

Jia Bharali catchment the basins are comparatively circular with higher value than the

alluvial and the piedmont zone basin. In the study area among the 41 sub basins 30

sub basins shows elongation value 0.6-0.8 represents high relief and steep ground

slopes.

144

To understand the relationship between bifurcation ratio and the elongation ratio a

regression line is constructed, which show a linear negative relation i.e. with increase

of elongation ratio, bifurcation ratio decrease (Figure 5.18)

Figure 5.18: Graphical plot of elongation ratio and bifurcation ratio shows

elongated basin have have a high bifurcation ratio. Development of lower order drainage is more in elongated basins.

Circularity Ratio (Rc)

The circularity ratio is a similar measure as elongation ratio, originally defined by

Miller (1953), as the ratio of the area of the basin to the area of the circle having same

circumference as the basin perimeter. The value of circularity ratio varies from 0 (in

line) to 1 (in a circle). The Circulatory ratio for all basins is in the range of 0.23 to

0.79. The Pakke River shows the lowest value, whereas the Pakoti Nadi shows the

high value of 0.79. Higher the value represents more circularity in the shape of the

basin and vice-versa. Naturally all basins have a tendency to become elongated to get

the mature stage. The observed combination of high Elongation Ratio and Circularity

values, especially in the central part of the basin shows circular in nature. Some of the

basins 6, 9, 16 show complicated value, high circularity ratio as well as the low

elongation ratio. This complicated shape parameter is the result of the presence of a

combination of lithological formations, leading to differential erosion and

consequently to watershed displacement. The circularity ratio shows somewhat lower

values for the basins 11 in eastern part of the study area where there is strong

structural control on the drainage development. Therefore the structural control of

drainage is probably responsible for the low values of circularity ratio.

145

Form Factor (Rf)

Form factor is the numerical index (Horton, 1932) commonly used to represent

different basin shapes. The value of form factor is in between 0.1-0.8. Smaller the

value of form factor, more elongated will be the basin. The basins with high form

factors 0.8, have high peak flows of shorter duration, whereas, elongated drainage

basin with low form factors have lower peak flow of longer duration. The alluvial

basins shows low form factor value represent elongated in nature of the basins. The

basin 13 shows high values of form factor 0.8 is ideal circular basin. The values

indicate the drainage central and western part of the study area shows high values of

form factor. The drainage development in these parts is high and the area has a

structural control.

Relation between different shape parameters

Mutual relationship of these parameters can be evaluated from the plot as shown in

Figure. It is found that for a given drainage basin that the elongation ratio, circularity

ration and form factor show a relationship of decrease in values the order viz.,

elongation ratio ˃ circularity ratio > form factor. The three measures thus are

conformable and suitable for defining basin shape. In four basins viz., 11, 13, 27, 35

the form factor value is complicated from the other value. This represents the

structural control on the basins. The Pakke River (basin index 11) has an elongated

course with curvature basins shape, totally controlled by the major trust, transverse

fault and lithology of the area. Whereas the basins having index 13, 27 and 35 are of

oval shape.

Figure 5.19 Relation between different shape parameters shows a decrease values

i.e. elongation ratio ˃ circularity ratio > form factor

146

Table 5.9 Shape parameters of entire 41 fifth order sub-basin

Basin Index

Basin Name Circularity Ratio (Rc)

Elongation Ratio (Re)

Form Factor (Rf)

Rc=4πAu/p2 Re=2{√(Au/π)}/Lb Rf=Au/Lb2

1 Dipota Nadi 0.4 0.5 0.2 2 Jorasar Nadi 0.3 0.4 0.1 3 Mansari Nadi 0.3 0.5 0.2 4 Dibru Nadi 0.6 0.8 0.5 5 Khari Dikrai Nadi 0.5 0.7 0.3 6 Upar Dikrai Nadi 0.6 0.7 0.4 7 Daigurang Nadi 0.4 0.6 0.2 8 Khaina Nadi 0.5 0.7 0.4 9 Lengtey Nadi 0.7 0.8 0.6 10 Diju Nadi 0.4 0.5 0.2 11 Pakke River 0.2 0.6 0.3 12 Tributary of Pakke River 0.7 0.8 0.6 13 Tributary of Kameng River 0.6 1.0 0.8 14 Pasa Nadi 0.4 0.6 0.3 15 Pani Nadi 0.6 0.6 0.3 16 Papu River 0.7 0.7 0.4 17 Chakrasong Nadi 0.5 0.7 0.4 18 Tributary of Pacha River 0.6 0.8 0.4 19 Pacha River 0.7 0.8 0.6 20 Lengpla Nadi 0.7 0.8 0.5 21 Phuchao Nadi 0.7 0.9 0.6 22 Kade Nala 0.7 0.7 0.4 23 Pakoti Nadi 0.8 0.8 0.5 24 Hoda Nadi 0.7 0.8 0.5 25 Huduri Nadi 0.5 0.6 0.3 26 Kaun or Hukubu Nala 0.5 0.5 0.2 27 Gayang River 0.6 0.9 0.6 28 Ki Nala 0.5 0.6 0.3 29 Miao Nadi 0.5 0.7 0.4 30 Upstream of Dinang Bru 0.6 0.8 0.5 31 Dibri Bru 0.5 0.6 0.3 32 Difya River 0.6 0.7 0.3 33 Khenda Nadi 0.7 0.8 0.5 34 Taamchin RI (Sashi Chu) 0.6 0.7 0.4 35 Meni Nadi 0.7 1.0 0.7 36 Nimsinggoto River 0.7 0.8 0.6 37 Dublo Kho 0.4 0.6 0.3 38 Tribtary of Tenga River 0.5 0.7 0.4 39 Dogong Kho 0.6 0.7 0.4 40 Sessa Nadi 0.6 0.6 0.3 41 Tipi Nala 0.3 0.5 0.2

147

Infiltration Number (If)

The infiltration Number is defined as the product of Drainage Density (Dd) and

drainage Frequency (Fs). The Jorasar Nadi has the low infiltration 2.5 and the Difya

River has the higher infiltration number of ~ 28.3. The Jorasar basin is found in the

alluvial plain thus it has a higher infiltration. On the other hand the Dify River, in

north of MBT having a higher infiltration number. The higher the infiltration number

the lower will be the infiltration and consequently, higher will be run off. This leads

to the development of higher drainage density. It gives an idea about the infiltration

characteristics of the basin reveals impermeable lithology and higher relief.

Length of Overland Flow (Lg)

The term length of overland is used to describe the length of flow of water over the

ground before it becomes concentrated in definite stream channels. Horton (1945)

expressed it as equal to half of the reciprocal of Drainage Density (Dd). It is an

important independent variable, which greatly affect the quantity of water required to

exceed a certain threshold of erosion. This factor relates inversely to the average slope

of the channel and is quite synonymous with the length of sheet flow to a large

degree. The length of overland flow bears an effective relationship with the drainage

density and constant channel maintenance.

The length of overland flow ranges between 0.1-0.3. Sub basin of alluvial plain

(zone-I) shows high value. Sub basins of zone-II show moderate value of 0.2

whereas the basins of zone-III show the value of 0.1-0.2. The basins north of MBT

show moderate to low value. More the value represents long time of flow in the

basin. The alluvial plain basins are elongated and have a high length of course. The

basins of the central part have a low value, these basins have a drainage density and

runoff is more but they have short course of flow. Smaller the value of overland flow

the quicker surface runoff will enter the streams represents well developed drainage

network with higher slope. In a relatively homogeneous area, therefore less rainfall is

required to contribute a significant volume of surface runoff to stream discharge

when the value of overland flow is small than when it is large. As the western part of

Jia Bharali basin exhibit less rainfall than the other area, it has a quick discharge that

leads to the development of the high drainage density.

148

Constant of Channel Maintenance (C)

This parameter indicates the requirement of units of watershed surface to bear one

unit of channel length. Schumn (1956) has used the inverse of the drainage density

having the dimension of length as a property termed constant of channel

maintenance. The drainage basins having higher values of this parameter, there will

be lower value of drainage density.

All the values are computed and shown in the Table (Table No 5.10). The alluvial and

the piedmont area basins show comparatively high constant channel maintenance.

Diputa Nadi shows highest value of 0.6 km-2 which has the least drainage density,

while Difya River and the Meni Nadi has lowest constant channel maintenance of 0.3

km-2 , and these two basins has the highest drainage density of 3.8 km-1 and 3.9 km-1 .

Higher value of constant channel Maintenance reveals strong control of lithology with

a surface of high permeability. Alluvial basin of plain and piedmont zone shows

highest value, as the permeability in this zone is high.

149

Table 5.10 Computed values of infiltration number, length of overland flow and constant of channel maintenance

Basin Index

Basin Name Infiltration Number

Length of Over land Flow

Constant of Channel

Maintance If=Dd.Df Lg=1/2.Au/∑Lu C=1/Dd 1 Dipota Nadi 2.5 0.3 0.6 2 Jorasar Nadi 2.5 0.3 0.6 3 Mansari Nadi 2.9 0.3 0.5 4 Dibru Nadi 13.9 0.2 0.3 5 Khari Dikrai Nadi 9.3 0.2 0.3 6 Upar Dikrai Nadi 8.9 0.2 0.4 7 Daigurang Nadi 14.7 0.2 0.3 8 Khaina Nadi 13.2 0.2 0.3 9 Lengtey Nadi 15.8 0.2 0.3

10 Diju Nadi 16.3 0.2 0.3 11 Pakke River 12.8 0.2 0.3 12 Tributary of Pakke River 18.0 0.2 0.3 13 Tributary of Kameng River 12.5 0.2 0.4 14 Pasa Nadi 10.9 0.2 0.4 15 Pani Nadi 19.4 0.1 0.3 16 Papu River 9.0 0.2 0.4 17 Chakrasong Nadi 13.0 0.2 0.3 18 Tributary of Pacha River 13.0 0.2 0.3 19 Pacha River 11.3 0.2 0.4 20 Lengpla Nadi 19.8 0.2 0.3 21 Phuchao Nadi 14.6 0.2 0.3 22 Kade Nala 11.8 0.2 0.4 23 Pakoti Nadi 16.3 0.2 0.3 24 Hoda Nadi 17.7 0.2 0.3 25 Huduri Nadi 19.2 0.1 0.3 26 Kaun or Hukubu Nala 17.4 0.2 0.3 27 Gayang River 14.8 0.2 0.3 28 Ki Nala 18.9 0.2 0.3 29 Miao Nadi 26.4 0.1 0.3 30 Upstream of Dinang Bru 24.4 0.1 0.3 31 Dibri Bru 18.7 0.1 0.3 32 Difya River 28.3 0.1 0.3 33 Khenda Nadi 18.2 0.1 0.3 34 Taamchin RI (Sashi Chu) 12.6 0.2 0.3 35 Meni Nadi 24.2 0.1 0.3 36 Nimsinggoto River 19.8 0.1 0.3 37 Dublo Kho 15.3 0.2 0.3 38 Tribtary of Tenga River 14.4 0.2 0.3 39 Dogong Kho 16.3 0.2 0.3 40 Sessa Nadi 19.3 0.1 0.3 41 Tipi Nala 13.1 0.2 0.3

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5.4 Relief aspects

Linear and areal features have been considered as the two dimensional aspect lie on a

plan. The third dimension introduces the concept of relief. By measuring the vertical

fall from the head of each stream segment to the point where it joins the higher order

stream and dividing the total by the number of streams of that order, it is possible to

obtain the average vertical fall.

Channel Gradient

Channel Gradient is the total drop in elevation from the source to the mouth of the

trunk channels in each drainage basin. In the present study area Diputa Nadi has the

lowest 1.7 m/km and the Sessa Nadi has the highest gradient of 250.1 m/km (Table

5.11). The alluvial basins shows low channel gradient whereas the basins around

MBT and western part of the basins shows comparatively high value than the eastern

part.

The Kameng River originates in the upper Himalayan ranges at an elevation of

~5400m. Its total route of ~242 km upto its confluence with River Brahmaputra,

carries the discharge of all its major and minor tributaries. The system is characterized

by steep gradient in its initial length of about 40 km from its origin and a much gentle

gradient in the lower reaches of about 200 km before joining River Brahmaputra. Jia

Bharali river show an average gradient of ~22m/km. However, in its upstream course

north of the MCT the gradient is ~112 m/km changing to ~8.3 m/km between MCT

and MBT and ~2.1 m/km between MBT and HFT. The alluvial segment shows a

substantially lower gradient of ~ 0.4 m/km.

Basin Relief (H)

Basin relief is the elevation difference of the highest and lowest point of the valley

floor. The sub basins relief range from 57 to 3207m, whereas the relief of Kameng is

6621m. Basins of north of MBT shows comparatively high relief shows elevation

source of basins of west of Kameng and north of MBT shows relatively high relief

than eastern part. Computed basin relief are tabulated in the Table 5.11

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Relief Ratio (Rh)

Relief ratio is defined as the ratio between the total relief of a basin i.e. elevation

difference of lowest and highest points of a basin, and the longest dimension of the

basin parallel to the principal drainage line (Schumn 1956).

This is a dimensionless height-length ratio and allows comparison of the relative relief

of any basin regardless of difference in scale or topography. Relief ratio is equal to the

right angled triangle and is identical with the tangent of the angle of slope of the

hypotenuse with respect to horizontal (Strahler, 1964). Thus is measure the overall

steepness of a drainage basin is an indicator of intensity of erosion processes

operating on the slope of the basin.

Relief ratio normally increases with decreasing drainage area and size of a given

drainage basin (Gottschalk, 1964). The Relief Ratio of the fifth-order drainage basins

varies between the values of 0.002 to 0.283 (Table 5.11). Basins’ consisting of

alluvium (Zone-I) shows the low relief ratio. Zone-III basins shows high relief ratio.

The western part of Kameng River, the fifth order basis shows high relief ratio than

the eastern part sub basins. In the zone-II the basins of Siwaliks and piedmont zone

has a low relief ration because of high erodability of the rock type. The high values of

Relief Ratio in the western part can be explained by the presence of highly resistant

rocks of Bomdila group underlying the basin. The high values of Rh indicate steep

slope and high relief and vice-versa. Relief controls the rate of conversion of

potential to kinetic energy of water draining through the basin. Run-off is generally

faster in steeper basins, producing more peaked basin discharges and greater erosive

power.

Ruggedness Number (HD)

Strahler (1968) describes ruggedness number (HD) as the product of maximum basin

relief and drainage density and it usually combines slope steepness with its length.

Extremely high values of ruggedness number occur when slopes of the basin are not

only steeper but long, as well. For the present sub basins, the ruggedness number

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varies from 0.09 for Diputa Nadi with low sloping area to 10.31 for Sessa Nadi

having higher basin relief with gradual change in slope of uniform nature (Table

5.11). The Zone-I basins shows a low value of ruggedness number, Zone-II basins

shows a moderate value whereas the Zone-III basins shows a high value of

ruggedness number.

The sub basins north of MBT show comparatively high ruggedness number, whereas

the sub basins of western side of Kameng shows high ruggedness number (3.74-

10.31) than the eastern side (2.66-5.50). The western part is highly dissected as the

high ruggedness number, higher drainage frequency with high channel gradient lead

more erosion and dissection. Basins are comparatively circular with low permeability

with homogeneous lithology reflects the tectonic influence on the basin. The fine to

very fine drainage texture with high relief and comparatively steep slopes leads to

development of high drainage density though the area exhibits less rainfall than the

other part. Drainage density and the lineament density map reflect the influence of

structural disturbance on the area.

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Table 5.11 Relief parameters of the 5th order sub basins

Basin Index

Basin Name Elevation of Highest Point on Basin Perimeter

Elevation of lowest point at the mouth

Maximum Basin Relief (H)

Maximum Basin Length (Lb)

Channel Gradient

Relief Ratio (Rh)


m m m km m/Km 1 Dipota Nadi 125 68 57 33.80 1.7 0.002 0.092 Jorasar Nadi 357 76 281 27.08 10.4 0.010 0.493 Mansari Nadi 428 76 352 28.81 12.2 0.012 0.704 Dibru Nadi 1560 183 1377 10.82 127.3 0.127 4.295 Khari Dikrai Nadi 1130 93 1037 15.36 67.5 0.068 3.056 Upar Dikrai Nadi 1472 106 1366 14.42 94.7 0.095 3.637 Daigurang Nadi 1126 110 1016 12.49 81.3 0.081 3.358 Khaina Nadi 1763 166 1597 14.06 113.6 0.114 4.729 Lengtey Nadi 1232 166 1066 11.28 94.5 0.095 3.4510 Diju Nadi 1366 121 1245 13.84 89.9 0.090 4.1311 Pakke River 1926 479 1447 32.55 44.5 0.044 4.3012 Tributary of Pakke River 1285 479 806 7.12 113.2 0.113 2.6613 Tributary of Kameng River 1287 295 992 5.70 174.0 0.174 2.8114 Pasa Nadi 2367 678 1689 20.37 82.9 0.083 4.6615 Pani Nadi 2340 895 1445 12.17 118.8 0.119 5.3416 Papu River 3320 1443 1877 15.86 118.3 0.118 5.1617 Chakrasong Nadi 3335 1443 1892 13.41 141.1 0.141 5.5018 Tributary of Pacha River 3040 1481 1559 6.97 223.6 0.224 4.6219 Pacha River 3250 1481 1769 10.78 164.2 0.164 5.1320 Lengpla Nadi 1640 515 1125 5.46 205.9 0.206 3.7621 Phuchao Nadi 2253 290 1963 8.45 232.2 0.232 6.07

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Basin Index

Basin Name Elevation of Highest Point on Basin Perimeter

Elevation of lowest point at the mouth

Maximum Basin Relief (H)

Maximum Basin Length (Lb)

Channel Gradient

Relief Ratio (Rh)


22 Kade Nala 2125 345 1780 10.15 175.3 0.175 5.1523 Pakoti Nadi 2348 364 1984 12.04 164.8 0.165 6.6324 Hoda Nadi 2516 995 1521 7.70 197.7 0.198 4.9225 Huduri Nadi 2936 635 2301 10.92 210.7 0.211 8.0426 Kaun or Hukubu Nala 2835 585 2250 14.23 158.1 0.158 7.7827 Gayang River 2835 585 2250 13.05 172.4 0.172 6.9028 Ki Nala 3135 880 2255 10.98 205.5 0.205 7.6329 Miao Nadi 3135 1550 1585 7.22 219.7 0.220 6.0430 Upstream of Dinang Bru 3605 1550 2055 9.87 208.2 0.208 7.7231 Dibri Bru 3605 1325 2280 12.84 177.6 0.178 7.9832 Difya River 3175 1175 2000 9.09 219.9 0.220 7.6633 Khenda Nadi 3080 1570 1510 6.30 239.6 0.240 5.2334 Taamchin RI (Sashi Chu) 3224 1190 2034 12.85 158.3 0.158 6.2035 Meni Nadi 3183 1260 1923 6.79 283.1 0.283 7.4936 Nimsinggoto River 3340 1578 1762 8.25 213.6 0.214 6.2537 Dublo Kho 2615 1445 1170 24.48 47.8 0.048 3.7438 Tribtary of Tenga River 3073 1408 1665 13.32 125.0 0.125 5.3839 Dogong Kho 3259 1280 1979 9.87 200.4 0.200 6.5940 Sessa Nadi 3094 165 2929 11.71 250.1 0.250 10.3141 Tipi Nala 3345 138 3207 22.45 142.8 0.143 9.82

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Hypsometric Curve:

There are two methods to draw a hypsometric curve. In the first type the ordinate is

the percentage of sub-catchments elevation relative to the maximum height of the

basin, while the abscissa is the percentage of the sub-catchment area relative to the

total basin area (Schumm, 1956). The second type pertains to hypsometry of the

individual sub-catchments where the ordinate represents the sub-catchments

elevations (h), normalized against its maximum height (H), while abscissa represents

the corresponding areas (a), normalized against the sub-catchment total area (A)

(Strahler, 1964). The value of relative area (a/A) always varies from 1.0 at the lowest

point in the basin (h/H=0.0) to 0.0 at the highest point in the basin (h/H=1.0).

Hypsometric curves are non-dimensional measure of the proportion of the catchment

area above a given elevation. According to Schumm (1956), Strahler (1964), Leopold

et al. (1964) and Hurtrez et al. (1999), hypsometric curves are related to geomorphic

and tectonic evolution of drainage basins in terms of their forms and processes.

Strahler (1952, 1957, and 1964) identified three types of landforms, namely, young,

mature and monadnock on the basis of hypsometric curve shape.

The second method is used for draw the curve for the entire 41 sub basins. Two

competing factors, namely, tectonic uplift and down wasting due to erosion control

landscape form and its evolution. The shape of hypsometric curves depends on the

degree and type of down wasting. Landscape evolution can be formulated as a

continuity equation relating uplift, elevation and erosion for sediment transport.

(Willgoose and Hancock, 1998). Sub-basins are delineated from the available Survey

of India toposheet. For all the basins the Digital Elevation Model is clipped from the

Shuttle Radar Topography Mission (SRTM) 3-arc second DEM. The areas are

calculated from the DEM in some equal elevation interval. The resulted hypsometric

curves are shown in the Figure 5.20 to 5.26.

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Figure 5.20: Hypsometric curve of different fifth order sub basins (having index 1, 2, 3, 4, 5, 6) of the study area (After Strahler, 1952)

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Figure 5.23 Hypsometric curve of different fifth order sub basins (having index 19, 20, 21, 22, 23, 24) of the study area (after Strahler, 1952)

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Figure 5.26 Hypsometric curve of different fifth order sub basins (having index 37, 38, 39, 40, 41) of the study area (after Strahler, 1952)

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Longitudinal Profile:

The longitudinal profile of a stream is a property of stream geometry that can provide

clues to underlying materials as well as insights into geologic processes and

geomorphic history of an area (Hack, 1960). The longitudinal profile of a stream

channel may be shown graphically by a plot of altitude (ordinate) as function of

horizontal distance in (abscissa).

The longitudinal profile is a graph of distance verses elevation. The construction of

longitudinal profile provides an interpretation of the surface history as they are the

erosional curves and the river course flows from the source to mouth at any stage of

evolution. (Kumar and Pandey, 1981). Longitudinal Profile for entire 41- 5th Order

sub basin of the Jia Bharali River catchment basins is constructed and shown in

Figure. The streams are taken from the SOI toposheet. The profiles are constructed

considering distance in the abscissa and the elevation as ordinate.

Two types of longitudinal profile can be generated taking the horizontal axes in

arithmetic scale and logarithmic scale keeping the vertical axes in arithmetic scale.

Both the profiles are well representing the structural disturbance along the course and

the lithology beneath the basin. The longitudinal profile constructed taking both scale

arithmetic shows the development of the knick point along the river bed. This knick

point represents the structural disturbance and the lithology control. In most of the

basin structure play a dominant role. All the major thrust and the transverse fault/

lineament are reflects as slope difference along the profile. It is observed that the

basin north of MBT and west of Kameng (basin 21-41), structure and lithology has

major role in the basin whereas in the eastern side basin (basin 11-20) structure play

major role.

It is also observed that basin higher elevation with low relief, in between MBT and

MCT (31, 32, 34, 35, 36, 37, 38, and 39) shows almost smooth river bed profile with a

minute change along lithologic contact. Basin of piedmont zone and south of MBT

shows well development of slope break along the Tipi thrust and other major

lineament. It reflects the streams of this zone are active with any deformation. Basin 2

and 3 shows a great slope break in their course representing the dominant role of

HFT.

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Figure 5.27 Longnitudianal profile for the Basins of Zone-I (Baisn 1, 2, 3) and Zone-II (Basin 4, 5, 6)

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Figure 5.28 Longnitudianal profile for the Basins of Zone-II (Basin 7, 8, 9, 10, 11, 12)

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Figure 5.29 Longnitudianal profile for the Basins of Zone-II (Basin13, 14, 15, 16) and Zone-III (Basin 17, 18)

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Figure 5.30 Longnitudianal profile for the Basins of Zone-III (Basin 19, 20, 21, 22, 23, 24)

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Figure 5.33 Longnitudianal profile for the Basins of Zone-III (Basin 37, 38, 39, 40, 41)

Drainage Basin Morphometry

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