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Chapter-IV

Drainage Morphometry

This chapter deals with the morphometric evolution of drainage network and its

characteristics as it applied to normally developed watershed in which running water and

associated transported load become most effective. Emphasis is given upon the geometry,

rather than upon the dynamic processes of erosion and transportation which shape the

present form. The study of drainage of any area is essential to work out the genetic aspect

of landforms. Drainage analysis is an important method to know the various characteristics

of the study area related with drainage texture, frequency and pattern. The analysis of

drainage basins has a particular relevance to geomorphology. Fluvial eroded landscape are

composed of drainage basins, and these provide convenient units with the help of which an

area may be sub-divided. Under the impetus supplied by Horton (1945), the description of

drainage basins and channel network was transformed from a purely qualitative and

deductive study to a rigorous quantitative science capable of providing hydrologists with

numerical data of practical value. Horton,s work was further developed in detailed by

Strahler (1950, 1952 and 1958) and his Columbia University associates (Morisawa, 1959

and Schumm, 1956).

The mathematical analysis and mathematical measurement of any area or any part

of the earth, thing or plant, is called 'morphometry'. In geometry, morphometry may be

defined as the measurement and mathematical analysis of the earth's surface and of the

shape of any landform. The present study deals with the most important study in the

analysis of landforms, that is morphometric analysis of Dhundsir Gad watershed net work.

Geomorphology is defined in term of its anatomy, process, and morphology

(Mukhopadhyay, 1978). 'The adjustment of stream lines to the landscape is rather an index

of the landform evolution, in a humid region in which rain water becomes the most

important sculpturing agency' (Asthana, 1968). In fact Horton (1945) framed the original

idea of interrelationships among different morphometric attributes and Strahler (1958)

modified it in as a technical framework. The morphometric aspect particular mention have

to be made of the contribution by Horton (1932,1945), Schumm (1954,1956,) Miller

(1953). The study of alter flow and sedimentation transport of a river is quantitatively

analyzed the behavior of the river. River morphology is the direct concern of the hydraulic

engineer, who provide detailed information pertaining to the amount of sediment denuded

by the river and volume and velocity of water that moves through the channel (Singh,

1978).

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Drainage System

Dhundsir Gad is the master stream of the study area. It is the 5th order right bank

tributary of the Alaknanda river in Lesser Himalaya. Alaknanda is the parental stream of

the Holy river Ganga in Holy Himalaya (Garhwal). The Dhundsir Gad rises from

Gaddikhal at the height of 2360m in the North. After flowing 17.5 km. towards southern

direction it joints the Alaknanda river at Dhundprayag. It is considered as a sacred river by

the people of the local area. Its reference is also found in Askand Purana as quoted below-

ßrr~ m/)Z izo”ksfg dSojkRioZrk }jkr~ lek;fr unh Js’Bk ekus äks”kk)[k.MdsÞA

¼dsnkj[k.M 182 vLdUn iqjk.k~½

The ahead at the distance half Kos (mile) of this sacred place (Dhundprayag) a holy

river comes from super Kuber Parvat. Kuber Parvat is the ancient mythological name of

the Gaddikhal mountain range in which Dhundsir Gad rises. The literal meaning of

Dhundsir is (Dhud= Rock, Sir = where the water rise). So, it can be said that the place from

where the water rise under a rock is called Dhundsir. It is a spring fed perennial riveres.

There is another story of the name of Dhundsir Gad. The name Dhundsir derived from the

Dhundeswar Mahadev (a name of God Shiva).There is a limestone cave at Semgarh which

is 4 km down stream from Dhari village. The cave is mainly devoted to Lord Shiva.

There is a perennial spring near the mountain top which fed the river Dhundsir.

During travel 17.5 km distance number of perennial and dry streams (locally known as Gad

and Gadheras) join in it and increase the volume of river. All the perennial streams are also

spring fed. The description of springs is given in chapter 5. It is clear that the Dhundsir

Gad is a fifth order stream in which 3 fourth orders, 17 third order, 60 second order stream

join in it from source to mouth. The importance of the river is not due to being the tributary

of Alaknanda River but it is also keep an importance role for the living of watershed

inhabitants. Mainly Dhundsir Gad river rises from 2360m height namely Dhundsir (Kuber

Parvat in Purana). Earlier its name was known as Udar Gad in local dialect. It is a right

bank tributary of Alaknanda River. The total area of Dhundsir Gad is 50.5km2. There are

eight main third order tributaries of Dhundsir Gad. Four tributaries are make confluence

with Dhundsir Gad river from left bank and three right bank direction (Fig.15) Before

joining the main stream many first, second and third order stream joins these tributaries

from left and right side. These streams mainly occur water from rain or springs. The north

part mostly drained by Udar Gad the main stream of watershed and after flowing about 8.5

km. it merges with river Chauni Gad and beyond this point it called Dhundsir Gad. Most of

62

tributaries are dry for major part of the year. A flood generally occurs during rainy season.

The detailed descriptions of these tributaries are as following-

(i) Dhankur Gad: Dhankur Gad is the parental third order stream of Dhundsir Gad which

originates from the same place where the master stream rises. After flowing 2km distance

towards south, it joins with Ulari Gad near Dhari village (1450m). It is a perennial stream

thoughout the course.

(ii) Ulari Gad: Ulari Gad is a fourth order left bank tributary of the Dhundsir which rises

from southern slopes of Gaddikhal range. After flowing 2.75 km towards south-west

direction it joins main stream near Dhari village. There are 2 third order, 5 second order

and 22 first order streams of the Ulari Gad. After that the river name is called Dhundsir

Gad.

(iii) Margaon Khad: Margaon Khad rises at the height of 2020m near Margaon village so

that its name is Margaon Khad. Khad is the local name of stream. There are three springs

which provide water to the stream. After flowing 2.5 km in east-west direction it makes its

confluence with Udar Gad at lower part of Dhari settlement (1450m).

(iv) Athani Khad: Athani Khad is a left bank tributary of Dhundsir Gad. It originates from

Athani top (2200 m). It is also a ever flowing stream of the basin. After flowing 3.1 km in

east to west direction on northern slope of Athani Dhar it make confluence with the

Dhundsir Gad at Koti village (1330m)

(v) Taula Gad: Taula Gad is a 4th order tributary of the Chauni Gad which comes also from

south-eastern part of Athani top (2262m). It flows between Nagraj Dhar and Athani Dhar.

It is a spring fed perennial stream. It flows in a very steep gradient. After flowing 4.5 km

distance it joins with Nagelagair Gad. Taula Gad having a well developed drainage of

perennial springs which indicate the moisture availability in the area and developed

irrigated agriculture system in its lower part.

(vi) Chauni Gad: In the middle valley of the study area there is a second important 4th

order tributary of Dhundsir Gad known as Chauri Gad. There are two parental stream of the

Chauri Gad i.e. Chauni Gad and Taula Gad. Chauni Gad originates from the western slopes

of the Chauni Khal Dhar from north of Silkakhal. Most of its tributaries rises from northern

slope of the Silkakhal Dhar. It flows between Nagraj Dhar and Silkakhal Dhar. After

flowing 5km distance it joins with Nagalagair Gad before joining the main stream. After

than it called Chauri Gad up to confluence (Plate-5). It is also a perennial stream which

flow in a very steep gradient.

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There are 14 other third 60 second order and 279 first order streams which joins

both the sides of the main stream and established their identity in the development of

drainage system. Among them main are Durha Khad and Thapali Khad, Khola Khad.

Drainage Pattern Each river system has its own plan or morphology guided by so many factors as

initial slopes, nature of rocks, structural control, recent diastrophism and recent geologic

and geomorphic history of the basin (Thornbury, 1954). The different type of rocks, folds,

faults, joints, dip angle, lithology and erosional nature determines the evolution and pattern

of the drainage system. It is of great help in the interpretation of geomorphic features.

Drainage pattern according to Thornbury (1969) provides a more practical approach to an

understanding of structural and lithological controls in landform evolutions. According to

encyclopedia of geomorphology "Drainage pattern or arrangement refers to spatial

relationship among streams or rivers which may be influenced in their erosion by

inequalities of slope, rock resistance, structure and geologic history of a region. Parvis

(1950) defines the drainage pattern as, “the manner or design in which a given set of

tributary streams arrange themselves within a given drainage basin”. A tracking of the

drainage plans from the topographical sheet including the geology of the region viz. rock

type, terrain are the fundamental determiner in their drainage network. It is fact that

drainage pattern may be reflect in original slope, structure and lithology. As the streams cut

under laying rock lithology, structure, and resistance to erosion give rise to characteristics

of drainage pattern. Single drainage pattern may be result of single multiple factors.

Therefore, this analysis has a signification and interpretation of basins geologic structure,

lithology, physiographic and climatic conditions of the area.

The drainage patterns of present study area are characterized by many small

seasonal streams flowing on different slope aspects. Three major rivers on the northern side

of hill constitute the drainage system of the area where two river merges with the main

trunk stream at Phayalgaon from eastern site. The major controlling factors of the drainage

patterns of the area are geological structure, anthropogenic factors, micro climatic

conditions, different rock types and erosional nature of stream. In a humid region like

Dhundsir Gad, streams are busy in rapid cutting and linking up of formerly isolated

drainage pattern. This downward cutting tends to erode the softer rocks more easily in the

lithologically alternated areas.

Dhundsir Gad have the collective picture of streams covering reflects the drainage

arrangement in relation to the geomorphologic history. The common patterns of drainage

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in relation to the area under study are dendrite, radial, parallel, rectangular, trellis and

faulted (Fig.16). The detailed of the drainage pattern are as fellows:

(i) Dendrite drainage pattern: Dendritic drainage pattern is the most common in the

Dhundsir Gad. The term 'dendritic' was first introduced by Russell (1904). The term

‘dendritic, means a nonsystematic or tree like (branching) pattern of valleys extending in

many directions. Except a few localities almost every tributary valley presents a dendritic

pattern. This type of drainage pattern is observed in the localities of Margaon Khad, Taula

Khad and Maninath Ka Danda.

(ii) Radial drainage pattern: In the radial drainage pattern the stream flows in various

directions from isolated hills or hill ranges. In the study area the radial or configurable

streams pattern is observed in the middle part of the basin where the first order stream of

Dhundsir Gad flows. Radial drainage may be developed on a structural or geomorphic

quaquavrersal basement. This pattern is observed in the localities of Dhundsir Gad,

Gaddikhal and Nagraj Dhar. (Fig.16 )

(iii) Faulted drainage pattern: Faulted drainage pattern is developed on both the side of

fault line in the study area. It is seen that wherever the fault lines are appeared the streams

follow the faulted course (Fig.16). This type of drainage pattern developed in the lower

part of Dang and Sema which are close to the North Almora Thrust (NAT).

(iv) Parallel drainage pattern: In the parallel drainage pattern the streams flows parallel

to each other streams. This pattern develops according to regional slope of the area. Along

the fault line the main stream flows through a fault while the first and second order streams

are formed a parallel drainage pattern from the both sides of the fault.

(v) Trellis drainage pattern: Development of trellis drainage pattern often takes place

where a secondary tributaries are in turn orthogonal to the major streams wills named such

an arrangement the trellis pattern because of its developed in glaciated areas. In this pattern

the streams meat each other right angle. The streams are usually subsequent in original

slope (Fig.16). This pattern is best developed in the northeast and lower part of the basin.

Such type of drainage pattern is common in areas of folded sedimentary beds.

(vi) Annular pattern: Annular drainage pattern generally is founds at the folds and

change in lithology and change in lithology. One of the typical annular drainage pattern is

found at Koti village where the master stream change her course from gneissic lithology to

quartzite lithology. The stream turns her course towards east and formed half circle type

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features and than enters southern direction.

Finally it can be summarized that mostly dendritic and sub-dendritic drainage

pattern is found in the quartzite dominated terrain of the study area.

Drainage Anomalies

Active tectonics in a basin plays an important role in controlling a fluvial system

through the changes in channel slope. The Dhundsir Gad watershed, an branching river

system has responded to ongoing tectonic deformation in the basin. The relatively flat

mountain terrain are deformed by several active deformation processes, which divide the

area in to different tectonic blocks. Each tectonic block is characterized by association of

fluvial anomalies viz. compressed meanders, knick point in longitudinal profiles, channel

incision, anomalous sinuosity variations, sudden change in river flow direction, river flow

against the local gradient and distribution of over bank flooding, and waterlogged area.

Such fluvial anomalies have been identified on the large scale toposheets and satellite

images i.e Google earth images and maps and interpreted through DEM and field

observations to understand the nature of vertical movements in the area. The sub-surface

faults in the Dhundsir Gad watershed cut across the river channel and also run parallel

which have allowed us to observe the effects of longitudinal and lateral tilting manifested

in avulsions and morphological changes. In this study an attempted has been made to

understand the surface deformation pattern along the subsurface faults with the help of

proxy data such as geomorphological anomaly, fluvial processes, and hydrological

characteristics.

Detection and characterization of geomorphic anomalies in the watershed have

provided an additional tool for recognizing the subtle tectonic movements in the region.

Conventional methods such as seismic data analysis and fault plane solutions of earthquake

data are often insufficient to relate active tectonic movements to any specific fault because

the trends of the transverse faults are almost parallel and several faults are closely spaced in

this area. This integrated approach using Google earth data and topographic observation

coupled with repeated field observations have provided information on the nature of

vertical movement of local faults. Dhundsir Gad river response to active tectonics depends

upon the nature and amount of vertical movement in the basin and the trend of the fault

with respect to river flow. In the Dhundsir Gad, most of the subsurface faults are cutting

across the river channel. The differential movements along these fault have produced tilting

that triggered channel avulsion and shifted river flow from NW to SE.

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Dominance of normal faulting in the central and western part may be related to the

slow rate of northward convergence (low value of horizontal stress component in

comparison with thick sediment over-loading). The eastern part of the watershed plains is,

however, characterized by high northward convergence in comparison to sediment loading

and this area is marked by strike-slip and dip-slip component. Thus following anomalies

are recognized in the study area-

(i) Compressed meander: One of the compressed meander can be recognized at village

Koti, there is a one km. band of river can be seen. The main stream is flowing in a state of

direction from NE to SW but the stream suddenly bands towards west and than turn to

southeast direction. It is the result of a active tectonic and folding of rocks. It seems like a

folded nose through which the stream flows in a semi circle rout (Fig.17).

(ii) Change in confluence angle: Generally, it is seen that the master stream band to join

in main stream either at an acute angle or at an right angle but in the study area many

examples where the main stream band to meet their tributaries which, flow in a state

course. At the place of Dharpayankoti the tributary streams flows in a state direction while

the main stream join in tributary stream from right angle. Similar type of drainage

anomalies is also recognized between Dhundsir Gad and its tributaries channels. Out of

these some other examples of confluence angle are also recognized in 3rd order and 2nd

order streams of many locations (Fig.17)

(iii) Change in channel course: The channel course of the stream suddenly change due to

faulting and linear features. Which also shows the evidence of active tectonics in the

Himalaya region. The main examples of this anomalies are near Dharkot in the upper

valley, second order tributary of Taula Gad (Khal Dhar) near the village Sirsed (Fig.-17)

and second order tributary of Nagelagair Gad near the village of Kafana. Last two

examples are the result of stream capturing during alternate deformation stages of the

region.

(iv) Channel course direction : Generally, the tributary streams joins in the main stream

either from right angle of in the acute angle. But one of the typical examples of course

direction is seen near Khark village. One of the third order stream and its tributary locally

known as Khad joins the master stream (Dhundsir Gad) from opposite directions at abuts

angle (150o) which shows that the stream flows in a major linear feature either fracture or

fault. Similar type of examples is also noted at Rankandiyal village (Fig.17).

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(v) Change in length, order and area: The main stream have longer course, large in areal

expansion and rises from highest elevation, but this criteria can not applied in case of

Dhundsir Gad and Dhankur Gad. The Dhundsir Gad rises at the higher of 2360m while the

Dhankur Gad rises at the higher elevation of 2300m. Secondly, before making their

confluence at Dhari the order of the Dhundsir Gad is lower (3rd) while the Dhankur Gad

order is higher (4th). It also shows that the tributary stream is a higher order stream than its

main stream. If we see the areal expansion of both these streams than we found that the

area of tributary stream is higher than the main stream. The tributary steams has also

straight course while main streams join in it from right angle (Fig.17).

An another example of change of order is also found between Dhundsir Gad and

Chauri Gad. Here the tributary stream of Chauri Gad is higher order (5th) while the master

stream of the area is lower order (4th). It is also a typical drainage anomaly in the study

area. It is observed that the area is highly disturbed by tectonic movements. A multiphase

of deformation can be identified in the lithology, drainage course and stream confluences.

The late phase of deformation had disturbed the early phase of deformation. Their impact

can also be seen on landform development. The drainage anomalies in the present drainage

basin may be result of continued tectonics disturbances in the Himalaya. In many cases

there are evidence for the uplift of the sources of the river and some times for the uplift of

valley floor (Nand & Kumar, 1989). After analyzing these anomalies it can be concluded

that no one criteria can be applied to the stream of the basin. It is difficult to determine

which the main stream is.

Thus the following conclusion can be drawn from above discussion-

1. The fluvial terrain in the study area have responded and adjusted to slow and subtle

active tectonic movements. These adjustments can be recognized using geomorphic

data.

2. All subsurface faults in the basin are presently active and have produced distinctive

response manifested as fluvial anomalies.

3. Typical responses to uplift included development of compressed meanders,

convexity in longitudinal profile, pinching of stream, anti flow direction, stream

piracy, and frequent channel avulsions. The area subjected to upliftment show

sudden change in flow direction because of the change in local relief and increased

over bank flooding.

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4. This study suggests significant differences in tectonic setting and activation of sub-

surface faults within Dhundsir Gad.

Geometry of the Basin Shape

Channel geometry deals with the geo-dynamics and geomorphic manifestations of

crustual deformation processes. The climatic variations are rather smaller and the

geomorphic markers which can be used for tectonic geomorphic studies. River terraces are

one of the most common examples of preserved sloping geomorphic features in a fluvial

terrain and serve as very useful geomorphic marks of active tectonic. The geometry of the

basin area can be divided into two parts:

(i) Linear aspect of the basin

Linear aspect of the basin includes the study of the channel patterns of the drainage

network in terms of links wherein the topological properties of the stream segments are

analyzed areal aspect of the basin. The drainage network which includes all the stream

segments of a particular river, is studied in graphic terms where stream junctions are

considered as points and streams are regarded as the lines which connects them. For this

purpose the numbers of all streams segments are measured and various inter-relationships

are analyzed. The linear aspect of the drainage basins include the analysis and

interpretation of stream order (u), stream number (Nu) bifurcation ratio (Rb) stream lengths

(lu) and sinuosity index.

(i) Stream ordering: Stream Ordering is the first step in the morphometric analysis of any

landscape. Firstly this system introduced by Horton (1945) in U.S.A. and later slightly

modified by Strahlar (1952). Woldenburg ( 1966) and Shreve (1967) have put forward

somewhat different stream ordering systems. According to Strahlar, the first order streams

are those which have no tributaries, similarly, the second order stream are those which have

as tributaries only first order streams, where two second order streams joined a third order

streams formed or where the two third order streams meet each to other the fourth order

stream formed i.e.1+1=2, 2+2=3,3+3=4…n. The notable point is that when the three order

stream join the fourth order stream or the second order stream joined the third order stream

there are no incensement will be indicated in the further order, than the trunk stream,

through which all discharge and sediment passes is the stream segment of the highest order.

In the present study the Strahlar stream ordering system is applied.

The scale play an important role in the stream ordering. In the present study the

topographic sheet prepared by survey of India (1/50,000) used because it show clearly the

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first order stream. In the present study area the trunk stream Dhundsir Gad, is of the 5th

order stream. Its important tributaries are fourth, third, second, and first order according to

Strahler’s stream ordering system (Fig.18). The area of the every order stream was

calculated by grid method. Following table gives the order, number, size, length, average

length and length ratio of the stream orders of Dhundsir Gad.

Table-4.1 Stream order length and area of Dhundsir Gad

Stream Order

No. of Streams

Length (km)

Area (in km2.)

% of Total area

Average stream length

Length ratio

I 279 104 26.08 51.6 0.37 1.21

II 60 27 15.05 29.8 0.45 0.97

III 17 7.5 24.95 49.4 0.44 6.81

IV 3 9 32.50 64.4 3.0 3.00

V 1 9 50.50 100.0 9.00 -

Total 360 156.5 100.0

Table 4.1 reveals that the total number of streams in the basin is 360 which having

about 156.5 km length. Maximum percentage of area is in 4th order stream (64.4%) and

minimum in 2nd order (15.05%). First order stream having the area of 51.6% out of the total

basin area. It shows that accept first order, as the order increases the area of the order

streams is also increases (Table-4.1)

(ii) Stream number: The number of stream segments in each order is known as stream

number, the law of stream order states that stream number decreases as order increases

(Horton 1945). The law of stream order also states that the number of stream segments of

each order from a diverse geometric series with the order number.

Table 4.1 shows order wise stream frequency in the tributary of the Dhundsir Gad.

It is marked that the Dhundsir Gad comprises of fifth order. The total number of first order

stream in the Dhundsir Gad is 279 which make 60 second order streams forming 17 third

order and 3 fourth order stream have been marked. The Table reveals a maximum

frequency in case of first order streams. Further it is noted that as the stream frequency

decreases as the stream order increases. The first order stream covers maximum length of

the stream tributary having maximum number. In the eastern part (Fig19) the frequency of

stream order associated maximum number because quartzite rock is founding in this part.

In the source zone, the number of streams are also higher on the quartzite terrain. Along the

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jointed quartzite terrain first and second order streams are developed in large numbers.

The lower part of the basin covers with less frequency of stream order. The

structure of the phyllite rocks and forest cover is responsible for this. The relation between

stream number and stream length is shown in Fig.19. It shows that the number of streams

against the order of streams indicates a linear correlation. Both the curves run parallel to

each other which show the positive relationship between them.

(iii) Stream length: The stream length is a severer component of a drainage network and

its surface. The total stream length of various orders of the Dhundsir Gad have been

measured by Rota meter from topographic maps and the average length is also calculated.

Table 4.1 shows that the total length of stream order is maximum in case of first

order streams. The total length is decreases as the order increases. The total length of first

order stream is 104 km. Second order stream is 27 km., third order is 7.5 km., fourth order

is 9km., and fifth order is 9 km. respectively. The total length of all the stream orders is

156.5 km. This data also reveals that when the stream order is highest the stream length of

same order is lowest. The difference due to variation in relief, geological structure,

vegetation, slope condition. It is noted that the fifth order stream mostly laying across low

altitudinal zone 500m-1000m.with moderate slopes. The cumulative length of channel

segments increases with the channel order, it being the lowest for the first order channels.

The law of the successive orders of a basin forms approximately a direct geometric series.

The law of stream numbers and length suggest that geometric similarity be maintained in

basins of increasing order.

(iv) Stream length ratio: It is the ratio of mean length of stream 1st order to the mean

length of 2nd order, mean length of second order to mean length of third i.e. length ratio is

ratio of every two order. This ratio is obtained by using the following formula

RL= Lū / Lū-1

Where ‘RL’ is the stream length ratio, ‘Lū-1’ is the mean stream length of order ‘u’

and ‘Lū-1’ is the mean length of segments of the next lower order.

It is noted that the stream length ratio, of each of the successive orders of the

Dhundsir Gad vary due to difference in slope and topographic conditions (Table- 4.1). The

table 4.1 reveals that 4th and 1st order length ratio ranges from 0.97 to 6.81. It is higher

(6.81) in third order streams while lowest (0.97) in second order basin. In the case of

Dhundsir Gad length ratio decrease in unsuccessive order but it is high in third. There is

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no specific pattern of length ratio in the basin. Third order length ratio is higher than IVth

order ratio and second order ratio is lower than first order.

(v) Bifurcation ratio: Bifurcation (Rb) ratio is related to the branching pattern of the

drainage net work. The bifurcation ratio, for a given density of drainage lines is very much

controlled by basin shape and shows very little variation where structural effects causes

basin elongation, however, this value may increase appreciably. Besides influencing the

landscape morphometry, the bifurcation ratio is important control over the 'peaked ness' of

the run off hydrographic (Chorley 1969). The bifurcation ratio defined as the ratio of

number of segments of a given order. The bifurcation ratio is considering the ratio between

the number of stream segments of any given order and the number of segments of the next

higher order, a proportion is designated as the bifurcation ratio. The bifurcation ratio

between successive order of Dhundsir Gad is tabulated in Table 4.2.

Table: 4.2 Bifurcation ratio of Dhundsir Gad

Stream order No. Stream Segments Bifurcation Ratio

I 279 -

II 55 4.65

III 14 3.23

IV 03 4.6

V 01 3

Table 4.2 reveals that the bifurcation is varies from order to order. The highest ratio

4.65.03 is in first order stream while the lowest ratio 3.0 is marked in fourth order stream.

The variability of bifurcation ratio is seen from average value of each order of each basin.

The above discussion does not give the definitive criterion between order and number. It

varies according to lithology, climate an vegetation cover of the area.

(vi) Sinuosity index: The stream channel geometry originates in sinuous form and this is

not possible to originate in geometric paths especially in the hilly region. The sinuosity

index means the measurement of deviations of drainage lines from their geometric paths.

The formation path of drainage line depends upon the under laying rocks structure, climatic

condition, vegetation, anthropogenic impact, and the time taken in the development of the

drainage system. There are many qualitative and quantitative methods for distinguish the

sinuosity index of any drainage basin. Generally, the ratio between channel length and

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channel valley length is called sinuosity index (Muller, 1968). It is obtained by quantitative

and qualitative techniques of the terrain analysis. Generally the value of S.I. ranges from 1-

4 or more, river having 1-1.3 sinuosity index are called sinuosity and those having indices

of more than called meandering (Leopold et al.,1964). Muller (1968) has taken the channel

length (CL), the valley length (VL) and the maximum air distance (AL) from source to

mouth of drainage basin as sinuosity attributes. Calculation of various type sinuosity index

are made on the basin of the following formula:

(i) Channel Index (CI) = Cl/Al (Hydraulic and topographic sinuosity)

(ii) Valley Index (VI)= VL/AL (Topographic sinuosity)

(iii) Hydraulic sinuosity Index (HSI) = % equivalent of CI-VI/CI-1

(iv) Topographic sinuosity Index (TSI) = % equivalent of VI-1/CI-1

(v) Channel Sinuosity Index (CSI) = CL/VL

(vi) Standard Sinuosity Index (SSI) = CI/VI

With time the mountain front sinuosity increases due to erosional processes. It is

commonly infurred that more sinuosity older is the tectonic uplifts in the areas. For

instance, in soft rock structure the degree of sinuosity is marked very high where the values

are recorded as 1 to 2. Table 4.3 shows the Channel Index (CI), Valley Index (VI),

Hydraulic sinuosity Index (HSI), Topographic sinuosity Index (TSI), Channel Sinuosity

Index (CSI) and Standard Sinuosity Index (SSI) for the main channel of Dhundsir Gad and

those of its tributary basins. The sinuosity indices of the main stream of the tributary basins

of the Dhundsir Gad , ranges from 1.02 to 1.13. Mostly the all stream are sinuous or

straight. The most straight courses area those of the stream are Dhundsir Gad (1.02),

Nagalagair Gad (1.13), Taula Gad (1.06), Dhankur Gad (1.05). The low hydraulic sinuosity

indices (HSI) and low topography sinuosity indices (TSI), indicating that these streams are

early mature stage of their development. The highest and lowest values of TSI have been

obtained in case of main stream, Taula Gad and Dhankur Gad.

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Table:4.3 Sinuosity index of Dhundsir Gad

Stream VL (Km)

CL (Km)

AL (Km)

CI VI HIS (%)

TSI (%)

SSI (Km.)

Dhundsir Gad 17 17.5 15 1.16 1.13 18.75 81.00 1.02

Nagailagair Gad

4.00 3.50 3.70 1.08 0.95 16.25 62.50 1.13

Taula Gad 4.25 4.00 3.70 1.15 1.08 14.00 53.33 1.06

Dhankur Gad 2.25 2.15 2.00 1.13 1.08 38.50 61.00 1.05

In early mature stage, the SSI and TSI fluctuate around 1.2 and 52.0 respectively

(Muller, 1968). This SSI is supposed to be 1.6 at fully maturity, which indicates strong

hydraulic sinuosity. It is a meaningful index for classifying drainage basins into varying

stages on the basis of SSI such as (i) Youthful (>1.15), (ii) early mature (1.15-1.30), and

(iii) mature (<1.30). Table 4.3 gives the SSI or a total of 3 tributary streams of the

Dhundsir Gad. Thus, all the tributary streams are in youthful stage.

(ii) Areal Aspect of the Basin

Surface configuration like absolute relief, relative relief, slope and dissection index

etc. are important factors which affect the development of the drainage system of any area.

It is also controlled by stratigraphy, structure of rocks, climate and biotic factors.

The application of principles of mathematical statistics to quantitative

geomorphology is essential if meaningful conclusions are to be achieved. A systematic

description of the geometry of a drainage basin and its stream channel system requires

aspects of the drainage network. Arial aspects of the drainage basin mainly controlled by

channel network and contributing ground slopes. "The drainage lines of an area reflect the

recent diastrophism geologic and geomorphic history of the basin concerned the erosion

characteristics such as size, shape, pattern and drainage density are controlled by the

factors which influence the denudation, i.e. initial slope, structure and stratigraphy of the

rocks, climate and biotic factors" (Singh, 1977). It varies inversely with the size of the

basin, it is the best indicator of stream spacing which infers on rock character of the terrain,

past and present processes which are operating to the terrain, slope characteristics and

natural vegetation cover (Dutt, 1983). The scale of fineness of the pattern is described by

the measure trend of the drainage density as first introduced by Horton (1945).

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Drainage Frequency

Drainage frequency is defined as the total number of stream segments per unit area.

In the present study the later method applied by Horton (1945) had been applied. The

number of drainage lines has been counted in a grid unit of one Km2 where the topographic

map divided in to 2 cm. grids, thereby making each grid to represent 1 km2. The total

number of streams found to each grid was calculated and than put in the center of the grid

to find out the drainage frequency for the study area (Fig.20). In general, the accurence of

stream segments depends on the structure of rocks, vegetation cover, amount of rainfall,

capacity of infiltration and geological structure. It was found that the drainage frequency

of the Dhundsir Gad have been put in certain category of 3 streams interval. Than the

different categories has been termed as course, moderate, moderately high, high and very

high. The drainage frequency of Dhundsir Gad characterized in the following table :

Table: 4.4 General distribution of drainage frequency in Dhundsir Gad

Frequency Classes

Area ( km2.) % Cumulative % Remark

< - 5 2.9 5.8 5.8 V. Course

5 - 8 27.42 55.3 61.1 Course

8 - 11 13.29 26.8 87.9 Fine

> - 11 5.89 11.8 100 Very Fine

Total 50.5 100 100

The Table 4.6 shows the distribution of drainage frequency that 55.3% of basin area

has course drainage density followed by 26.8% fine, 11.8% very fine, and 5.8% very

course drainage density respectively. The Table exhibits the distribution patterns of

drainage frequencies into different groups; the frequency data also presents higher

concentration of drainage frequency in the lower classes. The detail explanation of

drainage frequency distribution is given below.

(i) Very course drainage frequency: The category of low drainage frequency determined

below 5 streams per km2 which covers or 5.8% of the total basin area which is minimum in

the study area. The low or poor drainage frequency characterized in the lower valley slopes

of the Dhundsir Gad. Some more small patches of lower drainage density are seen on the

75

top of the ridges (Dhar) and near of the confluence of streams. Topographically the low

drainage frequency found in the Maniknath ka Danda, Kandi and Athani Dhar.

(ii) Course drainage frequency: The areal distribution of moderate drainage frequency

covers an area 55.3 % of total study area. The extend of this category in study area spread

in whole part except northern part. Course drainage frequency is found in the localities of

Margaon Syalsaur, and Bagaon, villages.

(iii) Fine drainage frequency: High Drainage frequency occurrs the number of streams

ranging from 8-11 covers an area 13.29 km2 or 26.8 % of study area. Mainly this category

stands in medium slope zone. The coverage of this category in study area is in north and

north -east part situated Kafana, Dharkot, Parkot, Koti etc.. A maturely developed

topography is characterized by fine drainage frequencies.

(iv) Very fine drainage frequency: The very fine drainage frequency occupies 5.89 km2 or

11.8% of the basin area only. This category of drainage frequency is noted in the

Shivalaya, Dhundsir and Chauri Khal of the basin. Other small patches cover in the

Margaon and eastern part of the basin. The youthful topography is typical of areas of high

to high drainage frequency.

Drainage Density

Drainage density means the total length of stream segments per unit area. The term

drainage density was first introduced by Horton (1932). Drainage density is calculated by

following formula:

DD = EL/A

Where 'DD" is drainage density 'EL' is the total stream length and 'A' is the areal

unit.

It is a function of the intensity of run off, erosion, proportionality factor, relief,

density etc. The drainage density map (Fig.21) shows a higher degree of consistency with

the spread of other morphometric attributes and reflect the effect of variation in relief, soil,

rocks, with permeable characters.

76

Table: 4.5 Drainage density of Dhundsir Gad

Category Area % Cumulative % Remark

Blow - 1 4.27 8.45 8.45 Very low drainage density

1 - 2 7.59 15.32 23.77 Low drainage density

2 - 3 24.42 48.35 72.12 Moderate drainage density

3 - 4 9.35 18.51 90.63 High drainage density

Above - 4 4.87 9.37 100 Very high drainage density

Total 50.5 100

The drainage density in the Dhundsir Gad , observed by measuring the total length

of stream segments in one square grids, ranges from .5 km/ km2 to 8.4 km/km2 (Fig. 21).

The category of drainage density values have been grouped into four classes. (i) Extremely

coarse drainage density (ii) Moderately coarse drainage density (iii) Coarse drainage

density (iv) Moderate coarse drainage density (v) Moderate fine drainage density. Table

4.6 revels that 48.35% area is under course drainage density. Fine drainage density is

characterized about 4% of the basin area. Extremely course to moderately course drainage

density is characterized 8.45% and 15.32 %of the study area respectively.

(i) Very Low drainage density: The area of this type of drainage density occupies 4.27

km2or 8.45 % of the total basin area. It covers the area of Rampur, Kirtinagar and near its

confluence. It covers a high forest density.

(ii) Low drainage density: This category of drainage density covers an area 7.59 km2 or

15.32 % of total basin area of normal sloping topography and flat surface water divides

occurring in the lower valley part of the study area such as Sema, Zirkoti, Sirsed, and in the

middle part of the basin. Other small patches of low drainage density are noted near

Margaon in the north -east part of the basin.

(iii) Moderate drainage density: The table reveals that the moderate drainage density

occupies 24.42 km2 or 48.35% of the total basin area. The maximum area of the basin is

under the moderate drainage density. The basin with such properties, lie in the quartzite

units ands lime stone having some resistant rock. It indicates that drainage development has

not crossed the region.

77

(iv) High drainage density: The area of high drainage density measures 9.35 km2 or

18.51% of total area of the study area. It is associated with the middle part of the ridges

and valley closed to the hill top of study area. Kaproli Dhar, Chauri Khal, Athani Khad ,

upper part of Syalsaur and Dharkot Village and Bagaon localities are also characterized by

this category of drainage density.

(v) Very High drainage density: Very high drainage density is associated with the rugged

and fractured terrains located on the high elevation. It covers about 4.87 km2 or 9.37% of

the total area and occurred in patches in the Kuniyar Top, Sil, Dharkot, Khola, and western

part of Bagaon.

Confluences Density

The consideration of confluences in analyzing the basin dynamics in indispensable,

for the total aggregation of streams uniting to form major ones reflect the position of a

stream in the hierarchy of the ability and strength of a stream to erode and transport.

Confluence density is an important factor for the analysis of hydrological study of the any

basin. Confluence density is directly related with drainage density, stream order and their

numbers.Streams with higher confluence numbers rank higher in the power hierarchy,

whilst streams with few confluences rank lower in the hierarchy of power. For the

calculation of confluence point the study area divided into 1 km2 grid and after than the

number of confluence point in per unit area was counted (Fig.22). According to the Table

4.6 the four category of confluence density was classified as described under:

Table-4.6 Confluence density in the Dhundsir Gad.

Confluence Density (per km2)

Area (Km2.) % Commutative % Remark

< - 3 7.25 14.35 14.35 Low

3 - 6 15.78 30.71 45.06 Medium

6 - 9 21.22 42.04 87.15 High

> - 9 6.52 12.90 100.00 Very High

Total 50.5 100.00 100.00

Table 4.7 revels that maximum percentage (42.04%) of confluence density is

found in the category of 6-9. The second highest percentage of confluence density is under

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3-6 category. The minimum density is found in above 9 (12.90%) followed by less than 3

(14.35%) confluence point in per km2.

(i) Low confluence density (0-3): This category occupies 7.25 or 14.75% of the total

area. Mainly this category stressed in the higher part of the basin such as in top of hill

ridges, water divides river terraces and convex spurs. The main localities are the watershed

boundary (Fig.23) i.e. Gaddikhal, Chauni Khal, Athani Dhar, Chauri Khal, and Kaproli

Dhar.

(ii) Medium confluence density (3-6): This category occupies 15.78 km2 or 30.71 % of

total area. Mainly this category stressed in gentle slopes gentle spurs and low hills of the

watershed. The Localities occupies this category are Nagraj Dhar, Mulana Nagraj Dhar,

Margaon, and Kafana villages (Fig.23).

(iii) High confluence density (6-9): High confluence density ranges between 6-9

confluence point in per km2 which occupies the maximum part 21.22 Km2. or 42.04 % of

the total area. The densities of confluences are found in the tectonically unstable zone of

the study area. The localities are Zirkoti, , Rankandiyal, Sarkena and Athani Top etc. Multi

phases of deformation change the courses of drainage lines and new drainage lines

developed along the linear features i.e. fold, faults and lineaments. Thus the maximum

drainage join near the highly fractured zone (Fig.23).

(iv) Very high confluence density (>-9): Very high confluence density stressed 6.52

Km.2 or 12.90% area of the basin. The factors for the development of vary high confluence

density are the same as found in the high confluence density. The main localities of very

high drainage density are Arari, Sirsed, Dharkot, Parkot and Dharpayankoti (Fig.23).

On the basis of confluence density it can be concluded that the main stream

occupies the higher density of confluence point in valley area. The confluence point density

can be employ to obtain the power of a stream to erode in the absence of discharge data.

The analysis provides a measure to specify the relative ability and power of streams,

especially of identical orders, other things being the same. The area with abnormally high

first order streams does not cover maximum confluence density in comparison to high

order (4th & 5th) stream.

Hypsometric Curve

Topography produced by stream erosion and associated process of weathering,

mass movement. and sheet runoff is extremely complex both in the geometry of the forms

themselves and in the interrelation of the process which produce the forms. Strahler

79

(1952), Langbein (1947) introduced hypsometric analysis of the forms of drainage basins.

Holmes also used a hypsometric curve to show the problem of the earth solid surface above

or below different altitudes. This technique has been applied by Strahler, Miller, Schumm

and others.

Hypsometric curve shows the ratio between the height and surface area of earth

surface. The percentage hypsometric curve is a ratio of relative height and relative relief

area with respect to the total height and total area of a drainage basin which is play a vital

role in geometric analysis. These curves have their practical application in different

branches of hydrology, geomorphology, soil erosion, and other branches of earth surface. It

is drawn with the help of the following ratios:

1. a/A: where a is the area enclosed by a pair of contours and A is the total basin area

.it is represent area and communalities area

2. h/H: where h is the heights elevation between each pair of contours and h is the

total basin height, it is plotted on the ordinate,

For the study area the hypsometric curve (Fig.24) drawn by Strahler’s method. The

figure shows the hypsographic curve of master stream and three tributary basins which

have been prepared on the basis of area and altitude. According to Strahler there are three

stages each representing the three distinctive stages of the geomorphic cycle or evolution of

the basin, viz.

(i) The young stage (inequalibrium stage),

(ii) Mature stage (equabilibrium stage)

(iii) The old stage (mondock stage)

The values of hypsometric integrals can be grouped into three categories each

representing one of the typical stages of basin dissection, viz, (i) youthful stage (60%-

100%) (ii) mature stage (35%-59%) and (iii) old stage (below-35%), (Pal, 1972)

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Table 4.7 Percentage hypsometric curve of Dhundsir Gad and tributary streams

Dhundsir Gad

Contour (mts) Area in (km2) Cumulative area (a) a/A h/H

520-800 3.0 3.5 0.069 0.152

800-1000 7.1 10.6 0.209 0.261

1000-1200 4.5 15.1 0.298 0.370

1200-1400 6.3 21.3 0.422 0.478

1400-1600 8.0 29.3 0.580 0.587

1600-1800 5.2 34.5 0.683 0.696

1800-2000 11.7 46.2 0.914 0.804

2000-2200 3.6 49.8 0.985 0.913

2000-2360 0.7 50.5 1.000 1.000

Total 50.5

Nagalagair Gad

< -1000 0.6 0.6 0.092 0.111

1000-1200 0.8 1.4 0.214 0.333

1200-1400 1.57 2.97 0.453 0.556

1400-1600 1.99 4.96 0.757 0.778

1600-1800 1.59 6.55 1.000 1.000

Total 6.55 - - --

Taula Gad

< -1000 0.06 0.06 0.008 0.077

1000-1200 0.60 0.66 0.093 0.231

1200-1400 1.94 2.60 0.367 0.385

1400-1600 2.10 4.70 0.664 0.538

1600-1800 1.06 5.76 0.814 0.692

1800-2000 0.80 6.56 0.927 0.846

2000-2200 0.52 7.08 1.000 1.000

Total 7.08 - - -

81

Dhankur Gad

1400-1600 0.34 0.34 0.098 0.208

1600-1800 0.92 1.25 0.368 0.417

1800-2000 0.75 2.01 0.589 0.625

2000-2200 1.22 3.23 0.947 0.833

2200 - > 0.18 3.41 1.000 1.000

Total 3.41 - - -

Table 4.4 reveals the hypsometric integrals for the study area. The forms of

hypsometric curves and the values of the hypsometric integrals has been taken together, to

identify the stage of basin development. It is notable that 46.66% area of the Dhundsir Gad

shows erosional integral while rest 54.44% area is hypsometric integrals that indicates the

early mature stage of geomorphic development. All other three tributary stream are passing

through maturity stage of geomorphic development which ranges 43 to 59 % of

Hypsometric integrals.

Basin Parameters and Hydrology

Drainage density: An average drainage density of Dhundsir Gad found to be km-2. which

indicates the permeable formation for the better ground water discharge and severe erosion

problem in catchment. The heights drainage density of Dhundsir Gad reveled the well

developed channel network and would produce more sediment and causes serious erosion

(Chow, 1964). The heights values of relative relief and slope (1840m. and 135m/km. ) of

Dhundsir Gad also support high sediment erosion and water discharge.

Basin geometry: Basin Geometry like form factor elongation ratio, etc depend the shape of

watershed and its impact on runoff generation. Thus heights values indicter that watershed

is more compact and runoff hydrograph is expected to be sharper with a great peak with

shorter duration. It was found that in the majority of watershed circulatory ratio varied

from 0.6-0.7, which indicate that Dhundsir Gad watershed has homogeneous geological

formation. On an average elongation ratio of catchment was found to be 0.79 reveled that

the Dhundsir Gad were strongly relief steep ground slopes.

Drainage network: The highest order of stream was 5th in Dhundsir Gad, where most of it

tributaries were order 3rd. Bifurcation ratio of Dhundsir Gad, ranged from 3.49 to 4.27.

Higher values of Dhundsir Gad was mainly due to its physiographic nature. The result

82

indicated that the basin is still in immature stage of development and geologic structures

had full control on the nature of drainage pattern of Dhundsir Gad. The bifurcation ratio of

means that on an average, there are 3.9 times as many channel segments of one order as the

next higher order. An average length of stream was found to be 4025.5 km. This indicate a

well defined drainage system Thus constituting higher channel storage characteristics of

basin.

Hypsometric curve and hydrology: Hypsometric analysis is useful to comprehend the

erosion status of a watershed and priorities them for under taking soil conservation

measures. The analysis can be performed with easily extractable information from

toposheets of an area (Panday, 2004). Hypsometric analysis revels the geological stage of

watershed and is a measures of its maturity, indicating the susceptibility of the watershed to

erosion.

The hypsometric values for the Dhundsir Gad and its tributaries ranged from 0.108

to 0.367. none of the tributary streams is at matured stage. Which is the evident from the HI

values of less than 0.35. Thus these sub watershed required soil conversation measures

they are likely to experience more further erosion.

*****