ACKNOWLEDGEMENT

Q am grateful to Professor Sandipan Chakroborty, Dept. of Geography, Presidency

College, Calcutta, for his guidance during the field study in Garhbeta, Midnapore)

^1and for his non stop motivation to carry out studies in the post field work.(His

ideas, remarkable understanding of Fluvial Geomorphology and support has

greatly contributed in carrying out this research work!)

am also indebted to Sri Jayanta Sen, Research Scholar of Vidyasagar

University, Midnapore West Bengal for supplying the useful maps anddocuments?) ^

1 am also grateful to my parents who always inspired me to carry out my

dissertation work.

,/CONTE NTS

HAPTER 1:

a. Introduction

b. Location C. Objectivesc. Methodology

d. Previous Literature

APTER2:

a. Geologyb. Climatec. Natural Vegetationd. Soil I

.CHAPTER 3:a. Progressive growth of gulliesb.Types of water erosionc. The cause and processes of linear erosion

CHAPTER 4:

a. 3 tier gully development!! H b. Shapes of gullies

c. Longprofile of gullies

d. Micro relief features

y<5HAPTER 5:y

a. Information about Garhbeta Badlandb. Impactc. Conclusion

ydHAPTER 6:

Bibliography Annexture

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i near Garhbeta, AMedinipur district, West

Bengal, India has given rise to a mesoscale

badland landscape. Exquisite chromatic

association of land forms and awe-inspiring

character of topography calls for investigation of

geomorphic processes that have dominated the

terrain in the past and are operating even today

in the area.

LOCATION

The Garhbeta Badlands (22° 49'N, 87°

27'E) is situated in west Medinipur district of West

Bengal, India. This area is locally known as

4Ganganir Danga' (Land of Fire). The area lies on

he Howrah-Adra-Chakradharpur route of the

South-Eastern Railway and is located at a distance

of 176kms. from Calcutta and is approachable by

both road & railways.

v/dBJECTIVES

The Specific objectives of the study are - (i)

to delineate the nature and characteristics of

gullies, (ii) to detect the Causes of the

development of rills and gullies of the area; (Hi) to

classify the gullies based on their nature and

extension;

^METHODOLOGY

The entire work has been performed by

different phases and methods are -(I) Pre-field; (ii)

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field method. In Pre-field methods the maps and

data products (digital-imagery) have collected from

different Govt. Sources. In the field, extensive field

work has been done in each sector and phase

according to the levels of development for micro

level study and to observe the nature and

delineate the morphological characteristics of the

study area. In post field work the data have been

processed and analysed by modern Geomorphic

and analytical techniques and ultimately attempt

have been taken to delineate the impact of ravine

development on surrounding.

PREVIOUS LITERATURE

Besides depending on the fieldwork at

Garhbeta, other geomophological data &

informations are taken from different journals of

Bondhopadhyay S, Jayanta Sen, Suman Sen,

Kanailal Das & other's who have done work in this

area.

sy GEOLOGIC DEVELOPMENT

The region around our study area have thick mantle of laterite

occupying the high lands along the bank of river Silai. They are believed to be

of Pleistocene age. The thickness of this laterite capping varies gradually

between 6-25 metres.

The result of exploratory boreholes in the area revealed that there is a

gradual increase in depth of the basement rock (granite gneiss) with

consequent increase in the thickness of the semi-consolidated or loosely

consolidated sediments including the laterite from west to east and southwest

directions. This view also was corroborated by the findings from the

geophysical studies in the area. The palaeontological evidence also indicated

a gradual increase in the base of Pleistosene sediments from 106 to 152

metres to the east (Goswami, 1964-65).

Geology of the area is concealed under a blanket of laterite and laterite

soils. Based on he critical appraisal of the lithological logs and electrical logs of

the boreholes drilled in the area the lithological sequence works out as

follows:-

(i) Laterite Laterites, yellow & mottled clay, furriness sand and silt, yellow clay, gravels.

(ii) Quartzo-feldspathic sand Clay, grey, silty medium to coarse-sand. Grey and brownish grey with intervening clay.

(iii) Ferro-Magnesian sand Clay, grew to brownish grey silt, fine to medium sand, micaceous gravel bed.

(iv) Clay Clay, grey semi-cousolidated contain fossil. Fossil pockets mainly pelecypods and gastropods.

Base unknown

CLIMATE

The climate of the study area has been identified as sub-humid

monsoon type. Hot dry summer season (March - May), wet monsoon season

(June -October) and dry-cool winter (December - January) are the three

important seasons that cover most of the time of the year. During summer, the

maximum temperature increases to 45°C or more. The bare and dark coloured

lateritic surface produces maximum radiation of heat energy during this time.

The area receives an average rainfall of 140cm yr"1. Dry and cool winter

season lasts about three months in a year when minimum temperature goes

down to below 9°C. The seasonal fluctuations of

temperature and humidity have a great impact on laterisation processes and

badland development over the study area.

^NATURAL VEGETATION

Our study are was once covered with mixed deciduous forest and

was a part of Jangal mahal of Rarh upland before independence. Sal

(Shorea robusta) was the most important tree associated with Shimul

(bombax ceibal), Mahua (madhuca indica), Jarul {lagerstroemia

speciosa) etc. Presently, low sub-soil acidity, high subsurface calcium and

absence of organic matter are indicative of poor growth and regeneration of

sal. In most of the places the topsoil has been washed away which is not

favourable to the ecosystem.

|: t/^OIL FORMATION

The region is characterised with loose and dry surface soil with

presence of highly indurated duricrust. The sediments of the area are mostly

concealed under a blanket of duricrust. As laterite is heavily leached tropical

subsoil, when exposed, it dries and gets rock-like due to cementing of

ferruginous concretions by iron oxide colloids (Mallick and Niyogi, 1970). It is

not a fertile soil. At Garhbeta laterite also consists of aluminum

oxyhydroxides with smaller amounts of iron oxyhydroxides and a little bit of a

clay mineral called halloysite. Silica, calcium, magnesium, potassium and

sodium are present in very low amounts of absent. Laterite formations span

several kilometers on the right bank of river Silai. The topography very much

resembles the Australian "breakaways" with a broad flattish and dissected

top and undercut softer materials below (Mallick and Niyogi 1970, Biswas

1987). L

ATERITIC PROFILE AT GARHBETA BADLAND

Sequence Name

Slope Thickness (m) Characteristics

1 Surface Layer

3" or less 0.5 A Surficial cover of red clayey soil, recorded in many places, with some sands, & minute concretions.

2 Laterite duricrust

5U-15° 2.0-4.0 A layer of nodular duricrust, partly cemented containing iron concretions or spaced nodules, which are tabular & sufficiently large to be called pipes often draining out

water, from the solutionai & collapse holes developed on the surface, the highly indurated layer being often cut away vertically by gullies running down to the river.

3 Mottledclaylayer

Nearly 60°

4.0-6.0 A layer of redish & sometimes purplish mottled clay, mired with some five as well as course sand, traversed in places by thin hardpans, cut away by rills & gullies at the scarp face.

4 Palledzonelayer

35° -45° 5.0 A pallied layer of yellowish white clay containing very little of sand somewhat irregular in occurrence, pure clay occuring only in pockets, producing on the break away.

We can also describe the nature of soil and sediment properties in the study

area by the following table >

Nature of Soil & Sediment Properties in the Study area

No Specifications SoilPh

Organic Carbon

%

%0fSand

%of Silt

%ofClay

Textural Class

Available N

AvailableP

S1 Laterite durienst / upland surface

6 8 0.22 51.9 15.8 32 8 Sci 120 20

S-2 Pallid zone surface of western gully fringe

5 5 0 06 499 35.8 14 3 L 32 3.6

S-3 Gullychannel bed / by the sideOf River silat

5 8 Nilm- - -.......„ .

,

927 1.0 6.3 S 25 Trace

S-4 Erosionallateriteuplandcultivableduring wetperiod

5.5t

0 62•

41.8 4.9 16.3 L 401 85.0

QUANTITATIVE ASSESSMENT OF GROWTH OF GULLIES IN

Following Table gives clear indication on progress

of the badland based on estimation of authentic

secondary information viz. Survey of India topographical

maps (1:50,000), Aerial photographs (1:60,000), satellite

data (IRS LISS III Geocoded, 1:50,000; IRS ID PAN

Image - 2001, and ground survey since 1995. It can be

seen that the affected area has increased to about

234.48% during the last 73 years.

SI. Source of Information Year of Observation Affected area km1 SOI Topographical map 1930-31 1.45 km22 SOI Topographical map 1968-69 2.10 km23 IIRS 1C Lisslll Geocoded

Image1995 2.95 km2

4 IRS 1D PAN Image 2001 3.28 km25 Mapping with GPS and

field monitoring2003 3.40 km2

Introduction of Global Positioning System opened up a

new frontier in surveying, with unprecedented accuracy especially

in this terrain which had to be mapped to investigate fluvio-

geomorphological processes so that such spatial database may

assist in adopting necessary reclamation schemes. GPS survey

carried out during 2000-2001, brought about exact extent of

actual present area under badlands, shape and length of the

escarpments, rate of gully headwall retreat, location of micro and

ARHBETA

meso scale geomorphic features, gully networks etc. The GPS

hardware and software used in the survey (Trimble TDC 1 and

TCS-1 receiver with Pro XR antenna and Pathfinder Office V 8.2

software) were capable of providing sub meter accuracy after

post processing of the collected data. Universal Transverse

Mercator (UTM Zone North - 45) projections was used in the

study as this was found to be the most convenient projection

system for transferring the GPS-generated vectors directly to

Geomatica V8.2, the RS/GIS software used for mapping.

Four stages of Gully development at Garhbeta Badland:

EVOLUTION OF GARHBETA BADLANDS IN MEDINIPUR

DISTRICT OF WEST BENGAL

Initially this area was a flat-topped lateritic upland.

Shifting of river Silai towards the upland and erosion along its

concave bank produced a steep escarpment (>20m) revealing 4

to 5 distinct indurated horizons. Gullies dissected the duricrusted

surface and extended headward resulting in rapid scarp retreat.

The badland of Garhbeta have two distinct parts viz. the

less mature Southwestern part (about 0.40 km2) & more mature

North-Eastern part (about 0.85 km2). The maximum retreat of

the gully head was found to be about 60cm/year.

DEFINITION AND CHARACTERISTICS OF BADLAND

'Badlands', as the name implies, are

barren areas of little or no economic value;

generally devoid of vegetation and often

having an extremely rugged terrain, which makes

human access difficult; they are generally regarded

as useless lands. The term can be traced to early

settlers in western North America where scattered

areas of badlands are widely distributed. (Campbell

1989) Encyclopedia of Geomorphology by R. W.

Fairbridge describes badlands as extremely

dissected landscape difficult to cross on horseback

and agriculturally useless. French

Geomorphologists define badlands as areas

dissected by very fine drainage networks and short

steep slopes with narrow interfluves. The slopes

may terminate abruptly in pediments on a miniature

scale and are often completely free of vegetation.

RAINSPLASH EROSION

It occurs when raindrops fall [raindrop fall at

914 cm/s (30ft/s)) on unprotected ground. When

raindrop strikes the ground surface the soil particles

become more loose and splash due to impact force.

A momentary building up of the pressure gradients

towards the edges of the drop disintegrates the soil

and shoots some particles out. The slashed particles

reach to heights ranging up to 2-5cm and horizontally

upto an average of 5cm depending on their size and

slope of the ground at Garhbeta. The important

influencing factors of rain splash are the mass and

velocity of raindrop and the soil character.

SHEET EROSION

At lateritic Garhbeta badland region sheet

erosion result significant surface wash over the

undulating upland surface upto the gully head during

high intensity precipitation events. The western

section is much bare that results tremendous sheet

flow and surface removal. Whereas the eastern gully

section though the gully channels have more width

and length, the upland surface is less undulating and

gradient averages to 2°-5°. Here the sheet or

overland flow becomes active when sufficient rainfall

occurs (100 mm/hr). The surface particles are also

little smaller (<3mm) compare to western gully sector,

which results high ground water percolation and

steady overland flow especially when sufficient rainfall

occurs.

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RILL EROSION

Studies of hydraulic characteristics of the flow

show that change from overland flow to rill flow

passes through four stages at Garhbeta; (i)

Unconcentrated channel flow, (ii) Overland flow with

concentrated flow paths, (iii) Micro-channels without

head cut and (iv) Micro-channels with headcut.

The greatest differences exist between the 1st

and 2nd stage, suggesting that the flow concentration

within the overland flow should strictly be treated as part

of an incipient rill system (Merritt 1984). In the 2nd stage,

small vortices appear in the flow, which, in the 3rd stage,

develops into localised, spots of turbulent characterised

by roll waves and eddies.

Based on the surface slope and velocity of flow

the rill channels on Garhbeta lateritic upland can be

classified into three types :

(a) Small or minor rills, (b) Moderate rills, (c) Major or developed rills.

GULLY EROSION

Gullies are open erosion channels at least

30cm deep which conduct ephemeral runoff and are

frequently characterized by steep sidewalls and a lack

of vegetation. Gullies tend to become deeper with

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n remove vast amounts of soil. Removal of topsoil and

subsoil by fast-flowing surface water creates abrupt

deep and wide gullies, of two different kinds: scouring

gullies and headward erosion. In scouring gulling,

run-off water concentrated in rills or depressions

removes soil particles. Material commonly moved is the

size of fine to medium sand or may be derived from

slaking, when large aggregates disintegrate upon

wetting. Scouring is often associated with gently

undulating landscapes.

THE CAUSE &

PROCESSES OF

LINEAR EROSION (i.e.

Rills & Gullies) IN

GARHBETA

The cause of linear erosion is to be sought in runoff

energy, which depends on runoff volume and its

squared speed.

3 THEORIES OF THE ONSET OF RUNOFF

1. Horton's theory (1945): Runoff starts when rainfall

intensity exceeds soil absorption capacity.

Comparing infiltration to rainfall intensity,! absorption

decreases over time partly because capillary potential falls as the wetting front

penetrates into the soil, and partly because soil structure at the surface

was deteriorated.

2. Soil saturation theory: Runoff starts when all the pores in the soil are

filled with water. In the cause of a simulated rainstorm, if runoff starts

after rain has soaked the soil, it will increase until it stabilizes at a level

corresponding to the absorption capacity of the soil. However if the

rainfall persists (runoff may rise again, reaching a new plateau of

stabilized infiltration. This simply means that the tilled horizon has

reached saturation, so that the macroporous storage capacity of this

horizon is filled to overflowing. If the underlying horizon is totally

impervious, the amount of runoff will correspond precisely to that of the

simulated rainfall; there may, however be a corresponding to that of the

plough pour. When the soil is totally saturated, any drop of rain will runoff

respective of rainfall intensity.

3. Theory of partial watershed surface contribution to runoff: The runoff

measured at the river-level depends on the area of the saturated soil in the

valley bottom. If watershed surface runoff is measured during the dry

season, it is seen that the river reacts very quickly to rain storms whereas

no runoff is seen on the slopes! The volume of is less during this dry period

because only a narrow ship in the valley bottom is saturated - often only

the minor bed. At the end of the winter, however, when the whole soil

cover has been soaked to capacity, the slightest rainfall replenishes the

aquifer, which will spread out sideways, saturating a greater areas of the

valley. As a result, even if there is no runoff on the slope during the rainy

season, the entire watershed well contribute to the volume of flow in the

river through extension of the saturated area, in as much as the ground

water is recharged directly by draining the entire basin.

The stages of weathering and erosion observed in the region are:

1. The Preparatory Stage

During this stage the surface is prepared for sculpturing. Based on seasonal

characteristics of climate such preparatory stage can classified into winter and

summer conditions.

1a. Surface preparation during winter condition (December -

February) : Just after the monsoon the surface moisture is

reduced gradually due to lowering of atmospheric humidity.

Significant fluctuation of diurnal, temperature about 18° -20°C, is

found which results destru :tion of seasonal vegetation mainly

grasses at different stages of the badland sector of Garhbeta.

During December and January when the minimum temperature

further goes down below 9°C and atmospheric moisture goes

down below 65% the surface of the terrain become very dry and

loose and numerous cracks and joints progresses with surface

contraction over the lateritic upland.

The depth to ground water level in the phreatic zone gets

low in winter months and varies between 1.5m to 9metres below

land surface. The winter season persists upto February and

before onset of summer a transitional period occurs for about 15 -

20 days.

1b. Surface preparation during summer condition (March - May):

During summer the atmospheric temperature at daytime at

Garhbeta increases up to 45°C. However, at night, the

temperature goes down to 25°C. This fluctuation encourages

significant processes of mechanical weathering. The bare dark

colored and granular surface of the lateritic upland of Garhbeta

makes suitable conditions for weathering processes to be

maintained. Occasional occurrences of thunderstorms (locally

called Kalbaisakhi) transport loose and unconsolidated surface

materials, which are afterwards washed out more easily by the

surface runoff or sheet wash.

From middle of May up to the 2nd week of June, the

groundwater regime further goes down from 2.8 to 18.0 metres

below land surface. This lowering of groundwater also has

significant impact of laterisation process and surface wash after a

prolonged dry season. Therefore, in the preparatory stage the

seasonal and diurnal fluctuation of air and surface temperature

along with the fluctuating groundwater make suitable

preconditions for fluvial erosion with formation of rills and gullies

during the rainy season.

2. Surface erosion stage / Processing stage

The surface erosion stage at Garhbeta starts from middle of

June at the onset of monsoon rains. The factors that influences

soil erosion by water is the mean annual rainfall and rainfall

intensity. Severe erosion in the badland sector of Garhbeta is

Types and Number of Gully Channels at Garhbeta badland (Eastern Sector)

associated and accentuated with high mean annual rainfall

(about 1400mm and poor growth of vegetation).

v^TIER GULLY DEVELOPMENT

As observed by Bandyopadhyay (1988), a distinct 3-tier

gully development, genetically unrelated to each often, is seen

in the region. Numerous but small (depth : 1-2m) gullies under

the first tier develop above the escarpment, etched on the top

most laterite hardcap. 4 to 5 gullies of the first tier open out into a

single gully of the 2nd tier (depth : 10 - 15m) that extends

headward with basal sapping 3-10m below the top level

duricrust & with the consequent retreat of the escarpment. The

material deposited by the 2nd tier gullies in the erosional plain

created by the retreating escarpment are found to be dissected

by the gullies of the 3rd tier (depth : 0.5 - 1m) which are

unbranched & drain directly into the Silai.

General Classification of gully channels at Garhbeta badland

No. Name TypeSpecifications

Depth (m)

Width (m) Side slope (%)

1 Very small gullies Gi <1.5 <10.0 <82 Small gullies G2 1.5-3.0 10.0-15.0 8-153 Medium gullies G3 3.0-9.0 15.0-18.0 15-454 Deep & narrow gullies G4 >9.0 >18.0 >45

SHAPE OF GULLIES

The riverine gullies of Garhbeta area are characterized

by three common morphological features e.g. gully-head,

gullyneck and gully body. The morphometric properties of a

sample gully draining into the Silai river include 'notched shape'

of gully head with a maximum width of 3.9m and constricted

section of 2.0m width, narrow gully neck of 2.5m thickness and

elongated shape of gully body of 35m length. Besides a few

exceptions, almost all of the gullies are characterized by plunge

pools'. The longitudinal profile of an active gully denotes the

presence of gully heads, gully heads, gully neck, cliff face,

plunge pools, and gully body on the basis of morphological

characteristics the gully heads have been divided into four types

viz. (i) pointed gully head (ii) circular gully head (iii) notched gully

head and (iv) digitate gully head.

The gullies of Garhbeta area vary significantly as regards

their shapes and morphological characteristics and thus they

have been classified into six types e.g. (i) linear gullies (ii) parallel

gullies (iii) gullies (iv) bulbous gullies (v) rectangular gullies and

(vi) mixed gullies represents different morphometric properties of

sample gullies. Linear gullies are long (13.9m to 60m) with

pointed narrow gully heads (ranging in length from 2.2m to 2.6m).

Sometimes, a few very small tributary rills also develop on either

side of the main gully body. It may be pointed out that linear

gullies no longer always remain narrow because their valleys are

broadened and are transformed into bulbous, trellis or mixed

types. They generally develop in the area having highest

concentration of surface run-off through a single channel. They

undergo the fastest rate of advancement through headward

erosion. In a single rainy season, the extension of linear gullies

ranges from 10m to 20m Parallel gullies, which represent group of

linear gullies, have developed on concave side of the Siiai river at

Garhbeta. Trellis gullies have developed on moderately sloping

ground with multiple channel flow of accelerated surface run off. It

is evident that trellis pattern of gullies is characterized by longest

length of gully heads (10m to 28m) and greater depths (8.1m to

15m).

Bulbous gullies have developed in areas having moderate

flow of surface run off with maximum exhumation of soluble

minerals from A horizon of the soil profile B, and B horizons.

Semicircular or amphitheatre like heads of bulbous gullies

generally develop due to buckling down of A horizon fostered by

excessive mudflow

y /

through B horizons. Rectangular gullies have very poorly

developed in the study area.

MORPHOLOGICAL CHARACTERISTICS OF SAMPLE GULLIES

S

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DETERMINATIO

N OF SHAPE OF

MACRO GULLY

IN WESTERN

SECTOR AT

GARHBETA

Shape of macro gully in western sector

of Garhbeta have been determined from which

idea of gully head, gully floor and gully side

walls can be done. Through the determination

of gully shape the following table can be

represented -

From Gully Head (facing Silai Nadi)

Right Wall Left WallTributary Gully angles

Intervening Spur angles

Tributary Gully angles

Intervening Spur angles

ZB = 130° ZC = 97° ZL= 130° ZQ = 28°ZD = 103° ZE = 76° ZR = 147° ZT = 21°ZF % 70° ZG = 68° ZS = 127° ZW = 56°Zl = 122° ZH= 120° ZU = 60* ZY = 136°ZK= 131° ZJ = 42° ZV = 100° ZZ= 179°ZL = 165° ZM = 87° ZX = 84° ZBt = 130° !

1—

ZN = 178° ZAi = 130° ZB = 59°ZB = 130° ZCi = 110°Average = 128°25'43"

Average = 81°40' Average =111° Average = 79°50'

^/WESTERN AND EASTERN GULLY

As seen before, the badlands of Garhbeta can be classified as

western (or less matured) and eastern (or matured) parts. In the western

part, gullies are short and discontinuous, slope of the gully wall is between

60-90°; their height varies between 18-25m. Whereas in the eastern part,

gullies have greater length; slope is gentle and convex (5-45); height of the

gully wall is below 15m. Our observation shows the orientations of the gullies

are very much integrated with nature and properties of laterite profile. The

profile shows, there are 4-5 distinct horizons and due to differential

sedimentary composition each profile has differential resistance to erosion.

As a result gullies in Ganganir Danga occur in different levels. One set of

gully drain the surface of the lateritic duricrust and the other cut into the lower

horizons originating from the retreating cliff line.

Distinct characteristic difference can be seen between eastern and

western gully channels. V-shaped gullies form in material that is equally or

increasingly resistant to erosion with depth. U-shaped gullies form in material

that is equally or decreasingly resistant to erosion with depth. As the

substratum is washed away, the overlying material loses its support and falls

into the gully to be washed away. Most V-shaped gullies become modified

toward a U shape once the channel stabilizes and the banks start to spell

and slump.

\/CONG PROFILE OF GULLIES

Long profile is the section or line which can be obtained by plotting

the axial line of the channel from source to mouth. As gully slopes are

commonly steep in the headward sides and gentle in the lower reaches

profiles are normally concave upwards.

Here Macro, Meso and Micro types of longitudinal profiles are

determined by the use of clinometer, Abney level and prismatic compass.

While determining the longitudinal profiles an idea can be done of the slope

of longitudinal profile. For e.g.,

cliff slopes are found on escarpment faces. Cliffs are so steep (40° or more)

that the products of weathering for the most part fall immediately to the base.

There is little or no accumulation of detritus on the cliff itself and it is therefore

commonly and meaningfully referred to by geomorphologists as a free-face.

Scree slopes are also found which varies from 35° or more in the

longitudinal profile. Aggradational slopes are seen in the longitudinal profile. It

varies from 20° -35°. Eventually the cliff may disappear entirely to be replaced

by a wholly aggradatinal slope at 20° - 35°. In its lower part, a longitudinal

profile will commonly exhibit a concave section. Rectilinear slope profile is

often observed in the Garhbeta badland area which is straight in profile.

MICRO RELIEF FEATURES IN GARHBETA

On the basis of survey by dumpy level and prismatic compass relief features

are obtained for a gully catchment area. Through this survey in a catchment

area it is found that high relief is found in the Eastern and Southern part.

Based on this variation of relief features serial profiles are drawn and they are

superimposed to identify the micro relief features of the gully catchment area.

Some useful data on Garhbeta badland:

SI Parameters Quantified Units1 Present total area covered by

badlands2 Area occupied by Eastern gully

sectorWestern gully sector

3 Average extension of area under badlands (for the last 8 years)

56.25 sq m

4 Total length of escarpmentRole of escarpment retreat Maximum 85 cm / yr

Average 10-12 cm5 Height of the escarpment Maximum

Average6 Average slope of the terrain

7 Area affected be sheet erosion

14% of total

8 Area affected by rill erosion9 Area affected by gully

erosion72% of total

10 Linear extension of rill channels

Maximum

Average11 Linear / headward extention of

gully channelsMaximum

MinimumAverage

12 Gully channel morphology Slide slope MaximumAverage

Depth MaximumAverage

Width MaximumAverage

Length MaximumAverage

IMPACTS

The impact of Gully Erosion are -

(i) Gully erosion means the loss of large volumes of soil.

(ii) Deep wide gullies, sometimes reaching 30m deep,

severely limit the use of the land.

(t«) Off-site deposition of soil causes water-qualify decline in

streams or rivers.

(iv) Large gullies disrupt normal form operations, creating

access problems for vehicles and stock.

(v) Low soil organic matter levels, lower fertility levels,

changes in soil pH, exposed subsoil and parent material

discourage crop production in gullies and rills.

(vi)

Soil erosion in the badlands of Garhbeta has serious

impact on the surrounding environment by decreasing soil fertility

and land productivity. It also reduces the capacity of soil to absorb

rainfall that often results in increased flooding and reduced

ground-water recharge, augmenting sediment loads in rivers and

streams. This degrades the quality of water supplied downstream

and cause silting of channels and reservoirs, in turn, increasing

risks of flooding and reduction in dry* season water supply. Such

an area was selected by us for study, because all stages of water

erosion, channel initialization, rill and gully development slope

evolution, and other land sculpturing activities are found in this

rather meso-scale topographic unit. Geomorphological

investigation of water erosion on land sculpturing, role of fluvial

action on a specific land and significance of climatic variables on

development of badland topography. The badland though covers

a small area, is a natural plot in itself for carrying out fluvio

geomorphological investigations and research through real time

monitoring techniques.

A greenbelt has been created by the State Agriculture

Department since 1969 to check gully erosion at Gangani. The

green belt is initiated along the divide region to the south of the

badlands mainly using cashewnut (Anacardium occidentale). But

the 2nd tier gullies of Gangani are advancing by undercutting. The

process is operating 4 to 10m below the protected surface. So the

plantation of cashewnuts may not be able to check the gully-

advancement. Trees of other species, such as Sal (Shorea

robusta), which are able to penetrate the root system below the

laterite horizon would perhaps make a better choice (It may be

noted that laterites are indurate only after their exposition to the

atmosphere. At present, the gullies in Gangani are creating

agricultural areas rather than destroying it. Crop-cultivation,

mainly rice & vegetables, is practised in small plots in the

recessional depositional

surface left exposed by the retreating cliff-line.

BIBLIOGRAPHY

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development over laterite duricrust. In Jog. S. R. (Ed.):

Indian Geomorphology, 1 Rawat Pub. New Delhi, pp. 31

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(iii) Fairbridge, R. W., Scheidegger, A. E., and Schumm, S.

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(iv) Faniran, A., and Jeje, L.K. 1983:/-/t//77/af Tropical

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(vii) Leopold, L. B., Wolman, M. G. and Miller, J. P.

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