ekhar
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ty (surface and
. activity/needs.
as assessed by
1 data in a GIS
>s, the thematic
GIS package.
o arrive at the
| the correlation
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y the suitability
) most suitable
ops etc. Land
that 92% of the
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in effective tool
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vere integrated
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Aur taluk (432
carnataka State,
N 12° 48'2" to
75° 48'22" to
cultural land is
rops grown are
Pulses (Census
tant commercial
loffee, Potato,
e, Cotton, etc.
/ery poor in this
tivity depends
| receives good
errain runoff is
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ation is around
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3. DATA BASE GENERATION
The Alur data base consists of
various thematic maps (on 1:50,000 scale)
such as ground water potential zone, soils,
land use, wasteland, village boundaries,
contour map, etc. (Table-1). Data were
digitized using CALCOMP and BENSON
digitizers and later converted into
ARC/INFO format. All the data were
edited, rectified, transformed and labelled,
thus final data was made ready for analysis.
4. METHODOLOGY
In any given area, the slope, soil,
water (ground and surface water), rainfall
and climate decide the land suitability for
any purpose, although human activity/
needs plays a significant role (FAO, 1976).
To evaluate the land suitability a
theoretically simple model is best because it
is possible to make use of the planner's
knowledge while evaluation. Accordingly,
the ranking/weights method is believed to
be one of the best models and therefore was
applied to evaluate the suitability of land
for various crops/plantation (Hiroshi,
1988). Therefore, the same method with
two approach has been adopted. In the first
approach slope, soil and ground water were
integrated to arrive at the suitability. The
suitability map thus obtained was correlated
with the land use map. Further, land use
map was integrated with suitability map to
refine/modify the suitability classes. It may
be noted that average rainfall in the study
area is around 100 cm annually and the data
available is for the whole taluk, since there
is no variation within the study area this
layer was not used for integration.
Climatically also there are no significant
changes, hence, not considered while
integrating.
The weights were assigned to
different classes of soil, slope, ground
water and land use maps based on their
suitability for cultivating different crops.
In each natural resources theme, the
suitability of that particular class was
assessed and weights were assigned; the
highest weight was assigned to the class
which is highly suitable for cultivation and
least value for least suitable class (Table-2).
Weights were assigned in the following
Scale: 0 - Unsuitable; 1 - Least suitable; 2 -
Less suitable; 3 - Suitable; 4 - More
101
suitable and 5 - Most suitable. In number
of studies initially weights were assigned to
classes of each layer, then these weights
were subjected to statistical analysis and
modified weights is obtained for that
particular class (Hiroshi, 1988; Mukund,
1991). However these exercise have
improved the overall impact marginally
hence the authors adopted simple weights
method only.
After assigning the weights, soil,
ground water, slope and lineament
(fracture) maps were integrated. Thus a
layer with basic information for assessing
the land suitability for cultivation was made
available. The resultant map (from ground
water, soil, slope and fractures, termed as,
GSSL) consists of a number of polygons,
where each polygon has a soil, slope and
ground water weights. These weights were
added (cumulative) as well as multiplied, to
generate two separate suitability layers
named as SUMGRP and MULTGRP
respectively. These were further grouped
into different suitability classes such as 1 -
Highly suitable; 2 - Most suitable; 3 - More
suitable; 4 - Suitable; 5 - Less suitable; 6 -
Least suitable and 7 - Unsuitable.
In the case of cumulative weights,
the weights of each layer in a polygon were
added to get the total weight of that
particular polygon. These were regrouped
into 7 groups i.e. from unsuitable to highly
suitable group. (Group) ah (where n is the
total number of groups considered) consists
of polygons which have the weights varying
from
wt to wt,
where E wt, is the total weight from soil,
slope and ground water for the 'i'th level of
suitability. That is group 1 is best land for
cultivation and group 2 is next best, etc.,
and group 7 is not at all suitable.
In the case of multiplication, the
weights of each layer in a polygon were
multiplied to get the total weights, and
regrouped into 7 suitability classes.
(Group) ad) consists of polygons which are
having the weights varying from
m wt, to m wt, ,
where, v wt. is the product of soil, slope
and ground water weights for the 'i'th level