ad been made to 
is of the region, 
rainage conditions 
iral aspects (Beg, 
:e in 1947, a sate- 
d Plains adjoining 
t surge of migra- 
ly no site specific 
planning. 
Studies 
of drainage, the 
'79), conducted a 
the main findings 
icies, which both 
ated the drainage 
:y has no surface 
•m water creating 
iownpour of high 
Secondly, due to 
ige the watertable 
region) has come 
vy damage to the 
infrastructures, 
abad and the city 
00 has not been 
:hocking of main 
necting sewerage 
t during monsoon 
soil wetness were 
;corded on rigid 
observations per 
oed area and 8 
remaining areas, 
nly 21 hydraulic 
t at the rate of 
The soil profiles 
texture, struc- 
■ ble, but overall 
h which all the 
The textures 
broader classes: 
; and fine. The 
ed according to 
;. Texturally 82 
. and 67 percent 
on, other than 
e good drainage 
infiltration rates 
ral distribution, 
d was described 
of the remaining 
derate drainage 
1 poor drainage 
rcent. 
was determined 
ty tests, despite 
ue of 60 percent 
meter per day, 
t unfortunately, 
•age of all the 
meter per day. 
^erse hydraulic 
o be supporting 
ises of variation 
:extural groups 
y was available 
ysiographic soil 
:ation. Through 
survey of the 
areas around the region had already been conducted 
and results of studies published. Reference knowledge 
gathered from these surveys had revealed certain 
physiographic and morphological aspects which have 
an important bearing on the study of drainage condi 
tions of the region. 
Soils were identified and mapped as natural bodies 
having well defined landscapes and unique sets of 
profile characteritics. Soil drainage as a land quality 
was inferred both from the landscape characteristics 
(landform, relief, landuse, and surface salinity), 
and profile characteristics (texture, structure, poro 
sity, watertable/saturation). According to these stu 
dies, the region is largely a young floodplain, pro 
fusely marked by riverain features. The surface 
has a complex relief changing at short distances. 
Soil salinity is found associated with well-defined 
landscape positions. 
The sediments are estuarine in nature and are 
deposited by river floods of abruptly decreasing 
velocity. They are extremely sorted and are dominant 
in very find sand and silt fractions (Jalal-ud-Din, 
etal, 1970). As a result, the sediments are characte 
rized by inherent capillary porosity due to which 
water is held in the soil profile against the gravity. 
The ground water or perched water pockets have 
created saturation fronts, far above their actual levels. 
From the wet spots the moisture is attracted even 
laterally towards the unsaturated parts. Further, 
under stress conditions the saturated very find sandy 
and silty soils have very low bearing capacity (Syal, 
1973). 
It is also understood that presence of heavy clay 
lenses within the profile (upto a depth of 250 cm) 
may create perched watertable conditions due to per 
colating rain, irrigation or sewerage water. Thickness 
of such layers usually does not matter much, even 
a thin layer may create situation equal to a thick 
layer. Similarly, the topography of the underlying 
rocks may be too uneven to ensure prompt movements 
of the underground flow of water. All of these 
factors locally affect the internal drainage conditions 
to varying degrees. 
Dense saline-sodic soils are unsuitable for economic 
agricultural development, bur they are readily avail 
able for non-agricultural uses. Some special measures 
are needed to use these soils for housing or industry 
(Mian and Brinkman, 1970). 
3.3 Soil drainage: Conditions and requirements 
Soil drainage represents the rapidity and extent to 
which a soil is capable of disposing off its surplus 
water externally (by run off) and internally (by 
leaching) (Soil Survey Staff, USDA, 1954). The con 
cept holds good regardless of land use of the region— 
agricultural or non-agricultural. How easily and effec 
tively a soil is drained depends on depth to watertable 
or of ponding, soil permeability, depth to bedrock, 
flooding and slope (SCS., USDA, 1983). Drainage 
conditions are best studied under stereoscopes by 
landforms, relief graytone and site conditions. Relation 
of these photo elements with soil/site condition is 
high (Buringh, 1960). A coarse loamy soil on a 
concave position and the same texture on convex 
slope surely has different surface drainage conditions, 
which could be easily readable on the aerial photo 
graphs and delineated on a map. 
A very detailed physiographic soil map representing 
soils at phase level, coupled with deep auger observa 
tions (5-10 meters) at representative sites could be 
the most useful document to group the soil phases 
according to site conditions to be evaluated for urban 
expansion (Tahir and Mushtaq, 1977). The natural 
drainage conditions of a site dictate that either it 
should not be brought under a township or adequate 
drainage should be provided and adapted architectural 
design made in the light this knowledge (Mian and 
Brinkman, 1970). 
3.4 Main short falls of the studies 
The studies of Southern Zone Planning (WAPDA, 
1979) did not employ the systematic terrain analysis 
technique of photo interpretation. Conversely, it 
appears that photographs were used only as base 
maps for field guidance. Soil mapping was done 
on the basis of rigid grid sampling procedure which 
is not adequate in Flood Plain areas wherein vertical 
and horizontal veriations in soil materials and land 
scape conditions are rather too frequent. Similarly, 
instead of using available soil maps or the aerial 
photographs, topographic maps of 1:50,000 scale were 
used to delineate specific drainage development areas. 
In doing so, relief inaccuracies were encountered. 
Consequently, very precise network of open and 
tile drains could not be proposed. Further, the 
effect of effluent from the high-lying old city and 
runoff from the denuded rock plains could not be 
estimated properly. As physiographic processes res 
ponsible for terrain evolution were not studied, drain 
age deterioration could not be attributed to real 
processes on site-specific basis. 
Effect on subsoil drainage has not been duly consi 
dered, of the impervious shale and its internal topo 
graphy observed at shallow depth under the alluvium. 
Instead, the problem has been solely attributed to 
unfavourable nature of the overburden. Further, 
it is assumed that the canals system has no appreciable 
seepage zone to act as a barrier for natural internal 
drainage. This does not appear very convincing 
in case of inherent high capillarity of the soils 
of this region. Similarly, the role of seepage water 
brought in the region by old abandoned river creeks 
entering the area in the north has not been duly 
assessed. Water column in the barrage may also 
contribute seepage water to the region internally. 
Soil Survey reports of the country have not provided 
interpretation of land resource data for urban and 
engineering uses. Stress on interpretations for agri 
cultural development has lead the urban planners 
to assume that the available soils information is 
inadequate. The scale of soil mapping (1:250,000) 
is also not enough for making detailed predictions 
about soil behaviour for urban development. 
4 PHYSIOGRAPHIC PHOTOGRAPHIC 
INTERPRETATION 
4.1 Material and method 
Semi-controlled photo mosaics of 1:40,000 scale were 
studied visually to identify broad photo-patterns 
representing main landtypes of the region. Each 
landtype was analysed in detail under the Ziess-Aero- 
topo stereoscope using panchromatic, black-and- 
white, semi-matt aerial photographs taken in 1953. 
The resulting terrain units were described in detail. 
Using another set of aerial photographs of scale 
1:30,000 taken in 1976 (during the same season), 
similar photo interpretation study was carried out 
objectively. The resulting terrain units were compared 
in respect of changes in photo image characteristics. 
The systematic physiographic procedure of aerial 
photographic interpretation (Vink 1963) was employed 
leading to understanding of the type of sediments, 
their mode of occurrance in the terrain and of 
the factors affecting the drainage conditions in the 
region. "The theme of physiographic analysis is 
to find and describe features of the stereo photo 
image which are characteristics of certain physio 
graphic processes; can be used to identify these 
processes and so on, in turn, will provide important 
clues for delineating the soil pattern" (Goosen, 1967). 
Deductions about photo image characteristics based 
on local reference knowledge were the most significant 
aspects of the physiographic photo interpretation 
procedure. 
875