ited levees 
>and-7 image, 
r. The light 
e and near- 
are typical 
c matter: In 
1 floodplain 
1-5 image of 
to the dark 
s and bare 
re white on 
res, basins, 
3 partly as 
of 1974 and 
indicate an 
n both visi- 
lectromagne- 
for highly 
t, sediments 
areas might 
1 floodplain 
ant organic 
ly buried by 
3nly as dark 
contain high 
in the lower 
s with time 
ours on both 
E different 
entification 
'Odplain the 
3 pattern on 
r on that of 
3 colours of 
etated long 
light-grey 
nd dark co 
rn the large 
L change of 
a boundary 
The basins 
Lble images, 
mages while 
e channels, 
d that fine 
sins of the 
tg the large 
er distance 
iplain some 
the Meghna 
i vegetation 
miform dark 
' images of 
>pearance of 
.cally indi- 
sat and clay 
:ir location 
¡ist of "mud 
and between 
ituated far 
els. Except 
and a few 
de channels 
ometry. The 
erent years 
ndition. As 
e played an 
e composite 
1 and river 
flooding by 
r than min- 
wet basins 
A - tidal floodplain 
B - river floodplain 
C - composite floodplain 
Figure 3. Drainage pattern map 
of Bangladesh delta area 
Landsat image 
Figure 4b. Embroidery floodplain landscape 
Landsat image 
far from active river channels. Moreover, rainwater 
flooding can only redistribute the finest sediments 
in the direction of low basins while leaving the 
relatively coarser ones such as sand and silt at the 
place where they were deposited by river or tidal 
flooding. According to differences in colour on 
both visible and near-infrared images of different 
years the composite floodplain is subdivided into 
smalle units as peat, thin clay cover over peat, 
thin sand-silt cover over peat, sandy-silty deposits 
and swamp deposits. 
Peat: The largest part of the composite floodplain 
appears black and dark grey on the 1974 band-7 im 
age. On the band-5 image, however, the black areas 
also appear black while dark grey areas are lighter, 
medium grey in colour. The black areas are also 
black on the band-7 image of 1975. The black colours 
on both images of different years are typical for 
very wet peat materials. These black areas must 
correspond to the lower parts of the composite 
floodplain where thick layers of peat could devel 
op. 
Due to differences in moisture content and vegeta 
tion cover at different times, peat areas do not 
appear with the same shape and size on images of two 
years. However, the real boundary of peat areas can 
be drawn by comparing the near-infrared images of 
these two years. 
Thin clay cover over peat: The finest clay accumu 
lates in the lowest parts of the floodplain. The 
areas around and between the peat layers appear 
medium grey on band-5 and dark grey on band-7 images 
of 1974. The clay materials normally show similar 
colours on visible and near-infrared images. When 
clay is highly saturated, as was the case during the 
1975 recording, it appears black and blackish on 
near-infrared images just like the peat layers. By 
comparing the near-infrared images of 1974 and 1975 
the boundary of clay deposits, which possibly cover 
parts of the peat layers, can be drawn. 
Thin sand-silt cover over peat: The areas in the 
Southeast and in the North of the composite flood- 
plain appear light grey on band-5 and medium grey on 
band-7 images of 1973 and 1974. These colours indi 
cate that the materials are coarser and less satu 
rated than clay accumulations. These areas, which 
are at the boundary with tidal and river flood- 
plains, might consist of sandy-silty sediments part 
ly transported and spread over the peat area by a 
few tidal and river creeks, and partly accumulated 
through rainwater flooding. 
Thick sandy-silty deposits: A few small areas in 
between the black coloured peat layers can be easily 
distinguished by their light grey colour on band-5 
and band-7 images of 1973 and 1974. The light colour 
indicates the presence of sandy-silty deposits. 
These areas, possibly having thick sandy-silty sedi 
ments, form relatively higher lying places in the 
lower parts of the composite floodplain. 
Swamp deposits: Small areas in the Chitra and 
Madhumati River floodplains appear black in colour 
and similar in size and shape on band-7 images of 
1973 and 1974. On the band-5 images of the same 
years, however, the same areas are dark grey. These 
colours are a typical indication of highly saturated 
peat, organic matter and clay materials. Considering 
the relations of these areas with the respective 
rivers, however, they are covered possibly mainly by 
water, organic matter and clay than by peat. They 
can be identified as "swamp deposits". 
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