Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
759 
am from 1972 
th respect to 
14 years the 
¡velop methods 
lications of 
satellite in 
o stop trans- 
in itself in- 
POT satellite 
be abundant 
environmental 
s need can be 
iata. 
should not be 
ibility of new 
nd ground re- 
cience itself 
d accuracy of 
itical demands 
sciences will 
ctive offered 
ially evident 
:h and inves- 
strations may 
>f tracing the 
inges, appear - 
novelty with 
te data. But 
d use of all 
'dent benefits 
all possible 
ts, decision- 
in the state 
sat example of 
nnica 11: 55- 
Lsat classifi- 
the Bothnian 
:h 250: 45-51. 
Mature 319: 4. 
sea. Photo- 
>1. 
mating shore- 
inland) water 
Landsat data. 
dsat data for 
iren, Sweden, 
ila, Sweden, 
illsten 1984a. 
atic areas of 
lern Finland. 
llymaa 1984b. 
ill lake water 
ata, Kuusamo, 
i Planets 31: 
rkimaa 1984c. 
ittoral areas 
iia, Finland) . 
Landsat study 
:e Luodonj arvi 
.c Botany 21: 
per was per- 
,SA Resident 
lsion Labora- 
Analysis of Landsat multispectral-multitemporal images 
for geologic-lithologic map of the Bangladesh Delta 
A.Sesoren 
Geological Survey of the Netherlands (RGD), International Institute for Aerospace Survey and Earth Sciences (ITC), 
Enschede, Netherlands 
ABSTRACT: Geological interpretation of Landsat images of delta areas is very difficult since the delta depo 
sits are lithologically very similar, they do not produce identifiable morphologic features, and they are not 
even well exposed because of dense vegetation cover during most of the year. Nevertheless, it is demonstrated 
in this paper that lithologic-geologic interpretation of Landsat images of delta areas is possible by a 
proper planning of the interpretation. 
1 GEOLOGIC-LITHOLOGIC INTERPRETATION OF THE 
BANGLADESH DEL"”' 
The Bangladesh Delta (fig. 1) has been studied in 
order to verify whether a detailed geologic-litholo 
gic map of a delta can be obtainted from Landsat 
multispectral-multitemporal images by a specially 
planned interpretation based on a step by step sepa 
ration of the units present in the delta. 
A hierarchical classification of the delta areas is 
applied based on genetic classes, geomorphological 
units, and on spectral, spatial and temporal charac 
teristics of materials. A good background knowledge 
of the development mechanisms of deltas is required. 
This classification allows the distinction and map 
ping of lithologically similar but genetically dif 
ferent deposits, and provides detailed information 
about sedimentation processes and deposits (fig. 
1) . 
1.1 Subdivision of the delta area into genetic clas 
ses 
On the multispectral-multitemporal Landsat images of 
the Bangladesh Delta different drainage and land 
scape patterns can be recognized (fig. 2) . They 
result from processes related to different flow 
regimes. Each type of flooding (e.g. river flooding, 
tidal flooding, rainwater flooding) can transport 
and accumulate other types of sediments, building up 
floodplains distinguished by their specific drainage 
and landscape patterns. By subdividing the delta 
into different types of floodplains, deposits that 
were developed under distinct conditions will also 
be separated, and genetic classes of sediments are 
obtained. Although a landscape pattern can not al 
ways be detected from Landsat images because of its 
small size or because it is masked by dense vegeta 
tion, however, a drainage pattern of delta areas - 
even through a dense vegetation - is always detect 
able on band-7 (near-infrared) images and therefore 
can be effectively used for the sub-division of 
deltas into floodplains areas. 
By a combined analysis of the near-infrared images 
of three years (fig. 2) , the drainage map of the 
Bangladesh Delta has been prepared (fig. 3). 
On this map, area (A) it is identified as "tidal 
floodplain", as it is crossed by a close network of 
innumerable rivers and creeks, typically making 
"zigzag" band and interconnected with each other as 
well with the main rivers. Obviously, tides may 
advance far inland in dry seasons when the water 
level of main rivers is at a minimum, and retreat 
in wet seasons when main rivers are in flood. 
Area (B), constituting a large belt parallel to 
the Ganges River and crossed by the Arialkhan and 
tributary rivers, is designated as "river flood- 
plain" . Typical features are a density of drainage 
lower then that of area (A), and "curved bends and 
meanders" of the rivers which are connected with 
the main rivers. Locally, abandoned channels and 
lops of cut meanders can be recognized. 
Area (C) looks different from the areas (A) and 
(B) due to the absence of active important creeks. 
The drainage pattern, which is hardly visible, is 
produced by straight and geometrical shapes of man 
made channels. Only one small river crosses the 
area in between its narrow floodplain. The area is 
located far from the main rivers and ative chan 
nels, because of its perennially wet nature and the 
occurrence of large peat areas, rainwater flooding 
is likely to be the dominant factor. Nevertheless, 
the development of area (C) may have undergone some 
influence by tidal flooding entering the area in 
dry seasons from one side, and by flooding of the 
main rivers in wet seasons from the other side. 
Therefore area (C) has been defined as a "composite 
floodplain". 
1.2 Subdivision of river floodplain into géomor 
phologie classes 
A major river in flood normally deposits different 
amount and types of sediments in different parts of 
its floodplain, in a well-known sequence ranging 
from sandy to silty to loam and clay, depending 
mainly on topography and velocity of flow. 
Changes in landscape patterns and differences in 
spectral signatures allow a subdivision of the 
river floodplain into geomorphological sub-classes. 
An "upper river floodplain" or "meander floodplain" 
occurs along the Ganges River bank, where large 
meanders, lops of cut menaders, long and curved 
ridges and abandoned channels have produced a kind 
of meander landscape pattern (fig. 4a) . Further 
downstream curved ridges and wide basins come 
closer together and smaller, abandoned channels, 
large meanders disappear, and the whole pattern 
looks like an "embroidery on canvas" (fig. 4b), 
hence this part of the floodplain is designated as 
"lower river floodplain" or "embroidery flood- 
plain". Of course, the latter term is not an offi 
cial morphological term, but it is. used here be 
cause it very clearly describes the landscape pat 
tern as seen on satellite images. 
Some areas, which do not show either a meander or 
an "embroidery" pattern, are separated from the 
upper and lower floodplain areas and are interpret-