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Figure 1 
ed as "old river floodplain remains". 
1.2.1 Subdivision of the upper river floodplain into 
lithologic units 
Using differences in landscape patterns and spectral 
signatures the upper river floodplain is subdivided 
into two lothologic units: sandy deposits and sandy- 
silty deposits. 
Sandy deposits: The meandering area along the 
Ganges River can be expected to consist of sandy 
materials deposited at flood times by fast flowing 
water (fig. 2) . These areas appear white on band-5 
(visible) and light-grey on band-7 (near-infrared) 
of the 1975 images, which corresponds to the fact 
that sand and silt reflect high amounts of energy in 
the electromagnetic spectrum. 
Silty-sandy deposits under a clay mantle: In the 
areas further away from the Ganges riverbank, the 
basins appear uniform dark on the band-7 and light 
in colour on the band-5 images (fig. 2). Vegetation 
covered straight and curved ridges are clearly seen 
with their light colours occurring through dark co 
loured basins on band-7 and with their dark colours 
occurring through light coloured basins on band-5 
images. A uniform dark appearance of basins on near 
infrared images suggests that they are covered by a 
clay mantle. This kind of clay mantle is often 
observed in floodplains where basins formed, long 
abandoned by the river and flooded again by very 
slow moving water. The basins under the clay mantle 
possibly consist of silty-sandy materials, depos 
ited in a transition zone with decreasing water 
velocity. 
1.2.2 Subdi 
litho 
The "embroi 
floodplain 
5 images (f 
nation of v 
ges River 
Northwest a 
basins and 
contain fin 
A sharp cor 
of areas on 
ed a subdi 
under a cla 
Silty dep 
on the banc