10 
Records of the Geological Survey of India. 
[vol. VI. 
the floods, and to constant erosion and re-fonnation by the action of the current. Khddar- 
rnati is very nearly the native equivalent for ‘ alluvial land.’ But though there is always a 
large total area of true alluvial land in the Khadars of the great rivers, it is possible that, 
on the whole, these Khadars are undergoing denudation, that the river-bed is deepening, 
and that the new alluvial land formed by its changes of position may be progressively lower 
than the older patches removed by the same process. It has not yet been defined how 
much, or if any portion, of the eastern districts come within the sub-deltaic conditions 
that prevail in the Lower Provinces, where the river-action is broadly formative. The whole 
of the province of Oude would come under one or other of these descriptive terms— Bhangar 
or Khddar land. 
Whether the great rivers are raising or lotvering their Khadars. —The question 
whether the great rivers have at present a tendency to deepen or to raise their channels is 
one of much importance in relation to engineering ■ works, and of great interest to the 
geologist. Within deltaic regions, where the rivers are essentially formative, the process is 
sufficiently understood: the bed and banks of the main channel are raised, till the contrast 
of level determines a gradual set of the water to lower ground through some minor distri¬ 
butary ; the new channel is at first scoured out to the capacity of the main channel, when the 
raising action recommences. Within the narrow river-plain of the Khddar, there might be no 
general feature to betray which process is in force. The river would oscillate pretty much 
alike in either ease, removing and replacing the patches of alluvial land. Still it seems likely 
that careful enquiry among the natives cultivating the Khadars would elicit some grounds 
for judgment: as, if any very old patches of alluvium were no longer inundated by the 
highest flood, one might infer that the river had lowered its channel. The a priori con¬ 
ditions may be stated briefly thus: Whether a river is cutting or depositing depends, 
of course, upon its velocity and upon the charge of solid matter, wholly or partially 
suspended in it. As regards the first condition, it can be broadly stated that the slope 
(and hence the velocity) within the Khadars is everywhere much above that at which 
silt-carrying rivers become on a large scale depositing rivers: at Kanhpur the fall is 
nineteen inches per mile, at Allahabad thirteen; while in the sub-deltaic region at 
Patna and Rajmahal it is only six inches; and in the Delta proper it lowers to three 
inches.* It is moreover certain that for eight or nine months of the year, the great 
rivers rush from their gorges in the mountains as torrents of clear water, or only, in the hot 
months, discoloured by fine g'laciul mud; immediately upon entering the Khddar, however, 
the water becomes more or less charged with silt and continues so throughout its course. 
For these months then the river must be denuding its channel. During the flood season, 
on the contrary, the water issuing from the mountains is highly charged with de¬ 
tritus; which is, to some extent at least, gradually deposited as the slope of the 
channel becomes lowered in the Khddar. Tt would be difficult to conjecture to what 
distances within tho plains coarse shingle and gravel might be rolled along by the scour of 
the current in extreme floods during successive seasons. Large stones not being found in the 
bed of the river in the dry season may not be a safe indication of the case; as it is conceiv- 
a ble that, they should always be buried under lighter deposits as the flood subsided. Whether 
or not the rivers are able, even with tho assistance of the clear water for eight months of the 
year, to carry out of the Khddar all that they carry into it in the flood season, cannot he 
determined without careful observation; but from all the considerations mentioned, it would 
seem likely that throughout the greater part of the Khddar the balance is in favor of erosion. 
Any tendency of the Ganges and Jamna to lower or to raise their bed at the mouth of their 
gorges ought to be discoverable from the effect on the canal-heads at Hard war and Fyzab&d. 
These figures are quoted from Mr. Fergusson's paper in the Quart. Jour. Geol. Soc., Lond., Vol. XIX, 1863. 
