Accepted Papers - 3.pdf - UNESCO

tend to move out of the Himalayan region in explosive
ways. Landslides seem to be a major contributor of
deposits of soil to the rivers. Himalaya rivers have
constantly changed their course long before
deforestation began. For example, archaeologists and
scientists now believe that at the time of the Indus
civilisation, Yamaha probably did not flow into the
Ganga, nor Satluj flew into the Indus. Instead they
flowed into the Ghagar, a small seasonal river that
emerges from the Shivalik foothill in Chandigarh –
to make it a mighty, perennial river that flowed
straight into the Arabian Sea without joining the
Indus-probably the much worshipped Saraswati of
the Vedic times. The forests can tolerate minor and
medium floods but the human society will have to
learn to live with the major floods. Afforestation has
a limited impact in terms of changing hydrological
conditions. It is interesting to note that de-forestation
as a cause of floods has come to be cited only
recently. The District Gazetteer Of Poornia and
Saharsa regions in the last century though concerned
about the high silt load of the river Kosi, have never
eluded to de-forestation as a contributor factor.
Instead their recurrent occurrences was on the
geological instability of the rivers’ upper catchment.
To understand the problem of increasing floods in
the Indo-Gangetic plains, it may be more instructive
to study the logical changes that have taken place in
the flood plains themselves. Natural factors contribute
more to floods in Assam, than de-forestation or
shifting cultivation. Tributaries of the Brahmaputra
come from more forested areas than the southern
ones and yet create more floods. Natural erosion
processes in the Himalaya are so intense that they
dwarf the changes posed by deforestation.
Afforestation will help the local economy but will
not large floods in the Himalayan regions”.
‘The deep gorges of Himalayan rivers seem
sufficient to transport excess rainwater. Surprisingly,
this is not true. Floods have been taking place in the
Himalayan plains since time immemorial. The
breathtaking photograph of the landslide that blocked
the Bhagirath showed a densely green hillside had
come tumbling down. Was it the fragile Himalayan
geology or deforestation that was the main trouble?
While reviewing this report, the New York Times,
New York, reported “So this report takes little known
fact; the impact of environmental degradation on
floods in densely populated Assam and the Indo-
Gigantic plains”. So this report takes on a very big
myth; that floods in the plains are forced by
deforestation in the Himalayas. An Indian
494
environmentalist has touched off a furious debate
by challenging the conventional view that
deforestation in the Himalayan hill is a primary cause
of devastating seasonal floods”.
Late Dr. Anil Aggarwal, Director, Centre for
Science and Environment in the introduction of
the above report highlighted “In fact this report
points out some of the environmental myths that
cam crop up when we continue to deal with major
problems which occur in different ecological
settings. For instance, the report points out that
floods in the plains below the vast Himalayan
ranges may not be greatly exacerbated by deforestation.
Floods are, in fact, and will remain
an inherent feature of these plains where the
Himalayan mountains are well cleared with a
green covered area or are deforested and
deprived. The Himalayan mountains constitute
an extremely fragile geological system. They are
the youngest mountains in the world and
therefore, highly erodable. They are lashed by
rain streams by an intensity that probably no other
mountain system faces. Water and silt move out
of the mountain in a flood and shifting of river
courses is, therefore, inevitable. Deforestation
can aggravate the problem but afforestation can
not get rid of it.
Once the soil is saturated, all excess water must
run-off as rejected recharge or be lost to evaporation.
Forests do increase residence time by intercepting
rainfall and letting it down gradually, by absorbing it
in humus and leaf litter and in facilitating infiltration
through the root structure which too acts both as a
passage and sponge, but once the sponge is full its
retention capacity is exhausted. A cloud burst
produces torrential rain of an order that no forest
can absorb, resulting in severe flash floods such as
many parts of the basins experience every year with
regular frequency. To blame these floods on
deforestation is mistaken. What forests do is to
reduce erosion and consequent sedimentation.
It is believed that forests mitigate drought
by storing water and releasing it over time through
more even stream flows. This is only related to
the point of saturation storage. We also should
account for the loss due to evapo-transpiration
by the forest which drinks up water for its
sustenance. Forest interception of rain can also
enhance evaporation loss from leaves. The net
water balance will vary in accordance with
conditions and circumstances.
Forests are also believed to create or induce