Flat land (or plains) in a Himalayan
country like Nepal is very significant. In
general, such plains occur along the
Himalayan front marked by the Siwalik
hills (both as Indo-Gangetic plains to its
south and intermontane valleys to its
north); these areas also accommodate
significant part of the total deformation
in the Himalaya and are prone to large
earthquakes as evidenced by past surface
ruptures1
. A large part of the plain area
in Nepal is contributed by intermontane
valleys (duns) developed within the SubHimalayan
Siwalik belt (locally known
as the Churia zone). The Chitwan Dun in
Central Nepal represents one such intermontane
valley developed to the SW
of Kathmandu. With an area of about
1575 sq. km, the Chitwan Dun is the largest
intermontane valley in Nepal.