Sediment dynamics in the mountainous region of the Central Nepal
Madhusudan B. SHRESTHA and Toshitaka MIYAZAKI
Abstract
It could be considered that the sediment dynamics of a basin is characterized
by its geomorphometric features, and knowing these features lead to appropriate
performances in controlling and mitigating sediment disasters. Almost every year,
during the monsoon, due to massive contribution of sediments from the Mahabharat
and Siwalik Ranges of the Central Nepal, have been causing countless miserable
events to the inhabitants and havoc in the regions. In order to understand the
sediment dynamics of the regions, geomorphometric analysis on 16 sub]basins of
the regions were conducted. Due to unavailability of sediment discharge and deposition
data for the studied areas, floodplain coverage of the studied areas was used
to evaluate the sediment dynamics of the regions. All the geomorphometric parameters
were determined from 1/25,000 topographical maps and DEMs. Regarding the floodplain
coverage, topographical maps and Landsat]5 TM data acquired in 1988 were used.
Apart from the aerial photographs interpretation, field surveys were also carried
out to investigate and evaluate the sediment dynamics of the regions. It is suggested
from the study that: 1) small basins of the Siwalik Hills have tendency to deposit
sediment within the basin; thus, development of floodplains are predominant in
the Siwalik Hills; and 2) Mahabharat basins have capability to flush out most
of the sediments yielded in the basins due to their high basin relief and stream
drops. The study showed good response to the relationships between morphometric
characteristics and sediment dynamics of the studied basins.