TITLE:
Sediment-Loading Processes in a Forested Catchment: Modeling and Observations
AUTHORS:
Md. Motaleb Hossain, Kazuhisa A. Chikita, Yoshitaka Sakata
KEYWORDS:
SWAT, Slope Failure, Landslide, Bank Collapse, Forested Catchment, Sediment Load
JOURNAL NAME:
Open Journal of Modern Hydrology,
Vol.13 No.2,
February
3,
2023
ABSTRACT: In order to investigate
sediment-loading processes in a catchment, the daily time series of river
discharge and sediment load were applied to a semi-distributed model,
the Soil and Water Assessment Tool (SWAT). The time series of discharge and
sediment load were obtained by monitoring the river stage and water turbidity
of the Oikamanai River, Hokkaido, Japan, in the rainfall season (April-November) of 2011-2014. The
catchment is forested (ca 90% area) but underlain by the Neogene sedimentary
rocks with currently active faults and forest soils with tephra layers, which
tend to frequently produce slope failure such as landslide and bank collapse by
rainfall or snowmelt. The water turbidity, T, in ppm was converted into
suspended sediment concentration, SSC, in g/L by applying the linear relationship
between T and SSC. The acquisition of the time series of discharge, Q (m3/s)
and sediment load, L (=Q·SSC in g/s) of the river
allowed us to distinguish the fluvial sediment transport, accompanied by slope
failure in the upstream, from that under no slope failure. The SWAT was used to
simulate soil erosion and identify the region prone to the soil erosion in the
Oikamanai River basin. The model’s results showed a satisfactory agreement
between daily observed and simulated sediment load as indicated by the high
Nash-Sutcliffe efficiency. This evidences that the upper mountainous region of
the catchment provides a main sediment source, accompanied by slope failure.