Merbok river catchment situated in the Kedah State receives its input from Bongkok River
and Puntar River flowing down and joining Lalang River to flow down to the Merbok
Estuary. The Merbok catchment (440 km2) is experiencing several degrees of complex
land uses activities that poses some impact on the suspended sediment production of
the Merbok river. A study was conducted to investigate the suspended sediment loading
of rivers draining the Merbok catchment from January to December 2013. Suspended
sediment budget of the Merbok catchment were estimated. The river suspended sediment
concentrations (SSC) and suspended sediment (SS) load increased during wet season
compared to dry season. The SS loads increases from upper catchment to river mouth. The
sediment loadings were divided into three segments- the upstream, middle segment and
lower segment. The SS loads increased from 10 t yr-1 in the upper part of Bongkok river
to 3336 t yr-1 in upper segment. The sediment loading then increase to 4299 t yr-1 in the
middle segment of the catchment (at Bongkok 4), and then exiting the Merbok Estuary, as
the lower segment, with a total amount of sediment output estimated at 7156 t yr-1. From this
total sediment output, most of the sediment
source came from the tributaries; the
Bongkok River at B3 (3337 t yr-1), Puntar
River (2924 t yr-1) and Lalang River (1370
t yr-1), which were much higher than its
proportion in terms of its length and drainage
area. As a conclusion, the inconsistence in
SSC in the river were influenced by the
various anthropogenic activities (especially
agriculture and urbanization activities) in the catchment area which necessitate future land use and sediment control to avoid sediment
and possible nutrient loading into the estuary.