The Semenyih River Basin consists of 36 sub-basins with areas ranging from 1.37 to
35.57 km,2
The basin comprises seven different major land uses such as forests; agricultural
land; settlements; and industry; rubber and oil palm plantations; exmining
land and water bodies. In order to classify the relative stability of each sub
basin, the relationship between the seven land use categories, human activities and
five physical parameters of the Semenyih Basin, i.e. a) water quality and water
quality index, b) hydrological aspects such as surface compaction and drainage density,
c) grade of weathering, d) landform or slope gradient, and e) population density
were evaluated. The basin’s stability classification results were concluded in four
outcomes, namely (a) “Good”, indicating that the whole area is covered by forests or
parts are rubber plantation or characterized by water quality index Class I or IIA and
considered to be stable. (b) “Fair”, the land use in the area is mostly plantations such
as rubber plantation or fruit trees or indicated by water quality index Class IIB. (c)
“Slightly Disturbed”, characterized by settlements and other mixed activities such as
oil palm plantations, quarries or mine or indicated by water quality index Class III,
and finally, (d) “Disturbed” sub basin, characterized by urban and industrial activities
or indicated by water quality index Class III to V and considered to be least stable