Development of Malaysian river stability index by incorporating morphological assessment in normal flow conditions
Various river-related issues continue to escalate throughout the year. The situation is exacerbated further when river stability assessment is extremely limited. Numerous rivers are unable to maintain an equilibrium flow regime, and unintentionally, Malaysia's rivers that have not been encro...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2021
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/103983/1/NOR%20AZIDAWATI%20-%20IR.pdf |
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| Summary: | Various river-related issues continue to escalate throughout the year. The
situation is exacerbated further when river stability assessment is extremely
limited. Numerous rivers are unable to maintain an equilibrium flow regime, and
unintentionally, Malaysia's rivers that have not been encroached upon have
suffered due to the country's development. During development, too much
suspended and bed sediment enters the river channel, and the channel
undergoes excessive geomorphic responses, jeopardising the river's stability.
Malaysia's Department of Irrigation and Drainage (DID) currently uses
hydrodynamic modelling analysis to manage various river issues, including river
pollution, erosion, and sedimentation. In the evaluation, the current methods
were lacking in determining the river stability index. It is therefore essential to
provide immediate attention to the development of the Malaysian River Stability
Index (MRSI), which incorporates river morphological assessment in normal flow
conditions as the primary goal of this research. Through tools and readily
available results, MRSI enhances the evaluation of river stability. It is crucial to
classify the selected rivers' physical and hydraulic properties, assess the river's
flow regime, equilibrium hydraulics geometry, and geomorphic responses that
changed the river's morphology, and develop MRSI's river stability incorporate a
morphological assessment. The researcher carried out the research in five
stages. In stage I, the site was chosen using the REFCON approach. The
selected rivers were Lepoh, Congkak, Sekayu and Rasau River. In stage II, the
extensive river measurement and laboratory work were completed. The raw data
was then analysed in stage III to obtain hydraulic information. The physical and
hydraulic elements of river morphology were identified in stage IV, where four
forms of morphology have been studied: cascade, pool, step-pool, and plain bed.
The flow regime and equilibrium hydraulics geometry analysis were then
performed by charting the log-log graph as a power function of flow discharge
and velocity, width, and depth. The geomorphic response of each river crosssection
has been identified through a calculation based on the geomorphic response formula. Three steps are involved in stage V: (i) determining the index
value for each sub-index (indicator) and selective criteria (optional criteria) of
MRSI using the Analytical Hierarchical Process (AHP); (ii) developing the MRSI
scoring system using the Likert Scale; and (iii) developing MRSI tools named SMRSI
using the Visual Basic application. AHP was the most suitable method to
disentangle the inclination evaluations among the choices of index stability
indicators using pairwise comparison. It was determined through AHP
consistency that the highest index value indicates the most crucial indicator of
river stability. The MRSI index, based on the Likert scale, indicates the degree
of river stability, which consists of excellent (MRSI score 47–55), good (37–47),
satisfactory (27–37), poor (17–27) and very poor (2–17). Several calibrations
were performed by comparing the MRSI to the existing stability assessment. A
Cronbach’s Alpha value of 0.81 indicates that the stability assessment's
consistency was robust. The MRSI and the existing stability index were
equivalents. |
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