Flood hazard and risk assessment through incorporating gis with hydrodynamic modelling: case study of Muda River
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Date
2009
Authors
.A. Hussein, Rabie A.
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Abstract
Muda River has been for many years experiencing seasonal floods and causing
serious damage and economical loss to human settlements and property in the Muda
basin. The 2003 flood was the most devastating event throughout the history of the
river. The geomorphological changes, flood behavior and impacts of the ~uda River
have been investigated in this study using integration of specialized software packages
and computer modeling techniques to envisage the consequent changes projected on
the river, and assisting in predicting and communicating the flooding risk. Ground
surface roughness was delineated through several field visits to the study area. This
ground roughness acts as a significant input data for hydraulic modeling purpose. The
results of one-dimensional hydrodynamic modeling showed a wide spatial extension of
flooding inundation in the vicinity of the floodplain, and indicated damage severity on
households and agricultural land use features located in these highly inundated areas.
Hazard assessment and risk analysis on these two land use types revealed that the
economical damage of the 2003 flood (RM 27.6 million) was five times than that of the
last flood (1982) in a 20-year-period (RM 3.87 million). This enormous loss can be
attributed to the dramatic changes imposed on the riverine system by much historical
and contemporary unsustainable human exploitation of the Muda basin land assets,
increasing its vulnerability to erosion hazards and decreased ground surface
roughness. The 1 00-year flood event model was also reconstructed in order to
investigate the effectiveness of the proposed bund in controlling the increase in water
depth during extreme flooding conditions. The modeling indicated that the proposed
bund has enough capacity to contain safely the flood water, with an additional capacity
of containing extra 1.5 m of flooding water without exceeding the breaching point. The
modeling result also suggests the effectiveness of the proposed bund structure in
reducing the flooding risk, protecting thereby the human activities in the floodplain. On
the long run, the engineered river may experience localized geomorphic adjustments
without initiating flood hazard; but under futuristic extensive and extraordinary channel
instabilities, geomorphic adjustments may become magnified, initiating thereby flooding
event in the study area. The computer modeling performed in this study improved the
understanding of the long-term behavior of Muda River and its flooding behavior.