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Kuala Lumpur, 10 – 14 August 2009
Flood Defence SystemsFlood Defence SystemsJan T.L. Yap - AguaJaringJan T.L. Yap - AguaJaring
Integrated Flood ManagementIntegrated Flood Management
Flood Embankment in Action
Flooded Flood Plain
Failed Flood Embankment
Piping through Embankment
Confined Seepage
Strengthening Flood Embankment
Good Performanced Embankment
Failed First-line Embankment
Emergency Intervention - Blow-up
Kuala Lumpur, 10 – 14 August 2009
Flood Defence SystemsFlood Defence Systems
Philosophy of Risk Management
Failure MechanismsFailure TreeProbabilistic Design
Overview design methods of embankments
• Initialy: pure based on experiences. Crest level established with reference to the highest known water level;
• In the 50s: applying statistical techniques to determine the “Design
Water Level” → Deterministic design method using fixed design values for the various parameters;
• Since the 70s – 80s: Probabilistic Design Method → using stochastic character of the various load and strength parameters →
based on an analysis of failure mechanism and their probabilities.
Review deterministic design methods
• Crest level only one of the design parameters of embankment profile. Slope, crest width & berms: stability, maintenance, construction and usage of crest;
• Hydraulic conditions & soil mechanics parameters essential for embankment stability → limited degree of accuracy → Safety factors applied based on experience, tradition and intuitive judgement;
• Only determined per embankment stretch or section, while it is in fact part of a flood defence system → many stretches of different characteristics, and many structures like sluices & water gates and …….. protecting different regions: number of inhabitants, invested capital, strategic utilities, future land use, etc.
Components of a flood defence system
Shortcomings deterministic design methods
• Various embankment sections in a defence system do not provide same degree of safety;
• It is not known which failure mechanism gives the greatest contribution to the probability of failure of an embankment section;
• The overall length of the embankment system has no influence upon the design of the embankment section;
• Magnitude of damage or loss has no influence on the design;
• The actual probability of inundation (flooding) of the protected area is not known
Principle of Risk Analysis
Risk = Probability x Consequence
• Probability of an undesirable event: explosion, inundation, etc.
• Consequence of the occurrence of that event: → economic loss, damage, loss of life, etc.
Risk Analysis: the whole set of activities asimed at
Quantifying
the probability of an undesirable event ..and .. the consequence of the occurrence of that event.
Advantages of Probabilistic Approaches
• The flood system is analysed and described as a whole;
• Components of the system can be better inter-related, i.e. less over- and under-designing;
• Various uncertainties are rationally incorporated in the assessment of the safety of the system;
• Better insight into the sensitivity of probability of failure of the system related to the various uncertainties;
• Better insight into the priority for improving the flood defence system (maintenance).
More …..
Failure tree analysis
Probability of Failure
Design Point
Kuala Lumpur, 10 – 14 August 2009
Flood Defence SystemsFlood Defence Systems
Reducing Flood Damages
Flood FightingFlood ProofingTemporary & Demountable Flood Defence Structures
Emergency Measures - Flood Fighting
Controling Under-seepage
Sand Migration due to Underseepage
Road System as Floodway
Temporary Flood Wall
Emergency Flood Wall
Emergency Flood Wall (2)
Local Flood Fighting
Flood Proofing to Reduce Damage
Columns for Emergency Flood Walls
Movable Flood Wall
Floating Houses
Floating Houses (2)
Kuala Lumpur, 10 – 14 August 2009
Thank you……Thank you……
