Flood Defence Systems(97)
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Flood Defence Systems(97)






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Flood Defence Systems(97) Flood Defence Systems(97) Presentation Transcript

  • Flood Defence Systems Jan T.L. Yap - AguaJaring Integrated 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
  • Flood Defence Systems Philosophy of Risk Management Failure Mechanisms Failure Tree Probabilistic 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
  • Flood Defence Systems Reducing Flood Damages Flood Fighting Flood Proofing Temporary & 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)
  • Thank you……