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Flood Defence Systems(97)
 

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
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    • 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
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    • 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……