Vorlesungen

“Probability that a tsunami of a particular size will strike a particular section of coast. “

-> Tsunami hazard assessment

1.       Understanding of tsunami hazard source

2.        Understanding of tsunami phenomenon

3.       Identification of most vulnerable locations at the coast

4.       Modelling of tsunami inundation

Special about tsunami hazard:

• tsunami events are relatively infrequent

• tsunami hazard is hard to predict and mitigate

• tsunami events are highly destructive and pose greater risk of lives that the cumulative effect of smaller and more frequent disasters

• tsunami hazard exists on local and global scale

• sparse information on source, frequency and characteristics of past events

• poorly defined mix of near-field and far-field tsunami hazard

• unknown potential impacts of future tsunami events

• complexity of coastal communities

• lack of other detailed data, e.g., bathymetry

Risk = Hazard x Exposure x Vulnerability

Exposure

• People, property, systems or other elements present in tsunami hazard zones that are thereby subject to potential losses

• Exposure reduction measures

  • Land use planning

  • Location decisions

  • Other means of risk mitigation and prevention

Vulnerability

• Degree to which a community or area is susceptible to the negative impacts of a tsunami

  • Physical vulnerability: physical environment

  • Economic vulnerability: economic assets and processes (i.e., business interruption)

  • Social vulnerability: social groups (e.g., the poor, single parent households, pregnant, handicapped, children, elderly)

  • Environmental vulnerability: flora, fauna, ecosystems, biodiversity

• Vulnerability reduction measures

  • Implementation of building codes

  • Public education and awareness

  • Emergency service and preparedness

  • Insurance and social protection

  • Relief (help after disaster)

Resilience

• Ability of a community or area to withstand and recover from the impacts of tsunami

• Effectively adapt to and cope with the physical, economic, social and environmental impacts

• Responding or reorganizing in ways that maintain the essential function, identity and structure

• Reduce either exposure or vulnerability

• Human/social impact

  • Loss of life and injury

  • Disfunctioning of the society

  • Diseases due to damage to sewage

  • Psychological problems

  • Increased poverty

  • Loss of cultural assets

• Physical impact

  • Private property damage

  • Infrastructure damage

  • Fires and releases of hazardous material (e.g., oil fuel)

  • Scouring

• Environmental impact

• Economic impact

  • Business disruption

  • Costs of restoration of infrastructure and property

• Political impact: difficult to quantify (e.g., violation of democratic system)

Wave nonlinearity (nonlinear effects) described by

• Nonlinearity parameter (epsilon)

• Wave steepness s

Frequency-dispersion effects

• Dispersion parameter (mü)

Relative effects of wave nonlinearity and frequency dispersion

• Ursell number Ur

• Describes nonlinear effects (amplitude-dispersion effects)

  • Wave crests move faster in comparison to wave troughs à leading to wave steepening

• Nonlinear waves usually have a non-symmetric form

  • Narrow, steep wave crests and wide, shallow troughs

• Determines wave breaking conditions

• Describes frequency-dispersion effects causing a separation of a progressive wave into numerous components propagating with different frequencies

  • i.e., the wave velocity does not depend upon wave height, yet the wave frequency

• velocities of the wave components are proportional to the wavelength

• Ur < 1 frequency-dispersion effects are dominating

• Ur = 1 amplitude and frequency-dispersion effects of similar magnitude

• Ur > 1 amplitude-dispersion effects are dominating

• Indicates relative magnitude of nonlinearity and dispersion parameters