Flood risk mitigation Flashcards
What is the classic approach to flood risk mitigation?
Identify the assets in need of protection.
▪ Choose a return period T (e.g. 100 years) relevant to the assets.
▪ Determine the flood that is expected to be exceeded, on average, once every T years.
▪ Design and build a structure which can protect the asset against the T-year event.
Why is it necessary to consider the sub-design event failure in flood risk assessment?
How can we incorporate this information in the assessment of risk of failure?
Most flood damages are due to medium floods, not very extreme floods. There are way more of them.
System uncertainty analysis is necessary to incorporate e.g., sub-design event failure risk
What is the main difference between the classical and risk-based approach of flood risk mitigation?
Risk-based design can be optimized.
Modern approach: risk analysis
• Take account of damage due to “super-design” events.
• There is a risk of damage from “sub-design” events.
• Assessment includes uncertainties from several sources.
The problem is to determine the optimal structure sizes/capabilities associated with the least expected annual cost:
Choose a level of protection, x, so that we minimise
Total Expected Annual Cost
Name a few structural and non-structural approaches of flood mitigation.
Reservoirs - gated, unregulated, off-stream
Embankments
Diversion - if a section of a river has adequate capacity, you can divert the river to another river
Chanel modification - clear debris, straighten up, pave with concrete to speed the flood water passing
Land use management
Flood plain control - flood hazard mapping, flood proof building
Warning system - evacuation of endangered area, removal of valuable equipment, and temporary flood proofing
