Lec 7 - Role of Civil engineers in ex-ante risk reduction (hazard reduction and mitigation) Flashcards
Key connections to make with previous lectures:
Hazard assessment approaches; risk reduction case studies; the need for a comprehensive approach (paradigms and perspectives); and the role of civil engineers in moving from repeated disaster cycles to sustainable development
Remember to learn the disaster risk cycle - look at slides - in bold shows the involvement of Civil Engineers
Examples of civil engineering actions ex-ante DRR and ex-post DRR
ex-ante (b4 event):
• Planning for evacuations, logistics, shelter, supplies, communications etc
• Structural measures to reduce hazard occurrence or the impact of hazards.
ex-post:
•Provision of water and shelter
• Damage assessments, restoration of critical infrastructure
• start to ‘build back better’
Definitions of prevention, mitigation and preparedness from UN
1) Prevention = Activities and measures to avoid existing and new disaster risks.
- prevention aims to reduce vulnerability and exposures e.g. dams for flood risk or land-use regulations that do not permit any settlement in high-risk zones
- Prevention measures can also be taken during or after a hazardous event/disaster to prevent secondary hazards or their consequences e.g. measures to prevent the contamination of water
n.b. prevention not used a lot these days as there an understanding that most hazards cannot be stopped…
2) Mitigation = The lessening or minimising of the adverse impacts of a hazardous event
- nb though, The adverse impacts of hazards cannot be prevented fully but scale can be lessened.
- mitigation measures include engineering techniques or soft approaches
—> Both definitions above focus on reducing hazard impacts by targeting exposure and vulnerability. There is NOT a specific recognition of hazard reduction actions i..e. reducing the likelihood of a hazard of a certain magnitude at a certain location
3) Preparedness = The knowledge and capacities developed by governments, response and recovery organisations, communities and individuals to effectively anticipate, respond to and recover from the impacts of likely, imminent or current disasters
- based on a sound analysis of disaster risks and good linkages with early warning systems
- This reinforces the the point that all DRR actions should be informed by an analysis of disaster risk (see DRR framework)
nb. Hazard and risk assessments (stuff done in lec 2) inform prevention and mitigation
Possible ex-ante disaster risk reduction actions for Floods - all about building resilience!
Remember there different types of flood: GW, river (fluvial), coastal and surface water floods (pluvial)
nb. this lecture focuses more on the the Engineering and Behavioural paradigms, not so much on later ones
Type of action •description - possible civil engineering measure
1) Hazard reduction
• reduce likelihood of flood occurring - some options available but limited! :
- Watershed management; ‘working with nature’
- SuDs –> reduces peak runoff rates and increase infiltration and GW recharge therefore attentuates flow
- Storage facilities, wetlands
2) Mitigation
• Control the size or path of a hazard
- e.g. Flood defences (sea walls, embankments,)
- dams and flood controls
- Conveyance (routing potential flood waters via natural or artificial channels) e.g. straightening channels; increasing bank heights; dredging; relief channels; culverts –> remember think of the long term consequences of this… leeve effect?
• Reduce overall exposure to the hazard
- Flood inundation modelling
- Land use regulations (planning zonation)
• Reduce vulnerability of exposed elements to damage - Design or retrofit infrastructure, buildings and internal fittings to be flood resilient
3) Preparedness
• Early warning to reduce short-term exposure to hazard
- Weather forecasting combined with flood modelling and river gauge observations (flood frequency analysis!!! link to WRM unit)
• Build capacity to improve response and recovery
- Education and awareness; evacuation route and shelter planning
