L7 : The role of Civil Engineers in ex-ante risk reduction Flashcards
What is ‘ReliefWeb’?
ReliefWeb is the leading humanitarian information source on global crises and disasters. It is a specialized digital service of the UN Office for the Coordination of Humanitarian Affairs
(OCHA).
UNISDR definitions for ex-ante DRR actions: prevention
Activities and measures to avoid existing and new disaster risks.
The term is not widely used nowadays, probably because its not really possible to prevent hazards.
UNISDR definitions: mitigation
The lessening or minimizing of the adverse impacts of a hazardous event.
UNISDR definitions: preparedness
The knowledge and capacities developed by governments, response and recovery organizations, communities and individuals to effectively anticipate, respond to and recover from the impacts of likely, imminent or current disasters.
Summary of possible ex-ante DRR actions.
Give the descriptions for each of the following type of action:
Hazard reduction
Mitigation
Preparedness
Hazard reduction - reduce likelihood of a hazard occurring
Mitigation - control the size or path of the hazard
- reduce overall exposure to the hazard
- reduce vulnerability of exposed elements to damage
Preparedness - early warning to reduce short-term exposure to hazard
- build capacity to improve response and recovery
Define risk identification
recognise and describe the risks (may be associated with a single hazard or multi-hazards) and the scope of the assessment
Define risk analysis
understand the nature and sources of the risk and estimate the level of risk (a quantitative or qualitative calculation of H, E, V and risk)
Define risk evaluation
compare risk with risk criteria (acceptable, tolerable, unacceptable)
Landslide hazard reduction, 3 slope stabilisation measures
Reducing driving forces: reduce slope gradient, improve drainage
Increasing the resisting forces: reinforce with soil nails, rock anchors, geotextiles etc. or retain with gravity retaining walls, gabions etc.
Replacing materials: excavate and reform with a denser surface soil layer
4 types of models for assessing landslides
Analytical - Static Equilibrium Analysis, wedge analysis, method of slices
Dynamic LEM - Slope hydrology (or other dynamic processes) modelled over time and F calculated each time step
Analysis of continua - stress-strain analysis based on rheological equations
Discrete element models - Movement of individual rigid elements, from grain scale to blocks of material
Types of flood
River floods (fluvial) Surface water floods (pluvial) Groundwater floods Sewer floods Coastal floods
Flood and hazard assessment in the UK
Models
Maps
Forecasting
Flood risk management UK case studies
SUDS and working with natural processes
Temporary defences, flood controls (hydro-break
Managed coastal realignment
Property-level flood resilience
Structural measures for flood hazard reduction and mitigation
Flood defences and protection; barriers, embankments (temp/perm)
Conveyance; routing potential flood waters via natural or artificial channels f(channel cross section, slope, frictional resistance): straightening channels, increasing bank heights, dredging, relief channels, culverts
Storage; attenuation of surface water runoff reduces peak flows within the channel: on-line and offline attenuation and storage
Drainage systems, urban infiltration and permeability; without careful design, urban impermeable surfaces, storm drains and sewers increase rainfall runoff rates into rivers, and drain capacities can also be exceeded: SUDS
GW management; part of the catchment water storage system and also used as a water supply; recharge vs extraction, protect from pollution, alternative water supplies
Wetlands and environmental buffers
Building design, resilience and resistance
