GEO4-4425 Hazards and Risk Assessment
Different hazards: earthquakes, tsunamis, cliff erosion, a lot of rainfall (triggered landslides),
eruptions (brought dust and particles into the stratosphere and troposphere, which cool the
higher atmosphere), multi-hazard, storms and floods.
- Flooding of Honda factory 24-10-2011
- Earthquake Turkey of 7.8 at 02:17 followed by 7.5 at 13:30 on 6/2/2023.
- Tsunami Tohoku earthquake: tsunami waves up to 40 m and nuclear disaster at
Fukushima
- Coastal cliff erosion in Normandie, France
- Benelux flooding July 2021: 243 fatalities, damage of over 10 billion euros, 271.5 mm of
rain in 48 hours in Jahlay, Belgium
- Eruption of the Hunga Tonga-Hunga Haapai, 15-01-2022. Plume rose more than 39 km,
cooling the atmosphere.
- Chamoli catastrophic mass flow: multi=hazards sequence events (rock fall/ice
avalanche, slide, debris flow, flash flood with more than 200 fatalities
- Storm Daniel: Mediterranean tropical cyclone with strong winds and extreme rainfall
(1092 mm in 36 hours in Greece. This caused derna flood in Libya 10-09-2023: 4352
fatalities, 43000 displaced, 8000 remain missing. Two dams collapsed, there was poor
maintenance due to political unrest and economic situation.
Emergency response unit map: ERCC
Planetary boundary concept: framework describing limits of impacts of
human activities on system Earth. Concept is influential in the international
community, UN Conference on Sustainable Development, international
organizations and governments.
La Conchita landslide in California: 1995, 2005, 2017, 2019, 2021 and 2022. In
1995 it was triggered by 378 mm rainfall in a few days and 300 mm in months
before. It is one of the best documented, monitored, active and discussed landslides.
- Steep slopes due to sea cliffs. Uplift area for the last 40 kyr. Earthquakes trigger
landslides
- Weak rocks: clay and siltstone. Low cohesion values and low internal friction angles.
- Land cover/land use.
- Human impact
- Erosion: gully and rill.
- History of landslide: known area for landslides, proven for last 140 years and probably for
1000s of years
- Period of occurrence of intense rainfall (atmospheric rivers, pine apple express).
Mediterranean type of climate. Every 6 to 14 years (El Nino?) much rain.
Solutions to landslide problems La Conchita
- Structural control: retaining walls, drainage.
- Change the land use: buy all the houses and move the high way.
- Reforestation/stabilize the slopes: buffer and roots.
- Install warning system: create awareness, detect slope movement by sensors and
monitoring rainfall intensity/volumes.
- Do nothing, bear future losses: future landslides will occur, the only question is when.
,Ultimate goals: understand processes, develop models, produce hazard (risk) zonation maps,
mitigation of impact, communication/awareness.
Flood simulation models: dike breach, how fast, what water levels, values of side dikes,
elements of risk, damage estimates.
- Deep seated landslides: pine trees on slope stay. So, the failure plane is deep, below the
root zone.
- Earthflow/rock flow landslide: slides down.
Major natural hazards over the last year(s):
- Earthquakes: Turkey, (Feb); Morocco, 6.9 (Sept); Afghanistan 6.4 (Oct). Iceland (Sept ).
- Forest fires Chile (current), Australia, California, Canada, Greece
- Drought: Catalonia (actual), South Africa,
- Heat waves: Asia, Central Europe, Brazil (42°C ^) Floods Belgium, France, Australia,
Bangladesh, California, China, Italy
- Hurricane Otis (Oct): unexpected behaviour, track, strength, stronger after landfall.
- USA, Scandinavia: winter storms / polar vortex
- July 2021: Germany, Belgium, Netherlands floods & landslides. > 240 fat. 43b. US$
- NL: 7 strong storms in 2023, normal is 2 to 3.
- Covid-19 (millions of dead, costs: ?)
- Others: Drought Chad (1970-2021), lake Chad lost since 1970: 90% of its size (26.000 sq.
km → 1500 sq. km). Heatwave in California & west Canada (July 2021)., forest fires, temp
record: 49.6 ˚C Locust plague, East-Africa to India (2020)
,Why is it that hazards seem to occur more frequent and do more damage (fatalities, economic,
emotional)?
- Population growth
- Urbanization
- Economic growth
- Increased mobility and prosperity
- Land pressure: building on slopes (Rio de Janeiro), constructions in flood plains
(Roermond, Alexander Polder), living in deltas. Building on faults (San Andreas)
- Vulnerable objects: roads, power lines, tunnels
- Technical developments and dependency on e.g. power, telephone, GPS
- Climate change, Global change, shifting patterns of weather.
Disaster Management Cycle: Event, Response, Recovery (rebuild),
Mitigation (reduce damage), Preparation. Framework defining stages of a
disaster. Used by organisations to prepare for and respond to disasters of
every kind (natural disasters, technological disasters, and human-made
disasters). To identify potential hazards, assess the risks, and develop
plans to prevent, mitigate, and respond to them. Example room for the
river (2.5 billion euros): floods in 1993 and 1995, rescue aid and
evacuation, clear damage, rebuilt infrastructure, relocation of dykes, sides
channels, depth channels, removal obstacles.
What processes do we see?
- Rockfall
- Debris flows (scar, flow, levees)
- Rock flow
- Rock avalanches
- Creep
There is no risk here, because it is a natural area, with no roads, or hikers or houses.
Hazards in the Netherlands: flooding (area below sea-level but also river flooding), peat dike
failures, storms (Corrie: damage to dunes and coastal erosion).
, What are important driving forces behind natural hazards?
- Internal structure of the Earth: Plate tectonics, sea floor spreading, hot spots Causing
o Volcanism: lava flows, tephra, ash, eruptions, lahars, pyroclastic flows,
jökulhlaups
o Earthquakes
o Tsunamis
- Extreme weather conditions (climate change ..?):
o Flooding: slow floods, flash floods
o Landslides
o Hurricanes, tornados
- Sea level rise: Coastal erosion, flooding
- Human activities:
o Deforestation
o Land use change.
o River channelization: levees, dams
o Building in flood plains, mountainous regions, below sea level, steep hills,
volcano slopes
o Mining (ground water, gas, peat): soil subsidence
Why studying Natural Hazards?
IMPORTANT because:
- Forces of these natural hazards are enormous as well inside as at the surface of our
planet.
- Many victims e.g.: Nepal Earthquake 10.000; tsunami 2004: 230.000; earthquake; Haiti:
240.000; earthquake Pakistan: 80.000; Hurricane Katrina: 1600; Turkey 2023: > 8100.
- Enormous economic damage (Katrina: $100 billion; Sandy $50 billion)
- Emotional damage
- Frequency of hazards seems to increase.
- Vulnerability of society for hazards increases.
USEFUL because:
- Hazards are predictable from scientific studies.
- Risk analysis can reduce number of victims and economic damage.
- Hazards and physical environment are linked e.g. earthquakes may cause landslides &
tsunamis. Hurricanes cause flooding & landslides.
- Human activities may increase impact of hurricanes: poor land use like deforestation ->
flooding, poor constructions -> landslides.
- Proper land use planning, regulation, engineering may reduce impact So, studying
Natural hazards may prevent events or reduce their impact.
Hazards are triggers for (international) conflicts. Water scarcity, sea local effects, urbanization
influence food scarcity, which is influenced by land degradation and determines the food prices
and with that food riots/conflicts.
The tragedy of the commons: individuals want to earn more
money, so they add more sheep to the land. The carrying
capacity of the land has limits. Then, the carrying capacity
goes down until it collapses. The economic interest is more
important than the individual impact.
