12ial-Hazards-Multihazard Zones

​Multiple Hazard Zones: The Philippines and California

By Aimee Cooper

​When Hazards Collide: The Philippines and California

​Today we’ll explore why some regions face several different hazards at once, and how people manage that complex risk.

​By the end of this lesson you will be able to:
1 Describe what makes an area a multiple-hazard zone.
2 Explain how physical and human factors combine in two case studies: the Philippines and California.
3 Evaluate how far good planning and development can reduce risk.

Open Ended

1 Which factor most reduces vulnerability?
2 What does the World Risk Index measure?
3 Name one country with a very high WRI score.
4 Why do isolated areas face high secondary losses?
5 Which factor has the biggest influence on disaster outcome?

​Introducing Multiple Hazard Zones

​A multiple-hazard zone (or disaster hotspot) is a place exposed to more than one major hazard type. These areas suffer overlapping events – for example, a volcanic eruption that triggers landslides, or an earthquake followed by a tsunami and then typhoon rains. Physical causes link hazards together, while high population and poverty increase their impact.

​Where Multiple Hazard Zones Occur

​They tend to cluster in: tectonically active belts (earthquakes + volcanoes), tropical coastal regions (cyclones + floods), mountain belts (quakes + landslides + floods), and rapidly developing countries where exposure is high.

The Philippines and California both face many hazards but differ greatly in wealth and capacity to cope.

Open Ended

Why is the Philippians at risk?

​Location and Setting

​An archipelago of more than 7 000 islands in Southeast Asia, lying on the western edge of the Pacific Ring of Fire and close to the Equator. Population ≈ 114 million. Tropical climate, high rainfall, steep volcanic slopes, and dense coastal settlements create exceptional exposure.

​Tectonic Hazards

​The country sits where the Eurasian plate subducts beneath the Philippine

Sea plate. This produces frequent earthquakes and numerous volcanoes – around 20 are active.

Major examples: Mount Pinatubo (1991) – explosive eruption; ash > 30 km high; ashfall reached Manila; ≈ 350 deaths but > 200 000 homes damaged.


Luzon Earthquake (1990) – magnitude 7.8; > 1 600 deaths; collapse of buildings and landslides.

​Hydro-Meteorological Hazards

​The Philippines lies directly in the path of western Pacific tropical storms.

Around 10 typhoons strike each year, mostly from June to November.

One of the strongest recorded, Typhoon Haiyan (2013), brought 313 km/h gusts, 7 m storm surges and > 6 000 deaths. Flooding and landslides are common secondary effects when storms hit deforested slopes.

​Secondary and Linked Hazards

​Typhoons saturate volcanic ash, increasing landslide risk.

Earthquake damage can weaken flood defences, making later storms worse.


The sequence of drought → fire → flood → typhoon is not unusual in El Niño years.

Open Ended

Why is it harder to manage hazards when several types interact?

​Human and Economic Vulnerability

​Rapid population growth ( > 1 million added each year ), poverty and informal housing push communities onto steep slopes and floodplains.

Around 25 % of Filipinos live below the poverty line.
Urban density in Metro Manila > 20 000 people/km².
Limited healthcare and reliance on agriculture make recovery slow.

​Preparedness and Response

​Despite high risk, the Philippines has improved resilience through:
community-based early-warning systems,
school evacuation drills,
national mapping and hazard education (via PHIVOLCS and PAGASA),
international aid partnerships.

However, inconsistent local governance and funding gaps limit success.

​Remote Sensing and GIS https://www.esri.com/arcgis-blog/products/arcgis-online/mapping/analysis-using-living-atlas-earthquake-map-part-ii

​Evaluating Risk

​Strengths: educated population, strong local volunteer networks, improving early warning.

Weaknesses: high poverty, exposure to multiple hazards, poor infrastructure outside cities.

Overall risk = very high but trending downward as preparedness grows.

​https://www.statista.com/topics/5845/natural-disasters-in-the-philippines-at-a-glance/?srsltid=AfmBOop-EQehm6p1JbhXfr0AVLwt2lF8hvWG9qBNbBFYXlkWAZyE0HiL#topicOverview

​Carry out some research into the natural hazards which affect the Philippines. As a starting point, search online for Statista and find the “Natural disasters in the Philippines at a glance” page. Create a detailed fact sheet to describe and explain: The main types of hazard affecting the Philippines The regions most at risk How the hazards interact (e.g. typhoons triggering floods or landslides) One or two named examples for each type

Open Ended

To what extent do you think the Philippines’ level of development affects its ability to manage natural hazards effectively?

Open Ended

What is California's Risk?

​Location and Setting

​A large US state on the western Pacific margin; population ≈ 39 million.

Mediterranean climate: wet winters, dry summers.

Economy: $4 trillion GDP (2023). Highly urbanised (Los Angeles, San Francisco, San Diego).

Sits astride the San Andreas Fault, a major conservative boundary between the Pacific and North American plates.

​Tectonic Hazards

​Frequent shallow earthquakes – most minor, but occasional large events.

Historical examples: 1906 San Francisco (~3 000 deaths, firestorms destroyed 80 % of city). 1989 Loma Prieta (M 6.9, 63 deaths). 1994 Northridge (M 6.7, 57 deaths, $40 billion damage).

Volcanic hazards: Mount Shasta and Lassen Peak in the Cascades chain remain active but infrequent.

​Hydro-Meteorological Hazards

​California also faces extremes of weather: Drought – prolonged dry periods (e.g. 2012–2016) reduced reservoir levels by 40 %, triggering wildfires and crop losses.



Flooding – El Niño years bring intense winter storms and flash floods. Wildfires – long dry summers and Santa Ana winds produce large fires (e.g. Camp Fire 2018 destroyed 18 000 buildings, killed 85).

​Human Factors

​High urban density along fault lines (e.g. Los Angeles Basin) and expensive infrastructure mean large potential losses.

However, high income, strong governance and advanced technology limit casualties. Strict building codes, emergency drills, and the US Geological Survey’s monitoring systems all raise capacity to cope.

​Preparedness and Risk Management

​California invests heavily in hazard reduction: Early-warning systems for quakes and wildfires.

Reinforced infrastructure and retrofitted bridges. Strict planning zones restricting building on unstable slopes. Community evacuation training and disaster apps. Despite this, escalating population and climate change increase exposure.

Open Ended

Explain why the Philippines experiences a greater range of hazards than California.
Use both physical and human reasons in your answer.

​By the end of this lesson you will be able to:
1 Describe what makes an area a multiple-hazard zone.
2 Explain how physical and human factors combine in two case studies: the Philippines and California.
3 Evaluate how far good planning and development can reduce risk.

​Homework

​https://www.thegeographeronline.net/uploads/2/6/6/2/26629356/gf731_what_makes_people_vulnerable_to_natural_hazards.pdf