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date: 15 November 2018

Natural Hazards Identification and Hazard Management Systems

Summary and Keywords

Society expects to have a safe environment in which to live, prosper, and sustain future generations. Generally, when we think of threats to our well-being, we think of human-induced causes such as overexploitation of water resources, contamination, and soil loss, to name just a few. However, natural hazards, which are not easily avoided or controllable (or, in many cases, predictable in the short term), have profound influences on our safety, economic security, social development, and political stability, as well as every individual’s overall well-being.

Natural hazards are all related to the processes that drive our planet. Indeed, the Earth would not be a functioning ecosystem without the dynamic processes that shape our planet’s landscapes over geologic time. Natural hazards (or geohazards, as they are sometimes called) include such events as earthquakes, volcanic eruptions, landslides and ground collapse, tsunamis, floods and droughts, geomagnetic storms, and coastal storms.

A key aspect of these natural hazards involves understanding and mitigating their impacts, which require that the geoscientist take a four-pronged approach. It must include a fundamental understanding of the processes that cause the hazard, an assessment of the hazard, monitoring to observe any changes in conditions that can be used to determine the status of a potential hazardous event, and perhaps most important, delivery of information to a broader community to evaluate the need for action.

A fundamental understanding of processes often requires a research effort that typically is the focus of academic and government researchers. Fundamental questions may include: (a) What triggers an earthquake, and why do some events escalate to a great magnitude while most are small-magnitude events?; (b) What processes are responsible for triggering a landslide?; (c) Can we predict the severity of an impending volcanic eruption? (d) Can we predict an impending drought or flood?; (e) Can we determine the height of a storm surge or storm track associated with coastal storm well in advance of landfall so that the impact can be mitigated?

Any effective hazard management system must strive to increase resilience. The only way to gain resiliency is to learn from past events and to decrease risk. To successfully increase resiliency requires having strong hazard identification programs with adequate monitoring and research components and very robust delivery mechanisms that deliver timely, accurate, and appropriate hazard information to a broad audience that will use the information is a wide variety of ways to meet their specific goals.

Keywords: natural hazards, management systems, earthquakes, volcanoes, landslides, geomagnetic storms, floods and droughts, coastal storms, policy

Introduction

On September 25, 2015, at the United Nations (UN) headquarters in New York, leaders from all 193 UN member countries gathered and universally ratified 17 Sustainable Development goals for the world that will be priorities for the organization until 2030. These goals are ambitious in scope, unprecedented in scale, and expand on the UN Millennium Development Goals. Several of them relate to the mitigation of natural hazards, and all are designed to improve the quality of life of the global society. A number of them relate to natural hazards, to wit: (a) ending poverty in all its forms everywhere; (b) ensuring healthy lives and promoting the well-being for all, at all ages; (c) ensuring the availability and sustainable management of water and sanitation for all; (d) building resilient infrastructure; and (e) making cities and human settlements inclusive, safe, resilient, and sustainable (United Nations General Assembly, 2015).

Society requires a safe environment in which to live, prosper, and sustain future generations. Traditionally, the global society has built and developed major urban areas where economic development was most effective, but they were not sited with the purpose of avoiding natural hazards. The first human-induced threats that we tend to identify are overexploitation of our water resources, pollution, and soil loss. However, natural hazards, which are not easily avoided or controlled (or, in many cases, predictable in the short term), have profound impacts on our safety, economic security, social development, political stability, and individual well-being.

Natural hazards are impacts on humans by natural processes that drive the Earth. Understanding the nature and extent of natural hazards is critical to managing risks to society. In 1990, the Circum-Pacific Council, as a contribution to the UN International Decade for Natural Disaster Reduction (INDR), produced a map showing the natural hazards of the Circum-Pacific region (Lockwood et al., 1990). The map includes weather hazards, tornadoes, tsunamis, earthquakes, and volcanoes, and it is unique because it compiles all these hazards into a single place. It shows that a large portion of the Earth is subject to the impacts of natural hazards of one type or another, and often by multiple such hazards.

The Earth would not have a functioning ecosystem without the dynamic processes that shape its landscapes throughout geologic time. Natural hazards (or geohazards, as they are sometimes called) include events such as earthquakes, volcanic eruptions, landslides and ground collapse, tsunamis, floods and droughts, geomagnetic storms, and coastal storms such as hurricanes, cyclones, and typhoons. All these hazards can result in the loss of human life and have the potential to cause very significant economic damage as well. The United States ranks second only to Japan in economic damages resulting from natural disasters. Table 1 lists some of the impacts related to natural hazards in the United States (USGS, 2007).

Table 1. Selected Natural Hazard Impacts in the United States

  • Earthquakes have the most potential for causing catastrophic casualties, property damage, and economic disruption.

  • Over 75% of declared federal disasters are related to floods

  • More than half the population lives within 50 miles of a coastline. Many of these areas, especially the Atlantic and Gulf coasts, will be in the direct path of future hurricanes.

  • Landslides affect every state, causing $3.5 billion in damages and between 25 and 50 deaths annually.

  • The United States faces significant tsunami threat to the East Coast, Hawaii, Alaska, and its island territories in the Caribbean and the Pacific.

  • The United States has 169 active volcanoes capable of producing a wide range of hazards that threaten people and infrastructure on the ground, as well as aircraft in flight.

  • In 2004, wildfires burned more than 8 million acres in 40 states. (Note: Wildfires are beyond the scope of this article, but they are also increasing globally because of changing climate and increasing human populations in remote areas.)

Source: Modified from USGS (2007).

A key component to understanding natural hazards is knowledge of the processes responsible for the hazard and mitigating the impacts of the hazardous event when it occurs. This requires a fourfold approach (Fig. 1) by geoscientists, which must include (a) a fundamental and complete understanding of the processes that cause the hazard, (b) an assessment of the hazard, (c) monitoring changes in conditions to determine the state of a potentially hazardous event, and perhaps most important, (d) timely and reliable delivery of information to the public and decision-makers to evaluate the need for action. The first three elements (process understanding, monitoring, and assessment) form a cycle that feeds off each other element. For example, greater monitoring often informs greater process-understanding efforts, and improvements in process understanding increase the accuracy of hazard assessments. The elements are conducted simultaneously and continuously with the goal of mitigating the impacts of a hazard or improving resiliency to quickly recover from the impacts of the hazardous event.

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Figure 1. Conceptual Approach to Hazard Management Showing the Cycle of Elements Used to Assess Natural Hazards, Goals for the Information, and Audiences for the Information.

Understanding Geologic Processes

A fundamental understanding of processes requires research that typically is the domain of academic and government researchers, exploring basic science issues and concepts. Fundamental questions may include: What triggers an earthquake, and why do some events have great magnitude while most remain small-magnitude events? What processes are responsible for triggering a landslide? Can we predict the severity of an impending volcanic eruption? Can we predict an impending drought or flood? Can we determine the height of a storm surge or storm track associated with coastal storm well in advance of landfall so that the impact can be mitigated?

Earthquakes

The development of robust and timely earthquake predictions has proved to be elusive, as understanding earthquake mechanisms is challenging and a very active area of research. Understanding earthquake processes requires data and observations at the depth where earthquakes are generated. Recently, in 2007, a deep borehole was drilled on the San Andreas Fault at Parkfield, California, and heavily instrumented to collect a wide array of information during a long-awaited earthquake. Similar studies, although expensive and long term, are needed.

Landslides

Landslide processes are complex, chaotic, and not fully understood, as most mass movement involves solids moving as a liquid does. Addressing landslide risks requires a predictive understanding of triggering mechanisms and thresholds for triggering. Once improved and more realistic models of landslide processes are developed, they will need to be applied to real-time warning systems. A key input to building these improved models requires modern geologic maps at a high degree of resolution. Unfortunately, geologic maps at the necessary resolution are not available in most parts of the world, including large areas of the United States.

Tsunamis

Tsunamis are almost exclusively generated by specific types of earthquakes, although landslides are responsible for about 15% of tsunamis worldwide (Geological Society of London, 2014). Tsunamis are generated mainly by earthquakes that tend to be greater than a magnitude of 7.0 that occur underwater on major thrust faults along the edge of subducting tectonic plates. Because of global seismic monitoring and the speed at which data can be analyzed relative to the accurate epicenter location, magnitude, and type of faulting, geoscientists can determine if an event has the potential to generate a tsunami. This information, coupled with the ability to monitor wave height in real time and robust modeling of the speed and direction of the tsunami waves, have allowed for significant early warning of an approaching tsunami. Although more research is needed to improve the performance of models, there currently are functional tsunami warning systems in most of the at-risk parts of the world. The Fukushima earthquake that struck in Japan in November 2016 resulted in the issuance of an effective tsunami warning that demonstrates the robustness of the warning network.

Assessing the long-term frequency of tsunami threats requires detailed geologic mapping of tsunami deposits. This mapping will provide information to support more accurate hazard assessments of the areal extent, thickness of tsunami deposits, and frequency of occurrence of tsunamis. In recent years, the identification of tsunami deposits in the Caribbean has led to a better understanding of tsunami risks, and in turn to the installation of more seismic monitoring stations and sea-surface-level monitoring buoys, resulting in a real-time tsunami warning system.

Coastal Storms

In 1900, a powerful hurricane (known as the Great Storm of 1900) swept across the Gulf of Mexico, making landfall on Galveston Island in Texas in the United States. Because modern monitoring was not available at the time, this hurricane was essentially unpredicted by the weather service, and no significant warnings were issued. The storm resulted in the deaths of about 8,000 of the 37,000 residents of Galveston. It still ranks as the worst natural disaster in U.S. history because of the large loss of life—indeed, there was more loss of life in this storm than in all 325 of the major coastal storms that struck the United States from then until 2011 (Hudson, 2011). Since 1900, numerous other major storms (predominantly hurricanes, typhoons, and cyclones) have caused major loss of life and economic losses throughout the world. Some notable examples include Hurricane Katrina in 2005 and Superstorm Sandy in 2012 in the United States, and Typhoon Haiyan in 2013 and Cyclone Tracy in 1974 in Asia. What is remarkable about these storms is the impact that these coastal storms had on heavily populated urban areas. Cyclone Tracy caused unprecedented damage to Darwin, Australia, and Typhoon Haiyan, characterized as a superstorm because of its vast size, caused enormous damage to the Philippines and China. Hurricane Katrina resulted in the near-complete flooding of New Orleans, Louisiana, following the failure of levees that proved to be inadequate for this scale of storm. Economic losses in the United States during 2005, largely due to Katrina, totaled in the hundreds of billions of dollars, making it the most expensive hurricane season in U.S. history. Superstorm Sandy made landfall in New Jersey and went on to cause major damage to New York City and Long Island as well. The storm surge resulted in widespread flooding, including parts of the metropolitan New York commuter transit rail systems. Recovery and rebuilding after the event were well underway in 2016, but much remains to be done to ensure that future storms will not be as catastrophic. These storms all affected urban settings, demonstrating that society must recognize the risk of natural hazards on significant infrastructure in areas with high population densities that may not be able to withstand the impacts of such events.

In addition, research is needed to better predict the severity of storms and more accurately determine their tracks. Much has been accomplished to date, but more accuracy is needed to effectively mitigate impacts of the storm. Better prediction of rainfall, storm surge, wind velocity, and coastal erosion is needed.

Hazard Assessment

A hazard assessment, which is often conducted by governmental geoscience institutes, focuses on the spatial extent of where a hazard exists, its severity, and when it may occur. For example, earthquakes occur along faults as accumulated strain is released, so if fault locations can be identified, geoscientists will have information relative to the earthquake hazard in particular areas. Unfortunately, precise identification of hazard sources is often very difficult. For example, the significance of the earthquake hazard in the Pacific Northwest of the United States was underestimated until detailed mapping and research on the nature of the tectonics of the area was completed.

Earthquakes

Historical information on previous hazardous events like earthquakes is critical to assessing what events can be expected in the future. For example, does a particular fault have a history of producing large-magnitude earthquakes, and at what frequency do these large events occur? One example is the North Anatolian fault in Turkey, which has generated large earthquakes in a fairly consistent manner for thousands of years (USGS, 2000). The magnitudes of these events typically are about the same, but the location of the ruptured fault segment moves generally east to west on each subsequent event. The last earthquake along this fault occurred in Izmit, Turkey, in 1999, and because Istanbul lies to the west along the same fault, the hazard from an earthquake in the Istanbul region was elevated. Fortunately, a global seismic hazard map (Fig. 2) was produced by a consortium of international geoscience organizations to define the level of hazard and ground shaking in large regions of the globe (Giardini, Grunthal, Shedlock, & Zhang, 2003).

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Figure 2. Global Seismic Hazard Map.

Although this global view is important, more resolution is required for policymakers to mitigate the seismic hazard through the creation of building codes designed to reduce damage. Policymakers also need to implement programs to educate the public on appropriate responses during such events to reduce injury and death. Figure 3 presents a map of the conterminous United States that illustrates the seismic hazard and peak ground acceleration that can be expected with a 2% probability of exceedance in 50 years (Petersen et al., 2015). It is noteworthy that the seismic risk has been elevated in north-central Oklahoma and southern Kansas, area due to recent increase in seismicity induced by the injection of fluids into the subsurface related to human activities.

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Figure 3. Map of the Conterminous United States Showing Seismic Hazard and Peak Ground Acceleration in 2014.

Tsunamis

Tsunamis are almost exclusively generated by earthquakes, and because of effective global seismic monitoring, it is possible to determine, in a matter of minutes, if a specific earthquake potentially can generate a tsunami. Robust models exist that can predict the arrival of a tsunami even an ocean away from where it was generated. Of course, from a public safety perspective, evacuation of people requires time, and often the areas near the earthquake lack adequate response time; this was the case in both the Sumatra-Andaman and Tohoku earthquakes of 2004 and 2011, respectively. Both these events caused major economic losses and loss of life because of the size and location of the event relative to people and infrastructure.

Volcanoes

In the case of volcanic eruptions, geoscientists have a distinct advantage because the locations of the world’s volcanoes are generally known. However, the hazards can have a high impact, including lava flows, volcanic gases, pyroclastic flows, ash falls, and lahars (wet debris flows that clog rivers and have the potential to cause major flooding events). Figure 4 shows a world map of volcanoes, earthquakes, impact craters, and plate tectonics (Simkins, Tilling, Vogt, Kirby, Kimberly, & Stewart, 2006). However, to fully understand the risk from a specific volcano requires both monitoring it and taking its detailed eruptive history to determine the frequency, type, and severity of eruptions. Documenting such an eruptive history requires detailed geological mapping, which involves extensive field efforts. The information regarding a volcano’s potential severity or magnitude is described by the Volcanic Explosivity Index (VEI). The VEI was proposed in 1982 and is based on several criteria, including duration of eruption and height of eruption column (Newhall & Self, 1982). The VEI is shown graphically in Figure 5 (American Geosciences Institute, 2016).

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Figure 4. Global Map of Volcanoes, Earthquakes, Impact Craters, and Tectonic Plates.

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Figure 5. Graphic Representation of the Volcanic Explosivity Index.

Geomagnetic Storms

Geomagnetic storms are another, if less obvious, natural hazard. The Earth’s magnetic field is defined by two processes. The secular field results from the unequal rotation of the core and mantle of the Earth, called the dynamo. Short-term changes in the magnetic field are caused by solar or geomagnetic storms triggered by coronal mass eruptions that pummel the Earth with highly charged ions that rain down on it in 11-year activity cycles. On March 13, 1989, a geomagnetic storm resulting from a solar outburst struck the Earth, triggering instabilities in the electric power grid that serves much of eastern Canada and the United States. The storm led to blackouts for more than 6 million customers and caused tens of millions of dollars in damage and economic losses. In addition, geomagnetic storms may disrupt telecommunications (with the advent of smartphone technology, personal communication has been put at risk as well), damage satellites, endanger the safety of humans in space, cause navigation problems because of the disruption of global positioning satellite (GPS) systems, and damage long north-south trending electrical lines and pipelines that transport fuel and water (because corrosion rates are accelerated). Insurance losses are expected to increase with society’s increasing reliance on electronics. Research is needed to improve the predictability of future geomagnetic storms so that their impacts can be reduced or avoided. Several articles that have been published in EARTH magazine provide a good overview on geomagnetic storms (Morton, 2014; Thompson, 2013; Viereck, 2015).

Landslides

Landslides have not been extensively mapped globally, and only a handful of landslide-prone areas are actually monitored. Almost all nations face significant landslide and ground failure hazards. Landslides occur due to slope instability and can occur either very rapidly or so slowly as to be imperceptible in real time. They can be triggered by rainstorms, earthquakes, wildfires, volcanic eruptions, and human activity. Landslide inventories are the basis for susceptibility mapping, and ultimately hazard and risk assessment mapping as well. Generally, because of the lack of understanding of landslide processes, probabilistic modeling is used to create landslide hazard maps. Landslide inventories are determined by identifying and locating old landslide features and understanding the complex interactions among slope, soil, rock type, vegetation, and groundwater-table height. Detailed geologic, soil, and hydrogeologic maps at appropriate scales are needed, along with detailed field reconnaissance.

Although it is very difficult to get accurate estimates because of the obvious mass failures and less obvious creep, both of which cause substantial infrastructure damage. In the United States, an estimated 25 to 50 deaths annually are a result of landslides and ground failure. In addition, annualized economic losses in the United States are estimated at $2 billion to $3.5 billion (USGS, 2007). In general, the economic loss tally is based on large landslides; the costs of restoration related to smaller events that may close a stretch of highway (and are generally repaired quickly by local government or homeowners) are not included in the estimates of economic losses, so the true costs may be significantly larger. Globally, numerous large catastrophic landslides have occurred since 1900 (AGI, 2016), and these are noted on Table 2.

Table 2. Selected Historical Catastrophic Landslides Since 1900—Worldwide

Year

Country (State/Province)

Name and Type(s)

Triggering Process

Volume of Material (m3)

Details

1911

Tadzhik Republic

Usoy rockslide

Usoy earthquake (M = 7.4)

2.0 × 109

Destroyed Usoy village; 54 killed; dammed the Murgab River, impounding 65 km, still existing.

1919

Indonesia (Java)

Kalut lahars

Eruption of the Kalut volcano

185 km2

5,110 killed; 104 villages destroyed or damaged. Draining of the crater lake caused hot mudflows.

1920

China (Ningxia)

Haiyuan landslides

Haiyuan earthquake

100,000 killed; many villages destroyed; 675 large loess landslides created more than 40 lakes.

1933

China (Sichuan)

Deixi landslides

Deixi earthquake (M = 7.5)

> 150 × 106

6,800 killed; 2,500 drowned when landslide dam failed. Several major landslides occurred; the largest formed a 255-m-high dam on the Min River.

1939

Japan (Hyogo)

Mount Rokko slides and mudflows

Major typhoon, heavy rain

505 dead/missing; 130,000 homes destroyed/badly damaged by mass movements, floods, or both. 50%–90% of the impact of Japanese typhoons is caused by mass movements.

1949

Tadzhik Republic

Khait rockslide

Khait earthquake (M = 7.5)

12,000–20,000 killed or missing; 33 villages destroyed. Began as rockslide; transformed into large loess and granite debris avalanche.

1953

Japan (Wakayama)

Arita River slides

Heavy rain

460 dead/missing; 4,772 homes destroyed by mass movements; mudslides and debris flows, and floods.

1958

Japan (Shizuoka)

Kanogawa slides

Major typhoon, heavy rain

1,094 dead/missing; 19,754 homes destroyed or badly damaged by mudslides and debris flows.

1962

Peru (Ancash)

Nevados Huascaran debris avalanche

13 × 106

4,000–5,000 killed; much of the village of Ranrahirca destroyed. Major debris avalanche from Nevados Huascaran; average velocity of 170 km/h.

1963

Italy (Friuli-venezia-Griulia)

Vaiont Reservoir rockslide

250 × 106

2,000 killed; Longarone city’s total damages: $200 million (in 1963 dollars). Rockslide caused 100-m waves to overtop the Vaiont Dam.

1964

United States (Alaska)

1964 Alaska landslides

Prince William Sound earthquake (M = 9.4)

Estimated $280 million damages. Major landslide damage in the cities of Anchorage, Valdez, Whittier, and Seward.

1967

Brazil (Serra das Araras)

Serra das Araras slides

Heavy rain

1,700 dead from landslides and floods. Many landslides, avalanches, and debris/mudflows in mountains southwest of Rio de Janeiro.

1970

Peru (Ancash)

Nevados Huascaran debris avalanche

Earthquake (M = 7.7)

30–50 × 106

18,000 dead; the town of Yungay destroyed; debris avalanche from same peak as in 1962; attained average velocity of 280 km/h.

1974

Peru (Huancavelica)

Mayunmarca rockslide–debris avalanche

Rainfall? River erosion?

1.6 × 109

Mayunmarca village was destroyed, with 450 killed; 150-m-high landslide dam failed, causing major flooding. Debris avalanche with average velocity of 140 km/h dammed Mantaro River.

1980

United States (Washington)

Mount St. Helens rockslide- debris avalanche

Eruption of Mount St. Helens

2.8 × 109

World’s largest historic landslide; only 5–10 killed (evacuation saved lives), major destruction of homes, highways, etc. Rockslide deteriorated into 23-km-long debris avalanche, average velocity of 125 km/h; surface remobilized into 95-km-long debris flow.

1983

United States (Utah)

Thistle debris slide

Snowmelt and heavy rain

21 × 106

No deaths. Destroyed major railroad and highways; dammed Spanish Fork flooding town of Thistle. Total losses: $600 million—50% direct losses, 50% indirect losses.

1985

Colombia (Tolima)

Nevado del Ruiz debris flows

Eruption of Nevado del Ruiz

Four towns and villages destroyed; flow in the valley of the Lagunillas River killed more than 20,000 in the city of Armero when hazard warnings were not passed to residents.

1986

Papua, New Guinea (East New Britain)

Bairaman rockslide–debris avalanche

Bairaman earthquake (M = 7.1)

200 × 106

The village of Bairaman was destroyed by debris flow from breached landslide dam; evacuation prevented casualties. The debris avalanche formed a 210-m-high dam that impounded 50-million-m3 lake; dam failed, causing 100-m-deep debris flow–flood downstream.

1998

Honduras, Guatemala, Nicaragua, El Salvador

Hurricane Mitch flooding; landslide debris–flows

Hurricane Mitch

Approximately 10,000 people killed by landslides and flooding. 280-km/hmph winds in Honduras. Torrential rains at 10 cm/h. The Casitas volcano in Nicaragua experienced large debris flows.

1999

Venezuela (Vargas)

Vargas debris flow

Coastal storm

1.9 × 106

30,000 fatalities caused by a heavy storm that deposited 911 mm of rain in only a few days.

2005

United States (La Conchita, California)

La Conchita landslide

Deep infiltration of rainfall

200,000 m³

10 deaths; remobilization of colluviums from 1995 slide into a debris flow.

2013

United States (Salt Lake City, Utah)

Bingham Canyon Mine landslide

Trigger undetermined

55 × 106

No fatalities; possibly the largest nonvolcanic, terrestrial landslide in North America.

2013

India (Kedarnath, Uttarakhand)

Kedarnath landslide

After Uttarakhand Floods

5,700 deaths; second-highest loss of life since Gansu landslide 2010.

2014

United States (Oso, Washington)

2014 Oso mudslide

Structural weakening

10 × 106

43 deaths; the midmorning event covered a rural community in 2.5 square kilometers of debris. Total of 49 structures destroyed or affected.

2014

Sri Lanka (Badulla District)

Badulla landslide

Monsoon rains

100 × 106

300+ fatalities; searches called off because of heavy rains and unstable slopes.

2015

Guatemala (Santa Catarina Pinula)

Guatemala slide

Heavy rainfall

150+ fatalities caused by successive failures of a hill overlooking the town. Local rivers rose by 1 m during the preceding week. Disaster was exacerbated by the location of the town in a deep ravine.

Source: AGI (2016).

The U.S. Geological Survey (USGS) last published a landslide hazard map for the conterminous United States in 1982 (USGS, 1997). With the advent of new technology such as light detection and ranging (LIDAR), very accurate and precise measurements of topography can be taken. This technology is being used in specific areas for landslide mapping and for other natural hazard work like fault mapping, volcano studies, and coastal mapping. Expanded global use of this technology and other advanced remote sensing techniques that will be developed in the coming years are critical to meeting the basic need for assessing natural hazard risks globally.

Much progress has been made toward understanding the triggering of precipitation-induced landslides; however, rainfall monitoring at the detailed spatial resolution required is still quite rare. For example, in the United States, the USGS and the National Weather Service partnered to develop a demonstration early warning flash-flood and debris-flow system in 2005 (USGS, 2005a). The project focused on southern California, where there is adequate real-time data on rainfall. These data were derived from a network of advanced radar sites and from a dense network of real-time rain gauges. In addition, significant research has been conducted in this area on the rainfall thresholds required to initiate debris flows. The demonstration worked as planned, and it could be replicated across the globe with adequate investment in infrastructure, monitoring, and research.

Tsunamis

On November 21, 2016, a magnitude 6.9 earthquake was reported by the Japan Meteorological Office and the USGS off the coast of Fukushima Prefecture in Japan. This earthquake produced a small tsunami in the area but did not cause significant damage. This is in stark contrast to the March 11, 2011, magnitude-9 event in approximately the same area, which claimed 18,000 lives and caused significant damage to infrastructure, including the Fukushima Daiichi nuclear power generating facility, which caused significant widespread environmental contamination. These examples highlight the challenge of large earthquakes causing tsunamis near populated areas with sensitive infrastructure. Without the advantage of distance, there is a limited warning time during which tsunami hazard zones can be evacuated. These factors must be incorporated into hazard and risk assessments and any proposed actions to mitigate the hazard.

Monitoring Conditions

The third element of the hazard identification approach is monitoring. Monitoring coverage both by type of hazard and spatial distribution of monitoring locations varies globally. The ability to actively monitor for hazards is often controlled by the ability to monitor at the spatial scale that is useful, while sometimes it is a function of uncertainty in the dynamics that trigger a hazard.

Earthquakes

Some nations have invested heavily in the development of extensive seismic monitoring networks, including Japan and Taiwan, which have among the world’s densest arrays of seismic stations. Figure 6 shows a map of Japan and a map of California that identify the location of seismic sensors as part of the Advanced National Seismic System in the United States and the national government in Japan. The high density of seismic sensors in Japan is needed to ensure adequate early warning of earthquakes (http://earthquake.usgs.gov/research/earlywarning/nextsteps.php). Where the probability of seismic events in areas with dense population and infrastructure is high, the investment in such seismic systems is economically defensible. On the other hand, global monitoring can help as well. The United States maintains a global seismographic network of approximately 100 state-of-the-art seismometers that are capable of monitoring moderate- to large-magnitude events anywhere on Earth. The stations are strategically located around the world. Interestingly, there is a station at the South Pole in Antarctica that has what is generally considered the quietest seismometer on Earth because of its remote location and the lack of background noise associated with human activities. A map showing the location of seismic stations and all earthquakes larger than 6.0 for the period from 2000–2010 is presented in Figure 7 (Gee & Leith, 2011).

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Figure 6. Maps of Japan and California Showing the Location of Seismic Stations.

In the case of seismic monitoring, having near-real-time information and advanced instrumentation vastly improves the quality of information for researchers, national security agencies, emergency management workers, and the general public. Initially, seismometers were analog devices designed to be accurate for a certain range of frequencies of vibration and amplitude of motion. These band-limited instruments were technology limiting for the seismologist, generally requiring networks of weak motion seismometers to monitor small, local earthquakes and large, distant earthquakes. In addition, networks were established to monitor the strong motion required to understand the intense ground shaking that affects structures. It is also noteworthy that since this instrumentation was analog, most analysis required intense human involvement, which took significant time and did not allow the quick real-time response that society needed to reduce the risk to life and property substantially.

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Figure 7. Global Map Showing the Location of Seismic Stations and all Earthquakes Larger than 6.0 for the Period from 2000–2010.

With the advent of digital technology, modern instrumentation has replaced the analog instruments of the past. These seismic monitors have both broad frequency-band capability and large dynamic ranges to measure ground shaking accurately. In addition, because the monitors produce digital records, information can be analyzed in near-real time and automatically through the use of high-speed computing. This advancement has created an entirely new audience for earthquake information—namely, emergency responders and the general public.

In 1998, there were approximately 1,700 weak-motion seismic instruments and 1,400 strong-motion seismometers in the United States (NRC, 2006). This network is in need of improvement, and the USGS has advocated a significant increase in the seismic monitoring network for the United States (USGS, 1999). It proposed a significant expansion and modernization of the seismic network (i.e., adding several thousand instruments) for a capital cost of approximately $170 million and an annual operating cost of $47 million in 1999 dollars. One aspect of the proposal was to enhance seismic monitoring in urban areas. The number of stations in each urban area is determined by the earthquake hazard and the size of the population at risk.

Los Angeles and San Francisco were the highest-priority urban areas, each requiring about 1,000 instruments. It is interesting to note that at the same time, significant government investment was being made in the United States to support a major research effort to understand the deep geologic structure of the land. This research effort, entitled EarthScope, used seismic monitors to accomplish their research goals. Portable regional arrays of seismometers were moved across the country to better understand the geologic structure of various regions. As these studies were completed, some of the instrumentation has been left in place to support the proposed expansion and modernization of the seismic network of the United States. This is a good example of the efficient and effective dual use of expensive instrumentation.

Generally, robust seismic monitoring is designed using a tiered approach including a global component, national component, regional component, and local component. In some instances, buildings themselves are instrumented to determine the response of the structure to intense ground shaking. This information is particularly valuable to structural engineers and building code officials. Also, pilot efforts are under way to use seismic monitoring as a rapid response tool. For earthquakes that are located moderate distances from infrastructure, it is possible to issue a warning after the earthquake occurs, but before the arrival of potentially damaging seismic waves. Although it does not constitute a prediction, it does allow certain actions to be taken that can lessen the impact of the shaking. For example, trains could be stopped so that they don’t derail, electrical grids could be shut down so that they could be brought up more quickly (and with less damage) following the shaking, surgeons in hospitals could be given a moment of advance warning so that they could react accordingly during their procedures, and bridges could be closed so that traffic was not on them during the shaking.

On December 26, 2004, a magnitude-9.0 earthquake off the coast of Sumatra, Indonesia, generated a major tsunami that resulted in the loss of 200,000 lives in 11 countries. The lack of tsunami hazard assessment, as well as inadequate monitoring and lack of public awareness, contributed to the scale of the loss. Following the event, significant effort was spent increasing seismic and other monitoring to mitigate the tsunami hazard in the Indian Ocean. A key lesson learned from that process is the critical need for free and timely sharing of seismic data following major events such as the Sumatra earthquake that have a significant, if not global, impact. Unfortunately, the free sharing of information is often not permitted in many nations because of concerns about national security. Multilateral and diplomatic efforts are needed to improve the rapid exchange of data.

Volcanoes

Globally, Japan, Indonesia, and the United States have the largest number of active volcanoes within their borders. These nations have very good monitoring programs, but the systems require consistent upgrades as new advances in monitoring are made. Many volcanoes are monitored through the use of satellite imagery, particularly in remote areas. This technology has been used effectively in several instances. The successful evacuation at Mount Pinatubo in the Philippines in 1991 can be attributed directly to the availability of advanced remote sensing data that provided geoscientists the necessary information to determine that an eruption was imminent.

Although it is less sophisticated, remotely sensed information is critical to monitoring active volcanoes worldwide. For example, there are 41 active volcanoes on the islands that make up the Aleutian chain. Many of these islands are very remote, and some do not have access to either power or telecommunications. However, the risk to air safety and native peoples is significant. There has been a major effort during the past 25 years to install seismic monitoring equipment on many of these islands so that early warning of volcanic unrest can be observed. Also, monitoring is increased during periods of volcanic unrest. More sophisticated remote sensing is deployed if possible, along with the deployment of additional seismic stations whose records can be analyzed to determine the movement of magma in the subsurface. In addition, advanced monitoring of volcanic gases is employed to determine if an eruption is imminent. Precise measurements of changes in elevation are also made on the volcano to detect any deformation of the land surface that is a result of its volcanic activity.

There are also a number of volcanic observatories located around the world. These are located at high-risk volcanoes or at volcanoes that are ideally suited as field laboratories for detailed research studies into volcanic processes. The first of these observatories was founded in the early 1900s at Kilauea volcano on the Big Island of Hawaii. The observatory was founded specifically in response to the catastrophic eruption of Mount Pelee on Martinique in the Caribbean in 1902, which resulted in an almost complete loss of human life (only one survivor was reported) in the island’s capital, St. Pierre.

Flooding and Drought

The United States has an effective network of real-time streamflow monitoring gauges and groundwater observation wells. This national network is critical for determining the severity of flooding that an area may experience under various flow conditions. It is also useful for determining drought conditions. The streamflow and observation well information is freely available to the public through the Internet and is used by a variety of audiences ranging from recreationalists to determine optimum conditions for fishing and boating to emergency managers for flood and drought response. Real-time monitoring of floods is critical to determining the extent of potential flood damage and to avoiding economic losses and loss of human life. Figure 8 shows a series of maps of the United States for November 30, 2016, depicting current streamflow characteristics, flood conditions, previous-day streamflow, and current drought conditions. Other nations have similar networks, but regrettably many parts of the world lack this information.

Natural Hazards Identification and Hazard Management SystemsClick to view larger

Figure 8. Maps of the United States for December 21 and 22, 2016, Depicting Current Streamflow Characteristics, Flood Conditions, Previous Day Streamflow, and Current Drought Conditions.

Now coupled with the extensive NEXRAD network, which tracks precipitation rates of active storms, the data from stream gauges are used in flood prediction and stream response models, which leads to accurate and rapid warnings. In addition, the integration of these data has led to advanced modeling techniques so that the streamflow and stage can be estimated for ungauged stream reaches.

Satellite and other remotely sensed data are now being used routinely to monitor hazards. Landsat satellites can be used to compute a greenness index, which can be used as an early warning system for drought. This has been effectively used, specifically in Africa to ensure that relief supplies are strategically located to mitigate the human toll associated with famine. Similarly, the GRACE satellite can determine the volume of groundwater in storage and be used to estimate areas of land subsidence and diminished groundwater availability. Given multiple passes by the satellite, data can be analyzed to determine how the system is changing. These examples show the potential for remotely sensed data in hazard monitoring.

Coastal Storms

The impact of coastal storms is another hazard that can cause severe long-term consequences, in addition to human and property losses. With the advent of advanced remote-sensing information using LIDAR, it is possible to determine the affected areas very accurately for various storm surge scenarios. In some cases, communities have relocated at significant expense to higher and safer ground. Following concerns about increased coastal erosion during storms, two communities in the United States that have recently decided to relocate farther inland to avoid inundation, the loss of infrastructure, and ensure public safety are Isle de Jean Charles, Louisiana and Shishmaref, Alaska.

Social Media and the Internet

With the advent of social media, more information is being supplied by citizen scientists through a process called crowdsourcing. Several examples of crowdsourcing exist within the earthquake community. Some use apps on smartphones that allow volunteers to report the intensity of the shaking in the area where the phone is located. Other apps use a smartphone’s internal sensor to detect shaking and send data to a central database. Earlier efforts focused on reporting over the Internet (Deatrick, 2016).

The advent of citizen scientists plays a critical role in increasing general public awareness of natural hazards and other phenomena. However, the observations made by various citizen scientists also provide timely and important data to geoscientists. For example, one program called “Did You Feel It?” encourages people worldwide to go online and report their observations during an earthquake. This information is used to construct near-real-time maps of shaking intensity and damage caused. This is extremely valuable to emergency responders and researchers alike. Also, individuals who participate in the program feel satisfied that they have somehow contributed positively to a difficult situation. Similarly, citizen scientists are also contributing to earthquake research and have installed inexpensive seismographs in their homes or offices.

The landslide community in the United States also has implemented a program that allows citizen scientists to report their landslide observations. The goal is to have a much more comprehensive database upon which to base a national landslide hazard assessment (USGS, 2012). Finally, there are numerous citizen scientist programs globally addressing water availability and water quality observations. One such program is the World Water Monitoring Challenge, which engages people to conduct basic monitoring of their local bodies of water.

The use of social media and the Internet has a great deal of potential to assist in natural hazard monitoring, and advances across all hazards can be expected for many years to come.

Timely and Effective Delivery of Information

Of course, hazard information is most valuable when it is used effectively by nongeoscientists to save lives and to reduce the economic and social consequences of events.

Volcanoes

To emphasize the importance of public safety, it is important to note that an estimated 500 million people live close enough to active volcanoes to be negatively affected during eruptions (Geological Society of London, 2014). One example that highlights the importance of monitoring information to assist the public dealing with hazardous events is the disruption of civil air travel in 2010 as a result of the eruption of Eyjafjallajökull in Iceland, which caused havoc to the traveling public across northern and western Europe. The air travel disruption caused economic losses, as well as much personal inconvenience. Another example is the near-crash of KLM Flight 867 on December 14, 1989. On a final approach to Anchorage Airport following an uneventful flight over the North Pole from Amsterdam, a 747 jumbo jet with 245 passengers lost power in all engines after flying through a volcanic ash plume from the eruption of Mount Redoubt. Fortunately, the pilots were able to restart the engines during the descent and land safely in Anchorage with no loss of life, but $80 million worth of damage was done to the aircraft.

This was not the first time that commercial aircraft have encountered volcanic ash plumes. For example, in 1982, a British Airways jumbo jet had lost its engines while flying into an ash cloud from Galunggung in Indonesia. After the Anchorage event, however, it became clear that the traveling public were facing a major volcanic ash hazard. In response, the World Meteorological Organization and the International Civil Aviation Organization developed training programs and a series of global centers, called Volcano Ash Advisory Centers (VAACs), in the mid-1990s to track volcanic ash so that information on dangerous plumes could be provided to civil aviation in an effort to avoid the ash hazard (Guffanti & Miller, 2002). During the 2010 Icelandic eruption, such procedures and information were used to avoid volcanic ash for commercial air traffic.

Earthquakes

The users of hazard information include government leaders, emergency managers, relief managers, the media, decision-makers (who determine where public funds should be committed), insurance underwriters, social scientists such as psychologists and social workers, the medical community, the business community, and the general public. Some audiences have response responsibilities immediately following a disaster, while others play a strong role in anticipating a hazardous event and implementing appropriate mitigations either for direct impact of the event through strengthened infrastructure and preparedness or reduce the loss of life and property following the event. Generally, groups that respond to an event want timely and accurate information so that their response is focused and goes smoothly, resulting in the saving of lives. PAGER is an example of the rapid delivery of damage assessment information globally following any major earthquake. Developed by the USGS, PAGER distributes alarms on numerous social media outlets (USGS, 2005b). The system provides near-real-time information on the location, magnitude, and depth of an earthquake, as well as an estimate of the number of people exposed to varying levels of shaking, a description of the region’s infrastructure to shaking, and a measure of confidence in the information. This information is extremely useful in terms of an efficient and effective emergency response to an event.

Groups that have a strong role prior to an event want information that can be used to identify risk. Risk reflects the potential impact on a community or region. A generalized risk diagram with the risk for various natural hazards identified is shown in Figure 9. As you can see, natural hazards cover a wide range of frequencies of occurrence and severity of impact. For example, there are numerous earthquakes annually that have magnitudes less than 6, which generally cause little damage or significant human death. However, there are many fewer earthquakes with magnitudes greater than 6, which may cause great damage and significant loss of life.

Natural Hazards Identification and Hazard Management SystemsClick to view larger

Figure 9. Generalized Risk Diagram for Selected Natural Hazards.

Risk is defined as “the probability of harmful consequences or expected losses resulting from interactions between natural hazards or human-induced hazards and vulnerable conditions” happening in a given time frame (Executive Office of the President, 2005, p. 17). For example, if there is a high likelihood of a large earthquake in a region, what is the size of the population that will be affected? Is the infrastructure of the region built to withstand potential shaking? Risk can be computed for all hazards, but the accuracy of that assessment requires understanding the likelihood of an event of a given severity and the expected impact on life and property.

Flooding

Floodplain mapping is a good example of minimizing both loss of life and economic loss due to flooding. In the United States, the annualized economic losses due to flooding exceed all other natural hazards. In the 1990s, flood loses totaled $50 billion in the United States (NWS-HIC, 2001). In 2012–2013, insurance losses in the United Kingdom due to flooding were approximately £1 billion ($1.4 billion) (Geological Society of London, 2014). A key product that should be used to determine risk-associated flooding is the floodplain map, which delineates the potential extent of flood-associated events that have a low probability of occurrence (often the so-called 100-year or 500-year flood is used as a benchmark).

Policymakers may decide to mitigate risk by reducing building in floodplain areas. But certainly, insurance providers base their premiums on the location of structures relative to the floodplain. Similarly, more stringent building codes may be enacted in earthquake-prone areas to reduce building collapse, thereby saving lives and the cost of repair and rebuilding and ensuring that critical infrastructure such as hospitals and schools are located in the most risk-minimized locations.

Mitigation and Resilience

Finally, any effective hazard management system must strive to increase resilience, which is defined in a 2005 report of the U.S. National Science and Technology Council (NSTC), Subcommittee on Disaster Reduction as “the capacity of a system, community, or society potentially exposed to hazards to adapt, by resisting or changing, in order to reach and maintain an acceptable level of functioning and structure (Executive Office of the President, 2005, p. 17).” The only way to gain resiliency is to learn from past events and to decrease risk. To succeed in increasing resiliency requires having strong hazard identification programs with adequate monitoring and research components and very robust mechanisms to deliver timely, accurate, and appropriate hazard information to a broad audience that will use the information in a wide variety of ways to meet their specific goals.

In addition, it is important that society has adequate information on the population at risk and the infrastructure in harm’s way. Maps showing land use and detailed information in infrastructure, along with population density at the appropriate scales, are needed. Remotely sensed information has advanced significantly and is available from both government and private sectors in most parts of the world. Satellites that collectively are part of the Landsat program have provided 30-m-resolution imagery of almost the entire planet for the last several decades. These assets are freely available to the public and, along with other similar remote sensing assets, can be used effectively to assess risk.

Building codes are one way of improving the fragility of buildings, assuming that hazard assessments are used to create them. For example, what intensity of ground shaking is expected for particular types of buildings should an earthquake of a certain size occur? Obviously, it is not practical to design every structure to the same level of resilience at the same time. More critical infrastructure, such as hospitals, bridges, nuclear power plants, and schools must be prioritized for either retrofitting or replacement. Each industry also has different needs in terms of the continuity of their operations. Manufacturing needs may be quite different than those of health providers, and the requirements of the banking sector may be different from those of the government.

Public awareness and training are also important in terms of mitigation and resiliency. Public information campaigns relative to individual behavior during natural hazard events are designed to save lives. Some examples include information on preparing for an earthquake (e.g., earthquake survival kits and instructions on how to prevent personal injury), operating motor vehicles in flooded areas (many deaths in the developed world are due to individuals driving automobiles into floodwaters and then being swept away), and seeking higher ground during tsunami warnings. Unfortunately, such campaigns are often short lived or totally unavailable in many nations. Mandatory evacuations have also been used effectively to mitigate the impacts of volcanic eruptions and coastal storms. Policymakers, geoscientists, emergency responders, and the public all have a role to play in such efforts.

The Way Forward

Natural hazards are inherently part of the human condition and experience. However, it is within the realm of geoscientists, emergency managers, policymakers, and the general public to mitigate their impacts and prevent the occurrence of natural hazards from becoming regional, national, and global disasters (Leahy, 2006). In the United States, the Executive Office of the President, through the National Science and Technology Council, released a report in 2005 that outlines six grand challenges necessary to reduce the impact of natural disasters (Executive Office of the President, 2005). The recommendations included providing hazard and disaster information where and when it is needed, understanding the natural processes that produce hazards, developing hazard mitigation strategies and technologies, recognizing and reducing vulnerability of interdependent critical infrastructure, assessing disaster resilience using standard methods, and promoting riskwise behavior. These goals are quite broad and can be applied to all hazards, although each hazard may require different priorities and most certainly different levels of investment.

In the National Landslide Mitigation Strategy for the United States (Spiker & Gori, 2003), nine major elements were identified as necessary for a successful mitigation of landslide hazards. These elements span a wide array of items, from research to policy development and implementation. For example, the report highlights the need for research to develop a predictive understanding of landslide processes and triggering, increased real-time monitoring of active landslides with high risk, development of robust information transfer to the nonscientific community, training, public awareness, implementation of loss reduction measures, and enhancing preparedness, response, and recovery. The report also points out the need to establish and nurture more effective partnerships among government agencies at all levels, as well as in the private sector. One example of an effective partnership between USGS and the American Planning Association is a report entitled “Landslide Hazards and Planning” (Schwab, Gori, & Jeer, 2005), which was designed to inform the planning community about the significance of landslide hazards and actions that the planners may implement to avoid or mitigate landslide risk. The training of most urban and rural planners lacks any discussion of the geoscience aspects of land-use planning. As a result, most decisions on land use are proposed and implemented without consideration of the potential natural hazard impacts or other geoscience constraints.

For earthquake and volcanic hazards, more monitoring is needed. These needs span the range of approaches from onsite seismometers to more advanced remote sensing techniques. The widespread availability of cost-effective unmanned autonomous vehicles (UAVs) holds great promise for the future. UAVs can go places that are too dangerous for observers, so they can make critical and timely observations. For example, entering the crater of a volcano showing unrest is a very dangerous endeavor, whereas a UAV can make the needed observations without putting humans at risk. Drones of every type may be used to collect data on natural hazards, either by geoscientists or civilian scientist volunteers with appropriate training and guidance.

Fundamental geologic information is needed as the basis for any research efforts in natural hazards, as well as the development of hazard assessment. The most critical need is geologic mapping. Most nations of the world lack modern geologic maps at the appropriate scales needed for natural hazard work. Even if a nation has modern geologic maps, it is unlikely that they will afford complete coverage of it; therefore, much scientific effort remains to be done on a global scale.

Natural hazards also have a cascading nature. For example, flooding may cause landslides, earthquakes may trigger landslides and tsunamis, and volcanoes may trigger landslides and flooding. For example, the lateral blast of the eruption of Mount St. Helens in 1980 triggered what has been called the largest observed landslide on Earth. Most hazard assessments are prepared for a single hazard, so the impacts of a multihazard event may be underestimated. More effort is needed to develop appropriate approaches to account for multiple hazards in an area.

Much work remains to be done in the realm of collecting information, including more efficient delivery, analytical approaches to use the much more robust data streams that can be expected in the future, and the timely development of new and understandable products designed for specific audiences. Also, the interoperability and free and open exchange of natural hazard information globally are needed. There has certainly been progress in some areas, such as the availability of data from seismic monitoring in many parts of the world, the centers that issue volcanic ash advisories, and weather forecasting. However, national and international bodies must improve the situation in the future.

Policymaking and regulation are challenging. When they make decisions, policymakers have to weigh and trade off many variables, including economics, public safety, societal support, practicality, philosophical values, political realities, and science. Often, some of these factors conflict and require compromise and adherence to a long-term vision. In addition, critical factors all too often are ignored (or worse not considered at all) in the decision-making process. The role of geoscientists is to provide the best available scientific information and advice to decision-makers. In addition, the information must be put into the appropriate societal context and solutions must be posed that include investment in research, assessment, monitoring, outreach, and policy.

All these actions require significant investment by society. There are always conflicting needs, and typically investments in identifying, mitigating, and improving resilience to natural hazards are made after such an event has occurred. This approach is reactionary and short term, and as such, lacks a committed social license to forge long-term change and success. Natural hazard science has made great strides in the last half-century. More advancements can be expected in the future. However, as the world population increases, we can expect that more people and critical infrastructure will be in harm’s way. A continuous, determined, and prolonged effort will be required by geoscientists, policymakers, emergency responders, and the public to reduce the impact of natural hazards.

Further Reading

Leahy, P. P. (2006). USGS: Science to build safer communities. Sea Technology, 47(1), 16–18.Find this resource:

National Research Council (NRC). (2011). National Earthquake Resilience-Research, Implementation and Outreach. Washington, DC: National Academies Press.Find this resource:

Schuster, R. L. (1996). The 25 most catastrophic landslides of the 20th century. In J. Chacon, C. Irigaray, & T. Fernandez (Eds.), Landslides: Proceedings of the 8th International Conference and Field Trip on Landslides. Rotterdam, The Netherlands, and Brookfield, VT: Ballema.Find this resource:

U.S. Geological Survey (USGS). (2015). Catastrophic landslides of the 20th century—worldwide. Landslide Hazards Program; retrieved from http://landslides.usgs.gov/learn/majorls.php.

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