On-Shore Tsunami Effects

As tsunami waves run-up onto coastal areas, there is churning of silt, sand, and organic matter that is then thrown onto the shore. Onrushing seawater, sand, and debris cause direct damage to structures and roads (Figure 39.2). In addition, persons in the path of the tsunami waves are swept into onrushing waves. They suffer drowning and aspiration of seawater with suspended material as well as blunt injury from heavy debris captured by the waves. Tsunami waves destroy and damage essential service areas, waste management systems, flood control systems, and structures. Because tsunamis are high-energy waves, boats and other offshore objects can be torn from moorings. These objects, along with anchors and other fittings, are thrown violently against the shore, causing direct damage to sea walls, buildings, and other objects in the path of the wave. Once tsunami waves run-up on shorelines, it is not uncommon for automobiles, buses, refrigerators, trees, large rocks, and other debris to be thrown against any object in the path of the waves. Many coastal areas have electrical lines close to shore, raising the risk for disruption of these lines and secondary electrical injury to humans and animals. The rolling, crushing nature of tsunami waves can cause release of biological and chemical toxins from storage containers, automobiles, electrical devices, gasoline stations, and other damaged sources.⁸

Figure 39.2.

During tsunami events, heavy debris is churned onto and off shore, as shown by this large coral rock thrown on shore in the Solomon Islands during the 2007 tsunami.

Source: NOAA, by John Beba, Woodlark Mining Limited.

As tsunami waves recoil, debris and toxins are pulled into the ocean with forces that are close to that of the energy of the oncoming waves (Figures 39.3 and 39.4). Because tsunami waves present in series, debris, chemicals, and suspended material are churned and thrown back and forth to the shoreline and ocean. In addition to damage from heavy objects, toxins, and silt, tsunami run-ups are associated with on-shore fires as natural gas lines and flammable materials and liquids are exposed.¹²

Figure 39.3.

Sri Lanka 2004 tsunami wave striking shore, submerging bases of trees and low-lying buildings. Note the forceful churning of water as the wave is striking.

Source: NOAA, by Chris Chapman, Cambridge, UK.

Figure 39.4.

A Sri Lanka 2004 tsunami wave receding and pulling debris and objects into the ocean with forces that nearly equal the energy of the incoming wave.

Source: NOAA, by Chris Chapman, Cambridge, UK.

Tsunami waves have little effect on deep-water structures as they traverse open waters. They dissipate large amounts of energy as they run-up to shore. Shoreline coral reefs and ecosystems can be severely affected by tsunami strikes, causing long-term loss of marine life and habitats, requiring centuries to replace.¹² Loss of coastal marine ecosystems can lead to loss of fishing grounds and affect tourism and other human industries. Tsunami run-ups in industrialized coastal areas can cause release of environmental toxins including paints, oils, gasoline, detergents, and solvents. Release of these toxins can affect both marine and human populations for extended periods. Release of human and animal biological waste can contaminate and damage food and water supplies for extended periods.

Tsunami waves striking industrialized areas often break natural gas and electrical supply lines. As water recedes, the risk of fire is high from ignition of combustible material left in the wake of the waves. Many of the secondary fires are caused by ignition of oil products, including gasoline, diesel fuel, plastics, and solvents. Because water alone will not extinguish these types of fires, and these burning materials are lighter than water, subsequent onrushing tsunami waves can spread fire and burning debris throughout the affected area. Both thermal and chemical burns of survivors are to be expected when tsunami waves strike industrialized shorelines.

Immediate Tsunami Risks for Humans and Animals

Drowning is the obvious risk for humans and animals when a tsunami strikes an inhabited shoreline. Many persons survive the initial effects of an oncoming rolling wave but are swept to sea to drown in open ocean waters that are churning as tsunami waves strike. Because of this phenomenon, children, women, and the disabled are more likely to drown because they may lack the strength to hold onto stationary objects to avoid being swept out to the open ocean.³ Attempts to survive by clinging to floating debris are often futile because the waves strike and recoil from the shoreline in a churning, mixing motion.

In addition to drowning, death occurs by blunt force injury as heavy objects are thrown against persons and structures as the advancing waves hit the shore. Fatal crush injury and blunt trauma are reported as the second most common cause of death related to tsunamis.¹³ Mortality is also associated with impalement by large pieces of glass and sharp, protruding metal, wood, and vegetable matter formed and exposed by the forces of the tsunami waves (Figure 39.5). Descriptions of persons found impaled through the torso on bamboo shoots, metal rods and pipes, and splintered tree branches and trunks are common. Closed head injury secondary to blunt trauma and blunt force solid organ injury with subsequent hemorrhage are also recognized causes for fatal injury related to tsunami events.¹³ Building collapse from tsunami waves undermining structural foundations is another cause for crush injury.¹³

Figure 39.5.

This picture taken in Karaikal, India, after the 2004 Indian Ocean tsunami shows the debris field left by the tsunami waves. High-force movement of heavy debris and sharp objects within a tsunami wave cause major injuries to exposed humans and animals.

Source: NOAA, by Joseph Trainor, University of Delaware, Disaster Relief Center.

Prolonged serious medical conditions resulting directly from tsunami events are uncommon and most persons either survive to be “ambulatory” or are killed suddenly during the event.^3,14 Table 39.1 lists injuries that can be anticipated in survivors. Lacerations, soft tissue injuries, and orthopedic injuries are most often encountered in the aftermath of a tsunami strike. Because those suffering these injuries are in a contaminated environment, tetanus prophylaxis is a primary concern. In opposition to standard practice in which most soft tissue wounds and lacerations would be immediately sutured or closed, wounds presenting during the acute disaster phase of a tsunami event are often left open to heal by secondary intent or delayed primary closure after thorough irrigation and debridement. Avoiding primary wound closure is necessary because of the contaminated nature of the injuries and concern for retained foreign bodies.

Eye injuries secondary to flying debris and direct injury are common during tsunami events. Frequent episodes of tympanic membrane rupture are also reported and are most likely caused by pressure gradients when victims are submersed in the water of a rolling wave. Facial injuries and dental trauma are also to be expected.

Orthopedic injuries are predominately long bone fractures but also include pelvic fractures and spinal injuries (including cervical spine injury and compression fractures of the thoracic and lumbar spine regions). Amputation of digits and partial hand and foot amputations are commonly reported and are the result of crushing and severing caused by heavy floating debris churned within tsunami waves. Dislocations of the shoulder, elbow, and knee are also to be expected during tsunami events.

Pulmonary injury due to aspiration of contaminated water is frequent in relation to tsunamis.³ Although pneumothorax due to blunt chest injury and barotrauma would be expected, it has not been reported as a predominate injury. Thermal and chemical burns are reported and expected because caustic toxins can be released from containers and fires occur in the aftermath of a tsunami strike.

Public Health Aspects of Tsunami Events

The immediate public health concerns from tsunami events include loss of shelter, food, water, and clothing. Starvation and hypothermia or sunburn and sun exposure are common public health issues immediately after a tsunami strike.¹³ Survivors are often left partially clothed without access to potable water or food. Because debris, including broken glass, splintered trees, and destroyed buildings, are distributed throughout the immediate environment by the waves, mobility is limited and access to food, water, and shelter is difficult. After tsunami events, initial public health activities generally include environmental health actions to develop safe, protected shelter and ready access to drinking water and clothing.³ Providing food appropriate to the cultural norms for the area struck by the tsunami is an important public health priority.

When the immediate needs of the surviving population have been addressed and survivors have moved to safe locations, organized assessment of health-related needs should be conducted. Initial assessments include survey of shelters and survivor collection points; random-cluster analysis of the affected community is often preferred as soon as feasible.¹⁵ Knowledge of local health risks and challenges is essential in planning and conducting a rapid health analysis. For example, if it is known that malaria is endemic in an area struck by a tsunami, those doing a health assessment would survey for accessibility to protective mosquito netting for sleeping quarters and access to DEET or other appropriate mosquito repellents. The recovery phase of the 2004 Indian Ocean tsunami provides an interesting illustration of the importance of knowing local health hazards. Outside experts made unnecessary strong recommendations for complicated cholera vaccination programs in areas struck by the tsunami when cholera was not a threat and had not been present in the area for decades.¹⁶

Information obtained during rapid public health assessments of an affected population is used to plan and implement immediate health responses. Table 39.2 lists the elements most often addressed during a rapid health assessment following a sudden-onset event such as a tsunami. The focus of these health assessments is to make prompt estimates of the health needs of an affected population.¹⁵ Visual inspection, interviews with key personnel, and surveys are the mainstay tools for rapid health assessments.¹⁵

World Health Organization (WHO) evaluations performed during the December 2004 Indian Ocean tsunami provide examples of the importance of rapid health assessments in tsunami events. Evaluation immediately after the event showed that burial of the dead, sheltering survivors, waste and debris removal, and provision of water and food were crucial first efforts to prevent public health failures within the surviving populations. Later health assessments showed that malnutrition, childhood diarrhea, hazardous waste management, and disposal of rotting animal carcasses were a priority. Importantly, rapid health assessments detected measles cases among children in eastern parts of the affected area, allowing for an intensive vaccination program that prevented a measles outbreak among a generally unvaccinated pediatric population.¹⁷

Public health providers must know the hazards and risks that exist within a community and anticipate the challenges these may present in a tsunami event. This is illustrated by the 2011 Tōhoku Earthquake and Tsunami with the release of radioactive material when a nuclear power plant was flooded with ocean water. Knowing the risk that the nuclear plant posed allowed for graduated evacuation from radiation zones and permitted public health officials to anticipate the health and welfare needs of those evacuated, including their mental health support requirements.