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Catastrophe Risk Management

Understanding the Vulnerability of Hospitals to Natural Disasters

Nathan Gould | December 1, 2004

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Hospitals play a critical role in providing treatment and support to victims in the aftermath of a disaster. For this reason, both hospital administrators and medical staff are extremely sensitive to the types of functions and medical equipment that are necessary to support this vital role. Although the primary focus is, understandably, on patient treatment and care, perhaps an overlooked aspect in the preparation of a hospital complex for disaster response is the vulnerabilities of its structural and mechanical systems to natural disasters like flooding, extreme winds, or earthquakes.

What are the consequences when these vulnerabilities are not understood? Regrettably, when the risks posed by natural hazards are not properly addressed, hospitals may themselves become victims of the disaster. The impact of past natural disasters on hospitals provides a valuable lesson for future preparation.

Tropical Storm Allison

The effects of Tropical Storm Allison on patient care at Houston-area hospitals in June 2001 provided several informative examples of what can go wrong when flood vulnerabilities are not clearly understood. In this case, flooding of the hospitals occurred not from nearby bayous overflowing their banks as was typically expected, but from sheet flow due to intense, short-term rainfall. Figure 1 shows a rainfall map for Harris County, Texas, as a result of Tropical Storm Allison. As rainwater runoff began to overwhelm existing storm drainage systems, the resulting floodwaters flowed overland, inundating basement, ground, and first-floor levels of hospitals throughout the area. The entire electrical room, shown in Figure 2, was inundated with water. Particularly hard hit was the Texas Medical Center. A key vulnerability in almost every case was the location of electrical switchgear and automatic transfer switches.

Figure 1: Rainfall in Harris County, Texas as a result of Tropical Storm Allison

Rainfall in Harris County, Texas as a result of Tropical Storm Allison

Figure 2: Electrical Room that was Fully Inundated as a Result of Tropical Storm Allison

Electrical Room that was Fully Inundated as a Result of Tropical Storm Allison

Electrical switchgear in a building serves as a junction box between the transformer vault, which receives power from the local utility, and large electrical conduits that branch out into a hospital, directing power to numerous sources. If inundated, the switchgear will malfunction, resulting in a complete blackout of the hospital. Repair and replacement of this equipment can cost millions of dollars and take weeks to complete.

To be sure, hospitals have emergency generators to provide back-up power in the event of a loss of main power from the local utility. Transfer from main power to the emergency generators occurs automatically through a transfer switch. However, automatic transfer switches are susceptible to the same type of flood damage as switchgear. Ironically, the emergency generators of many of the hospitals functioned properly, yet were of no value since the automatic transfer switches also failed.

With both types of equipment, the question is "what type of flooding event (e.g., 500-yr storm surge) might be expected to occur, and if such an event happened, are the switchgear and automatic transfer switches protected"? In the case of Tropical Storm Allison, flooding due to sheet flow was not fully accounted for by many of the affected institutions. Moreover, most of the equipment was located below grade in basements that were not adequately protected from flooding.

2004 Hurricanes

In the case of extreme winds, the hurricanes of 2004 that struck Florida provide useful insights into what can go wrong even when the type of event has been taken into account. Hurricane Charley, a weak Category 4 storm, made landfall in Charlotte County along the western coast of Florida. A regional medical center located in the area sustained significant damage to its roof and windows, resulting in rainwater infiltration into patient rooms and other medical service areas. As the storm passed through the area, the hospital lost main power, resulting in the activation of its emergency power generators. However, the generators only had enough diesel fuel to keep the facility operating for 28 hours. A back-up emergency generator and fuel tank, shown in Figure 3, had to be brought in to provide power after the existing generator ran out of fuel. The local water utility also was unable to provide fresh water to the hospital. Hence, patients were evacuated to nearby hospitals on Sunday after the storm hit the site.

Figure 3: Supplemental Emergency Generator and Fuel Supply

Supplemental Emergency Generator and Fuel Supply

Main power was restored to the hospital four days after Hurricane Charlie struck, followed by water service a day later. A month passed before the hospital became fully operational. Given its exposure in a hurricane prone region, the hospital had anticipated, and ostensibly was prepared for, a power outage. However, even though priority is given to restoration of power to medical facilities like a hospital in the immediate aftermath of a hurricane, past experiences have revealed that it can take several days before power is back on following a major hurricane. Hence, it is advisable to have at least a 72-hour supply of fuel available to power the generators.

A four-story patient building of another hospital in Charlotte County sustained major damage to its roof covering and windows, along with an adjoining two-story building housing the operating room, intensive care unit, and the cardiac catherization lab. The resulting rainwater intrusion forced evacuation of patients from these areas. However, nearby a newer, one-story building that housed the emergency room sustained no damage. A major reason was the use of impact-resistant window glazing systems, as shown in Figure 4. In this case, compelled in part by the enforcement of stricter building codes, the designers of the new emergency room were able to mitigate the detrimental effects of wind-borne debris that often cause much of the damage to a building.

Figure 4: Acute Care Facility with Impact Resistant Windows

Acute Care Facility with Impact Resistant Windows

A community hospital located in De Soto County, north of Charlotte County, also sustained widespread damage to its windows and roof coverings. The subsequent intrusion of rainwater and broken glass into the patient rooms resulted in the relocation of patients to interior areas on the first floor. However, though main power was lost as the storm passed through the area, the emergency power generators were able to provide backup electricity to the facility until main power was restored 36 hours later. Moreover, although the local water utility was unable to provide fresh water to the facility, the hospital had a well on-site that they could rely on as a back-up source for fresh water. Hence, the facility was able to remain operational during, and in the aftermath of, the storm.

Hurricane Frances, a weak Category 2 storm, made landfall roughly midway along the Atlantic coastline of Florida, resulting in limited overall damage to a regional medical center located in the area. However, two elevator penthouses on top of the main six-story patient building of the hospital sustained major damage, resulting in a complete loss of the elevator equipment inside, thus rendering all four elevators in a patient tower, serving floors two through six, inoperable. Subsequently, a majority of licensed beds in the obstetrics, pediatrics, and intensive care units were not accessible. Apparently not as much consideration was given to the design of the penthouses in terms of their vulnerabilities to hurricane-force winds and the associated wind-driven rain that accompanies them. Repair of the hospital penthouses following the Hurricane is shown in Figure 5.

Figure 5: Repair of Hospital Penthouses Following Hurricane Frances

Repair of Hospital Penthouses Following Hurricane Frances


The 1971 San Fernando earthquake in California focused considerable attention on seismic safety for hospitals within the State of California. The Veterans Administration hospital in San Fernando and the Olive View hospital in Sylmar experienced significant structural damage with loss of life as a result of the earthquake.

In 1994 the State of California adopted State Senate Bill 1953 (which amended the 1983 Alquist Act) that provided additional requirements to ensure that both structural and nonstructural components in hospitals perform adequately in the event of strong ground motion.

However, there are many areas of the United States that can be classified as being in either a moderate or high region of seismicity that do not have the same stringent requirements as California for the design of hospitals or acute care facilities. Although the new International Building Code will help to enhance the design requirements for new hospitals in the regions outside of California, existing hospitals or acute care facilities will typically not receive the same scrutiny. Considerable attention should be paid to emergency power generation systems and other utilities, in both new and existing hospitals, to ensure that the equipment performs adequately in the event of strong ground motion.


There are important lessons to be learned from past natural disasters. Hospital administrators must first have a clear and complete understanding of the types of natural disasters that can affect their facilities, specifically the magnitude and probability of occurrence. Given these exposures, they must identify vulnerable areas of the hospital complex, particularly those areas that provide essential support to the facility: namely electrical rooms, air handling equipment, fire protection systems, medical gases, and communications. Finally, once exposures and vulnerabilities are identified, they must establish a cost-effective mitigation plan to minimize the risks. Several methods are available to determine the optimal amount of funding to invest in order to reduce the risks posed by natural hazards. Such an investment in mitigation will ensure that a hospital is able to fulfill its essential role as a provider of critical care to victims following a natural disaster.

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