Natural Hazards in Baltimore

According to FEMA, since 1962, the City of Baltimore has been impacted by the effects of at least 24 major declared natural disasters. Six of those events have occurred in the past three years. The increasing amount of high value commercial and residential development projects in the City, coupled with successful major public events, has contributed to the rising visibility of Baltimore as a desirable international destination that needs to be protected from risks.

The intersection of infrastructure- and population-driven factors, with the potential for an increasing frequency of medium- and high-impact natural hazards, is likely to exacerbate the City’s vulnerability to these hazards.


Click each item below to learn about the natural hazards that the Disaster Preparedness Project and Plan identified as events which the City of Baltimore has faced in the past and is likely to encounter again in the future.

The following hazard descriptions are extracted from the Disaster Preparedness Project and Plan (2013) document.

FLOODING

Hurricane Able 1952
Hurricane Able 1952

Flooding occurs when rivers, creeks, streams, ditches, or other hydrological features receive too much water. Three categories of flood are common in the State of Maryland: flash, riverine, and coastal. Learn more flood facts.

Dam Flooding
There are also risks of flooding associated with dam failure, the collapse or breach of a dam structure, for which there is often either very little or no advance warning. While most dams in the Baltimore region have relatively small water volumes and failures would therefore have little or no repercussions, dams with larger storage volumes can have disastrous consequences should they fail.

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COASTAL HAZARDS

Isabel Trees_Tropical Storms and Hurricanes
Tropical storms and hurricanes are very intense, low-pressure wind systems that form over tropical or subtropical waters. Both tropical storms and hurricanes are considered tropical cyclones; the distinction, however, is based on wind speeds and, typically, on the amount of destruction produced (i.e. the “impact”).

In Baltimore, hurricanes and tropical storms have produced wind damage, riverine flooding along tributaries, and inundation of shorelines and harbors by way of intense storm surges.

Sea Level Rise Data for Baltimore, MD
Sea Level Rise Data for Baltimore, MD

Sea Level Rise
For a number of reasons — including climate change and an anticipated increase in global temperature — the world’s sea levels have been rising in the past 100 years. In Baltimore, NOAA sea level gauges at Fort McHenry, as well as other official reports, have shown that relative sea level in the Harbor area has increased by 12 inches since 1900. The most current sea level data from the Maryland State Climate Change Commission, and from the Intergovernmental Panel on Climate Change, indicate that sea levels in the Baltimore region could experience an additional rise of 1.5 to 3 feet in the next 50 years. Approximately 1.33 percent of Baltimore City land is within the projected sea level rise zone.

Tsunamis
As stated in the 2011 Maryland State Hazard Mitigation Plan, “a tsunami is a series of sea waves caused by the displacement of a large volume or body of water. Tsunamis may result from local or distant large-scale seafloor displacement, including seismic activity, volcanic activity or landslides that generate uplift or drop in the ocean floor.”

Recent oceanic events have introduced new concerns regarding potential vulnerability of coastal areas such as Baltimore to unusual hazards such as Tsunamis.

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PRECIPITATION VARIABILITY

October 29, 2012 - Hurrican Sandy 028-LThe amount of precipitation that falls will vary widely as global temperatures increase. Precipitation events are likely to increase in magnitude in Baltimore City, leading to increased flash flooding. Among the many harmful effects of climate change, increased stormwater runoff and demand for stormwater management are anticipated to be some of the greatest challenges facing cities.

 In Baltimore, studies suggest that precipitation could increase by as much as 227mm each year by the middle of the century. At the same time, the Northeast Region is expected to experience more frequent heavy precipitation events — where more than 2 inches of rain falls within a 48 hour time period — while the intensity of heavy precipitation events is projected to increase by 12-15 percent.

Thunderstorms
When atmospheric conditions combine to provide moisture, lift, and warm unstable air that rapidly elevates, a thunderstorm is formed. Thunderstorms can occur at any time of day and in all months of the year, but are most common during summer afternoons or evenings and in combination with frontal boundaries. Thunderstorms are considered a significant hazard due to their ability to spawn tornadoes, hailstorms, strong winds, flash floods, and damaging lightning. Maryland experiences approximately 20-40 thunderstorm days per year, and thunderstorms frequently occur in Baltimore.

Lightning in Federal Hill [Source: weblogs.marylandweather.com]
Lightning in Federal Hill [Source: weblogs.marylandweather.com]

Lightning
Every thunderstorm is accompanied by lightning; in fact, the actual sound of thunder is a direct result of lightning. Lightning often strikes outside of areas where rain is actually falling, at times appearing as far as 10 miles away from rainfall. It can strike from any part of the storm, and may even strike after the storm has seemed to pass. Additionally, a lightning bolt can warm the surrounding air to temperatures as high as 60,000° Fahrenheit. In Baltimore, lightning strikes have been the cause of significant property damage throughout the years, and have even taken the lives of City residents. As the frequency and intensity thunderstorms increases, so will the lightning associated with these storms.

Hail
Hail is another dangerous by-product of severe thunderstorms. In Baltimore, the largest size hail measured between 1950 and 2012 had been 1.75 inches. Although hail in Baltimore had not caused significant economic losses during this period, hail causes about $1 billion in damages annually in the U.S. Hail is already a known occurrence in Baltimore. Though climate scientists predict more frequent and intense severe storms in the future, it is difficult at this point to establish any long-range projections regarding the future impact of hail in Baltimore.

[Source: Ready.gov]
[Source: Ready.gov]

Winter Storms and Climate Influences
Winter storms produce more than just snow. Winter weather can take many forms, including freezing rain, sleet, extreme cold and high winds. These conditions may occur singly or in any combination. Regarding winter weather projections, the noticeable uptick in major winter storm events in Baltimore since 1996 has been compared to the relatively snowy periods in the 1950’s and 1960’s. This suggests that although climate change has influenced average temperatures, it is also possible that the Baltimore region could experience increased precipitation in the form of snowfall due to increased moisture content driven by rising evaporation from warmer bodies of water.

Nor’Easters
Some of the most significant winter storms that affect Maryland are known as “Nor’easters” because they are accompanied by strong northeast winds. Winter storms can be life-threatening events. From reports between 1993 and 2010, Winter Storms accounted for a total of 8 deaths and 166 injuries in Baltimore City.

Drought
Droughts are extended periods of dry weather, caused by a natural reduction in the amount of precipitation over an extended period of time. While occurring less frequently in Baltimore City than in surrounding jurisdictions, meteorological and hydrologic droughts are natural hazards that present major threats to the City and regional water supply. Such droughts may ultimately evolve into socioeconomic droughts in which the City’s ability to deliver water to residents or businesses becomes limited. Additionally, Baltimore provides public water to areas outside of the City’s boundaries; therefore, a drought may greatly diminish water supplies that are available not only to the City of Baltimore, but also to the surrounding counties.

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WIND

Wind is the motion of air past a given point caused by a difference in pressure from one place to another. Wind poses a threat to Maryland in many forms, including winds that are produced by severe thunderstorms and tropical weather systems. The effects of wind can include blowing debris, interruptions in elevated power and communications utilities, and intensified effects of winter weather. Harm to people and animals, as well as damage to property and infrastructure, may result.

Tornado_Baltimore_June2013_TwimgTornados
A tornado is a violent atmospheric disturbance characterized by one or more twisting and funnel-shaped columns, extending from a thunderstorm cloud toward the ground. Tornadoes can touch the ground with winds over 300 mph. While relatively short-lived, tornadoes are intensely focused and are one of nature’s most violent storms.

Tornado season is generally noted to last from March through August — although tornadoes may occur at any time of the year — and more than 80 percent of tornado strikes happen between noon and midnight.

Nationwide, tornadoes account for an average of 70 fatalities and 1,500 injuries each year. From events reported between 1950 and 2010, tornados in Baltimore produced a total of $203,617 in reported property damage, or $3,338 annually.

Derechos
DerechoDerechos are large thunderstorm clusters that produce widespread and long-lasting winds which can be extremely damaging. The impact of a derecho is similar to that of a hurricane making landfall, and can be many miles wide and several hundred miles long.

Derechos occur most often in the Midwest and Great Lakes region during the summer months. In the Mid-Atlantic region, derechos are less common — occurring once every two to four years in Maryland. Consequently, residents have typically been less familiar with this type of storm designation. The term, however, was recently marked in the memories of many Baltimore residents following the devastation of a June 29, 2012 Mid-Atlantic and Midwest derecho. According to the National Weather Service, this storm, which was exceptionally severe in the Baltimore/ Washington region, brought gusts of wind between 65 and 75 mph. As a result, numerous overhead electrical units suffered damage, two individuals were electrocuted by downed power lines, and more than one million customers across the region were left without power.

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EXTREME HEAT

A diagram illustrates the Urban Heat Island (UHI)
A diagram illustrates the Urban Heat Island (UHI)

An extreme heat condition is identified when prolonged temperatures are 10° or more above the average high temperature for a region. In Baltimore’s past, between the 1950’s and the 1970’s, an average of 60 percent of summer days had met the maximum temperature extremes. In the 2000’s, that percentage grew to approximately 75-90 percent of summer days reaching maximum temperature extremes. Studies predict that Baltimore may experience between 85-95 percent such days before the middle of the century, or between 90-95 percent by 2100.

Extreme heat events are the most dangerous natural hazard in the United States, contributing to an average of 675 deaths per year. In fact, on average, excessive heat claims more lives each year than floods, lightning, tornadoes and hurricanes combined.

According to the U.S. State of the Climate report, 2012 was the warmest year on record in the contiguous United States, in records dating to 1895. In 2012, Baltimore City had its warmest year on record since 1949.

For more information on preparing for heat events in Baltimore City, please visit: http://baltimorehealth.org/info/emergency/code-red/2009_06_25CodeRedGeneralreduced.pdf

Air Quality & Respiratory Illnesses

A Baltimore Resident suffers in the heat
A Baltimore Resident suffers in the heat

Health risks associated with heat — particularly risks that worsen symptoms triggered by respiratory diseases — are further provoked by diminished air quality. Trees and other vegetation cool the surrounding air and are shown to help to improve air quality. According to the American Lung Association, Baltimore City received a D Grade in the 2013 Air Quality Report Card.

Vector-Borne Diseases
Warmer, wetter conditions help insects and diseases flourish. In a changing climate, increases in average temperature, precipitation, and humidity will enable disease-carrying vectors and pathogens to infiltrate urban environments more easily. These conditions create favorable environments, for example, for breeding mosquitoes, which are known carriers of disease. Already, Baltimore has experienced a growing population of the tiger mosquito, originally native to Southeast Asia.

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LAND HAZARDS

Did you feel the 2011 earthquake that originated in Virginia?
Did you feel the 2011 earthquake that originated in Virginia?

Earthquakes
An earthquake, also called a seismic event, is a trembling of the ground caused by the sudden movement of large sections — called tectonic plates — of the Earth’s outermost crust.

While no earthquake epicenters have been located within the City of Baltimore, strong earthquakes are capable of being felt for hundreds of miles. In 1897, the Giles County Virginia Earthquake measured 2.0 MMI in Baltimore. The strongest earthquake felt in the Baltimore region, however, was another Virginia earthquake that measured an intensity of 5.8, originating in Louisa County on August 23, 2011. This event caused considerable damage in Baltimore; a number of buildings were damaged, including the historic and celebrated Baltimore Basilica, which reported between $3-5 million in damages.

Subsidence
Land subsidence is the gradual settling or sinking of the Earth’s surface. Subsidence may be gradual or sudden and can range in extent—from broad, regional reductions in elevation to localized areas of collapses.

Regional subsidence is believed to be the result of post-glacial rebound following the last glacial maximum. The mass of the ice sheet had displaced land, pushing the surrounding land upward at the ice sheet’s coverage (Chesapeake Bay region in Maryland). Ever since the ice sheets retreated, the elevated area has been subsiding. At the regional level, Maryland has been subsiding at a rate of approximately 1.5 mm/yr. Recent climate assessments have reported Baltimore’s rate of land subsidence to have been roughly half a foot in the last century. When coupled with rising waters, local land subsidence can exacerbate relative sea level rise.

Monument Street Sinkhole
Monument Street Sinkhole

Urban Karst/Sinkholes
The term “karst” refers to land that is characterized by various subterranean features—including sinkholes, caves/caverns, underground streams, and other features that are formed by the dissolution of calcium and magnesium oxides in certain rocks.

In addition to natural processes, however, sinkholes can be induced through human actions. Human-induced sinkholes can be triggered by simple alteration in the local hydrology. Inadequate drainage along highways and increased runoff from pavement can also be sources of sinkhole development. In Baltimore, infrastructure-related sinkholes have been the primary concern.

In August of 2012, following heavy rains, a sinkhole opened on Baltimore’s East Monument Street above a 120-year-old drainage culvert. When another storm released an estimated one to three inches of rain on top of the repair effort, emergency workers were forced to once again evacuate the site.

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