Rohn Emergency Scale
Encyclopedia
The Rohn Emergency Scale is a scale
on which the magnitude (intensity) of an emergency
is measured. It was first proposed in 2006, and explained in more detail in a peer-reviewed
paper presented at a 2007 system sciences conference. The idea was further refined later that year. The need for such a scale was ratified in two later independent publications. It is the first scale that quantifies
any emergency situation based on a mathematical model
. The scale can be tailored for use at any geographic level – city, county, state or continent. It can be used to monitor the development of an ongoing emergency event, as well as forecast the probability and nature of a potential developing emergency and in the planning and execution of a National Response Plan
.
(a) scope;
(b) topographical change (or lack thereof); and
(c) speed of change.
The intersection of the three dimensions provides a detailed scale for defining any emergency, as depicted on the Emergency Scale Website.
, Gross Regional Product
, or any similar measure of economic activity appropriate to the entity under emergency.
Non-topographical emergencies are situations where the emergency is non-physical in nature. The collapse of the New York stock market in 1929
is such an example, and the global liquidity crisis of August 2007 is another example.
The model treats topographical change as a continuum ranging between 0 and 1 that gives the estimated visual fractional change in the environment.
.
These parameters are defined as follows:
The model loosely assumes that a society whose majority of the population (70% in this model) is affected and half of its GNP is drained as a result of a calamity reaches a breaking point of disintegration. Sociologists and economists may come up with a better estimate.
or zero for non-topographical events.
and 
comprise the rate of change that is of utmost importance to society and therefore incorporated in the model.
Scale (social sciences)
In the social sciences, scaling is the process of measuring or ordering entities with respect to quantitative attributes or traits. For example, a scaling technique might involve estimating individuals' levels of extraversion, or the perceived quality of products...
on which the magnitude (intensity) of an emergency
Emergency
An emergency is a situation that poses an immediate risk to health, life, property or environment. Most emergencies require urgent intervention to prevent a worsening of the situation, although in some situations, mitigation may not be possible and agencies may only be able to offer palliative...
is measured. It was first proposed in 2006, and explained in more detail in a peer-reviewed
Peer review
Peer review is a process of self-regulation by a profession or a process of evaluation involving qualified individuals within the relevant field. Peer review methods are employed to maintain standards, improve performance and provide credibility...
paper presented at a 2007 system sciences conference. The idea was further refined later that year. The need for such a scale was ratified in two later independent publications. It is the first scale that quantifies
Quantification
Quantification has several distinct senses. In mathematics and empirical science, it is the act of counting and measuring that maps human sense observations and experiences into members of some set of numbers. Quantification in this sense is fundamental to the scientific method.In logic,...
any emergency situation based on a mathematical model
Mathematical model
A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used not only in the natural sciences and engineering disciplines A mathematical model is a...
. The scale can be tailored for use at any geographic level – city, county, state or continent. It can be used to monitor the development of an ongoing emergency event, as well as forecast the probability and nature of a potential developing emergency and in the planning and execution of a National Response Plan
National Response Plan
The National Response Plan was a United States national plan to respond to emergencies such as natural disasters or terrorist attacks. It came into effect in December 2004 , and was superseded by the National Response Framework on March 22, 2008....
.
Existing emergency-related scales
Scales relating to natural phenomena that may result in an emergency are numerous. This section provides a review of several notable emergency related scales. They concentrate mainly on weather and environmental scales that provide a common understanding and lexicon with which to understand the level of intensity and impact of a crisis. Some scales are used before and/or during a crisis to predict the potential intensity and impact of an event and provide an understanding that is useful for preventative and recovery measures. Other scales are used for post-event classification. Most of these scales are descriptive rather than quantitative, which makes them subjective and ambiguous.- 1805 Beaufort ScaleBeaufort scaleThe Beaufort Scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort Wind Force Scale.-History:...
- 1931 Modified Mercalli Intensity Scale
- 1935 Richter Scale
- 1969 Saffir-Simpson Hurricane ScaleSaffir-Simpson Hurricane ScaleThe Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds...
- 1971 Fujita scaleFujita scaleThe Fujita scale , or Fujita-Pearson scale, is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation...
(superseded by Enhanced Fujita ScaleEnhanced Fujita ScaleThe Enhanced Fujita Scale rates the strength of tornadoes in the United States based on the damage they cause.Implemented in place of the Fujita scale introduced in 1971 by Ted Fujita, it began operational use on February 1, 2007. The scale has the same basic design as the original Fujita scale:...
in 2007) - 1982 Volcanic explosivity indexVolcanic Explosivity IndexThe Volcanic Explosivity Index was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions....
- 1990 International Nuclear Event ScaleInternational Nuclear Event ScaleThe International Nuclear and Radiological Event Scale was introduced in 1990 by the International Atomic Energy Agency in order to enable prompt communication of safety significance information in case of nuclear accidents....
- 1999 Air Quality IndexAir Quality IndexAir quality is defined as a measure of the condition of air relative to the requirements of one or more biotic species or to any human need or purpose. Air quality indices are numbers used by government agencies to characterize the quality of the air at a given location...
- 2001 US Homeland Security Terror Alert Scale
Variables common to all emergencies
According to the Rohn Emergency Scale, all emergencies can be described by three independent dimensions:(a) scope;
(b) topographical change (or lack thereof); and
(c) speed of change.
The intersection of the three dimensions provides a detailed scale for defining any emergency, as depicted on the Emergency Scale Website.
Scope
The scope of an emergency in the Rohn scale is represented as a continuous variable with a lower limit of zero and a theoretical calculable upper limit. The Rohn Emergency Scale use two parameters that form the scope: percent of affected humans out of the entire population, and damages, or loss, as a percentile of a given Gross National Product (GNP). Where applied to a specific locality, this parameter may be represented by a Gross State ProductGross state product
Gross state product is a measurement of the economic output of a state or province...
, Gross Regional Product
Gross Regional Product
A metropolitan area's gross regional product, i.e. GMP or GRP, is one of several measures of the size of its economy. Similar to GDP, GRP is defined as the market value of all final goods and services produced within a metropolitan area in a given period of time.-See also:*List of European...
, or any similar measure of economic activity appropriate to the entity under emergency.
Topography
A topographical change means a measurable and noticeable change in land characteristics, in terms of elevation, slope, orientation, and land coverage. These could be either natural (e.g., trees) or artificial (e.g., houses).Non-topographical emergencies are situations where the emergency is non-physical in nature. The collapse of the New York stock market in 1929
Wall Street Crash of 1929
The Wall Street Crash of 1929 , also known as the Great Crash, and the Stock Market Crash of 1929, was the most devastating stock market crash in the history of the United States, taking into consideration the full extent and duration of its fallout...
is such an example, and the global liquidity crisis of August 2007 is another example.
The model treats topographical change as a continuum ranging between 0 and 1 that gives the estimated visual fractional change in the environment.
Speed of change
An emergency is typified by a departure from normal state of affairs. The scale uses the change of the number of victims over time and economical losses over time to calculate a rate of change that is of utmost importance to society (e.g., life and a proxy for quality of life).Emergency scale mathematical model
The scale is a normalized function whose variables are scope (S), topography (T), and rate of change (D), expressed as.These parameters are defined as follows:
Scope
- where
- where
- β is a coefficient which the model creator calculated to be 1.26 ± 0.03,
- and
, - where
The model loosely assumes that a society whose majority of the population (70% in this model) is affected and half of its GNP is drained as a result of a calamity reaches a breaking point of disintegration. Sociologists and economists may come up with a better estimate.
Topographical change
or zero for non-topographical events.Rate of change
and comprise the rate of change that is of utmost importance to society and therefore incorporated in the model.
Simplified scale for public communications
In some instances, it may be preferable to have an integral scale to more simply and dramatically convey the extent of an emergency, with a range, say, from 1 to 10, and 10 representing the direst emergency. This can be obtained from the function above in any number of ways. One of them is the ceiling function. Another one is a single number representing the volume under the 3D emergency scale.External links
- http://memagazine.asme.org/web/LargeScale_Disasters.cfm "Large-Scale Disasters as Dynamical Systems" (ASME) provides an alternative measure of general disaster scaling.