Volcanic Risk at Santa María

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This Landsat Thematic Mapper image (ID # 5021050009504010) was collected on February 9, 1995. The false color display has band 5 displayed in red, band 4 in green, and band 2 in blue.

The image shows the entire volcanic hazard zone associated with Santa María Volcano, extending downslope to the south from the volcano (3770 m elevation)to the sea level. The volcano itself is located at the upper right of the figure, and a transparent eruption cloud (white) which is drifting to the south of the volcano can also be seen. The false color image shows heavily vegetated area in green tones, agricultural areas in red and unvegetated rock as blue. The blue tones highlight the volcano and the areas of hazard associated with consequent sedimentation along the Rio Samalá and other rivers of the aggrading alluvial fan of volcanic sediments south of the volcano all the way to the Pacific Coast.

This image was processed by Paul Kimberly at the Laboratory of Atmospheric Remote Sensing at Michigan Tech, and is a part of an effort to map changing hazards using satellite data.

Volcanic Risk Map for Santa María, Guatemala:
What can Risk Maps Contribute to Volcanic Hazard Communications?

B D Green (School of Business and Engineering Administration
Michigan Technological University, Houghton, MI 49931-1295;
e-mail: bdgreen@mtu.edu)

W I Rose (Geological Engineering, Michigan Technological University,
Houghton, MI 49931-1295; 906-487-2531;
e-mail: raman@mtu.edu)

Santa María, an international decade volcano in Guatemala, presents significant volcanic hazards to its surrounding populations from its activity, which has been continuous since 1922. We have prepared a GIS array for the volcano and its surroundings, which combines volcanic hazard zonations with four layers of economic and population data (population, infrastructure, land use, and standard of living). The goal is to present on a single map, the risks of volcanic activity in terms that the public can better understand. The map, which shows the cost of the volcano to the Guatemalan government, to be between 3.3 and 8.4 million dollars U.S. a year, is developed and shared using an internet world wide web vehicle, which facilitates some complex overlays.

Although volcanic hazard maps are now available at many hazardous volcanoes, volcanic risk maps are very rare and may offer some special advantages in Volcanic Hazard Communications efforts. They can be used to forecast the cost of volcanic activity, which may be helpful in securing budgeting for mitigation efforts. They may be used for planning mitigation expenditures, because sensitivity analysis of uncertainties in hazard zonation or recurrence intervals of various types of activity can be tested against economic and population data for cost effectiveness.



Santa María is located in southwestern Guatemala
14.758 degrees N latitude, 91.548 degrees W longitude

Purpose of the paper

To illustrate a methodology for the development
of a Volcanic Risk Map which may be used for:

- forecasting the cost of volcanic activity
- planning mitigation expenditures

Santa María Volcano Hazard Zone Map (fig. 1)

Nature and Source of Hazard Information

1. What geographic area would be affected in a volcanic event?
2. What type of destructive force would take place in that geographic area?
3. What are the probabilities of a volcanic event in a given time period?

Questions 1 and 2 were determined by using an existing Volcanic Hazard Map for Santa María. (Rose, W.I., R. Mercado, O. Matías, and J. Girón, Evaluation de Riesgos del Domo de Santiaguito, Guatemala (Inform Preliminar), INSIVUMEH Guatemala, 21 pp, 1989b)

Probabilities for a volcanic event were estimated by using historic data.
Zone 1: 3 - 8 events in past 20 years
Zone 2: 1 event in past 70 years
Zone 3: Same as Zone 1 due to close relationship between laharic
sedimentation peaks, and block and ash flows with subsequent intense rainfall
Zone 4: Dependence on rainfall and hurricane occurrence

Nature and Source of Economic Data

Standard of Living (adjusted GDP per capita)
Population Density (# of people/hectare)
Infrastructure (kilometers of higways, electrical distribution and transmission lines)
Landuse (dollar value/hectare)


Guatemalan Agencies;
Committee on National Emergencies
Division of Roads
Division of Electrification
Military Institute of Geography
Bank of Guatemala
USAID - Chamber of Industry
U.S. Embassy - Agricultural Section
GIS overlay technique

1. Four maps were compiled using a Geographic Information System (GIS).

Standard of Living (fig. 2) - Based upon municipal boundaries, and also
incorporates; crowding, housing conditions, basic sanitation, availability of potable water, access to basic education, and basic needs. cross section (fig. 2a)
Population Density (fig. 3) - person per hectare. cross section (fig. 3a)
Infrastructure (cross section: fig.4) - high and low voltage transmission lines, and highways.
Land Use (fig. 5) - all economic activities contributing to Guatemalan GDP. cross section (fig. 5a)

2. Maps were rectified to match the same geographic region as Santa María.
3. Maps were then individually overlain with the Hazard Map boundaries.
4. Area (hectares) was calculated for each of the municipalities and hazard zones.

Development of total cost of the volcano

Value = Standard of Living * Population Density + Infrastructure + Landuse
Vulnerability - Measures a proportion (0-100%) of the value likely to be lost
in a given event
Hazard - The probability of a given area being affected by a potentially
destructive process within a given period of time

VOLCANIC RISK = Value * Vulnerability * Hazard

Expected Loss Due to Volcanic Risk (By Hazard Zone) (fig. 6)

    (1 year period)				  VOLCANIC RISK
     U.S. DOLLARS				(dollars/hectares/year)


 1	146,918		323,221			97.34		214.15

 1a	59,915		119,830			96.22		192.43

 1b	33,722		67,444			87.90		175.79

 2a	13,815		27,630			19.02		38.04

 2b	9,357		18,714			7.52		15.04

 3	785,076		1,727,167		863.53		1899.76

 3	1,649,395	3,628,669		209.17		460.18

 4	132,491		519,368			106.63		417.98

 4a	492,612		1,931,039		21.75		85.25

 TOTAL:	3,323,301	8,363,082

Total Economic Value (fig. 7)

   TOTAL ECONOMIC VALUE - By Municipality

   El Palmar:  $1,632.39/ha/yr

   San Andres Villa Seca:  $1,887.83/ha/yr

   Retalhuleu:  $2,067.59/ha/yr

   San Felipe:  $8,920.21/ha/yr

   San Martin Zapotitlan:  $9,365.97/ha/yr

   Santa Cruz Mulua:  $1,071.92/ha/yr

   San Sebastian:  $11,384.24/ha/yr

   Champerico:  $890.53/ha/yr

Areas for further analysis

Which hazard zone is most important economically and what does uncertainty in hazard zones contribute to the risk estimate?

Zone 3:
low estimate $785,076 expected loss due to volcanic risk per year
high estimate $1,727,167 expected loss due to volcanic risk per year
Zone 3a:
low estimate $1,649,395 expected loss due to volcanic risk per year
high estimate $3,628,669 expected loss due to volcanic risk per year

Loss expressed on per hectare per year basis

Zone 3:
low estimate $864/ha/yr
high estimate $1,900/ha/yr
Zone 3a:
low estimate $209/ha/yr
high estimate $460/ha/yr

Consequently, Zone 3 deserves further study because there is large uncertainty in the expected risk.

Additional Considerations: Inclusion of a .5km buffer zone (fig. 7) around the hazard zone (fig. 6) shows a substantial increase in total value.

		Total Hazard Area 	Hazard Area 
		     (fig. 6)		(with .5km buffer zone fig. 7)

Tot. Value  	$70,711,540		$102,672,649

Tot. Area	37,174.90 ha		46,220.92 ha

		Value increase 45%	Area increase 24%

Consequently, further study is needed on the exterior boundary

Other applications for Volcanic Risk Maps

  1. Economic sensitivity analysis of areas around hazard areas
  2. Boundry determination of hazard zones
  3. Potential GDP loss to occupy compared to other potential natural disasters

How can volcanic risk be best represented on a map?

Volcanic Risk can be represented in the following ways;

1. Inclusion of Expected Loss due to Volcanic Risk map (fig. 6) with Volcanic Hazard maps (fig. 1)
2. Use colors to differentiate amounts of risk.
3. Include in the legend a dollar amount expressed by "the expected loss due to volcanic risk"
4. Include maps of the principle economic data used in risk assessment (fig. 2-5)

Such maps are better than strict hazard maps because:

Volcanic Risk maps use data from hazard maps
Volcanic Risk maps incorporate probability of volcanic event
Volcanic Risk maps incorporate economic value and activity
Volcanic Risk maps incorporate vulnerability to destruction

We conclude:
Volcanic Risk maps are a tool to evaluate the real cost of living near a volcano.
This data can be compared with the cost of monitoring and assessing hazards.
The data can be used to assess which areas to focus hazard field work.

Further questions about Volcanic Risk maps

1. Does a volcano bring a positive economic influence to an area?
2. Are there particular economic data that could be efficiently used for calculating volcanic risk?
3. Is the addition of volcanic risk a tool planning agencies would? use?


The volcanic risk map project has demonstrated a methodology that allows for the calculation of the economic impact of an active volcano in dollar terms. It may be useful for disaster preparedness planning, because the real cost of the volcano can be compared with costs of mitigation and monitoring efforts. The assembled data in the GIS format allows ready determination of areas of greatest risk within volcanic hazard zones.


Financial support for this work has come from the National Science Foundation, the U.S. Geological Survey, Volcano Crisis Assistance Team, and from Michigan Technological University.

Many individuals helped:

Ciro Sandoval, Humanities, Michigan Technological University, Houghton, MI.
Patrick Joyce, School of Business Engineering and Administration, Michigan
Technological University, Houghton, MI.
Otoniel Matías, INSIVUMEH, Guatemala City, Guatemala
Rodolfo Morales, INSIVUMEH, Guatemala City, Guatemala
C. Dan Miller and John Ewert, Cascades Volcano Observatory, United States
Geological Survey, Vancouver, WA.
Ann Maclean, Forestry, Michigan Technological University, Houghton, MI.
Mark Books, GIS, Michigan Technological University, Houghton, MI.
Mike Hyslop, GIS, Michigan Technological University, Houghton, MI.
Dulci Bosma, Geological Engineering and Sciences, Michigan Technological
University, Houghton, MI

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