Transcript The 1999 Venezuelan Flood

The 1999 Venezuelan Flood
Presented
by
Tibi Marin
KDHE/KSU
DEDICATED TO THE
PEOPLE OF VENEZUELA
WHO LOST THEIR LIVES
IN THE 1999
VENEZUELAN FLOOD
MAP OF VENEZUELA
Information about Venezuela
Officially Republic of Venezuela
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Estimated Population: 21,005,000
Surface Area: 352,143 sq mi (912,050 sq km)
Venezuela has a coastline 1,750 mi (2,816 km)
long on the Caribbean Sea in the north.
It is bordered on the south by Brazil, on the west
and southwest by Colombia, and on the east by
Guyana.
Dependencies include Margarita Island,
Tortuga Island, and many smaller island groups
in the Caribbean.
The capital and largest city is Caracas.
INTRODUCTION
Landslides have caused major
socioeconomic impacts on people, their
homes and possessions, industrial
establishments, and lifelines, such as
highways, railways, and communications
systems.
Socioeconomic
losses due to slope
failures are great
and apparently are
growing as the built
environment
expands into
unstable hillside
areas under the
pressures of
expanding
populations and
urban development.
Human activities disturb large volumes of
earth materials in construction of buildings,
transportation routes, canals, and
communications systems, and thus have been a
major factor in increases in damages due to
slope failures, and increasing the extent of
natural disasters such as the 1999 Venezuelan
Flood.
Topography of the Area in Study
• Venezuela is extremely steep and rugged. The crest of the
Sierra de Avila reaches 2,700 m within about 6-10 km of
the coast. The rivers and streams of this mountainous
region drain to the north and emerge from steep canyons
onto alluvial fans before emptying into the Caribbean Sea.
In Vargas little relatively flat area is available for
development with the exception of the alluvial fans.
Nature of geologic event:
• An unusually wet period in 1999 resulted in rainfall
accumulation at sea level on the Caribbean coast of
293 mm for the first 2 weeks of December, followed
by an additional 911 mm of rainfall from December
14 to 16 (MARN, 2000).
• Fifteen days of constant and intense
rainfall in Venezuela culminated on 16
December 1999 in extensive flooding and
massive landslides in seven northern
states of the country.
• Rivers overflowed their banks and swept
through poor districts in the capital city of
Caracas.
THE FLOOD
• The disaster started when
torrential rains triggered
landslides that crashed down
from Mount Avila, a mountain
separating Caracas from the
Caribbean coast.
• The floods affected the South
American country's entire
northern coast, stretching
from the tourist resort
Margarita Island to the
western Zulia state bordering
Colombia.
Nature of geologic event:
• The mountain soil had been weakened by the removal of
vegetation through deforestation caused by urban
development and migration from other nearby countries.
(shantytowns )
• The heavy rainfall caused massive flooding and
debris flows in the channels of major drainages that
severely damaged coastal communities along the
Caribbean Sea.
• In coastal valleys, mud slides buried most of
the towns of Macuto and Caraballeda while
the towns of Los Corales, Camuri Chico and
Carmen de Uria totally disappeared under
avalanches of mud.
GEOLOGIC MAP OF VENEZUELA
• On December 15 and 16, 1999,
landslides (mostly debris flows) and
flash floods along the northern coastal
zone of the state of Vargas and
neighboring states in northern
Venezuela killed an estimated 30,000
people (USAID, 2000), caused extensive
property damage, and changed
hillslope, stream channel and alluvial
fan morphology.
• These shantytowns and resorts had been developing in
the dry riverbeds and on steep unstable hillsides outside
the larger city as part of a wide-scale population shift
from farming regions to urban areas, especially those
migrating from countries such as : Colombia, Ecuador,
Peru and others in search for better jobs.
DEBRIS FLOW IN THE AFFECTED AREA
According to the national government, the
partial figures on the disaster in the country are
projected as follows:
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Persons affected: 331,164
Persons left homeless: 250,000
Disappeared persons: 7,200
Deaths: 50,000
Housing units affected: 63,935
Housing units destroyed: 23,234
• Within this region the Venezuelan
Geological Survey and the Ministry of
Ambient and Natural Resources
characterized geologic conditions where
landslides initiated on hillsides and
examined the texture of debris-flow deposits
in the channels of nine drainages.
Boulders up to 5 m long were carried
along by the flows, impacted structures
causing serious damage, and were deposited
on the fan.
• The volume of debris-flow and flood
deposition on the fan was measured to be
about 2 million cubic meters.
• The total volume of material transported and
deposited by landslides throughout the
Vargas region ranks this as one of the most
severe historical erosional events worldwide.
• Large populations live on or near alluvial
fans in locations such as Los Angeles,
California, Salt Lake City, Utah, Denver,
Colorado, and lesser known areas such as
and Vargas, Venezuela.
• A combination of debris flows that transported
massive boulders, and flash floods carrying
extremely high sediment loads were the
principal agents of destruction
• On virtually every alluvial fan along the
Vargas coastline, rivers incised new channels
into fan surfaces to depths of several meters,
and massive amounts of new sediment were
disgorged upon fan surfaces in quantities of up
to 15 metric tons per square meter.
• Sediment size ranged from clay and sand to
boulders as large as 10 m in diameter.
Sediment and debris including massive
boulders were deposited up to several meters
thick across large sections of alluvial fans in
Camuri Grande and Caraballeda
• The states of Zulia, Falcón, Yaracuy, Sucre,
Anzoátegui and Nueva Esparta were also
affected, but in less degree.
• The fact remains, however, that the
environmental hazards of disease transmission
are heightened, and epidemic outbreaks are
possible, which makes it necessary to assign
priority to epidemiological and environmental
surveillance so that proper sanitary measures
may be taken.
EPIDEMIOLOGICAL REPORT
• The epidemiological and environmental
information was analyzed to determine the
effects on health and the needs for allocation
of resources.
• The states hardest hit by the disaster were
Vargas and Miranda. The effects on the Federal
District (D.F.) was also considered owing to its
geographic contiguity to them and to the fact
that it shares their population dynamics and
similar geololgical makeup
The following factors operate in
the transmission of diseases in
the wake of a disaster:
• The diseases already present in the population prior to
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the disaster and their endemic and epidemic levels.
The environmental changes caused by the disaster.
Population shifts.
Damage to public facilities.
Shortcomings in surveillance and in disease-control
programs.
Changes in the resistance of individuals to diseases.
Diseases already present in the
population
• The danger of an epidemic in the wake of a disaster is
a function of the preceding endemic and epidemic
levels of diseases in the population.
• The recurrently most important diseases are the
diarrheas, dysentery from different causes, measles,
airway infections, meningococcal meningitis,
intestinal parasitoses, scabies and other dermatoses,
tuberculosis, and malaria.
• Predisaster situation of the leading endemoepidemic diseases in Venezuela Malaria: the
cumulative reported incidence in the country in
1999 was below that of 1998.
• In the six epidemiological weeks prior to the
disaster incidence was on the rise. The entire
country was affected, and the states at greatest
risk for this disease were Zulia, Vargas, Sucre,
Portuguesa, Miranda, Falcón, Barinas, and the
Federal District. The situation was aggravated
by the presence of hemorrhagic dengue.
Environmental changes brought
about by the disaster
• These changes could alter the possibilities for
the spread of diseases, the most important of
which are the vector-borne (mainly
mosquitoes) and the water-borne.
• Floods heighten the risk of leptospirosis.
Inadequate collection of solid wastes leads to
the multiplication of flies as a physical vector
for diarrheas and conjunctivitis.
• The water supply is reportedly greatly compromised
in the states of Vargas and Miranda, and water
disinfection is a high priority for the prevention of
water-borne outbreaks (diarrheas, including cholera).
• In building a scenario for the effects on the health of
the population in the short and middle run, it is also
necessary to take account of the outbreaks of diseases
in the wake of natural disasters —among them
leptospirosis, typhoid, food poisoning, minor
infections of the airways, diarrheas, cholera, and
malaria.
MITIGATION
• Because most of the coastal zone in Vargas
consists of steep mountain fronts that rise
abruptly from the Caribbean Sea, the alluvial
fans provide practically the only flat areas upon
which to build.
• Rebuilding and reoccupation of these areas
requires careful determination of hazard zones
to avoid future loss of life and property.
ACTIVITIES TO BE CARRIED OUT
FOR MITIGATION OF RISK FACTORS
1. Internal cleaning of buildings
Mud removal
Rubble removal
Removal of unserviceable articles
2. Cleaning of surroundings and common
areas.
Removal of mud from streets and avenues.
Removal of rubble from streets and avenues.
3. Collection and final disposal of wastes.
Sanitary landfills.
Spillways.
Incineration.
4. Health surveillance and education
Framing and circulation of directives.
5. Provision to the community of reliable
access to drinking water.
6. Repair of the drinking water distribution
system.
7. Health surveillance and education.
8. Ensuring that foods supplied to disaster
victims are in wholesome condition.
9. Sanitary evaluation of establishments that
process foods and dispense them to the
community.
Conclusions
• In Venezuela, the extremely steep,
tectonically active Cordillera de la Costa
forms the boundary with a tropical sea.
• Easterly trade-winds can force moist air
masses upslope and precipitate large
rainfall volumes, creating conditions for
high-magnitude debris flows and flash
floods such as the one in 1999.
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This example from Venezuela shows the
potential for extreme loss of life and
property damage where a large
population occupies an alluvial fan
Without careful planning of human
settlements, the impacts of these types
of disasters are likely to increase in the
future.
• By building communities and other
infrastructure on alluvial fans, dramatic
natural hydrologic processes have been
changed into major lethal events such as
the ones in: California, Venezuela, Peru,
Colombia, Chile, Panama, Kansas.
REFERENCES
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MARN, 2000. Informe Preliminar Sobre los
Aspectos Ambientales Vinculadas al Desastre
Natural Ocurrido en Venezuela Durante el Mes de
Diciembre de 1999.
Wieczorek, G. F., B. A. Morgan, and R. H.
Campbell, 2000. Debris-Flow Hazards in the
Blue Ridge of Central Virginia. Environmental &
Engineering Geoscience, 6(1): 3- 23.
• Garner, H.F., 1959. Stratigraphic-Sedimentary Significance of
Contemporary Climate and Relief in Four Regions of the
Andes Mountains. Geological Society of America Bulletin
70(10): 1327-1368.
• El Nacional. Venezuelan Newspaper El-Nacional.com
• El Universal. Venezuelan Newspaper. El-Universal.com.
• CNN.COM
• www.fema.gov
Report of the Flood in Caraballeda, Venezuela. (Debris-Flow
Deposits and Contours of Maximum Boulder Size on the
Caraballeda Fan, Venezuela)
Wieczorek, G.F., Larsen, M.C., Eaton, L.S., Morgan, B.A.
and Blair, J. L. U.S. Geological Survey
MARN, 1999, Cronica Cartografica de la Catastrofe de
Venezuela: Ministerio del Ambiente y de los Recursos
Naturales (MARN), Servicio Autonomo de Geografia y
Cartografia Nacional, 15 p.
MARN, 2000, Comison ambiental para la evaluation y
tratamiento intergral de las cuencas torrenciales del Estado
Vargas, Informe de advance: Marzo, 2000, 43 p.
•Pierson, T.C., and Costa, J.E., 1987, A rheologic classification
of subaerial and sediment-water flows, in Costa, J.E., and
Wieczorek, G.F., eds., Debris flows/avalanches: Process,
recognition and mitigation: Geological Society of America,
Reviews in Engineering Geology, v. 7, p. 1-12.
•Salcedo, D.A., 2000, Los flujos torrenciales catastróficos de
Diciembre de 1999, en el estado Vargas y en Caracas:
Características y lecciones apprendidas. Memorias XVI
Seminario Venezolano de Geotecnia, Caracas. p. 128-175.
•Schuster, R.L., Salcedo, D.A., and Valenzuela, L., in press,
Catastrophic landslides of South America, S. Evans and J.
DeGraff, eds., Reviews in Engineering Geology, v. 14,
Geological Society of America, pp.