Vargas tragedy

Vargas tragedy

Vargas State, Venezuela
Coordinates	10°36′18.67″N 66°50′58.21″W / 10.6051861°N 66.8495028°W / 10.6051861; -66.8495028
Deaths	10,000–30,000[1]
Location of Vargas in Venezuela

The Vargas tragedy was a natural disaster that occurred in

The coastal area of Vargas State has long been subject to mudslides and flooding. Deposits preserved on the alluvial fan deltas here show that geologically similar catastrophes have occurred with regularity since prehistoric times.^[2] Since the 17th century, at least two large-magnitude debris flow, landslide, or flood events, on average, have occurred each century within the modern boundaries of Vargas. Recorded events occurred in February 1798, August 1912, January 1914, November 1938, May 1944, November 1944, August 1948, and February 1951. In the February 1798 event, flash floods and debris flows severely damaged 219 homes. Spanish soldiers barricaded an upstream-facing entrance to a fort with cannons in order to prevent debris from filling it.^[2]

Prior to the 1999 disaster, the most recent major flood had occurred in 1951, but that event did not cause as much damage.^[2] Based on aerial photos and records of measurements, geologists were able to directly compare the 1951 event to the 1999 event. The 1951 event involved less rainfall than the 1999 event, fewer landslides were triggered, and less fresh debris was observed on the fans.^[2] The unusually strong storm in December 1999 dumped 911 millimeters (35.9 in) of rain over just a few days, triggering widespread soil instability and flow of debris.^[4] Adding to the devastation, Vargas State had experienced high population growth and development since the 1951 disaster, thus increasing the toll of casualties.

The alluvial fans built as sediments from floods and debris flows exit their channels and meet the oceans provide the only extensive flat surfaces along the mountainous coastline of north-central Venezuela. As such, many of them have been extensively developed and urbanized. This high population density increases the risk to life and property from flash flood and debris flow events.

As of 1999, several hundred thousand people lived in this narrow coastal strip in Vargas State. Many of these people lived atop

December 1999 was unusually wet along the north-central Venezuelan coast. The first, and less powerful, storm that month occurred 2–3 December and dropped 200 millimeters (7.9 in) of rain on the coast.[5]

Two weeks later, in a 52-hour span during 14, 15 and 16 December 1999, 911 millimeters (35.9 in) of rain (approximately one year's average total rainfall for the region) was measured on the north-central coast of Venezuela at

Because foliation planes are planes of weakness, these fabrics within the rocks strongly influence landslide and debris flow hazards.^[2] Where the foliation planes are dipping towards a free surface, failure is likely to occur along these planes.^[2]

The alluvial fans that spread out into the sea from valley mouths were built by previous flood and debris flow events.

On the Caraballeda fan, the extent of the 1951 event paled in comparison to the 1999 event. Much of the deposits that constitute the Caraballeda fan are of a thickness similar to those produced in the 1999 event and contain boulders of a size similar to those observed in 1999.[2]

The USGS geologists found paleosols with organic material above and below a 10-meter (33 ft) thick layer of debris flow deposits. The bottom paleosol was radiocarbon dated to 4267 ±38 years Before Present (BP), and the top one was dated to 3720±50 years BP. This means that, at least in this area, the bed aggraded 10 meters (33 ft) in 550 years, for an average rate of about 1.8 cm (0.71 in) per year (though the aggradation occurs only during short-lived events). The scientists were not able to tell whether the deposits were from a single debris flow or multiple events.^[2]

Alluvial fan deltas in this region have shallow slopes. They are poorly channelized because sediment is being added to them from upstream (infilling the channels) at a rate equal to or greater than the rate at which it can be removed.^[2]

Hillslopes are steepened past the angle of repose for noncohesive materials. This oversteepening is more than could be provided for by the frictional resistance of the sandy soils. Internal soil cohesion, negative pore pressure ("soil suction"), soil structure, and/or tree root reinforcement may be responsible for this.^[2]

The debris flows moved rapidly, and many of them were highly destructive. Based on the maximum sizes of boulders measured in the flood deposits and the amount by which the flow on the outside of a bend was higher than that on the inside, geologists estimate the flow velocities to range from 3.3–14.5 meters per second (11–48 ft/s). These rapid, bouldery flows resulted in much of the observed destruction.[2]

In addition to these debris flows, flash floods carrying extremely high sediment loads were very dangerous. Together the flash floods and debris flows destroyed hundreds of houses, bridges, and other structures. They incised new channels to depths of several meters into every alluvial fan delta on the Vargas state coastline, and they blanketed these fans with sediment.^[5]

Of the many communities that were affected by the disaster, the Caraballeda fan was one of the most hard-hit. The intensity of the disaster here is a combination of two factors. First, the Caraballeda fan was heavily urbanized, with many high-rise buildings and multistory houses. Second, it lies at the mouth of the Quebrada San Julián (Saint Julian Ravine), and this watershed produced very large boulders and a massive inundated area. Approximately one-third of the Caraballeda fan was inundated by debris flows, and the entire fan is built of past debris flow deposits.^[2]

The floods and debris flows of 1999 did not follow the eastern channel on Caraballeda. This channel, formed during the 1952 floods, had been lined with concrete and designed to safely transport the flows into the sea. Instead, the debris flows overwhelmed the channel and the flows overtopped the banks wherever the channel changed direction. Once free of the culvert, the channel rapidly avulsed across the fan and spread debris throughout the community. These overbank flows demolished 2-story houses and destroyed the first two stories of apartment buildings. Farther down the fan, the debris flows routed themselves down streets. As the flows progressed, they left thinner and thinner deposits, though they often still exceeded 1 meter (3 feet) in thickness. After several avulsions, the channel roughly followed the pre-1951 flood path.^[2]

USGS geologists estimate the deposit volume to be at least 1.8 million cubic meters (from comparing topographic scans) or 1.9 million cubic meters (from field measurements). This is among the largest rainfall-induced debris flow deposits in recorded history, though volcanic-induced debris flows can be ten times as large. Subaqueous deposition extended the shoreline an additional 40–60 meters into the sea. The deposit thicknesses range from 4–5 meters (maximum of 5.3 meters) near the center of the fan to around 0.5 meters near the pre-flood shoreline. Maximum boulder sizes decreased towards the shoreline due to the decreasing slope of the fan.^[2]

The disaster caused estimated damages between $1.79 and $3.5 billion US dollars.^[2][4] The death toll was considered to be between 10,000^[6] and 30,000^[2]—the exact number of casualties is difficult to determine as there is no reliable census data from the region at that time, especially about shanty towns and small communities that were completely wiped out. Moreover, only some 1,000 bodies were recovered, with the rest swept to sea by the mud or buried in the landslides.^[2] More than 8,000 homes and 700 apartment buildings were destroyed in Vargas, displacing up to 75,000 people.^[2][4] The mudslides significantly altered more than 60 kilometers (37 mi) of the coastline in Vargas. Over 70% of the total population of Vargas State was affected by the disaster. Public services, like water, electricity, phone lines, and land transportation (roads and bridges) completely disappeared in some places. There were no supplies of food and water for months, so most of the population had to be evacuated. Looting and sacking occurred everywhere, forcing the military to implement martial law for more than a year.^[2]

The disaster was of such magnitude that the president of the Red Cross initially presumed more than 50,000 dead. The first priority was to evacuate survivors; more than 100,000 people were ultimately evacuated.^[4] After the disaster, Venezuelan President Hugo Chávez advocated for other Venezuelans to open up their homes, and "adopt a family". Then-First Lady Marisabel Rodríguez de Chávez arranged the temporary sheltering of children that were feared orphaned in La Casona, the Presidential residence in Caracas.^[7] Others offered help, including Major League Baseball shortstop Omar Vizquel, a native Venezuelan, who helped raise over $500,000 in relief funds.^[2] After the initial emergency response, focus shifted to analyzing the causes of the disaster, and working to create a sustainable infrastructure for dealing with future torrential rains.^[2] A disaster relief team from the United States headed up by New Mexico state Senator Joseph Carraro arrived with a medical team and supplies to assess the damage and help those who were displaced. Contact was made with Los Alamos Laboratory in New Mexico to determine if any radioactivity was included in the debris field. Water purification and sleeping units were provided.^[2]

The disaster clean-up soon became politicized. Chávez initially accepted assistance from anyone who offered, with the United States sending helicopters and dozens of soldiers that arrived two days after the disaster. When defense minister Raúl Salazar accepted the United States offer of further aid that included 450 Marines and naval engineers aboard the USS Tortuga, which was setting sail to Venezuela, Chávez told Salazar to decline the offer since "[i]t was a matter of sovereignty". Salazar became angry and assumed that Chávez's opinion was influenced by talks with Fidel Castro; though he complied with Chávez's order.^[1]

As part of its medical internationalism, Cuba provided medical support after the landslides.^[8]: 131 Cuba sent a 450-member medical brigade, which remained in Venezuela after the conclusion of the emergency.^[9]: 162 This experience contributed to Chávez's view that Cuba would be an important partner in the Chávez administration's foreign policy.^[8]: 131

Despite initial dispersals of emergency funds, receiving tens of millions of dollars from international organizations and the announcement of reconstruction plans, little came of the process and Chávez grew distracted with political squabbles, abandoning attention on the tragedy with recovery ultimately halting.^[1] Survivors eventually left their refugee areas and returned to their homes in an attempt to rebuild.^[1] By 2006, the state was back to its pre-disaster population level, and projects were slowly being carried out to rebuild damaged infrastructure.^[6] Over a decade after the tragedy, thousands remained homeless and the value of real estate in zones untouched by the floods declined by as much as 70%, due to the destruction of infrastructure.^[1][2]

Three films were made about the tragedy by Venezuelan filmmakers, all released in 2011; this is said to show the lasting impact of the tragedy that people were still sharing these narratives, especially in a nation with a poor cinema industry.^[12]

• Armero tragedy – A similarly catastrophic debris flow event caused by a volcanic eruption in Colombia in 1985
• Floods in Venezuela