Dam Failure Case Study: El Guapo Dam (Venezuela, 1999)

The El Guapo Dam (constructed 1980) provided flood control and served as the principal source of potable water and irrigation for the Barlovento Region in the state of Miranda, Venezuela. Between December 1999 and January 2000, Venezuela experienced the most extreme period of rainfall ever recorded in the country, 23.14 inches were recorded at Maiquetía, Vargas, Venezuela (exceeding the 0.1% AEP event for many drainages); these events were concentrated over three states: Falcon, Miranda, and Vargas. On December 16th, the resulting runoff caused El Guapo’s reservoir level to rise to within 8 inches of the dam crest (19 feet above normal pool). The spillway chute walls began to overtop and embankment material along the landside of the spillway walls began to erode. Shortly after the chute walls overtopped, the governor of Miranda ordered the evacuation of the downstream population of approximately 10,000 people. The erosion of the embankment and eventual undermining of the spillway structure led to the breach of the reservoir through the spillway area, releasing the upper 98 feet of the reservoir at an approximate peak discharge of 1.8 million cfs. The flood wave, estimated between 25 and 40 feet, killed 10 people, and injured or otherwise affected 11,000 to 15,000 others; destroyed 790 homes and damaged 1,500 others. The dam has since been reconstructed with an RCC foundation for the upgraded spillway (three and a half times as wide as the original), that was designed for the probable maximum flood (PMF), and a new normal pool level 13.1 feet below the original level.