Dam Failure Analysis for Lago de Matrullas Dam, Puerto Rico
The USGS, in cooperation with the Puerto Rico Electric Power Authority, completed a hydrologic and hydraulic study to assess the potential hazard to human life and property associated with the hypothetical failure of the Lago de Matrullas Dam, located within the headwaters of the Río Grande de Manatí.
The Puerto Rico Inspection and Regulation of Dams and Reservoirs Program and the National Dam Safety Program require each dam owner to prepare an Emergency Action Plan (EAP). The EAP must be prepared, maintained, and executed to provide immediate defensive action to prevent or minimize property damage, injury, or loss of life in the event of an emergency-flooding situation caused by dam failure.
The USGS, in cooperation with the Puerto Rico Electric Power Authority, completed a hydrologic and hydraulic study to assess the potential hazard to human life and property associated with the hypothetical failure of the Lago de Matrullas Dam, located within the headwaters of the Río Grande de Manatí (http://dx.doi.org/10.3133/sir20155065). The hydrologic study yielded outflow hydrographs and peak discharges for Lago de Matrullas and other subbasins in the Río Grande de Manatí hydrographic basin for three extreme rainfall events: (1) a 6-hour probable maximum precipitation (PMP) event, (2) a 24-hour PMP event, and (3) a 100-yearrecurrence, 24-hour rainfall event. The hydraulic study simulated the hypothetical dam failure of Lago de Matrullas using hypothetical flood hydrographs generated from the hydrologic study and selected dam breach parameters.
The flood wave resulting from the failure was downstream-routed through the lower reaches of the Río Matrullas, the Río Toro Negro, and the Río Grande de Manatí for determination of water-surface profiles developed from the event-based hydrologic scenarios and “sunny day” (no precipitation) conditions. The Hydrologic Modeling System (HEC–HMS) and the River Analysis System (HEC–RAS) computer programs, developed by the Hydrologic Engineering Center (HEC) of the U.S. Army Corps of Engineers, were used for the hydrologic and hydraulic modeling, respectively. The flow routing in the hydraulic analyses was performed using the unsteady-state flow module available in the HEC–RAS model.
Results from the simulated dam failure of the Lago de Matrullas Dam using the HEC–RAS model for the 6- and 24-hour PMP events showed simulated peak discharges at the dam of 3,149 and 3,605 cubic meters per second (m3 /s), respectively. Dam failure during the 100-year-recurrence, 24-hour rainfall event resulted in a simulated peak discharge of 2,103 m3 /s directly downstream from the dam. Dam failure under sunny day conditions produced a simulated peak discharge of 1,696 m3 /s at the dam assuming the antecedent lake level was at the spillway invert elevation. Floodinundation maps prepared as part of the study depict the flood extent and provide valuable information for preparing an EAP.
Analysis indicated that a failure of the Lago de Matrullas Dam could result in flooding of many of the inhabited areas along stream banks from the Lago de Matrullas Dam to the mouth of the Río Grande de Manatí. Among the areas most affected are the low-lying regions in the vicinity of the towns of Ciales, Manatí, and Barceloneta. The delineation of the flood boundaries near the town of Barceloneta considered the effects of a levee constructed during 2000 at Barceloneta in the flood plain of the Río Grande de Manatí to provide protection against flooding to the near-by low-lying populated areas. The results showed overtopping in the aforementioned levee during 6- and 24-hour probable-maximum-precipitation dam failure scenarios. No overtopping of the levee was simulated, however, during dam failure scenarios under the 100-year recurrence, 24-hour rainfall event or sunny day conditions.
The USGS, in cooperation with the Puerto Rico Electric Power Authority, completed a hydrologic and hydraulic study to assess the potential hazard to human life and property associated with the hypothetical failure of the Lago de Matrullas Dam, located within the headwaters of the Río Grande de Manatí.
The Puerto Rico Inspection and Regulation of Dams and Reservoirs Program and the National Dam Safety Program require each dam owner to prepare an Emergency Action Plan (EAP). The EAP must be prepared, maintained, and executed to provide immediate defensive action to prevent or minimize property damage, injury, or loss of life in the event of an emergency-flooding situation caused by dam failure.
The USGS, in cooperation with the Puerto Rico Electric Power Authority, completed a hydrologic and hydraulic study to assess the potential hazard to human life and property associated with the hypothetical failure of the Lago de Matrullas Dam, located within the headwaters of the Río Grande de Manatí (http://dx.doi.org/10.3133/sir20155065). The hydrologic study yielded outflow hydrographs and peak discharges for Lago de Matrullas and other subbasins in the Río Grande de Manatí hydrographic basin for three extreme rainfall events: (1) a 6-hour probable maximum precipitation (PMP) event, (2) a 24-hour PMP event, and (3) a 100-yearrecurrence, 24-hour rainfall event. The hydraulic study simulated the hypothetical dam failure of Lago de Matrullas using hypothetical flood hydrographs generated from the hydrologic study and selected dam breach parameters.
The flood wave resulting from the failure was downstream-routed through the lower reaches of the Río Matrullas, the Río Toro Negro, and the Río Grande de Manatí for determination of water-surface profiles developed from the event-based hydrologic scenarios and “sunny day” (no precipitation) conditions. The Hydrologic Modeling System (HEC–HMS) and the River Analysis System (HEC–RAS) computer programs, developed by the Hydrologic Engineering Center (HEC) of the U.S. Army Corps of Engineers, were used for the hydrologic and hydraulic modeling, respectively. The flow routing in the hydraulic analyses was performed using the unsteady-state flow module available in the HEC–RAS model.
Results from the simulated dam failure of the Lago de Matrullas Dam using the HEC–RAS model for the 6- and 24-hour PMP events showed simulated peak discharges at the dam of 3,149 and 3,605 cubic meters per second (m3 /s), respectively. Dam failure during the 100-year-recurrence, 24-hour rainfall event resulted in a simulated peak discharge of 2,103 m3 /s directly downstream from the dam. Dam failure under sunny day conditions produced a simulated peak discharge of 1,696 m3 /s at the dam assuming the antecedent lake level was at the spillway invert elevation. Floodinundation maps prepared as part of the study depict the flood extent and provide valuable information for preparing an EAP.
Analysis indicated that a failure of the Lago de Matrullas Dam could result in flooding of many of the inhabited areas along stream banks from the Lago de Matrullas Dam to the mouth of the Río Grande de Manatí. Among the areas most affected are the low-lying regions in the vicinity of the towns of Ciales, Manatí, and Barceloneta. The delineation of the flood boundaries near the town of Barceloneta considered the effects of a levee constructed during 2000 at Barceloneta in the flood plain of the Río Grande de Manatí to provide protection against flooding to the near-by low-lying populated areas. The results showed overtopping in the aforementioned levee during 6- and 24-hour probable-maximum-precipitation dam failure scenarios. No overtopping of the levee was simulated, however, during dam failure scenarios under the 100-year recurrence, 24-hour rainfall event or sunny day conditions.