Case study: Dam safety during construction, lessons of the overtopping diversion works at Aguamilpa Dam

A study on risk analysis by overtopping of the diversion works of Aguamilpa Dam in Mexico was carried out to examine the overtopping event of January, 1992. Specifically, this study focuses on the upstream water surface elevation during the flood considering the tunnel discharge actual width and roughness. During this maximum flow event, the upstream cofferdam was overtopped and the discharge tunnels exceeded their maximum hydraulic capacity. The risk analysis was made considering the original hydrologic data (until 1992), the final constructed conditions, to establish a performance function that compares the risk of original deterministic analysis with a probabilistic analysis made in 1992. The study also focuses on practical improvements in the construction stage of tunnels; like lining the floor with hydraulic concrete and shotcrete in vaults and walls, that improves the safety of dams during construction and increases the real return period. The work here is presented as a case study because of the unique large-scale flow conditions that are registered in diversion works of dams.