Los Esteros Spillway, Pecos River, New Mexico: Hydraulic Model Investigation

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Los Esteros Spillway, Pecos River, New Mexico: Hydraulic Model Investigation

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Fletcher, Bobby P.

Tests to investigate the hydraulic performance of the Los Esteros Spillway and discharge channel were conducted using a 1:80-scale model. Emphasis was placed on the development of a design that would pass flows as high as 430,000 cfs without subjecting the downstream dam embankment to excessive surges and current velocities. Approach flows and flows pass1ng over the crest were satisfactory for all anticipated discharges. Discharges above 225,000 cfs induced adverse currents, surges, and stone failure on the downstream face of the dam. Portions of the ravine or discharge channel were excavated and the amount of turbulence, surges, and currents along the downstream face of the dam was reduced to an acceptable level. However, the cost of prototype excavations was considered excessive. Properly designed flow deflectors in the ravine were effective in reducing adverse hydraulic conditions at the downstream dam embankment. The deflectors shifted flow away from the dam and down the Pecos River. A fixed deflector (concrete wall) was effective but considered undesirable for economic reasons. The design adopted by the Albuquerque District consisted of a rock flow deflector in the ravine and a rock fill on the dam embankment constructed of material obtained from the spillway excavation. Although the model indicated that portions of the sacrificial type rock fill would be displaced when subjected to flows above 225,000 cfs, the safety of the dam was not endangered by discharges as high as the design flow of 430,000 cfs.