Improving Performance of Low-Head Labyrinth Weirs

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Design criteria are presented for optimizing the design of labyrinth weirs operating at low heads. The design data were developed as part of a model study of the Brazos Dam (Waco, TX). A labyrinth weir spillway was proposed as a replacement for the existing gated spillway. One performance criterion was a strict limitation on upstream head rise to minimize flooding of the City's river walk, as well as other private and public property. The labyrinth weir design was constrained by the width of the river channel and the fact that it had to fit within the footprint of the existing structure. Based on these constraints, a labyrinth weir with a sidewall angle in the 7-to 8-degree range was required to obtain sufficient weir length. Laboratory tests were conducted to optimize the performance of 7- and 8-degree labyrinth weirs at low heads featuring different crest shapes. An 8-degree weir with an ogee-type crest proved to be the most efficient design for this application.

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