Practitioners of hydraulic structures engineering find nonlinear weirs attractive because they can provide a hydro-economical solution for rehabilitation projects. Their complex flow patterns, wide range of geometries and applications have also contributed to their appeal in academia. In a world increasingly defined by ageing infrastructure, diverse project goals and hydrological extremes, nonlinear weirs, in particular labyrinth and piano key weirs, have emerged as a desirable option for construction.
This proceedings compilation presents the latest research results and innovations in the field on labyrinth and piano key weirs. Each contribution has been reviewed and selected by the International Scientific Committee of the 4th International Workshop on Labyrinth and Piano Key Weirs (7-9 October 2025, Atlanta, Georgia, USA). References to projects at the design and under-construction stage have also been included.
This publication is a useful guide for students, researchers and professionals interested in dams engineering, civil engineering and hydraulic structures engineering.
Sébastien Erpicum is civil engineer and holds a PhD in Applied Sciences from Liege University, Belgium, where he is currently Associate Professor. He is in charge of the Hydraulic Engineering Laboratory - HECE, where he teaches and develops for more than 25 years activities related to hydraulics and hydraulic structures engineering. His expertise covers experimental and numerical modeling with application to more than 50 dams, hydropower and flood risk related projects worldwide. He is the Belgium representative to ICOLD Committee on Hydraulics for dam and has served as Chair of IAHR Hydraulic Structures Technical Committee. In recognition of his work, he was awarded the ASCE Hydraulic Structures Medal in 2020 and the 22nd IAHR Arthur Ippen Award in 2021.
Brian Crookston is a civil engineer and holds a PhD in Water Resources from Utah State University, USA where he is currently an Associate Professor. His research and consulting activities are focused on water sustainability and resiliency in the areas of hydraulic structures, fluvial hydraulics, and modeling and technology. Brian has particular interest in spillways, energy dissipators, river and canal systems, scour and erosion, public safety at hydraulic structures, physical modeling, computational fluid dynamics, and flooding with experience in over 300 dam and flood projects including the design of multiple labyrinth and piano key weirs in the USA. He is the USSD Spillways subcommittee chair, a member of National Dam Safety Review Board Research Workgroup,Vice Chair of the Joint Task Committee National Inventory of Low-head Dams, and has served as Chair of the IAHR Hydraulic Structures Technical Committee.
Greg Paxson is a civil engineer specializing in assessment and design of dams and levees. He currently serves as National Practice Leader for Dams at Schnabel Engineering, where he is responsible for the technical direction of Schnabel’s dam engineering practice. He has expertise in the evaluation of and modifications to existing dams and in the design of new dams. Through his career, he has been involved in all aspects of dam engineering, with specific expertise in hydrologic and hydraulic analyses, hydraulic structures, dam safety, and risk analysis, with a focus on dam rehabilitation design. He has performed and led assessments, evaluations, analyses, and design for more than 100 dams and has been involved in the design of over 20 labyrinth spillways throughout the USA.
