Document Type : Research Article

Authors

• Shaghayegh Pourbabak ¹
• Ali Hosseinzadeh Dalir ²
• Davood Farsadizadeh ²

¹ Department of water engineering

² Department of Water Engineering, Tabriz University, Tabriz, Iran

Abstract

Spur dikes, also known as groynes, are transverse hydraulic structures constructed along riverbanks to protect shores from erosion. By diverting flow away from the bank and concentrating it toward the channel centerline, they improve the hydraulic efficiency of open channels and reduce bank erosion. These structures are commonly installed upstream of bridges. However, spur dikes are highly vulnerable to local scour, especially at the nose (head), due to flow acceleration and vortex formation, which can lead to structural failure. This experimental study examines the effects of nose shape (L-shaped, T-shaped, and straight) and different permeability percentages (0% to fully permeable) on local scour depth around rigid spur dikes under both submerged and unsubmerged flow conditions. Tests were conducted in a laboratory flume with movable bed. Results indicated that all configurations performed better under submerged conditions. Increasing nose and body permeability up to 42.77% significantly reduced scour depth around the body by approximately 35% and at the nose by about 10%. Fully permeable spur dikes showed the best performance in unsubmerged flow, while designs with a rigid body and permeable nose were most effective in submerged conditions. These findings provide practical insights for optimizing spur dike design to minimize scour and enhance stability.

Keywords

• local scour
• spur dike
• permeable spur dike
• compound spur dike
• nose geometry

Main Subjects

• Hydraulics