Fishway - Trapezoidal

Trapezoidal fishways are a pool-type fishway with a straight concrete channel divided by a series of precast single-unit baffles (similar to the cone fishway design, but the whole ridge acts as a baffle). Trapezoidal fishways are generally used on low weirs, and depending on the length of the fishway, resting pools are incorporated to allow fish to rest as they move upstream.

The unique trapezoidal configuration separates pools into two zones: a migration corridor (along the outsides) and an energy dissipation zone (central). This design has been found to produce low water velocities and turbulence which assist in passing small-bodied fish species.

Case Study - Wyong Weir

The original Wyong Weir fishway was constructed in 1993 and was a full width (natural) rock ramp. By the late 2000s, a number of issues had been identified with the fishway that reduced its effectiveness in passing fish, particularly at low flows.

An opportunity arose in 2010 to upgrade the fishway along with the proposed Wyong Council’s water management system. Following an extensive investigation, a trapezoidal fishway was determined to be the preferred design as it would provide a cost-effective fish passage solution during low flows while maintaining the original adjacent rock ramp fishway for high flow periods.