Leaky barriers: leaky enough for fish to pass?

Perceived as environmental-friendly hydraulic structures, leaky barriers used for natural flood management are introduced into rivers, potentially creating migration fish. Using sustainable, local materials to construct wooden across river channels in upper catchments, these aim slow down the flow, reduce peaks and attenuate flow reaching downstream communities. Yet little is known about their impact on hydrodynamics fish passage. Here, we examined two model barrier designs under 100% 80% bankfull conditions an open channel flume. These included a porous non-porous design, with latter emulating accumulation of brush, sediment leaf material between logs over time. Flow visualization velocity measurements recorded acoustic Doppler velocimetry characterized field upstream barriers. Our behavioural studies revealed that juvenile salmon ( Salmo salar ) movement sections flume was inhibited by design rather than discharge, influencing passage spatial preference, indicating importance criteria facilitate movement.