Fish Pass Design  /  Flow Modelling

Salmon leaping at man-made obstruction

Introduction

With fisheries in decline across the world the importance of protecting fish stocks and their spawning grounds is becoming ever more important. 

Most European rivers are heavily managed and have been regulated by industrial usage for the last 200+ years.  Rivers have been dammed and weirs or waterfalls built at intervals along their lengths to provide:  power for industrial use; protection to urban areas in times of flood;  or locks for navigation.  More recently hydro-power turbines and coastal flood defences have become serious barriers to migrating fish.

It is a statutory requirement that any new structure in a river system supporting migratory fish, or the repair of an existing structure that has been severely breached, must include effective fish passage arrangements.  It is of no benefit to protect adults by regulating fisheries if they cannot reach their spawning grounds. 

An existing pool and traverse fish pass in need of re-design—scouring of the channel bed has caused  a drop in water levels, this fish pass has become an obstruction to migrating salmonids.