Design, Construction, Installation and Operation of Three Large Scale Netting Fish Barrier Projects

Currently in North America, there are several significant large scale netting fish barriers successfully protecting various species of fish and wildlife in the aquatic and marine environments.  These systems allow major hydroelectric dams, pump storage facilities and nuclear power plants to continue operations while protecting fragile species within their habitat. 

Barrier design entails a thorough site assessment inclusive of species conservation goals, flow rates, forebay bathymetry, period of deployment, potential for debris entrainment, barrier loading and anchoring methods.  Additional operational requirements, such as controlled netting barrier submergence during high flow periods and variations of forebay elevations, are considered.  Following this initial assessment, actual net design commences with respect to netting mesh size, yarn type and gauge, rope supporting methods and material selections. 

In the past decade, significant advancements in high strength, lightweight and highly abrasion resistant synthetic yarns have allowed the development of substantially lower drag netting membranes with far less resistance to water flow.  Dyneema twine is as strong as steel wire of equivalent diameter with one tenth of the weight.  This allows for a much smaller diameter netting twine that is much stronger than more common nylon netting material.  Dyneema netting offers a 20-50% drag reduction, resulting in a substantial reduction in anchoring requirements and costs.  The most successful barrier net applications are constructed using Dyneema netting.  The additional costs of Dyneema netting are offset by superior properties, inclusive of higher strength, greatly reduced drag, low elongation and excellent abrasion resistance.  Dyneema netting is also easier to clean with simple pressure washing methods.

With recent advancements in engineering and design using modern materials, several barrier nets have been successfully operating continuously for more than five years in a variety of environmental conditions.   Three active, successful large scale netting fish barriers are discussed, along with their environmental advantages.