Flexi Baffle – Culvert Fish Baffle

Improve Fish Passage through Culverts with the Flexi Baffle®!

Second to dams, culverts are the most significant problem for Aquatic Organism Passage (AOP). Removing or replacing culverts is always the best option for improving fish passage and AOP. However, this is not always feasible due to excessive cost or adverse effects to transportation or infrastructure. The Flexi Baffle offers an inexpensive and simple option for improving AOP in culverts and similar conveyances.

A Fish Ladder and a Culvert with Flexi Baffles

Rigid baffles or weirs improve fish passage by reducing water velocities and increase water depth. However, the solid design decreases the hydraulic capacity of culverts and also trap debris, necessitating costly or hazardous maintenance. In contrast, flexible baffles offer an improvement in fish passage without the drawbacks associated with rigid structures.

The Flexi Baffle is a flexible baffle or weir used to improve fish passage through culverts, bridges, and similar structures. The “fish-friendly” design reduces water velocities and increases water depth to improve AOP. In contract to rigid baffles, the flexible design bens

Poorly designed or constructed culverts block salmon, trout, and other fish and aquatic species from their habitats. Repairing or removing culverts is often costly and requires considerable time and resources. We have developed culvert baffles that enhance fish passage effectively and economically.

The Benefits of the Flexi Baffle Design

Traditional solid baffles reduce the hydraulic capacity of a culvert and catch debris, leading to costly and dangerous clean-out requirements. The Flexi Baffle is designed to “bend over” in high flows, maintaining the hydraulic capacity of your culvert. This flexibility also allows debris to pass through the culvert unimpeded. Once the water flow declines, the baffle reorients and creates a fish ladder in your culvert.

Flexi Baffle in a culvert demonstrating improved hydraulic conditions

The Flexi Baffle creates a “weir and pool” design to establish resting pools in a culvert. This reduces water velocity and increases water depth, improving fish passage conditions. As a result, the Flexi Baffle is used to enhance habitat connectivity for a variety of strong and weak swimming species in hundreds of installations worldwide.

Flexi Baffles in a Concrete Flume

Baffles or weirs, like those found in fish ladders, are a proven method for improving fish passage and AOP.  However, a solid weir or baffle often adversely affects the hydraulic capacity of the culvert.  Solid structures can also be damaged during high flow events.  The Flexi Baffle can be adapted to a wide variety of culverts to reconnect fish and other aquatic organisms with their habitat.

Improve Habitat Connectivity

The Flexi Baffle culvert baffle can improve passage for a variety of weak and strong swimming species.  Populations of fish and other aquatic organisms can become isolated by poor culvert passage conditions.  Anadromous species, such as salmon and lamprey can be excluded from spawning grounds.  Poor culvert passage conditions block juvenile eels from important freshwater habitats.  Reconnecting these habitats is the key to conserving these species. 

Maintain Hydraulic Capacity of the Culvert

The Flexi Baffle culvert baffle or culvert weir has a flexible design which allows them to bend over and pass flows during high water events.  After the flood event, the baffle returns to vertical thereby creating resting pools and slowing water velocity which provides improved passage conditions.  The Flexi Baffle is therefore also “culvert friendly”!

The Flexi Baffle is Inexpensive and Simple to Install

Cut and Uncut Flexi Baffles

The Flexi Baffle can be installed in a variety of culvert shapes, sizes and materials. The baffle material is cut vertically at intervals to allow it to be bent and shaped to your culvert.  The Flexi Baffle culvert baffle is installed with common hand tools.  You don’t need expensive tools or a lot of expertise to install. A team of two can install these baffles in most typical culverts in just a few hours. 

We Can Assist with your Fish Passage Design

Our Fish Passage experts can assist you with your specific culvert baffle application.  Each culvert is different.  We can help design the type and configuration of Flexi Baffles that will provide the most benefit for your site.   

We have developed recommendations for the size and spacing of your Flexi Baffles based upon the size, shape and gradient of your culvert. Our intention is to maintain water through the culvert. Installation recommendations can be modified for your particular application or species of interest.

Learn more about our Flexi Baffle Size and Spacing Recommendations.

Flexi Baffles are also very simple to install with common hand tools. We have developed instructions and videos to assist you with installing Flexi Baffles in any type of culvert.

Learn more about our Flexi Baffle Installation Instructions

Check here for interesting articles about our various Flexi Baffle installations and success stories!

Flexi Baffle Blog

We are always available to talk with you about your passage project.

Learn more from our Fish Passage Experts


Before and After Flexi Baffle installation in the Bon Accord Creek Flume. Surrey, British Columbia


Flexi Baffles installed in a Box Culvert by the Nooksack River Salmon Enhancement Association. Whatcom County, Washington State

Staff from the Nooksack River Salmon Enhancement installed Flexi Baffles to improve fish passage through a large box culvert on a tributary of the Puget Sound in Washington State

Flexi Baffle Installation Mill Brook, VT

The White River Partnership installed Flexi Baffles in a culvert on Mill Brook to improve fish passage for brook trout. The installation improved fish passage while maintaining the hydraulic capacity of the culvert.

Johnson Creek Fish Passage Restoration
Portland, OR

After installation of the Flexi Baffles, fish passage conditions improved significantly.

Prior to Culvert Remediation

Before Flexi Baffle installation water flow through the culvert was shallow and fast

Before and After Fish Weir Installation

Improve Fish Passage with Culvert Baffles

Installing Fish Weirs in a Culvert to Improve Fish Passage

Fish Passing Culvert After Fish Weir Installation

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