Aquatic crossings, like culverts, play a crucial role in maintaining ecological connectivity and facilitating wildlife movement across landscapes fragmented by human infrastructure. Designing these crossings to be wildlife-friendly can significantly enhance biodiversity and support ecosystem health. Below are key considerations and strategies for creating effective aquatic crossings.

What is the guidance for creating aquatic crossings? Aquatic crossing guidance typically refers to the guidelines and the best practices for designing and constructing structures similar to bridges and the creation of safe passages for aquatic organisms. These guidelines are considered crucial for maintaining ecological continuity and minimizing the impact on stream habitats. These guidelines usually consist of hydrology, species needs, geomorphology, and construction practices.

Understanding the Needs of Wildlife

Before designing an aquatic crossing, it is essential to understand the specific needs of the wildlife species in the area. Consider the following aspects:

Species Diversity: Identify the different species that inhabit the area and their specific movement patterns.

Habitat Requirements: Determine the habitat features that are critical for these species, such as vegetation, water quality, and cover.

Behavioral Patterns: Study the seasonal and daily movement patterns of wildlife to ensure crossings are accessible when needed.

Design Considerations

Effective design of aquatic crossings should incorporate the following elements:

Appropriate Structure Type

• Bridges: Suitable for larger water bodies, bridges can allow for unobstructed flow and passage of aquatic species.
• Culverts: These are more appropriate for smaller streams and must be designed to accommodate both terrestrial and aquatic wildlife.

Natural Substrates: Use natural materials like rocks and native plants to mimic the surrounding environment, making the crossing more inviting and familiar for wildlife.

Size and Placement: Ensure that crossings are wide and high enough to allow the free movement of both water and animals. Place crossings in locations that align with natural wildlife corridors.

Environmental and Engineering Practices

Integrating environmental and engineering practices is key to creating sustainable aquatic crossings:

Hydrological Considerations: Design crossings to manage water flow effectively, reducing the risk of erosion and maintaining natural hydrological cycles.

Habitat Connectivity: Ensure that crossings connect key habitats, allowing wildlife to move freely between feeding, breeding, and shelter areas.

Monitoring and Maintenance: Regularly monitor crossings for blockages or damage and perform necessary maintenance to ensure they remain functional and effective.

Implementing aquatic crossings that are beneficial to wildlife offers numerous advantages:

• Biodiversity Conservation: Enhances the survival of multiple species by maintaining genetic diversity and population stability.
• Ecosystem Services: Supports ecosystem functions such as nutrient cycling and water purification.
• Reduced Human-Wildlife Conflict: Minimizes roadkill and other negative interactions between wildlife and human activities.

By considering these principles and integrating them into the design and construction of aquatic crossings, we can support the movement and survival of water wildlife, contributing to healthier ecosystems and more harmonious coexistence between humans and nature.

Check out the AQUATIC ORGANISM PASSAGE AT HIGHWAY CROSSINGS: AN IMPLEMENTATION GUIDE by the US Department of Transportation Federal Highway Administration.