Culverts

Culverts are small pieces of infrastructure with big impacts on rivers, roads, and communities. These structures carry streams under roads, railways, and trails, allowing water to continue flowing downstream while maintaining safe transportation routes above. Across the Sudbury, Assabet, and Concord (SuAsCo) watershed, thousands of culverts quietly move water beneath our infrastructure every day. When they function well, they protect roads from flooding and allow rivers, fish, and wildlife to move naturally through the landscape. But many culverts in our watershed were installed decades ago, before modern engineering standards and before the impacts of climate change were widely understood.

Culverts are one of the most common ways streams intersect with infrastructure. Because they control how water moves across the landscape, their design and condition directly affect:

Flooding and stormwater management
Road and infrastructure safety
Stream stability and erosion
Fish and wildlife movement
Overall watershed health

A well-designed culvert allows a stream to flow naturally beneath a road or trail. But when culverts are too small, poorly installed, or deteriorating, they can create major problems.

There are approximately 2,300 culverts in the SuAsCo watershed, and only around 350 have been assessed. Many crossings still need to be evaluated to understand their condition, flooding risk, and ecological impacts.

Building on Our Early Culvert Work

OARS first began looking closely at culverts in 2010, when volunteers conducted stream crossing surveys in the Nashoba Brook and Fort Pond Brook subwatersheds. During that effort, volunteers assessed more than 60 crossings to identify potential barriers to fish and wildlife movement and to better understand how road-stream crossings were affecting local waterways. The assessments showed that many crossings functioned as partial or significant barriers, highlighting the need for improved culvert design and replacement.

This early work helped build awareness about how road crossings affect rivers and laid the groundwork for more comprehensive watershed-scale assessments.

Today, we are building on that original effort and expanding our culvert assessment program across the entire SuAsCo watershed.

Expanding Culvert Assessments across the Watershed

OARS is working to expand culvert assessments to better understand infrastructure vulnerabilities and support climate resilience planning for communities throughout the watershed.

This work helps towns and cities:

Identify culverts that pose flood risks
Prioritize infrastructure upgrades
Support grant applications for culvert replacement
Improve stormwater resilience
Restore stream connectivity

Because water flows across municipal boundaries, assessing culverts at a watershed scale allows us to identify patterns and prioritize projects where they will have the greatest impact.

OARS uses standardized assessment protocols developed by the North Atlantic Aquatic Connectivity Collaborative (NAACC).

These assessments collect detailed information about each culvert, including:

Structure size and shape
Stream width and flow conditions
Evidence of flooding or erosion
Whether the culvert blocks fish and wildlife movement
Structural condition of the crossing

The data helps determine whether a culvert is adequately sized, a minor barrier, a moderate barrier, or a severe barrier. This information can then be used by municipalities, engineers, and state agencies to prioritize replacement or redesign projects.

Culvert Assessment Training

Help expand culvert assessments across the watershed! OARS will be hosting a Culvert Assessment Training where volunteers and municipal staff can become certified to assess culverts using NAACC protocols. Participants will learn how to evaluate road-stream crossings for flood resilience, infrastructure condition, and aquatic connectivity, contributing valuable data to support local and regional climate resilience efforts. This is a great opportunity to build skills, support your community, and play a direct role in improving watershed health.

Training dates: April 29, April 30, May 1

Participants will learn how to:

Conduct culvert assessments in the field
Collect standardized infrastructure data
Identify barriers to fish passage
Support watershed-scale climate resilience work

EMAIL ECOREST@OARS3RIVERS.ORG TO JOIN THE TRAINING

Culvert assessments will also play an important role in the SuAsCo Climate Collaborative, a regional effort to strengthen climate resilience across the watershed.

CLICK HERE TO VISIT THE CLIMATE COLLABORATIVE PAGE

~30%

of the SuAsCo rivers watershed is wetlands, crucial for wildlife habitat and water quality

~30%

of water samples in the SuAsCo rivers watershed contain PFAS, leading to increased monitoring and remediation by local authorities and environmental groups

~70%

of dams in the SuAsCo watershed are over a century old, requiring extensive upkeep and presenting obstacles to river restoration and fish passage

>40%

of the land within the watershed is publicly accessible, offering recreational opportunities such as hiking, boating, and birdwatching to the community

~15%

of the land in the SuAsCo rivers watershed is covered by impervious surfaces such as roads, rooftops, and parking lots. This contributes to stormwater runoff and water pollution issues

>40%

of the land within the Sudbury, Assabet, and Concord rivers watershed is publicly accessible, providing endless opportunities for paddling, hiking, and wildlife exploration.

What is a culvert?

Why Culverts Matter

Culverts and Climate Change

Culverts and River Connectivity

Our Approach

How We Assess Culverts

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