Stream Crossing Assessments
New Hampshire Stream Crossing Initiative
Together along with other project partners, we are working to address flood risks and make our infrastructure more resilient through a proactive approach by identifying and replacing problem culverts before they can fail and cause damage. Identifying crossings for replacement that will maximize ecological benefits while addressing infrastructure safety can save money and help to restore aquatic habitat in the long run. The goal is to assess and prioritize which crossings are the best candidates for replacement to improve public safety, infrastructure resilience and aquatic habitat restoration.
Improperly designed culverts create barriers to fish and other wildlife. The under-sized culverts can increase water velocity and prevent a natural streambed from forming inside the structure. Fast-moving water and lack of natural eddies and protected areas can prevent passage for smaller aquatic animals. Along with elevated or perched culverts can prevent any animal passage – many local aquatic species need to move freely.
Replacing culverts for watershed restoration: By removing crossings that are barriers to fish and wildlife contributes to watershed restoration goals. Waterways will be reconnected and both water quality and stream habitat will be improved. A suitable crossing will span the stream banks and have similar water flow, depth and substrate to the natural stream. A properly designed stream crossing can accommodate fish and wildlife passage and stream channel adjustments, while reducing flood hazards and expensive damage by allowing for flood flows.
Stream crossings are considered as any location where a road intersects a waterway requires a stream crossing to convey the water under the road. There are approximately 20,000 stream crossings in New Hampshire. Many are old, damaged and undersized, and need to be assessed and replaced. The undersized culverts present a public safety hazard. Undersized culverts can’t handle large stream flows and will cause flooding during heavy rain events or sudden snow melts. They are also prone to becoming blocked, further increasing likelihood of flooding. When water overtops a culvert, it can quickly erode road fill material, leading to washouts. This leads to stranded homes, expensive road repairs and impaired rivers and streams due to sediment being deposited into the water.
-Credit to NH Stream Crossing Initiative Partners Stream Crossings
We have been working on outreach to landowners and communities to increase the number of stream assessments in the area. New Hampshire uses a standardized assessment tool and database through the New Hampshire Stream Crossing Initiative, a multi agency group, working to assess stream crossings statewide. Their stated goal is to assess all 21,769 known stream crossings before the end of 2026. Currently, they report over 15,741 completed assessments (72.3%). This summer we teamed up with Trout Unlimited and were able to assess 474 culverts and crossings out of the 1,500-needing assessment in Coos.