Vulnerability Assessment

Water overtopping culvert.
Water overtopping culvert.

Risks posed by flooding are increasing as extreme precipitation events become more intense and more frequent. SNHPC conducted a region-wide assessment of culverts and small bridges within the region to evaluate the risks associated with extreme precipitation events. Extreme precipitation causes inland flooding which is the most destructive type of historic weather pattern in the region. Such rainfall events continue to threaten the functioning of region’s transportation network. To avoid and minimize disruptions to road networks and reduce the need for costly repairs under emergency conditions, vulnerabilities to the network need to be identified and a plan for adaptation and/or mitigation put in place. A working group was formed to address this need and developed a system for prioritizing culverts and small bridges based on sensitivity to and magnitude of risks posed to these assets.

This assessment and prioritization effort provide local communities and regional agencies with an additional decision-making tool to help them select adaptation and mitigation strategies for highest-risk locations. The assessment also creates a framework to share information and consider impacts to the road network. Communities within the SNHPC region can explore their Culverts and Small Bridges via an online GIS map which inventories data for many of these stream crossings.

Click here to visit the GIS Stream Crossing Map

The vulnerability assessment activities encouraged increased coordination and communication among relevant agencies. As a result, the report provides a means to increase coordination around emergency events and considers impacts of extreme precipitation on other system types which rely on the functionality of the road network.

The assessment results support the following recommendations for action to mitigate and adapt to known vulnerabilities within the SNHPC region:

  •  Improve the accessibility of stream crossing inventory data to municipal staff.
  •  Emphasize the need for coordination between NH DOT and Municipal Public Works.
  •  Refine the criteria for prioritizing risk to culverts and small bridges on an annual basis.
  •  Plan for mitigation in advance of the most severe projected changes in weather patterns.

Below is the Draft 2020 Regional Vulnerability Assessment Report. Additionally there are other documents of previous stream crossing assessments in the region.