Highways in the Coastal Environment: New Usa Guidance

Abstract

There are over 60,000 miles (100,000 km) of coastal highways in the United States (US) that are occasionally exposed to coastal waves and water levels. Wise stewardship calls for the integration of coastal engineering principles and practices in the planning and design of these roads and bridges to make them more resilient. A new, 3rd, edition of the primary guidance document Hydraulic Engineering Circular No. 25 (HEC-25), entitled “Highways in the Coastal Environment” was recently released by the Federal Highway Administration (FHWA). It provides guidance on a range of issues for the design, planning and operation of coastal highways. This manual should help those with little experience in coastal engineering to understand and, as appropriate, to apply scientific methods and engineering approaches that are unique to the coast. For experienced coastal engineers, this manual should serve as a reference document in providing specific highway-oriented assistance and consultation for FHWA and state Department of Transportation projects.

The Future of Developed Barrier Systems: 2. Alongshore Complexities and Emergent Climate Change Dynamics

“…Both modules are inspired by and parameterized for management strategies employed in North Carolina (NC), USA. In the first module, we simulate strategies commonly employed for roadway protection (Douglass & Webb, 2020; Velasquez‐Montoya et al., 2021), including construction of dunes to prevent overwash, maintenance of roadways at a low‐elevation to prevent scouring and pavement damage, removal of washover from roadways, and road relocation into the barrier interior. In the second module, we simulate strategies commonly employed to maintain communities in fixed cross‐shore positions, including nourishment of beaches, construction of tall dunes, washover removal from developed areas, and the blocking and filtering of overwash by development (both residential and commercial).…”

The Future of Developed Barrier Systems - Part II: Alongshore Complexities and Emergent Climate Change Dynamics

“…Both modules are inspired by and parameterized for management strategies employed in North Carolina (NC), USA. In the first module, we simulate strategies commonly employed for roadway protection (Douglass et al, 2020;Velasquez-Montoya et al, 2021), including construction of dunes to prevent overwash, maintenance of roadways at a low-elevation to prevent scouring and pavement damage, removal of overwash from roadways, and road relocation into the barrier interior. In the second module, we simulate strategies commonly employed to maintain communities in fixed cross-shore positions, including nourishment of beaches, construction of tall dunes, overwash removal from developed areas, and the blocking and filtering of overwash by development (both residential and commercial).…”

The Future of Developed Barrier Systems: 1. Pathways Toward Uninhabitability, Drowning, and Rebound

“…Transportation networks (roadways, bridges, and ferries) are the backbone of developed barrier systems: they connect communities, facilitate economic development, and provide evacuation routes. Efforts to maintain transportation networks on barriers include removal of washover from roadways, road relocation, dune construction, and stabilization of breaches and inlets (Douglass & Webb, 2020; Velasquez‐Montoya et al., 2021). Here we simulate strategies suggested by the U.S. Federal Highways Administration for preventing roadway pavement damage during overwashing events (Douglass & Webb, 2020).…”

“…Efforts to maintain transportation networks on barriers include removal of washover from roadways, road relocation, dune construction, and stabilization of breaches and inlets (Douglass & Webb, 2020; Velasquez‐Montoya et al., 2021). Here we simulate strategies suggested by the U.S. Federal Highways Administration for preventing roadway pavement damage during overwashing events (Douglass & Webb, 2020). These include rebuilding roadways at sufficiently low elevations to allow for burial by overwash (i.e., to avoid scouring of elevated roadways); constructing large dunes to reduce the likelihood of overwashing events and to serve as a sand reservoir for the burial of roads by overwash; and relocating the road into the barrier interior (Figure 1b).…”