Highways in the Coastal Environment

Scott L. Douglass and Joe Krolak
Hydraulic Engineering Circular 25
FHWA NHI-07-096
June 2008

This report provides guidance for the analysis, planning, design and operation of highways in the coastal environment. The focus is on roads near the coast that are always, or occasionally during storms, influenced by coastal tides and waves. A primary goal of this report is the integration of coastal engineering principles and practices in the planning and design of coastal highways. It is estimated that there are over 60,000 road miles in the United States that can be called “coastal highways.” Some of the physical coastal science concepts and modeling tools that have been developed by the coastal engineering community, and are applicable to highways, are briefly summarized. This includes engineering tools for waves, water levels, and sand movement. Applications to several of the highway and bridge planning and design issues that are unique to the coastal environment are also summarized. This includes coastal revetment design, planning and alternatives for highways that are threatened by coastal erosion, roads that overwash in storms, and coastal bridge issues including wave loads on bridge decks.

Highways in the Coastal Environment: Assessing Extreme Events

Scott L. Douglass, Bret M. Webb and Roger Kilgore
Hydraulic Engineering Circular No. 25, Volume 2
October 2014

The purpose of this manual is to provide technical guidance and methods for assessing the vulnerability of coastal transportation facilities to extreme events and climate change. The focus is on quantifying exposure to sea level rise, storm surge, and wave action. It is anticipated that there will be multiple uses for this information, including risk and vulnerability assessments, planning activities, and design procedure guidance.

Extreme weather events can profoundly impact coastal transportation infrastructure. In a more general sense, the term “extreme weather” includes severe or unseasonable weather, heavy precipitation, a storm surge, flooding, drought, windstorms (including hurricanes, tornadoes, and associated storm surges), extreme heat, and extreme cold. Extreme weather events can be described as rarely occurring, weather-induced events that usually cause damage, destruction, or severe economic loss. This manual focuses only on extreme events along the coast such as storm surge and waves found in hurricanes, nor’easters, fronts, and El Niño-related coastal storms on the west coast. Tsunamis are also discussed as extreme events.

A Primer on Modeling in the Coastal Environment

Bret M Webb
December 2017

This manual provides an introduction to coastal hydrodynamic modeling for transportation engineering professionals. The information presented in this manual can be applied to better understand the use of numerical models in the planning and design of coastal highways. Here, the term “coastal highways” is meant to generally capture the roads, bridges, and other transportation infrastructure that is exposed to, or occasionally exposed to, tides, storm surge, waves, erosion, and sea level rise near the coast. The hydrodynamic models that serve as the focus of this manual are used to describe these processes and their impacts on coastal highways through flooding, wave damage, and scour.

The primary audience for this manual is transportation professionals ranging across the spectrum of project delivery (e.g., planners, scientists, engineers, etc.). After reading this manual the audience will understand when, why, and at what level coastal models should be used in the planning and design of coastal highways and bridges; and when to solicit the expertise of a coastal engineer. This manual provides transportation professionals with the information needed to determine scopes of work, prepare requests for professional services, communicate with consultants, and evaluate modeling approaches and results.

The manual also provides guidance on when and where hydraulic and hydrodynamic models are used, and how they are used to determine the dependence of bridge hydraulics on the riverine or coastal design flood event.

The manual also gives recommendations for the use of models in coastal vulnerability assessments.