Coastal Engineering: An Overview (Adopted from the Coastal Engineering Manual)

Coastal engineering is one of several specialized engineering disciplines that fall under the umbrella of civil engineering. It is a composite of many physical science and engineering disciplines having application in the coastal area. It requires the rational interweaving of knowledge from a number of technical disciplines to develop solutions for problems associated with natural and human induced changes in the coastal zone, the structural and non-structural mitigation of these changes, and the positive and negative impacts of possible solutions to problem areas on the coast. Coastal Engineers may utilize contributions from the fields of geology, meteorology, environmental sciences, hydrology, physics, mathematics, statistics, oceanography, marine science, hydraulics, structural dynamics, naval architecture, and others in developing an understanding of the problem and a possible solution. The Coastal Engineer must consider the processes present in the area of interest such as:

1. Environmental processes (chemical, ecological).
   
2. Hydrodynamics processes (winds, waves, water level fluctuations, and currents).
   
3. Seasonal meteorological trends (hurricane season, winter storms).
   
4. Geological processes (soil and strata characteristics, stable and migrating sub-aerial and sub-aqueous features, rebounding or subsiding surfaces).
   
5. Long-term environmental trends (sea level rise, climate change).
   
6. Social and political conditions (land use, development trends, regulatory laws, social trends, public safety, economics).
   

Initial steps in the coastal engineering design process require an understanding of the physical processes governing the shoreline.  Waves, generated primarily by the wind, propagate from the ocean to the shoreline across the continental shelves. These waves undergo many processes before they dissipate in the surf zone including refraction, diffraction, shoaling, and breaking. The energy and momentum associated with the waves arriving at the surf zone is used to create longshore and cross-shore currents that mobilize and transport the sand comprising beaches. This sediment transport, if it carries more sand away from a site than towards it, results in beach erosion.

The ongoing rise in the sea level due to the glacial melting since the last ice age and now perhaps accelerated by the Greenhouse Effect creates a pervasive mechanism for shoreline retreat.

Tidal inlets, connecting bays or lagoons to the ocean, also contribute to the shoreline retreat by capturing beach sand into ebb and flood shoals.

The processes of coastal erosion are very complex, involving three-dimensional flow fields created by the breaking waves, unsteady turbulent sediment transport in both the water column and on the bottom, and a moving shoreline. Much research is being conducted worldwide to develop predictive models of this erosion process.

Numerous devices have been devised to stop the erosion process. These can be divided into two basic types: hard and soft structures.  Hard structures have been the traditional tool of the coastal engineer. These include groins (structures oriented perpendicular to the shoreline to slow the transport of sand along a shoreline), jetties (placed at inlets to keep sand from the navigational channel, breakwaters (to reduce wave action in harbors), and sea walls (to prevent the erosion of the upland).  Soft structures are those that are more natural. The primary example is beach nourishment, which is the placement of sand on an eroding beach. Nourishment is a short-term measure as it does not fix the cause of the erosion; however, it is the only method that involves directly adding sand to the coastal system