Reflection, Wave

– Reflection is the process by which wave energy is redirected seaward after impacting a structure or obstruction, such as a seawall or a steep beach face. Wave reflection can lead to complex wave interactions, increase turbulence, and generate scour.

Refraction, Wave –

Refraction is the process by which waves tend to change direction and become more parallel to the shoreline as they approach the shore. This phenomenon occurs because the portion of the wave nearer to the shore that advances in shallow water moves more slowly than the portion of the wave farther from the shore in deeper water (due to bottom friction), causing the wave crests to bend.

Relative Sea Level Rise

– See ‘Sea Level Rise’

Return Period

– The return period is a statistical value intended to provide design context on how often a specific value or event may occur. The inverse of the return period is the statistical percentage that the value or event will occur in any given year, also known as the exceedance probability. For example, a 100-year return period wind speed has a 1% chance of occurring within any given year.

Revetment

– A revetment is a structure used to protect a shoreline or embankment from wave or current impacts. It is typically installed directly on grade and is composed of concrete, stone, or other armoring.

Rip Current

– A powerful, swift current flowing seaward from the shore over a narrow portion of shoreline. It is typically formed due to an onshore-directed wave breaking over submerged nearshore sandbars and then flowing back out through a narrow opening between the bars. Rip currents are commonly called ‘rip tide’ and are particularly hazardous for swimmers.

Runup, Wave

– Wave runup is the vertical distance that the water surface will temporarily increase as a wave propagates up a sloped surface. The runup is caused by the wave directly interacting with a structure or the shoreline and will be affected by surface roughness, porosity, and geometry.