EM 1110-2-1100 (Change 1)
31 Jul 03
RIDGE AND RUNNEL
Beach topography consisting of sand bars that have welded to the shore during the recovery stage after a storm. At
low tide, water ponds in the runnels and flows seaward through gaps in the ridge (see Figure IV-2-31).
RIDGE, BEACH
A nearly continuous mound of beach material that has been shaped by wave or other action. Ridges may occur
singly or as a series of approximately parallel deposits.
RILL MARKS
Tiny drainage channels in a beach caused by the flow seaward of water left in the sands of the upper part of the
beach after the retreat of the tide or after the dying down of storm waves.
RIP
A body of water made rough by waves meeting an opposing current, particularly a tidal current; often found where
tidal currents are converging and sinking.
RIP CHANNEL
A channel cut by seaward flow of RIP CURRENT, usually crosses a LONGSHORE BAR.
RIP CURRENT
A strong surface current flowing seaward from the shore. It usually appears as a visible band of agitated water and
is the return movement of water piled up on the shore by incoming waves and wind. With the seaward movement
concentrated in a limited band its velocity is somewhat accentuated. A rip consists of three parts: the FEEDER CURRENTS
flowing parallel to the shore inside the breakers; the NECK, where the feeder currents converge and flow through the
breakers in a narrow band or "rip"; and the HEAD OF RIP, where the current widens and slackens outside the breaker line.
A rip current is often miscalled a rip tide. Also called RIP SURF.
RIP SURF
See RIP CURRENT.
RIP TIDE
Incorrect term for RIP CURRENT.
RIPARIAN
(1) Pertaining to the banks of a body of water. (2) Of, on or pertaining to the banks of a river.
RIPPLE
(1) The ruffling of the surface of water; hence, a little curling wave or undulation. (2) A wave less than 0.05 meter
(2 inches) long controlled to a significant degree by both surface tension and gravity. See CAPILLARY WAVE and
GRAVITY WAVE.
RIPPLE MARKS
Undulations produced by fluid movement over sediments. Oscillatory currents produce symmetric ripples whereas
a well-defined current direction produces asymmetrical ripples. The crest line of ripples may be straight or sinuous. The
characteristic features of ripples depend upon current velocity, particle size, persistence of current direction and whether the
fluid is air or water. Sand DUNES may be regarded as a special kind of `super'-ripple.
RIPPLES (bed forms)
Small bed forms with wavelengths less than 0.3 m (1 foot) and heights less than 0.03 m (0.1 foot).
RIPRAP
A protective layer or facing of quarrystone, usually well graded within wide size limit, randomly placed to prevent
erosion, scour, or sloughing of an embankment or bluff; also the stone so used. The quarrystone is placed in a layer at least
twice the thickness of the 50 percent size, or 1.25 times the thickness of the largest size stone in the gradation.
Appendix A Glossary of Coastal Terminology
A-65
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