Ring gateA ring- or annular-shaped steel drum operating in a recess or gate chamber in a spillway crest and controlled in a manner similar to a drum gate. See gate.
Ring seal gateSimilar to a paradox gate, however sealing is by a moveable seal, which is extended by water pressure when the gate is closed.
Ring-follower gateA gate consisting of a rectangular leaf and an opening equal in diameter to that of the conduit that forms an unobstructed passageway when the leaf is in…
Rip RapA layer of stones, broken rock or precast blocks placed in random fashion on the upstream slope of an embankment dam, on a reservoir shore or on the sides…
RiparianRelating to, living in, or located on the bank of a river, lake, or tidewater.
Riparian ZoneThe transition zone between the water and the upland zone. Can be identified by specific types of plants and soils.
RippleIn a streambed, a ripple is a small triangle-shaped elements having gentle upstream slopes and steep downstream slopes.
RiprapA man-made stretch of rocks or material of a hard composition that usually extends above and below the shoreline, often found near dams of big…
RiskThe possibility of loss; the uncertainty of future returns.
risk assessmenta scientifically based process consisting of the following steps: i) hazard identification; ii) hazard characterization; iii) exposure assessment; and iv)…
River BasinThe land area surrounding one river from its headwaters to its mouth. The area drained by a river and its tributaries.
River corridorA river and the strips of land adjacent to it, including the talus slopes at the bases of cliffs, but not the cliffs themselves.
River FloodingThe rise of a river to an elevation such that the river overflows its natural banks causing or threatening damage.
River Forecast (RVF)An internal product issued by RFCs to other NWS offices. An RVF contains stage and/or flow forecasts for specific locations based on existing, and…
River Forecast Center (RFC)Centers that serve groups of Weather Forecast Offices, in providing hydrologic guidance and is the first echelon office for the preparation of river and…
River Recreation Statement (RVR)A statement released by the NWS to inform river users of current and forecast river and lake conditions.
River Statement (RVS)A product issued to communicate notable hydrologic conditions which do not involve flooding, i.e., within river bank rises, minor ice jams, etc.
River Summary (RVA)A NWS summary of river and/ or crest stages for selected forecast points along the river.
River SystemAll of the streams and channels draining a river basin.
River trash wallWalls constructed to deflect heavy floating debris away from the upper ends of a fishway.
RockA player who plays very tight, not very creatively. He raises only with the best hands.
Rock anchorA steel rod or cable placed in a hole drilled in rock, held in position by grout, mechanical means, or both.
Rock boltA steel rod placed in a hole drilled in rock, held in position by grout, mechanical means, or both. A rock bolt can be pretensioned.
Rock excavationHard and firm parts of the earth's crust which is dug out and removed from a particular site or area, see rock.
Rock Fill DamAn embankment dam in which more than 50% fo the total volume comprises compacted or dumped pervious natural or crushed rock.
Rock fragmentDetached pieces of rock which generally are not rounded.
Rockfill DamAn embankment dam in which more than 50 percent of the total volume is comprised of compacted or dumped cobbles, boulders, rock fragments, or quarried…
RODA graduated staff used in determining the difference in elevation between two points.
Rolled Earth Dam (Earth Fill or Earth Dam)An embankment dam in which more than 50% of the total volume is formed of compacted fine-grained material obtained from a borrow area.
Rolled fill damAn embankment dam of earth or rock in which the material is placed in layers and compacted by the use of rollers or rolling equipment.
Rolled Filled DamAn embankment dam of earth or rock in which the material is placed in layers and compacted by using rollers or rolling equipment. Same as Rockfill dam.
Roller gateA gate rolled up or down inclined supporting rails by a hoist through sprocket chains around the ends of a cylinder.
Roller-compacted concrete damA concrete gravity dam constructed by the use of a dry mix concrete transported by conventional construction equipment and compacted by rolling, usually…
RollingA method of compacting soil using a sheepsfoot roller or a smooth drum roller.
Root zoneThe volume of soil or growing medium containing the roots of a plant. In soil science, the depth of the soil profile in which roots are normally found.
Rotten IceIce in an advanced stage of disintegration.
Route alertingA supplement to the public alert system; a method for alerting people in areas not covered by the primary system or if the primary system fails.
RoutingThe methods of predicting the attenuation of a flood wave as it moves down the course of a river.
Rubble damA stone masonry dam in which the stones are unshaped or uncoursed. See dam.
RunSeasonal upstream migration of anadromous fish. One or more lengths of pipe that continue in a straight line.
Run-of-river plantsThe regulated inflow of one powerplant is equal to the outflow from a powerplant upstream.