GLOSSARY
abrasion:
Removal of streambank material due to entrained sediment,
ice, or debris rubbing against the bank.
aggradation:
General and progressive buildup of the longitudinal profile of a
channel bed due to sediment deposition.
alluvial channel:
Channel wholly in alluvium; no bedrock is exposed in channel
at low flow or likely to be exposed by erosion.
alluvial fan:
A fan-shaped deposit of material at the place where a stream
issues from a narrow valley of high slope onto a plain or broad
valley of low slope. An alluvial cone is made up of the finer
materials suspended in flow while a debris cone is a mixture of
all sizes and kinds of materials.
alluvial stream:
A stream which has formed its channel in cohesive or
noncohesive materials that have been and can be transported
by the stream.
alluvium:
Unconsolidated material deposited by a stream in a channel,
floodplain, alluvial fan, or delta.
alternating bars:
Elongated deposits found alternately near the right and left
banks of a channel.
anabranch:
Individual channel of an anabranched stream.
anabranched stream:
A stream whose flow is divided at normal and lower stages by
large islands or, more rarely, by large bars; individual islands or
bars are wider than about three times water width; channels
are more widely and distinctly separated than in a braided
stream.
anastomosing stream:
An anabranched stream.
angle of repose:
The maximum angle (as measured from the horizontal) at
which gravel or sand particles can stand.
annual flood:
The maximum flow in one year (may be daily or
instantaneous).
apron:
Protective material placed on a streambed to resist scour.
apron, launching:
An apron designed to settle and protect the side slopes of a
scour hole after settlement.
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