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<br />GLOSSAR't' <br /> <br />A I isting of terms commonly used to describe streambank erosion and <br />insi;abi I ity mechanisms, as \ooJell as terms related to streambank <br />protection and river mechanics, is provided below: <br /> <br />AbrasilJ:n - Removal of streambank materia.! due to entn:lined H,?dirnent, <br />ice or debris rubbing against the bank. <br /> <br />Angle of repose - The maximum angle (as measured from the horizontal) <br />at which gravel or sand particles can stand. <br /> <br />Aggradation (bed) - A progressive bui Idup or raising of the channel <br />bed due to sediment deposition. Aggradation is an indicator that <br />a change in the stream's discharge and sediment load <br />characteristics is taking place. <br /> <br />All uv i "I fan - A cone-shaped depos I t of bed I ment formE.d at the <br />confluence of a stream and its tributar~, If the sediment load <br />of the tributary cannot be carried away by the stream, an <br />alluvial fan forms. <br /> <br />Armoring - (a) Natural process whereby an erosion-resistant layer of <br />relatively large particles Is formE,,:1 on a streambank due to the <br />removal of finer products by streamf low, (b) Placement of a <br />cover i ng on a streambank or f i I ter. .~:o prevent eras I on, <br /> <br />Articulated concrete mattress - Rigid concrete slabs L1slJally hingE!d <br />together with coroslon-resistant I..'if,a fasteners; primar.,I,! placed <br />for lower bank protection, <br /> <br />Asphalt block - Precast or broken pieces of asphalt that can be hand- <br />p I aced or dumped on a streambank or f i I ter for protect i on aga i nst <br />eroSion. <br /> <br />Asphalt (bulk) - Mass uncompacted asphalt usually dumped from a <br />(upper bank protection) or a barge (lower bank pr.otection) <br />is placed to protect the bank agaiost erosion. <br /> <br />t r.u c k <br />that <br /> <br />Avulsion - A change in channel course that occurs .when a strE!am <br />suddenly breaks through its banks; "slJally associated Io'i th a <br />catastrophic event, <br /> <br />Backfi II - The material used to refi \I a ditch or other excavation, or <br />the process of doing so. <br /> <br />Backwater area - The low-lying lands adjacent to a stream that may <br />become flooded during periods of h'gh water, <br /> <br />Bank - The side slopes of a channel between which the streamflow 15 <br />normally confined. <br /> <br />Bed - The bottom of a channel <br /> <br />63 <br />