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e Flanking . Erosion resulting from streamllow between the eroded bank and the landward end of a river-lraining or a grade-control structure. Roodwa)' - The channel of a stream and those portions of the llood planes adjoining the channel, which are required to carry and discharge the llood water. Row slid ~ - Saturation of a bank to the point where the soil mate.ial behaves more like more like a liquid than a solid; the soil/water mixture may then move downslope resulting in a bank failure. Rume - J..n open channel constructed of wood, steel, or reinforced concrete and used to convey water for various pmposes, including grade control. Fonn liner - A liner for concrete forms designed to produce a spedalfinish. Gabion - 1\ wickerwork: or wire mesh basket or cage fined with stone or other materials placed against a streambank to prevent erosion. Geomorp lology - That blanch of both physiography and geology that deals with the form of the earth, the general configuration of its surface, and the changes that take place due to erosion of the primary elements and in the buildup of erosional debris. Grade control structure - Any of several types of structures used to control erosion on channels usually with steep grades (see sill, stabilizer, drop structure, and lIume). Gravel - Particles of stone that can pass a 3-in. (76.2 mm) and be retained on a No.4 (4.76 mm) U. S. Standard Sieve (Unified Soil Classification System. Greenlree reservoir - A shallow reservoir in which water levels are manipulated for wildlife and timber production. Groundw.ller lIow - That portion of the discharge of a stream which is derived entirely from ground water, through springs or seepage water. Grout - A lIuid mixture of cement and water or of cement, sand, and water used to fill joints and voids. Hard point - A streambank protection technique wbereby "soft" or erodible materials are removed from a bank and replaced by slOne or compacted clay. Some hard points protrude a short distance into the channel to direct erosive currents away from the bank. Hard poinls also occur naturally along streambanks as passing currents remove erodible materials leaving non- erodible materials exposed. Headeut . A point of abrupt change in the longitudinal profile of a stream. Headcuts typically migrate upstream through time. e XVIII Colorado Erosion Control Manual