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<br />Concrete block - Precast concrete material placed on a streambank or <br />filter to prevent erosion, <br /> <br />ConFluence - The junction of two or more streams, <br /> <br />Constriction (Flow) - A reduction in channel cross-sectional area that <br />results in greater stream velocities and/or water depth, <br /> <br />Crib .- A frame structure, fi lied with ear.th or s.cone ballast, designed <br />to absorb energy and to deflect streamflow away from a bank. <br /> <br />Critical shear stress - The minimum amount of shear stress exerted by <br />passing stream currents required to initiate soil pal-ticle <br />motion, <br /> <br />Cross section - A diagram or drawing cut across a channel that <br />illustrates the banks, bed, and water surface. <br /> <br />Crossing - The relatively short and shallo,", reach of a s'b-earn betwllen b <br />ends; also called a crossover, <br /> <br />Current - Water flowing through a chann"l. <br /> <br />Cut bank <br /> <br />The concave wal I of a meandering stream, <br /> <br />CutofF - A new, relatively short channel (natural or artificial) <br />formed when a stream cuts or is rea Ii gned through the neck of an <br />oxbow or horseshoe bend. A cutoff can also develop as succeSSive <br />high-water flows develop a chute across the inside of a point <br />bar, <br /> <br />Degradati on (bed) - A progress i vEl lower i ng of thE' channe I bed due to <br />scour, Degradati on is an i nd i cator. that a change in the stream - 5 <br />discharge and sediment load characteristics is taking place. <br /> <br />Dike (groin, spur. Jetty) - A structure extending from a bank into a <br />channe I that is des i gned to (a) reclu"e the stream ve I oc i ty as the <br />current passes through the dike, thus encouraging sediment <br />deposition along the bank (permeable dike) or (b) deflect erosive <br />currents away from the streambank <impermeable dike), <br /> <br />Discharge - Volume of water passing through a channel during a given <br />time, usually measured in cubic feElt per second, <br /> <br />Drainage basin - An area confined by drainage divides, often having <br />only one outlet for discharge, <br /> <br />Eddy current - A vortex-type motion of a fluid flowing contrary to the <br />main current, such as the circular water movement that occurs <br />when the main flow becomes separated for the bank, <br /> <br />Energy grade slope - An incl ined represE!nting the- total energy of a <br />stream flowing from a higher to a iower elevation, <br /> <br />65 <br />