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• 2.0 DESIGN APPROACH <br />The traditional method for controlling stream bank erosion is to provide rip rap protection of the bank <br />to prevent further scour. While this method would be effective, it would require a large volume of rock <br />and has adverse visual impacts. Two alternative stream bank protection measures have proven to be <br />effective for stream bank protection: <br />• Vegetation stabilization with toe protection (bioengineering approach), and <br />• Rock veins with vegetation stabilization <br />Both protection measures involve structural control with vegetation stabilization which reduces the <br />volume of rock rip rap required and associated cost. Both methods provide excellent protection with <br />few failures and minimal maintenance. Rock veins have the additional advantage of improving stream <br />habitat for aquatic resources. The rock vein design was also found to be the most cost effective method <br />for stream bank stabilization at the Eagle Mines Site. <br />• <br />2. l Overview of Rock Vein Design <br />Rock veins or rock barbs, as described by Rosgen (1996), consist of rock jetties that extend from the <br />outer edge of a meander bend and angle down into the channel and upstream into the flow. However, <br />rock veins have significant functional differences. While jetties aze generally visible above the flow <br />line and force the river flows around the structure, rock veins aze mostly below the water line during <br />normal and high flows with water flowing over the structure similar to the bendway weir design <br />developed by the U.S. Army Corps of Engineers (USAGE) Waterways Experiment Station (LaGrone, <br />1995). Both rock veins and bendway weirs deflect the river current away from the bank at an angle <br />perpendicular to the rock vein and toward the direction of the bend. Thus, a rock vein or bendway weir <br />placed along the outside bank of a meander bend protects this bank for some distance downstream of <br />the structure, depending upon the radius of curvature of the bend. Rock veins also build stream banks <br />upstream of the structure by creating a reverse eddy which traps bedload and suspended sediments <br />along the outside of the meander bend thereby increasing bank stability. <br />• <br />AHA Fil<name Empir<Desig~ doc 4 07/30/99 <br />