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r 4-Site-Specific Indu• l Storm Water BMPs • <br />Chapter <br />Gradient Terraces <br />What Are They <br />rosion damage by capturing surface -and-channels constructed with suitablerunoff <br />Gradient terraces are earth embankments <br />duce ridge <br />and with an appropriate grade. They <br />directing it to a stable outlet at a speed that minimizes erosion. <br />nr7f- 77) <br />hen and Where to Use Them <br />W <br />F <br />Gradient terraces are usually limited to use on land that has no vegetation and that has a water terrace erosion problem, or where <br />oit is anticipated that water erosion will be a probm. n slopes with sandy or rocky soils. They will be effect ive'only whe es <br />should not be construsuct <br />suitable runoff outlets are or will be made available. <br />F Consider <br />W <br />Gradient terraces should be designed and installed according to a plan determined by an <br />engineering survey and layout. It is important that gradient terraces are designed withal et quatehould <br />outlets, such as a grassed waterway, vegetated area, or tile outlet. In all cases, <br />direct the runoff from the terrace system to a point where the outflow will not cause erosion or <br />other damage. Vegetative cover should be used in the outlet where possible. The design elevation <br />of the water surface of the terrace should not be lower than the design elevation of the water <br />and after majop stor1ms atPrdesign flow. Terraces should oper dust ont of p ocedures be <br />surface in the outlet at their junction, when <br />inspected regularly at least once year <br />should be followed while constructing these features. <br />• <br />• <br /> <br />4-93 <br />FIGURE 4.30 GRADIENT TERRACE <br />(Washington State, 1992)