Laserfiche WebLink
<br />DRAINAGE CRITERIA MANUAL <br /> <br />MAL10R DRAINAGE <br /> <br />Since the channel velocity varies through a transition, the maximum ~ <br />velocity in the transition should be used in selecting riprap size <br />after it has been increased by 20%. <br />Protection should extend upstream from the transition entrance at <br />least 5 feet and extend downstream from the transition exit at least <br />10 feet. <br /> <br />5.5 Wire Enclosed Riprap Linings <br />The geometric properties of wire enclosed rock permit placement <br />in areas where ordinary riprap is either difficult or impractical to <br />place. Proper design and construction is important to successful <br />operation and lifetime performance. Figures 5-5a and 5-5b depict some <br />of the more common ways wire enclosed rock is configured along channel <br />banks. However, use of wire enclosed riprap lining is is not encour- <br />aged, particularly in areas exposed to annual floods, and it is <br />recommended that ordinary riprap be used whenever it is feasible. <br /> <br />5.5.1 Side Slope Steeper Than 2h to Iv <br />Where channel side slopes must exceed 2h to lv, gabion baskets <br />(G36) may be stacked to form a retaining wall as well as erosion <br />protection along the channel banks as shown in Figure 5-5b. Adjacent <br />baskets should be tied together with heavy gauge wire and adequate <br />protection against channel bed degradation must be provided at the toe <br />of the lining. Stacked baskets must be sloped, or stepped into the <br />bank as shown in Figure 5-5b. Vertical stacking is not acceptable. <br /> <br />. <br /> <br />5.5.2 Counterforts <br />Channel linings should be tied to the channel banks with gabion <br />(G36) counterforts at least every 12 feet. Counterforts should be <br />keyed at least 12 inches into the existing banks with slope mattress <br /> <br />. <br /> <br />5-1-84 <br />