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Methods For Controlling Erosion e The Ienn 'refusal" applies to construction placed at the upstream end of each reveUoent segmenl,lpproximately nonnal to the bank1ine and direction of flow to prevent erosion from flan eng the structure. Figure 4-1 shows a schematic diagram of a reveUoent structure. These are commonly used on many types of erosion control structures. FIGURE 4. 1 Typical re'letment whh stone 2' Thick Min Existing BankIine Varies I Varies J N.W.S. ~ Existing Bed 2' .1. .- IV on t.5H Geotextiles ~ ReveUoe~ ts are very successful in stopping erosion on streams where the major problem is bank: ulldercutting from toe erosion or general erosion of the bank: by shear velocities of the river. They provide only a limited amount of protection against erosion on streams subject to headcuts or general bed degradation, ReveUoents must be properly designed and constructed with suitable material to be effective. Chapter 6 presents detailed design infonnation, Both positive and negative environmental effects result from the placement of reveUoems. Disruption from equipment activity and increased turbidity from earthwork are short-lived and should have no adverse effects on the environment Reduction of riparian ~abitat along the protected banldine is the primary negative effect. Riparian habitat aI'>ng the river provides a corridor for wildlife migration, Removal of riparian habitat may reduce both avian and mammalian use along revelled banldines. Benthic communiies benefit from subslrale provided by most reveUoent materials. Macroinvertibrate density is usually much grealer on reveUoents than on adjacent natura1 bllOklines or the bed, accOWlting for over 80% of the biomass within a reach. Fishery h mitat improves because of the diversity revetments provide. and stone riprap provides spawning substrate for many fish species. Water quality effects are insignitic;mt if non-objectiooabte materials are used. Stone-Fit Revetments - As the name implies. stone fill reveUoents are reveUoents construcb:d of slOne. They are oflen referred 10 as riprap. Stone-fill reveUoents have been used widely on streams of all sizes everywhere. They are the most commonly used structure. and on all rivers nationwide. Costs for typical revetmen:s structures may vary from $40 to $250 per linear foot, depending on the .. avaiJabili:y of stone. and the needed quantities, _ 28 COlorado Erosion COntrol Manual