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described in specific recommendations. Floodplains and terraces should not be suddenly narrowed by <br />buildings or other structures. Such constrictions force increases in velocity and water elevations that <br />can increase erosion. <br />3. Roughness should increase away from the central channel. <br />Roughness is resistance to flow contributed by vegetation, rough surfaces, or structures. Increasing <br />roughness away from the central channel tends to center high flows and slows velocities against the <br />more erosive stream banks and terraces. For example, the central channel should be relatively free of <br />vegetation and other obstructions. The areas immediately adjacent to the channel (floodplains) should <br />support dense thickets of shrubby vegetation (i.e., willows, etc) that bend with the flows (Figure 1). <br />Areas further away from the channel (terraces) support stiffer woody vegetation (cottonwoods, <br />Peachleaf willow, etc) that further slows flows. It should be noted that roughness implies a slowing of <br />the flow not necessarily stopping the flow. Structures that completely stop or redirect flow across the <br />floodplain/terrace should be avoided. <br />Homes <br />Pasture, <br />Orchards, etc <br />V <br />Cottonwoods, Tree Willows, <br />Denser Brush <br />ShrubbyI Central <br />Willows Channel <br />Figure 1: Roughness - Vegetation provides increasing roughness to keep high velocities in central channel <br />(Natural Channel Design, 2006) <br />This Technical Note addresses principle 3 - the addition of roughness to the channel. It should be noted <br />that planting vegetation in a riparian zone without giving serious consideration to where different species <br />of plants should go can cause more problems than those you are trying to fix. For more information on <br />where to plant riparian vegetation, see Riparian Planting Zones in the Intermountain ffest by Hoag et. al. <br />2001. <br />There are a number of steps that should to be completed prior to any planting. They include a site <br />assessment, an inventory of planting site, and a detailed survey and evaluation of the soils, water, and <br />vegetation. Once you have determined the cause of the erosion and where high priority areas are located <br />on the stream, you should develop a planting plan and determine where and how to plant the vegetation <br />that you will use. This Technical note describes how to select, harvest, treat, and plant riparian woody <br />species. <br />Site Assessment <br />Before jumping into the water and shoving cuttings in the ground, it is important to understand what is <br />causing the streambank erosion, how extensive it is, and which areas need the most work. A stream <br />assessment should be completed on the stream prior to any restoration or rehabilitation work. The <br />