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4-79 <br />• 4.7.4.8 Map Unit: RiAB - Rivra Gravelly Loam Variant, <br />0 to 8 Percent Slopes <br />This map unit is on nearly level to gently sloping low <br />terraces and flood plains. The slope is 0 to 8 percent. <br />The vegetation is mainly a greasewood-shrubland community. <br />Some portions of this map unit are in a big sage brush- <br />shrubland community. <br />Included in this map unit is about 5 percent Nihill soils <br />near the sandstone outcroppings above. <br />Typically, the surface layer of the Rivra variant is a <br />pale brown or light brownish gray gravelly sandy loam <br />about 8 inches thick. The substratum to a depth of 60 <br />• inches or more is light brownish gray to pale brown, <br />stratified very gravelly loamy sands, loamy coarse sands, <br />and sandy loam. <br />Permeability of the Rivra soil is very rapid. Available <br />water capacity is moderate. Effective rooting depth is <br />40 to 60 inches. Runoff is slow and the erosion hazard <br />for water is medium. wind erosion hazard is moderate to <br />moderately high. <br />The unit is mainly used for rangeland and wildlife habitat. <br />It is also used for pasture. <br />The present plant community consists of greasewood, four- <br />• caing saltbush and cheat grass. <br />