Vegetation cover

A Semi-quantitative Approach Erosion and Deposition. Over the centuries the primary impact of human activity has been to deforest the surrounding countryside and increase the rate of erosion and deposition into rivers. This results primarily from the destruction of vegetation cover which stabilizes soil systems on gradient. The ecological impact of erosion has at present reached catastrophic proportions. The magnitude of continental erosion into rivers is illustrated in Figure 3. 

Scott, G. A. J. (1975a). Relationships between vegetation cover and soil avalanching in Hawaii. Proc. Assoc. Am. Geogr. 7,208-212. 

It is important upon completion of grading to establish vegetation cover as quickly as possible. This cover is essential to help prevent drying and erosion. 

Although vegetation cover requires frequent maintenance, it prevents the more costly maintenance that would result from erosion of surface soils. 

The soil and plants employed on the cover are critical to success. A mixture of grasses native to the area is preferred to provide effective water removal from the cover in all years in spite of temporary changes in local conditions. Native grasses have already proven their ability to withstand local climate variations, insects, plant disease, periodic fire, and other factors. A mixture of native grasses assures an active vegetative cover during years when insects, plant disease, or other factors reduce the vigor of one or more species.11-38... 

Hauser, V.L., Shaw, M.A., and Weand, B.L., Effectiveness of soil-vegetative covers for waste sites, Proceedings, Superfund XV, Washington, DC, 1994. 

Rock, S.A., Vegetative covers for waste containment, review, Advances in Biochemical Engineering/ Biotechnology, 78, 157-170, 2003. 

For sites on very arid land or on steep slopes, an armoring system, or hardened cap, may be more effective than a vegetative layer for securing a landfill. Operators should not depend on an agricultural layer for protection in areas where vegetation cannot survive. Many States allow asphalt caps as an alternative to vegetative covers. Some closures at industrial sites have involved constructing... 

Loess settles when dust-laden winds slow down to speeds between 7 (on dry surfaces) to 14 meters per second (on moist surfaces). The pore distribution of loess lets it quickly be retained by capillary forces if it lands on a moist surface. The presence of a vegetation cover may also enhance the rate of loess deposition, and many authors maintain that the northern limit of loess deposition coincides with the northernmost extent of grass steppes during arid periods in the Pleistocene. 

The semi-arid areas receiving somewhat higher rainfall are covered by a steppe-like fairly continuous vegetative cover of Xerophilous shrubs and grasses. In the Central Asian Plains, east of the Caspian Sea, wind erosion and transport are the dominant features. Sand dunes dominate the landscape for hundreds of kilometers. 

Air temperatures in arid zones are generally high and show significant daily variations. Because of the absence of a protective vegetative cover and a specific thermal absorption and desorption effects due to surface or rock colors or slope aspect, air temperatures of 35-45°C may reach peaks up to 50-60°C or more on rock surfaces. 

Within about 500 km of coastal areas, the chloride content of precipitation is strongly related to the proximity of the shoreline. The ocean-derived chloride in the precipitation may commonly vary from 10 to 20 mg/L at the coast to less than 1 mg/L at a distance of 200 km from the coast. Precise amounts are related closely to climatological factors such as prevailing winds and total precipitation. Local vegetation cover and topographic effects may also be important, particularly in controlling dry fallout of sea-spray particles within a few kilimeters of the coast. 

In many mountain-industrial areas there are 3 1 landscape-functional zones with different extents of the anthropogenic transformation of natural environments. As a rule, the first zone is the spatial complex joining mines, pits and tails site area with almost whole degradation of soil and vegetation cover and high metal concentrations in dust, technogenic depositions, waters and plants. 

Wind (aeolian) transport (relocation by wind) can also occur and is particularly relevant when catalyst dust and coke dust are considered. Dust becomes airborne when winds traversing arid land with httle vegetation cover pick up small particles such as catalyst dust, coke dust, and other refinery debris and send them skyward. Wind transport may occur through suspension, saltation, or creep of the particles. 

Finally a vegetative cover was planned for restoration and continuing groundwater protection. 

Floodplains are periodically inundated areas along rivers or lakes. Their vegetative cover is variable. 

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