functional types: (1) trapping of sediments with vegetated buffer strips 

 and detention ponds; (2) diversion of runoff away from likely erosion 

 areas through grading, diversion cuts, and lined channels; and (3) 

 prevention of soil movement and erosion, by reseeding, mulching, and the 

 placement of netting over exposed soils (Figure 23). 



Vegetated buffer strips and artificial control systems such as 

 sediment basins can provide sound erosion control for on-going construction 

 operations. Buffer strips should be planned for all watercourses and 

 shorelines in order to trap sediment and other pollutants. Their width 

 should be determined according to the slope of the land, the severity of 

 erosion, and the existing vegetation types. 



Sediment basins (Figure 24) detain runoff and trap sediment, thus 

 preventing increased turbidities in adjacent water bodies [69][70]. Such 

 devices are required practice in many states and coastal communities. 



Figure 24. A temporary retention basin that prevents serious water 

 pollution from eroded soil (Source: Reference 68). 



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Diversion is also an effective method of erosion control. Run- 

 off can be channeled away from exposed soils with small parallel 

 diversions or troughs cut to intercept the surface water flow. Bench 

 terraces can be constructed across a slope to direct water either into 

 sediment basins or vegetated buffer strips where accumulated sedi- 

 ments can be removed. 



Grassed waterways (swales) can be used effectively in many situations 

 but are most effective in removing moderate amounts of sediment. The grass 

 protects the channel against erosion by reducing the velocity of the water 

 at the soil surface. The most suitable grasses to use are those that 



115 



