viburnums, staghorn sumac, choke cherry, elderberry, and barberry. 



Herb layer . — Included in this layer are all herbaceous plants 

 that grow on the floor of the woods. There are a great number of species 

 in this category, the most common being bloodroot, trillium, dog-tooth 

 violet, Virginia bluebell, Jack-in-the-pulpit , May-apple, and wild geranium. 



Each of these layers play an important role in the stability of 

 the woods (and, hence, erosion control), and any revegetation project 

 should take them all into account. 



CAUSES OF EROSION IN THE RAVINES 



Quite simply, the erosion is caused by too much water flowing too 

 quickly through the ravines. There are three basic types of erosion 

 in the ravines: 1) vertical cutting along the bottom channel, which will 

 eventually result in a wider ravine at the top as the side slopes seek 

 their natural angle of repose, 2) horizontal cutting along the sides of the 

 channel, which increases the effective angle of the ravine slope, and 3) 

 slumping or sloughing of the surface of the face of the slopes, which is 

 caused by surface and ground waters lubricating the interface between weath- 

 ered and unweathered soil materials. The latter situation is quite common 

 along the upper few feet of the slope that is just below the tableland, 

 where there is a relatively impermeable soil layer below a more permeable 

 top soil layer. As a result, water penetrates the upper few feet of soil 

 and moves laterally as it encounters the less permeable layer. Eventually, 

 this subsurface water seeps out of the sides of the ravines. This is a 

 serious problem in the ravines, and if a property owner detects a seepage 

 layer in his portion of a ravine, a consulting engineer and/or landscape 

 contractor (preferably both) should be brought in to see if some kind of 

 drainage system or terrace/retaining wall should be constructed to stabil- 

 ize the area. Vegetation cannot effectively control slumping. 



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