the most important thing for controlling 

 nonpoint source pollution in humid 



areas." 



•The Science 



At the Piedmont site, scientists 

 study the streamside buffer's ability to 

 remove nonpoint pollutants leaching 

 from an agricultural field. NCSU 

 researchers compare water samples taken 

 at three distances from the stream under 

 study. The first sample is taken at the 

 edge of the cornfield, the second from 

 the grassy area buffering the field, and 

 the third from the riparian forest near the 

 stream. Gilliam is also conducting a 

 similar experiment in the Coastal Plain, 

 measuring a riparian buffer's success 

 near a hog farm. 



From the small amount of research 

 conducted, says Gilliam, "We know 

 [riparian buffers] are doing a tremendous 

 job now." 



Under the right conditions, he adds, 

 these buffers can remove up to 50 

 percent of the phosphorus, 90 percent of 

 the sediment and 80 percent of the nitrate 

 (a form of nitrogen released from animal 

 wastes and fertilizers) between the field 

 and the stream. 



According to those who have 

 studied riparian areas, successful buffers 

 have three parts, or zones, which work 

 together to protect, purify and support 

 water quality. 



ZONE 1: Runoff Control 



The outermost zone consists of grass 

 and shrubs. This zone filters out sedi- 

 ment or solids that can clog streambeds 

 or smother aquatic plants and animals. 

 Near a field or pasture, this vegetation is 

 often shaped or mown in patterns that 

 encourage water to spread evenly over 

 the area, allowing for more filtration. 



The roots of these plants also take 

 up nitrogen and phosphorus, nutrients 

 that can lead to algal blooms, dead water 

 (water with no or low dissolved oxygen 

 levels) or fish kills. Because phosphorus 

 bonds to soil particles, says Gilliam, 

 some of this nutrient is also filtered out 

 with sediment. 



ZONE 2: Managed Forest 



The trees and taller shrubs of zone 

 two are occasionally harvested or 

 cleared to promote healthy forest 

 growth, increasing the water quality 

 benefits. In zone two, runoff continues 

 to be filtered and dispersed, and 

 nutrients continue to be absorbed by 

 vegetation. But the major water quality 

 function in zone two is a process called 

 denitrification. 



Unlike phosphorus, nitrogen 

 applied to crops or released from 

 animal waste doesn't bond to soil 

 particles. Instead, it bonds with water 

 particles, running through the soil with 

 rain or runoff. Almost all nitrogen 

 reaches a waterway in subsurface flow, 

 says Gilliam. 



But fungi and bacteria living in the 

 wet, oxygen-rich soil beneath stream- 

 side forests naturally convert nitrate, a 

 form of nitrogen, into a harmless gas. 

 This is released into the atmosphere, 

 leaving behind much lower levels of 

 the nitrogen. Although groundwater 

 below a farm may have 15 parts per 

 billion of nitrate, that number is often 

 reduced to less than 1 part per billion 

 by the edge of the stream. 



ZONE 3: Mature Forest 



The zone closest to the waterway 

 is untouched, undisturbed forest. In this 

 zone, you'll find filtration, water 

 dispersion, nutrient uptake and 

 denitrification, but you'll also find a 

 host of other water quality benefits. 



The well-developed root systems 

 of a mature forest protect streambanks 

 from erosion. Detritus and decay from 

 leaves and limbs provide food for 

 aquatic organisms. Branches and 

 boughs create shade, lowering the 

 water temperature. This keeps the 

 waterway livable for fish and other 

 aquatic species and also reduces the 

 chances of excessive algal growth or 

 periods of low dissolved oxygen. 



And trees around a waterway help 

 to increase the diversity of species 

 living in the environment — making 

 for healthy food cycles and a produc- 



tive river, creek or stream. 



But the business of buffers is still 

 a new one. Although the scientific 

 consensus is that buffers remove sedi- 

 ment, nitrogen and phosphorus, there 

 aren't solid answers to many questions. 

 The slope of the land, hydrology and 

 rainfall are all factors in a buffer's 

 success. Clay layers beneath the soil may 

 hinder the buffer. And in regions along 

 the tidewater area, where the land is flat 

 and the soil is sandy, other water quality 

 management practices may work better 

 than a riparian buffer. 



One current issue pits trees against 

 grass. Some say that grass alone may be 

 all that is needed to improve water 

 quality while taking up less valuable 

 space along a waterway. 



But Brian Bledsoe, an environmen- 

 tal engineer with the N.C. Division of 

 Environmental Management, says grass 

 isn't enough. 



"When you're dealing with subsur- 

 face flow of nitrate," he says, "forested 

 buffers are superior — the deeper roots 

 take up more nitrogen. If you just require 

 a grass buffer, a lot of the nitrate is 

 probably moving under the grass zone." 



Others argue that riparian buffers 

 may not be successful in North Carolina 

 because some farmers use ditches or 

 ravines that send water coursing through 

 the buffer zone too quickly for denitrifi- 

 cation or filtration. Gilliam disagrees. 

 Most phosphorus bonds to the soil before 

 it ever gets to the ditches, he says, and 

 almost all nitrogen flows under the 

 surface of the earth, below the depth of a 

 ravine or ditch. 



These and other issues, such as a 

 buffer's ability to filter out bacteria or 

 toxins, are being researched now. 



•The Status 



Today, says Gilliam, riparian buffers 

 are present on many of North Carolina's 

 small creeks, streams and stretches of 

 river. In the Neuse River basin, for 

 example, about 70 to 80 percent of the 

 creeks and feeder streams are protected 

 by some form of riparian buffers. 



Continued 



COASTWATCH 13 



