Includes five sites from the Henderson County line to the Madison County line.

In addition to the five sites on the French Broad River in Buncombe County, there are three sites in Transylvania County, two in Henderson County, and two in Madison County. This provides a comprehensive picture of water quality changes in the river from the headwaters in Transylvania County to the Madison County border with Tennessee.

Many factors affect water quality of the French Broad River.

Topography and land use patterns are key elements as non-point source pollution has become the critical determinant of water quality. Some of the watershed is in forested areas and the tributary streams from these forested areas that flow into the river are the main sources of high quality water. The urban streams are the main sources of chemical and heavy metal pollutants to the river. Nutrient sources come from both rural agricultural (especially livestock) areas and from urban runoff and wastewater treatment plants. Sediment is the most significant pollutant and there are many sources.

Although sediment concentrations start low near the headwaters of the French Broad River, concentrations increase greatly as the river flows through Transylvania County. Most of the tributaries flowing into the river in this area are not normally great contributors of sediment. However, there are significant areas of bank erosion along the river as many areas have very little or no buffer zones. Sediment concentrations level off in Henderson County where the river is deep and the descent is slow. In this section there are tributaries with significant sediment loads, but there are also some major tributaries with very high quality water. The net effect is a decrease in median sediment concentrations.

In Buncombe County sediment levels begin to increase as the river flows through Asheville and north Buncombe County all the way to Marshall in Madison County. In this section of the river the flow rate increases as the descent increases and the river spreads out. Several tributaries carrying large sediment loads flow into the river. The greater sediment input as well as the increased flow rate leave much of the sediment in suspension. Figures 13 and 14 show variations in median suspended solids concentrations at all of the French Broad River sites and average median turbidity and sediment concentrations at tributary sites in four sections of Buncombe County (southern rural and suburban, eastern rural and suburban, urban Asheville/Weaverville/Enka/Candler, and northern and northwestern rural and suburban).

The influence of the urban area of Asheville is most evident in analysis of conductivity and zinc. Conductivity levels increase through Transylvania County, level off in Henderson County, and increase again as the river flows through Asheville (Figure 15). Zinc concentrations follow a somewhat more erratic pattern prior to entering Buncombe County, but once again increase greatly in Asheville and reach a peak just downstream from Asheville (Figure 16). Figure 17 showing average median conductivity and zinc levels at tributary sites in four sections of the county shows may be an indication of the reason for this pattern. Wastewater effluent directly into the French Broad River also contributes to some degree.

Nutrient concentrations in the French Broad River are also influenced by urban runoff and runoff from agricultural areas with more extensive livestock operations, particularly livestock concentrated on more steeply sloping land (Figures 18, 19 and 20). However, the greatest influence on orthophosphate concentrations is clearly the Metropolitan Sewerage District plant. Median orthophosphate concentrations increase dramatically between the site in Asheville and the site downstream from the plant. Both zinc and orthophosphate concentrations are probably influenced by the plant. Zinc orthophosphate is added to the drinking water supply, but not removed before release of the effluent from the wastewater treatment process. The influence on nitrate concentrations, however, is clearly different. Median nitrate concentrations begin to rise in Asheville and reach a peak in Marshall. At this point all of the tributaries in the northern and northwestern part of the county which show the most elevated sediment and nitrate concentrations as well as the urban streams of the Asheville area have entered the river.

With only 30%, Buncombe County has a very low percentage of sites that rate excellent or good. In contrast, five of the seven counties in the program have at least 50% of their sites showing excellent or good water quality. Buncombe County is the most populous of the counties in the program and few watersheds remain undisturbed. Almost all of the sites that rate poor are either urban streams or are in the erosion sensitive northern and northwestern part of the county. The one exception is the site at the French Broad River at Corcoran Park. This site's rating fell from fair to poor in the past year because of exceptionally high pollutant levels that occurred when samples were collected following the passage of the air boat. The boat creates unusual turbulence near the banks which stirs up bottom sediment. Nutrients and heavy metals often collect on the bottom with the sediment and the turbulence brings these elements back into the water column. Most of these elements probably quickly settle out, but during the peak periods the boat makes frequent trips and the sediment is repeatedly churned up. The banks are very muddy in the section of the river where this site is located, so this may only be a local problem that does not affect the water quality downstream.