Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: FRIDAY, June 29, 1990 TAG: 9006300398
SECTION: SMITH MOUNTAIN TIMES PAGE: SMT-1 EDITION: BEDFORD/FRANKLIN
SOURCE: DAVID M. POOLE STAFF WRITER
DATELINE: LENGTH: Long
It would only be a matter of time, the Apco men explained, before tons of silt would make the upper end of the Blackwater River too shallow for most boats.
The prediction came true. The marina where Perdue once pumped gasoline and sold night crawlers is now buried under a sandbar overgrown with grasses and willow trees.
Siltation is a mixed blessing for Smith Mountain Lake. To biologists, the process diversifies the lake's ecology, improves water quality and provides a varied habitat for fish and wildlife. To landowners, siltation can mean the loss of boat docks and diminished property values.
"It's a natural process," said Ralph Williamson of the U.S. Soil Conservation Service office in Franklin County. "That whole lake will fill up one day."
Of course, that would take hundreds of years. For a long time, siltation will not be a concern for most sections of Smith Mountain Lake. Siltation is localized in the upper ends of creeks, the points where streams flow into the 20,000-acre reservoir.
The process works like this: Topsoil erodes from the banks of creeks and rivers and is carried downstream by the fast-moving water. When the creek hits the slow-moving lake, the soils suspended in the water fall to the bottom, forming silt deposits that inch their way downstream.
Some of the heaviest siltation can be found at Lynville Creek, Beaverdam Creek, Stoney Creek, Gills Creek and the Blackwater River.
Williamson said the silt dumped into the Blackwater alone amounts to hundreds of tons each year. The river's drainage area is made up of 100,000 acres, including some of the most intensively farmed sections of Franklin County.
Assuming an annual erosion rate of 200 pounds of silt per acre, the Blackwater deposits some 500 dump-truck loads of soil into Smith Mountain Lake each year, Williamson said.
Dredging requests have increased in recent years, as lot owners have endeavored to maintain the channel in front of their houses and as developers have sought to sell land in areas that is prone to siltation.
"A lot of the prime property - the deep-water property - is already sold," said Thom Leedom, a biologist with the U.S. Army Corps of Engineers. "So we have developers coming in and looking at the shallow water and steep land, trying to find ways to develop it."
Leedom's job is to enforce federal wetlands statutes, which often means explaining to people that although siltation may be unfortunate for individual landowners, it is not a bad thing for the biological well-being of Smith Mountain Lake.
"Like anything," Leedom said, "There are advantages and disadvantages."
The wetlands grasses and other vegetation that grows on silt-generated sandbars play an important role in diversifying and enriching the biology of Smith Mountain Lake, he said.
The wetlands grasses absorb phosphates and other pollutants from the water. The shallow areas formed by siltation provide cover for small fish. The vegetation provides nesting for birds and other animals.
Without siltation, the Smith Mountain reservoir would be what Leedom referred to as a "monotype lake" with generally uniform depths and rip-rapped shorelines, Leedom said.
The goal of diversifying the lake's biology is the last thing on the minds of landowners trying to fend off siltation.
Leedom said the U.S. Corps of Engineers tries to strike a balance when evaluating dredging permits, Leedom said. Generally, the corps requires a 20-foot buffer from each shoreline and a 50-foot buffer from the back of coves. Leedom said that allows landowners to maintain a navigable channel while preserving some shallow areas.
Wetlands vegetation, however, is off limits, protected by federal statutes, he said.
Tim Gardner of Moneta runs a dredging company at Smith Mountain Lake, and he agrees that preserving wetlands areas makes sense. "There's good sides and bad sides to what's happening," he said during a recent tour of siltation in Beaverdam Creek in Bedford County.
Last year, a Glade Hill man received a federal permit for an ambitious dredging project on the Blackwater River.
Palsey Law started from Brooks' Mill Bridge at Virginia 834 with plans to dredge for several thousand feet downstream. He planned to break even - pay for a dredging crew by selling the sand pulled from the river bottom.
Residents of nearby Windsor Point subdivision viewed Law as a godsend because the dredging would remove the silt that had landlocked their community boat dock.
But Law's crew stopped after dredging only 800 feet. "It ain't going as good as we thought it would," he said in a recent interview.
The sand from the Blackwater is riddled with mica deposits, making it unacceptable to cement and concrete manufacturers. The market for the sand has been limited to asphalt companies and farmers.
"We didn't give up. We're just kicking around a few ideas," Law said.
Leedom said Law's experience shows the difficulty of reversing the siltation process on a large scale.
"It's coming in there too fast," Leedom said.
by CNB