Efficacy of Undisturbed Vegetated Buffers in Capturing Suspended Sediment

Abstract

The U.S. Environmental Protection Agency’s Construction General Permit requires a 50 ft (15 m) undisturbed vegetated buffer to be maintained when construction activities are adjacent to a water body. However, maintaining a buffer is not always feasible, especially in highway construction activities; therefore, a contractor may use alternatives that capture sediment at an efficiency equivalent to an undisturbed buffer. However, little research has been conducted on the sediment removal efficacy of an undisturbed vegetated buffer. Several factors influence the sediment capture efficiency of a natural vegetated buffer, including climate, soils, topography, and vegetation characteristics. This research aimed to explore the sediment removal capabilities of various vegetated buffers with factors common to Nebraska roadway construction projects using the Revised Universal Soil Loss Equation 2 Model. A multiple linear regression model was developed to analyze relationships between 7,776 model iterations. Statistical analysis indicated that decreasing the slope of the buffer and the clay and silt content in the soil increased the sediment removal efficiency of the buffer; this finding matched the conclusions of past research on vegetated filter strips and vegetated buffers. Sediment removal ranged between 77% and 99%, with an average efficiency of 94%—comparable to the efficacy of manufactured sediment barrier practices commonly used on construction sites.

Large-Scale Performance Evaluation of Various Woven Silt Fence Installations under Nebraska Highway Conditions

“…of annual precipitation Erosion and stormwater runoff rates depend on site-specific conditions such as vegetation, climate, soil characteristics, and topography. Rates can vary widely region by region, even within states [9,10]. Due to this variation in conditions, developing a single sediment barrier installation that would provide adequate protection while being cost-effective for every site and location is not feasible.…”

“…of annual precipitation, while the state of Alabama averages 1407 mm (55.4 in.) of annual precipitation [9,16]. Despite past GIS analysis indicating that the state of Nebraska has more erosive soil on average than areas in the southeast, the increased rainfall results in states in the southeast, such as Alabama, being more prone to erosion than states in the Midwestern U.S. [8].…”

“…Sediment barrier designs are typically based on rules of thumb, with little scientific research being used in the design of most standard practices [10]. Some sediment barrier testing has been conducted to improve silt fence designs and implementations and increase the body of knowledge on the state of practice [9][10][11][12][13][14][15][16][17][18][19]. Past testing efforts can be divided into three general testing methods: (1) small-scale testing (typically in flumes), (2) the field monitoring of installations on active construction projects, and (3) large-scale testing that subjects entire installations to controlled conditions.…”