Jett McFalls

Comparison of Field and Laboratory Experiment Test Results for Erosion Control Products

The purpose of this study was to compare soil loss results from field and laboratory experiments on five rolled erosion control products (RECPs) and one spray-on bonded fiber matrix (BFM). Beginning in 1990, erosion control products to be used on Texas highway embankments, such as rolled blankets and hydromulches required evaluation of their soil erosion control effectiveness in a field laboratory developed by Texas Department of Transportation (TxDOT) and Texas Transportation Institute (TTI). Products were tested on 6.1-meter wide test plots on an embankment of either a 33% (21.3 meters long) or 50% (15.2 meters long) slope during vegetation growing seasons, using simulated rainfalls. Products that performed well received the approval for Texas highway application. This field testing program was revised in the end of 2001 and transformed to be conducted in an indoor laboratory. The standard test plot size was reduced to 1.8 by 9.1 meters. Tested slopes maintained at either 33% or 50%. The comparison results of field and indoor laboratory data indicate that regardless of the slope and the soil type, the soil loss ratio between field and indoor data maintains almost the same. The effects of rainfall magnitude, raindrop size, and test plot size are discussed.

Proposed Test Protocol for Evaluating Performance of Sediment Control Devices for Roadside Storm Water Runoff

This paper details an official testing program developed by researchers at the Texas Transportation Institute (TTI) to classify sediment retention devices on the basis of their sediment removal performance. The testing facility designed as part of this study was constructed at the Texas Department of Transportation–TTI Hydraulics, Sedimentation, and Erosion Control Laboratory (HSECL) located at the Texas A&M University Riverside Campus. The facility consists of a parabola-shaped testing channel 4.6 m (15 ft) wide and 5.5 m (18 ft) long with a maximum depth of 0.8 m (2.5 ft) at the center and a slope of 3%. Two commercially available artificial sediments were mixed in equal proportions to create the artificial storm water for testing. The flow rate and turbidity of the water entering and leaving the channel were monitored for the duration of the test. The turbidity measurements were converted to suspended solid concentration by using a relationship developed in the HSECL laboratory. A simple mass balance calculation was used to determine the amount of sediment trapped in the channel.