TWRI grant recipient determines efficacy of erosion control compost
By Emily Baker
Lindsay Birt, a graduate student at Purdue University and formerly of Texas A&M University studying watershed management and hydrology and a recipient of a 2005-2006 Texas Water Resources Institute research grant, evaluated the effectiveness of using compost rather than conventional hydroseeding or topsoil to reduce erosion from roadside construction.
The Texas Department of Transportation (TxDOT) has approved and promoted the use of compost as a stormwater best management practice during highway construction, encouraging compost application on the slopes of highways which frequently erode when topsoil and vegetation is removed. The addition of erosion control compost (ECC) supplies nutrients, retains moisture and helps establish vegetation on harsh growing sites where traditional erosion control methods have failed.
Through her research, Birt concluded that particle size, soil moisture capabilities and time at which rainfall is applied affect surface runoff. While TxDOT specifications use ECC at 5 cm depth on a maximum 3:1 slope, Birt found that an application depth of 1.3 cm is more effective for reducing first flush runoff and interrill erosion rates. According to Birt’s research, the depth of compost application can be minimized, possibly reducing construction costs.
Birt’s research relied on data from a constructed and calibrated indoor rainfall simulator that measured runoff rates, interrill erosion and interrill erodibility from five compost treatments in accordance with TxDOT specifications in order to determine the optimal application depth of compost to minimize runoff. The treatment applications Birt used in her research included untreated woodchips, composted yard trimmings, topsoil and fertilizer-paper mulch blend.
Birt was advised by Dr. Russell Persyn, assistant professor, Agricultural and Biosystems Engineering Department, South Dakota State University and formerly of Texas A&M University, and Dr. Patricia Haan, associate professor, Department of Biological and Agricultural Engineering, Texas A&M University.
Birt said she hopes that her research serves as a model for optimal use of ECC and, when applied to real-world situations, will aid and encourage TxDOT in its use of compost on hill slopes along highways.
For the full report of Birt’s research, click here.