A critical assessment of the research conducted at the hydraulics and erosion control laboratory – a focus on rolled erosion control systems applied to hillslopes

Abstract oncern over erosion and pollution potential of human modified hillslopes has caused a rapid expansion in the erosion control industry. One technology that has seen the most significant growth has been rolled erosion control systems (RECSs). Numerous systems have recently been marketed to take advantage of this growth industry. Unfortunately the performance specifications for many of these systems is limited. The result is a specifiers or land managers nightmare, because they are inundated with a variety of product claims, but limited formal testing to make an informed decision. To address this knowledge gap the Hydraulics and Erosion Control Laboratory (HECL) was established at Texas A and M University. One goal of this facility was to fairly assess, on an annual basis, the erosion and vegetation growth performance of a variety of RECSs. Thresholds for soil erosion and vegetation cover were formulated and if a system did not meet both criteria it was not placed on the Approved Product List for the Texas Department of Transportation. Additionally, several other state departments of transportation have started to consider using the results from HECL to fashion their own approval lists. Despite the many advances made at the HECL, a number of potential problems exist with their statistical framework and their research protocols. A detailed examination of the HECL data (1991–1996) is provided, and it is apparent that some modifications are justified to provide further insights into the fundamental operation of RECSs. Modifications in rainfall simulation protocol, data collection protocol, and incorporation of process observations are necessary to identify reasons why some RECSs are more effective than others in reducing erosion and enhancing growth of vegetation. Additionally, a new statistical technique is applied to the HECL soil erosion data to define thresholds to replace the arbitrarily set limits. The constructive criticisms and suggestions of this critique are presented in the hope that they lead to better characterization of the performance of RECSs and focus increased attention on their cardinal properties. It is argued that a process orientation in future work conducted at HECL will greatly advance the technology of RECSs and the erosion control industry.

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