Comparison of Erosion Control Methods in Steep Slopes

Steep soil slopes that have no vegetation or have a poor cover are rapidly eroded when rainfall occurs. This situation may also occur in cut sections of highways, or downstream of culverts because of flow concentration at the conduits' outlet. Protection at the outlet may be riprap, gabions, cellular confinement systems, biotechnology, soil cement or others, depending on materials availability. Peru is a very diverse country, with climates ranging from hyper arid in the Pacific Coast to very humid rain forests in the Amazon Jungle. In some areas of Peru, rocks suitable for erosion control are not available, such as the lower Amazon jungle or some valleys in the Andes. The use of riprap for erosion control becomes prohibitive because of the high costs of material that has to be brought from distant areas. In humid areas, vegetation offers protection against flows occurring naturally. However, cross drainage structures at low points collect water from gutters so that discharges are higher than those produced by Nature. Therefore, it is necessary to determine in which cases culvert discharges are allowed to flow directly into natural terrain and when reinforcement is needed. Native vegetation is preferable for use in erosion control. However imported species that have adapted well to the country and have not produced adverse results to the environment may be used. Studies have been carried out in the United States and other countries to protect the soil against erosion using vegetation or biotechnology. Studies by Temple have been conducted to explore the use of vegetation in the downstream slope of dams as protection against erosion by overtopping. Controlling the erosion has become a subject of research and design oriented publications have been printed in recent years. Although publications from FHWA include erosion control measures downstream of culverts using riprap and gabions, little information have been found on the use of vegetation or biotechnology measures downstream of cross drainage structures. This paper presents a preliminary experimental study conducted to explore the use of vegetation for erosion control. Copyrighted erosion control measures such as Geoweb ® and Mac Mat® have been tested in an independent study for its potential use in Peru in the situations describe above.