What techniques can be used to revegetate riverbank riprap?

Abstract

Riprap application on riverbanks is a biological interruption within the shoreline environment and the use of vegetation (plant-based engineering techniques) is preferable to it. Additionally, when the use of riprap is required, it is best to revegetate for landscape, ecological and occasionally mechanical reasons. Also for existing riprap, if it is not possible to remove or replace it with vegetative techniques, it is better to incorporate vegetation within the existing riprap. This article briefly reviews the various existing revegetation techniques and then presents the results of experiments to revegetate riprap conducted on the banks of the Arve River. Five techniques and their costs were compared. Among these techniques the simple covering of soil over rocks associated with seeding and live cuttings is the cheapest. The beneficial effect of the geotextile is not clear from this experiment, although it is known to improve the environmental conditions and hold the soil in early years, before being replaced by roots. The drilling technique to insert cuttings is very expensive, but allows for very high survival rates. Three unusual riprap revegetation techniques involved in the river Columbia in Canada are also presented.