Roles of the riparian vegetation: the antagonism between flooding risk and the protection of environments

Abstract

Since the beginning of the 20th century, man has domesticated his environment and caused the modification of hydraulic conditions during floods. In parallel, civil engineering has strongly progressed in the domain of hydraulic structures but especially the construction of dams and dikes has also massively increased and part of the population has lost the culture of risk by thinking they were completely out of danger from flooding. Events of hydrometeorological origin over the last 25 years has reminded man that the hydraulic infrastructures in place for a few centuries now, are not unalterable. An unmanaged vegetal colonization along the edge of watercourses (protection dikes, retention dams, appointed river banks, ect…) can present three types of inconvenience as (i) overflow in the case of watercourse containment, (ii) formation of woody jams which generate a risk of bridge obstructions or water retention, (iii) the presence of trees and their roots which damages the containment systems protecting the territories. It is important to manage the development of this vegetation in order to conserve the positive effects on the area while also limiting the negative impacts. The current boom in vegetation engineering techniques shows that man is relearning how to live as a ‘team” with nature.