Production, pattern and hydromorphic effects of woody debris in a stream of the Massif Central (France).

摘要

The majority of the scientists who have studied the effect of woody debris accumulations in headwater streams make reference to the rivers of North America. Within the framework of this article, we analyze the characteristics of woody debris and their effects on the hydraulic, granulometric and topographic conditions of the bed within an European geographical context: a headwater stream of the Donlon river sub-basin, within the Allier basin, whose banks have not been maintained since the middle of the 20th century. We found evidence of a riparian origin to the woody structures found in the bed and a variety of hydro-geomorphological conditions related to the presence of these structures in spite of relatively small quantities (7 to 32 m(3)-ha(-1)). These structures are not equally distributed along a continuum, rather their distribution is governed by various factors. The mechanisms of deadwood production and storage are controlled by the characteristics of the riparian forest and by fluvial forms that can change over decadal time scales because of anthropomorphic actions. The characteristics of dead wood accumulations and their hydraulic impact and role in sediment dynamics are distinguished by the geomorphological evolution of the reach or according to whether it is aggrading or incising.