Hydrogeomorphic adjustments of stream channels disturbed by urban runoff (Yzeron river basin, France)
Ajustement hydrogéomorphologique des lits de rivière perturbés par le ruissellement urbain (rivière Yzeron, France)
Navratil, O. ; Breil, P. ; Schmitt, L. ; Grosprêtre, L. ; Albert, M.B.
Type de document
Article de revue scientifique à comité de lecture
Affiliation de l'auteur
IRSTEA GRENOBLE UR ETGR FRA ; IRSTEA LYON UR HHLY FRA ; UNIVERSITE DE STRASBOURG FRA ; UNIVERSITE DE LYON II UMR 5600 FRA ; IRSTEA ANTONY UR HBAN FRA
Résumé / Abstract
This paper presents a field investigation on hydrogeomorphic adjustments of small streams in a 147 km2 periurban catchment, the Yzeron River catchment located in France. The rapid development of periurban areas in the world is now considered as one of the main factor impacting river systems. Urban disturbances are most of the time associated with irreversible alterations of the hydrological regime, the sediment yields, with major ecological impacts and additional socio-economical costs. Nineteen stream reaches have been considered in this study, with drainage areas ranging from 0.2 to 33.9 km2 and total impervious areas ranging from 1% to 52% of the basin surface. A regional analysis was led in order (i) to quantify the hydrogeomorphic adjustments of stream channels in this periurban context, i.e. the ratios between observed values and reference/rural values; and (ii) to identify the main anthropogenic controlling factors of these adjustments. Results show that urban river channels experience a global enlargement, with a mean bankfull discharge ratio of 1.8, bankfull width and depth ratios of 1.3 and a bankfull area ratio of 1.8. This study also outlines the global increase of hydrogeomorphic adjustments with the increase of the fraction of impervious area and the level of disturbance of the flood regime. However, local anthropogenic factors seem to be much more relevant to explain the highest adjustment ratios at several river reaches (enlargement ratio up to 55). The vicinity of a river reach with road sewers and/or the urban areas is identified to be a very important factor that affects significantly the smallest streams (drainage area less than 5 km2). On the contrary, at several reaches no significant deepening or widening was observed although roads/urban sewers and urban areas were identified in their catchment. Several hypotheses are proposed, but additional works with new data (river monitoring) would be needed to propose management and/or restoration guidelines in periurban catchments.
Journal of Hydrology, num. 485, p. 24 - 36