Hydraulic resistance in mixed bedrock-alluvialmeandering channels

FERNÁNDEZ, ROBERTO; GARCÍA, MARCELO H.; VITALE, ALEJANDRO J.; PARKER, GARY

JOURNAL OF HYDRAULIC RESEARCH

INT ASSOC HYDRAULIC RESEARCH

Lugar: Madrid; Año: 2020

0022-1686

We present an experimental analysis of hydraulic roughness variations due to changes in alluvial cover in a mixed bedrock-alluvial meanderingchannel with larger bedrock roughness than alluvial roughness. Three sets of experiments were conducted in a highly sinuous flume: one with barebedrock, and two with enough sediment to cover 21% and 78% of the bedrock respectively. We compare our results with data from experimentspreviously conducted in the same flume with flat- and smooth-bed, and data from experiments with fully alluvial conditions. Our results show that: (1)hydraulic resistance in a mixed bedrock-alluvial channel changes with the degree of alluviation; (2) hydraulic resistance is greater for bare-bedrockconditions, and decreases as sediment supply increases; (3) if bedforms appear, hydraulic resistance may be larger than for bare bedrock conditionsdue to form drag; (4) fluctuations in alluvial cover due to freely-migrating bars lead to instantaneous changes in hydraulic resistance.