Estimation of fine sediment stocks in gravel bed rivers including the sand fraction

ABSTRACT Fine sediment stored in the gravel bed is an important component of river systems. Current field protocols usually allow evaluation silt–clay fraction fine stocks only and neglect sand fraction. This study proposes a new protocol to quantify stocks, including inside matrix. were sampled within patches 0.30 m × on dry surface, separating surface layer subsurface layer. The grain‐size distribution samples was obtained by sieving (10 mm, 2 500 μm 100 μm) over bucket, using known volume water. mass below measured based concentration bucket. local then integrated whole reach assigning facies, which assumed be homogeneously distributed. methodology applied 1 km long River Galabre (Southern French Alps), characterized significant upstream input. Results from measurements show large amount both layers. quantity can up three times silt–clay. An estimation porosity showed that material may play role structuring bed, since increases with increasing content. potential stock re‐suspended due channel migration found same order magnitude as budget estimated flux hydrometric station studied reach.