Configurational stability in gravel-bed rivers
Simon Dadson (1) and Michael Church (2)
(1) Department of Earth Sciences, University of Cambridge, Downing Street, 
Cambridge, CB2 3EQ.  United Kingdom.
(2) Department of Geography, University of British Columbia, Vancouver, British Columbia, V6T 1Z2. Canada.


Gravel-bed rivers derive stability from the configuration of grains on the 
channel bed. Grains interact with each other to form clusters which are more 
stable together than their constituent grains would be individually. Here, a 
model is presented for the configurational stability of river beds which 
shows that structured gravel requires an order of magnitude greater shear 
stress for entrainment than unconfined material. These results are then used 
in ensembled monte-carlo simulations to investigate the growth of gravel-bed 
stability, and changes in sediment transport rate over time as 
configurational stability develops. The predictions made agree qualitatively 
with previously published field and experimental observations.  These 
theoretical and observational findings are discussed in the context of 
related work on structures and jamming in granular media.