CONTROLS ON POOLS: SOME RESULTS FROM A PARTICLE INTERACTIONS CELLULAR AUTOMATA MODEL OF STEEP, GRAVEL-TO-COBBLE CHANNELS

Influences on pool forms in steep, gravel-to-cobble channels were evaluated using a cellular automata model. Particle mobility in the model channels is dominated by particle interactions, in which the local mobility of particles of a given size is assumed to depend on the configuration of nearby particles. Model runs were conducted with varying levels of particle mobility, bed width, slope, and width of the particle size distribution. The channel bed surface obtained at the end of each run was analyzed to identify large connected deeps, with a length scale longer than half the channel width. For comparison, patches of coarse sediment were also identified, using the same size cutoff. The average spacing of pools and patches was identified for a range of values of four initial characteristics of the model channel: varying bed width, slope, sorting (width of the size distribution), and the degree of particle mobility. The strongest response in terms of pool characteristics was a strong decrease in pool spacing as the width of the particle size distribution increased, accompanied by a weaker increase in patch spacing. Pool spacing showed no trend with increasing slope, for slopes in the range of 1 to 10 percent. Trends with increasing particle mobility and bed width were weak.