Downstream hydraulic geometry describes systematic changes in river channel characteristics along the length of a river: as longitudinal slope (gradient) decreases downstream, channel width, depth, cross-sectional area, and discharge all typically increase (a direct/positive relationship exists between distance downstream and these parameters, meaning an inverse relationship with slope), while sediment (bedload) grain size typically decreases downstream (downstream fining) — meaning slope and bedload size are directly (positively) related, not inversely related.
As rivers flow from headwaters to mouth, longitudinal slope characteristically decreases while channel width, average discharge, and channel cross-sectional area all increase due to increasing...
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