Theory 26/River deltas/Threshold lens
Avulsion Follows a Slope Ratio
The claim
Delta avulsion occurs above a threshold in the ratio of channel slope to floodplain slope, so a channel slightly steeper than its surroundings eventually switches.
01Mechanism
Water seeks the steeper path; as the channel aggrades, the ratio crosses the point where the alternative is cheaper.
02Prediction
Avulsion should occur at a slope ratio.
03Refutation
Avulsion tracking flood magnitude would remove the slope comparison.