Alluvion

ALLUVION - The insensible increase of the earth on a shore or bank of a river by the force of the, water, as by a current or by waves. It is a part of the definition that the addition, should be so gradual that no one can judge how much is added at each moment of time. The proprietor of the bank increased by alluvion is entitled to the addition. Alluvion differs from avulsion in this: that the latter is sudden and perceptible.

AVULSION - Where, by the immediate and manifest power of a river or stream, the soil is taken suddenly from one man's estate and carried to another. In such case the property belongs to the first owner. An acquiescence on his part, however, will in time entitle the owner of the land to which it is attached to claim it as his own. Avulsion differs from alluvion in that in the latter case the change of the soil is gradual and imperceptible.
   

This entry contains material from Bouvier's Legal Dictionary, a work published in the 1850's.