estates. By this term is understood what retains the river in its natural channel, when there is the greatest flow of water. 2. The owner of the bank of a stream, not navigable, his in general the right to the middle of the stream. Vide Riparian Proprietor. 3. When by imperceptible increase the banks on one side extend into the river, this addition is called alluvion. When the increase is caused by the sudden transfer of a mass of earth or soil from the opposite bank, it is called an increase by avulsion.