avulsion

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The forcible tearing away of a body part by trauma or surgery.
• noun The sudden movement of soil from one property to another as a result of a flood or a shift in the course of a boundary stream.

from The Century Dictionary.

• noun A pulling or tearing asunder or off; a rending or violent separation.
• noun A fragment torn off.
• noun In law, the sudden removal of soil from the land of one man and its deposit upon the land of another by the action of water.

from the GNU version of the Collaborative International Dictionary of English.

• noun A tearing asunder; a forcible separation.
• noun A fragment torn off.
• noun (Law) The sudden removal of lands or soil from the estate of one man to that of another by an inundation or a current, or by a sudden change in the course of a river by which a part of the estate of one man is cut off and joined to the estate of another. The property in the part thus separated, or cut off, continues in the original owner.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The loss or separation of a body part, either by surgery or due to trauma
• noun An abrupt change in the course of a river, typically from one channel to another
• noun hydrology Movement of soil during a flood, or during a change in the course of a river, especially when a resulting change of land ownership is involved

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an abrupt change in the course of a stream that forms the boundary between two parcels of land resulting in the loss of part of the land of one landowner and a consequent increase in the land of another
• noun a forcible tearing or surgical separation of one body part from another