One who has land bounded by water may acquire title by accretion, or lose it by erosion. These words mean the gradual addition or subtraction of the riparian land by the action of the water in adding to of wearing away the shore. Such changes may add to land on one side of the water and take land from the other, changing the thread of the stream, and the extent of the land of the respective owners grows or diminishes accordingly.
The sudden breaking away of a perceptible body of land is said to be "avulsion," and it is said that the owner can claim the same unless he allows it to remain contiguous to other land until it becomes attached thereto.96
The rule generally applied in the apportionment of accretions is set out below.
In Kehr v. Snyder,97 the court says:
" 'Measure the entire river front of survey 759 as it existed in 1860, when the third division of Cahokia commons was first laid out,' and note the aggregate number of feet frontage, as well as that of each parcel or lot; then measure a line drawn as near as may be with the middle thread of so much of the stream as lies opposite the shore line so measured. Having done this divide the thread line thus measured in as many equal parts as there are lineal feet in the shore line giving to each proprietor as many of these parts as his property measures feet on the shore line; then complete the division by drawing lines between the points, designating the lot or parcel belonging to each proprietor both upon the shore and the river lines."
96. Missouri v. Nebraska, 196 U. S. 23.
97. 114 111. 313, at p. 317.