§ 230. New formations through accretion may be artificial or natural. They are artificial if they are the outcome of human work. They are natural if they are produced through operation of nature. And within the circle of natural formations different kinds must again be distinguished—namely, alluvions, deltas, new-born islands, and abandoned river beds.
Artificial Formations.
§ 231. Artificial formations are embankments, breakwaters, dykes, and the like, built along the river or the coast-line of the sea. As such artificial new formations along the bank of a boundary river may more or less push the volume of water so far as to encroach upon the other bank of the river, and as no State is allowed to alter the natural condition of its own territory to the disadvantage[451] of the natural conditions of a neighbouring State territory, a State cannot build embankments, and the like, of such kind without a previous agreement with the neighbouring State. But every State may construct such artificial formations as far into the sea beyond the low-water mark as it likes, and thereby gain considerably in land and also in territory, since the extent of the at least three miles wide maritime belt is now to be measured from the extended shore.
Alluvions.
§ 232. Alluvion is the name for an accession of land washed up on the sea-shore or on a river-bank by the waters. Such accession is as a rule produced by a slow and gradual process, but sometimes also through a sudden act of violence, the stream detaching a portion of the soil from one bank of a river, carrying it over to the other bank, and embedding it there so as to be immovable (avulsio). Through alluvions the land and also the territory of a State may be considerably enlarged. For, if the alluvion takes place on the shore, the extent of the territorial maritime belt is now to be measured from the extended shore. And, if the alluvion takes place on the one bank of a boundary river, and the course of the river is thereby naturally so altered that the waters in consequence cover a part of the other bank, the boundary line, which runs through the middle or through the mid-channel,[452] may thereby be extended into former territory of the other riparian State.
[452] See above, § [199], No. 1.
Deltas.
§ 233. Similar to alluvions are Deltas. Delta is the name for a tract of land at the mouth of a river shaped like the Greek letter Δ, which land owes its existence to a gradual deposit by the river of sand, stones, and earth on one particular place at its mouth. As the Deltas are continually increasing, the accession of land they produce may be very considerable, and such accession is, according to the Law of Nations, considered an accretion to the land of the State to whose territory the mouth of the respective river belongs, although the Delta may be formed outside the territorial maritime belt. It is evident that in the latter case an increase of territory is the result, since the at least three miles wide maritime belt is now to be measured from the shore of the Delta.
New-born Islands.