Opinion of the Court. 223 U.S. boundary was permanently fixed by the State Commissioners' high-water line and no subsequent encroachment of the water could affect the rights of the owner. (1) It is the established rule that a riparian proprietor of land bounded by a stream, the banks of which are changed by the gradual and imperceptible process of accretion or erosion, continues to hold to the stream as his boundary; if his land is increased he is not accountable for the gain, and if it is diminished he has no recourse for the loss. But where a stream suddenly and perceptibly abandons its old channel, the title is not affected and the boundary remains at the former line. Rex v. Yarborough, 3 B. & C. 91; S. C., 2 Bligh, N. S. 147; Gifford v. Yarborough, 5 Bing. 163; New Orleans v. United States, 10 Pet. 662, 717; Banks v. Ogden, 2 Wall. 57; County of St. Clair v. Lovingston, 23 Wall. 46, 67, 68; Jefferis v. East Omaha Land Co., 134 U. S. 178, 190-193; St. Louis v. Rutz, 138 U. S. 226, 245; Nebraska v. Iowa, 143 U. S. 359; Shively v. Bowlby, 152 U. S. 1, 35; Hale, De Jure Maris, Ch. 1, 4, 6, Hargrave's Law Tracts; Mulry v. Norton, 100 N. Y. 424. The doctrine that the owner takes the risk of the increase or diminution of his land by the action of the water applies as well to rivers that are strong and swift, to those that overflow their banks, and whether or not dykes and other defenses are necessary to keep the water within its proper limits. It is when the change in the stream is sudden, or violent, and visible, that the title remains the same. It is not enough that the change may be discerned by comparison at two distinct points of time. It must be perceptible when it takes place. "The test as to what is gradual and imperceptible in the sense of the rule is, that though the witnesses may see from time to time that progress has been made, they could not perceive it while the process was going on." County of St. Clair v. Lovingston, supra (p. 68). We are confined to the allegations of the bill. We have 223 U.S. Opinion of the Court. not the advantage of proof and findings, or even of a particularized description in the bill itself, as to the precise character of the alterations in the banks of Brunot's Island which took place during the long period to which the bill refers. It is alleged "that subsequent to the estab lishment in 1865 by said Commissioners of the line of high water mark, as aforesaid, a considerable amount of the soil of the shore of said Brunot's Island on the so-called back channel, within the said high water mark was washed away from time to time by heavy floods and freshets, so that a large part of the upland of the island, that is the land above high water mark, became and was overflowed and slightly submerged by water, but said land was not submerged to an extent sufficient to permit of navigation of any kind thereover." There is no other statement on the point save that the bill asserts that the complainant was entitled to reclaim "keeping at all times within the lines of the part that had been torn away by the violence of the waters." It is manifest that these allegations are inadequate to support the complainant's contention. The determining words are that the land was "washed away from time to time by heavy floods and freshets," and the reference is to what occurred in many years. This is far from a statement that at any particular time there was such a sudden, violent, and visible change as to justify a departure from the ordinary rule which governs accretion and diminution albeit the stream suffer wide fluctuations in volume, the current be swift, and the banks afford slight resistance to encroachment. For example, the general principle of accretion, which has that of diminution as its correlative, applies to such rivers as the Mississippi and the Missouri, notwithstanding the extent and rapidity of the changes constantly effected. Jefferis v. East Omaha Land Co., supra; Jones v. Soulard, 24 How. 41; Saulet v. Shepherd, 4 Wall. 502; VOL. CCXXIII- -40 Opinion of the Court. 223 U. S. County of St. Clair v. Lovingston, supra; St. Louis v. Rutz, supra. In Nebraska v. Iowa, supra, the question concerned the boundary between the two States, which, by the acts of admission, was the middle of the main channel of the Missouri River. Between 1851 and 1877, in the vicinity of Omaha, there were marked changes in the course of this channel so that in the latter year it occupied a very different bed from that through which it flowed in the former year. The opinion of the court describes in detail the physical conditions along the river. The court said (pp. 368-370): "The current is rapid, far above the average of ordinary rivers; and by reason of the snows in the mountains there are two well known rises in the volume of its waters, known as the April and June rises. The large volume of water pouring down at the time of these rises, with the rapidity of its current, has great and rapid action upon the loose soil of its banks. The only thing which distinguishes this river from other streams, in the matter of accretion, is in the rapidity of the change caused by the velocity of the current; and this in itself, in the very nature of things, works no change in the principle underlying the rule of law in respect thereto. Our conclusions are that, notwithstanding the rapidity of the changes in the course of the channel, and the washing from the one side and on to the other, the law of accretion controls on the Missouri River, as elsewhere; and that not only in respect to the rights of individual landowners, but also in respect to the boundary lines between States. The boundary, therefore, between Iowa and Nebraska is a varying line, so far as affected by these changes of diminution and accretion in the mere washing of the waters of the stream." And, in the same case, the decision clearly points the distinction between the losses and gains thus described, and an abrupt, visible change where at one place, at a particular time, the river having "pursued a course in the nature of an ox-bow, suddenly cut through the neck of the bow and made for itself a new channel" (p. 370). The present case falls within the category first mentioned, and according to general principles of law the owner would bear the losses caused by the washings of the river. The bill also alleges that "some years ago the United States Government, in the interest of navigation and in order to increase the depth of water in the harbor of Pittsburgh, caused a dam to be constructed across the Ohio River a short distance below said Brunot's Island known as the Davis Island Dam. The effect of this dam was to very decidedly increase the depth of the water in the channel back of Brunot's Island, and to cause the water of the river to flow higher upon the land of your orator, and to submerge same to a far greater extent and in fact to make said water which submerged your orator's land navigable at certain times, and for certain purposes, which was not navigable before the construction of said dam." It will be observed that it is said that the United States caused the erection of the dam in the interest of navigation. The complainant purchased the island subsequently, in the year 1896. And we are not concerned here with the question whether there was any appropriation of land of the former owner by the United States and a cause of action arose to recover its value. Gibson v. United States, 166 U. S. 269; United States v. Lynah, 188 U. S. 445; Bedford v. United States, 192 U. S. 217; Manigault v. Springs, 199 U. S. 473; C., B. & Q. Ry. v, Drainage Commissioners, 200 U. S. 561, 583, 584. So far as the bill shows the dam was lawfully built, and the allegations with respect to it wholly fail to state any case entitling the complainant to relief by reason of its construction. (2) The complainant, however, insists that the effect of the Pennsylvania statute was to fix the boundary of the island permanently at the State Commissioners' high water line, and hence that within that line it was entitled to make the desired reclamation and improvement. This statute (act of sixteenth April, 1858), provided that the Commissioners' lines approved by the court should "forever after be deemed, adjudged and taken firm and stable for the purposes aforesaid." The Supreme Court of Pennsylvania has held that the purpose of the act was to regulate the rights of the public in respect to navigation and to prevent private rights from being exercised to the prejudice of the public interest. Wainwright v. McCullough, 63 Pa. St. 66; Zug v. Commonwealth, 70 Pa. St. 138, 142; Poor v. McClure, 77 Pa. St. 214, 219; Allegheny City v. Moorehead, 80 Pa. St. 118, 139, 140. In Wainwright v. McCullough (1869), supra, that court, holding that the statute was not applicable to disputed boundaries between private owners, considered the navigable character of the rivers to which it related, the extent of riparian rights under the law of the State, and the meaning of the act in the light of the mischief which it was intended to correct. The court said (p. 73): "In order to arrive at the legal effect of the lines established by the commissioners under that act, we must ascertain its true purpose; and to reach this, it becomes necessary to examine the navigable character of the rivers Allegheny, Monongahela and Ohio, and the rights of the riparian proprietors upon their banks. These rivers are among the largest in the state; larger than the Schuylkill and Lehigh, recognized as navigable in the early history of the province, and have been repeatedly held by name to be rivers naturally navigable, and therefore classed with the Delaware and Susquehanna: Carson v. Blazer, 2 Binney, 478; Shrunk v. Schuylkill Nav. Co., 14 S. & R. 79, 80; Hunter v. Howard, 10 S. & R. 244. Many acts have been passed declaring tributaries of these rivers navigable. But an act perhaps most pertinent to this controversy is that of 8th April, 1785, 2 Sm. Laws, 317, |