Justia Federal District Court Opinions

On March 16, 1854, the Omaha Indian Tribe entered into a treaty with the United States in which certain lands, including 2,900 acres of land located in the then Territory of Nebraska in an area known as Blackbird Bend, were reserved by the Tribe as part of an agreement which ceded to the United States all other land west of the "centre of the main channel of said Missouri river . . . ."1 Act of March 16, 1854, Art. 1, 10 Stat. 1043. At the time the Omaha Indian Reservation was established the reserved land within Blackbird Bend was situated on the west side of the Missouri River. However, by 1923 the river had moved more than two miles to the west of the original boundary line so that much of the land contained within the original Blackbird Bend area was situated on the east side of the river. The defendants assert that early movements of the Missouri River had completely washed away the Reservation lands and that the land now existing within the former boundaries of the Barrett Survey is soil which has accreted to the Iowa riparian land.

As a result of this dispute the United States and the Omaha Indian Tribe, a duly organized corporate body, in 1975 sought equitable relief asserting their right to the 2,900 acres of land now situated in Monona County, Iowa. The United States throughout this litigation acts in the capacity of trustee of the Tribe's reservation lands.² The defendants claim title to the land in dispute and seek by way of counterclaims to quiet title in their names. The defendants are Roy Tibbals Wilson, Harold Jackson, a tenant of Roy Tibbals Wilson, Harold Sorenson, Luea Sorenson, Darrell L. Sorenson, Harold M. Sorenson, Charles Lakin, Florence Lakin, the State of Iowa and the State Conservation Commission, R.G.P. Incorporated, Travelers Insurance Company, mortgagee of R.G.P., and Otis Peterson, a tenant of R.G.P.

From at least the 1940's until April 2, 1975, the defendants and their predecessors in title had occupied, cleared and cultivated the land in dispute. After April 2, 1975, with the assistance of the Bureau of Indian Affairs and with the approval of the United States, the Omaha Indian Tribe seized possession of the land and is presently farming it. After the Tribe had seized the land the United States District Court, the Honorable Edward J. McManus presiding, granted a preliminary injunction permitting occupancy of the land by the Tribe during the pendency of this litigation, but requiring certain accounting procedures pertaining to the crops grown on the land be instituted. Following trial and entry of judgment in favor of the defendants, this court on May 13, 1977, entered a stay pending appeal maintaining in effect the terms of the district court's preliminary injunction.

After a lengthy trial the district court, the Honorable Andrew W. Bogue presiding, found that the boundary of the Omaha Indian Reservation had shifted with the movements of the Missouri River and quieted title in the defendant landowners. The court found that the plaintiffs had failed to prove that the river movements were controlled by the doctrine of avulsion and held that the river had changed by reason of the erosion of reservation land and accretion to Iowa riparian land. United States v. Wilson, 433 F.Supp. 67 (N.D.Iowa 1977). The district court supplemented its findings on the merits with an opinion resolving choice of law problems, setting forth principles governing avulsion and accretion and discussing the allocation of the burden of proof. United States v. Wilson, 433 F.Supp. 57 (N.D.Iowa 1977).

I. The Issues.

The dispute centers on the ownership of land in an area known as Blackbird Bend which was surveyed in 1867 by T. H. Barrett3 on behalf of the General Land Office of the United States.⁴ The basic issue on appeal is whether the boundary of the reservation remained at its 1854 location despite the significant changes in the location of the Missouri River since that time.

We vacate the judgment of the district court rendered in favor of the defendants; we find the trial court erroneously placed the burden of proof on the Omaha Indian Tribe and failed to properly apply governing principles of federal law relating to avulsion and accretion; we hold the evidence is too speculative and uncertain to show that the reservation boundary shifted by reason of accretion and that the defendants have failed to overcome the presumptive right of possession and title in the Tribe to the reservation lands.

II. The Historical Facts.

The Treaty of 1854 established the eastern boundary of the reserved land at the center of the main channel of the Missouri River.⁵ Because the exact location of the thalweg⁶ of the Missouri River could not now be established and since the Barrett Survey was conducted only a few years after the reservation was established, the trial court accepted the Barrett Survey as representing the original location of the reservation's boundary.⁷ See Plate I.

From 1854 until sometime near 1875 it is generally accepted that the Missouri River moved east until it reached the Iowa easterly high bank.⁸ The evidence shows the river was approximately 800 feet wide at that time. The first controversial movement of the river in this case occurred after it reached its easterly position against the high bank.⁹ By 1879 a survey conducted by the Missouri River Commission showed the river, at high flood stage, to be almost 10,000 feet wide covering as much as two-thirds of the Barrett Survey meander lobe. The thalweg had shifted from against the easterly high bank to a point nearly 6,000 feet to the west. See Plate II.

After 1879 the river moved to the northeast until it reached the Iowa northerly high bank¹⁰ sometime near 1912. See Plate III. The second dispute between the parties involved the movement of the river away from its northerly high bank location to a location significantly to the south in the period between about 1912 and 1923. See Plate IV. By 1923 almost the entire peninsula described by the Barrett Survey had been cut off by the river's movement.

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NOTE: OPINION CONTAINS TABLE OR OTHER DATA THAT IS NOT VIEWABLEIII. Choice of Law.

At trial the Tribe and the government asserted that federal law should control while the defendants contended that Iowa law should have been applied. The district court, however, applied Nebraska law in evaluating the facts of the case. On appeal the Tribe and the government renew their assertion that federal law should be applied in the resolution of this case. We hold that the governing principles of federal law vary significantly with the trial court's construction of state law and that the court erred in failing to apply that federal law.

A. Interstate Boundaries.

In Oregon ex rel. State Land Board v. Corvallis Sand & Gravel Co., 429 U.S. 363, 97 S.Ct. 582, 50 L.Ed.2d 550 (1977), the Supreme Court reaffirmed the basic rule that the laws of the several states determine the ownership of the banks and shores of waterways. Id. at 378-79, 97 S.Ct. 582. However, the Court recognized an important caveat to this rule:

If a navigable stream is an interstate boundary, this Court, in the exercise of its original jurisdiction over suits between States, has necessarily developed a body of federal common law to determine the effect of a change in the bed of the stream on the boundary.

Id. at 375, 97 S.Ct. at 589.¹¹

As the Supreme Court noted in Arkansas v. Tennessee, 246 U.S. 158, 176, 38 S.Ct. 301, 306, 62 L.Ed. 638 (1918):

(T)hese dispositions are in each case limited by the interstate boundary, and cannot be permitted to press back the boundary line from where otherwise it should be located.

Cf. St. Louis v. Rutz, 138 U.S. 226, 250, 11 S.Ct. 337, 34 L.Ed. 941 (1891).

Federal common law is applicable even where only a single state is involved in a controversy with a private party, see Cissna v. Tennessee, 246 U.S. 289, 38 S.Ct. 306, 62 L.Ed. 720 (1918), or where only private parties are involved, see Hinderlider v. La Plata River & Cherry Creek Ditch Co., 304 U.S. 92, 58 S.Ct. 803, 82 L.Ed. 1202 (1938); Committee for Consideration of Jones Falls Sewage System v. Train, 539 F.2d 1006, 1009 n. 8 (4th Cir. 1976); Port of Portland v. An Island In Columbia River, 479 F.2d 549 (9th Cir. 1973); Sherrill v. McShan, 356 F.2d 607 (9th Cir. 1966); Iselin v. La Coste, 139 F.2d 887 (5th Cir.), cert. denied, 321 U.S. 790, 64 S.Ct. 791, 88 L.Ed. 1080 (1944), as long as the interests of more than one state are sufficiently implicated in the potential outcome. The rendering of a decision in a private dispute which would "press back" an interstate boundary sufficiently implicates the interests of the states to require the application of federal common law.

In this case any claim that the reservation's eastern boundary had changed would of necessity have concerned the interstate boundary between Iowa and Nebraska, at least until 1943, thereby invoking federal law since both boundaries were located at the thalweg of the Missouri River. However, in 1943 Iowa and Nebraska entered into a compact under which the boundary between the states was permanently established at the middle of the main channel of the Missouri River in essentially its position in 1943. Iowa-Nebraska Boundary Compact, Iowa Code 1971, p. lxiv; 1943 Iowa Acts ch. 306; 1943 Nebraska Laws ch. 130. Ratified by Congress in Act of July 12, 1943, 57 Stat. 494 (1943).¹² To apply the compact it is nevertheless necessary to establish title good in one state or the other as of 1943. Iowa-Nebraska Boundary Compact § 3. Good title in a state prior to 1943 in turn depends upon the location of the thalweg of the Missouri River, a determination which would have been controlled by federal law. Thus, in this case, since the issue concerns who held good title to the land in question prior to 1943, federal law must be applied.

B. Indian Law.

An equally compelling reason for applying federal law is the special relationship between the United States and the Omaha Indian Tribe and the nature of the interest litigated. The trial court rejected this position under the authority of Fontenelle v. Omaha Tribe of Nebraska, 298 F.Supp. 855 (D.Neb.1969), aff'd, 430 F.2d 143 (8th Cir. 1970), where the Nebraska federal district court applied Nebraska law in an accretion-avulsion dispute between the Omaha Indian Tribe and individual Indians who traced their title back through individual patents issued to their predecessors by the United States.¹³ Instead, the trial court, finding no federal regulatory program involved¹⁴ and no specific act of Congress which displaced state law, reasoned, citing Herron v. Choctaw & Chickasaw Nations, 228 F.2d 830 (10th Cir. 1956), and Francis v. Francis, 203 U.S. 233, 27 S.Ct. 129, 51 L.Ed. 165 (1906), that local law governed title disputes between the Indian tribe and private claimants. 433 F.Supp. at 61.

It has long been held that the rights and incidents of ownership attaching to grants made by the United States of public lands bounded on streams or other bodies of water, navigable or non-navigable, made without reservation or restriction, are to be construed as to their effect according to the law of the state in which the land lies. The fact that a conveyance disposes of tribal lands of Indians under guardianship does not alter the rule. See Oklahoma v. Texas, 258 U.S. 574, 595, 42 S.Ct. 406, 66 L.Ed. 771 (1922). The Fontenelle decision and the other cases cited by the trial court fall within this settled doctrine. In Packer v. Bird, 137 U.S. 661, 669, 11 S.Ct. 210, 212, 34 L.Ed. 819 (1891), the Court observed:

The courts of the United States will construe the grants of the general government without reference to the rules of construction adopted by the States for their grants; but whatever incidents or rights attach to the ownership of property conveyed by the government will be determined by the States, subject to the condition that their rules do not impair the efficacy of the grants or the use and enjoyment of the property by the grantee.

The present dispute is not related to incidents or rights flowing from a conveyance of public land or related to a patent grant of Indian allotment lands. Instead, the direct challenge made by the Iowa landowners here affects the boundary line to the reservation land itself, as it was originally contained in the Barrett Survey and established by the Treaty of 1854. The claims asserted by the defendants attempt to extinguish the aboriginal rights of the Omaha Indian Tribe, guaranteed by treaty, in these lands.¹⁵ Here the Omaha Indian Tribe claims its right to occupy and possess the lands in question arises under federal law. Presumptively, at least, this right has never been extinguished. See discussion of 25 U.S.C. § 194 infra. Under the circumstances the Supreme Court's observation in Oneida Indian Nation v. County of Oneida, 414 U.S. 661, 677, 94 S.Ct. 772, 782, 39 L.Ed.2d 73 (1974), is applicable here:

In the present case, however, the assertion of a federal controversy does not rest solely on the claim of a right to possession derived from a federal grant of title whose scope will be governed by state law. Rather, it rests on the not insubstantial claim that federal law now protects, and has continuously protected from the time of the formation of the United States, possessory right to tribal lands, wholly apart from the application of state law principles which normally and separately protect a valid right of possession.

State law dealing with riparian rights cannot unilaterally extinguish or deprive Indians of their tribal lands. The land area involved in this appeal relates solely to the original reservation land. Therefore, germane here is the Supreme Court's statement in Oneida that: "There being no federal statute making the statutory or decisional law of the State of New York applicable to the reservations, the controlling law remained federal law; and, absent federal statutory guidance, the governing rule of decision would be fashioned by the federal court in the mode of the common law." Id. at 674, 94 S.Ct. at 781.¹⁶ Riparian ownership rights have been specifically held to be controlled by federal law where trust land is involved.

The nature and extent of riparian rights, if any, in the bed and banks of navigable waters is generally a matter of state law. This is a consequence of the rules that (1) the United States holds title to the bed and banks of navigable waters in trust for future states; and (2) upon admission of a state to the Union, the United States relinquishes to the state the ownership of the bed and banks of its navigable waters. The south half of Flathead Lake presents an exception. Title to the bed and banks of the south half of Flathead Lake below high water mark is held by the United States in trust for the Tribes. Thus, the basis for state determination of riparian rights is nonexistent. State law, therefore, is not applicable.

Confederated Salish & Kootenai Tribes v. Namen, 380 F.Supp. 452, 461 (D.Mont.1974), aff'd, 534 F.2d 1376 (9th Cir.), cert. denied, 429 U.S. 929, 97 S.Ct. 336, 50 L.Ed.2d 300 (1976) (citation omitted).¹⁷

See also United States v. Finch, 548 F.2d 822, 832-33 (9th Cir. 1976), vacated on other grounds, 433 U.S. 676, 97 S.Ct. 2909, 53 L.Ed.2d 1048 (1977). Cf. Bauman v. Choctaw-Chickasaw Nations, 333 F.2d 785, 787-89 (10th Cir. 1964), cert. denied, 379 U.S. 965, 85 S.Ct. 658, 13 L.Ed.2d 559 (1965).

Finding the land in dispute affects an interstate boundary at the time the controversial movements occurred, and because the Tribe's right asserted to Indian trust land arises under federal law, we hold that the governing law is federal law.

IV. Burden of Proof.

Section 194 of Title 25 of the United States Code¹⁸ provides:

Trial of right of property; burden of proof

In all trials about the right of property in which an Indian may be a party on one side, and a white person on the other, the burden of proof shall rest upon the white person, whenever the Indian shall make out a presumption of title in himself from the fact of previous possession or ownership.

(Emphasis added).

The trial court reasoned that application of the statute to accretion or avulsion cases would be "unreasonable and circuitous" and "inextricably entwined with the merits." The court's analysis was apparently based on the idea that to apply § 194 would require the court to presume that the land originally occupied by the Indians within the Barrett Survey is exactly the same land in place today. To do so, the court believed, would be to decide the merits and compel it to decide that the same land remained by reason of avulsive movements of the river. On the other hand, the court reasoned, if the land had washed away and new land had accreted to the Iowa riparian owners, the Indians had never "possessed" the new land and it would not be proper to apply the statute.

We reject this reasoning.

Application of § 194 is not a self-answering inquiry to the issues at hand.¹⁹ To hold otherwise, one must presume that the reservation land has in fact been destroyed. Furthermore, the trial court's reasoning would negate the application of the § 194 statutory burden upon a pleading that simply recites Indian land had been destroyed by the erosive action of a river. Thus, under the trial court's rationale a party making claim to Indian land could defeat the congressional mandate by mere allegation without proof. We cannot accept the proposition that congressional policy can be so easily thwarted.

It is undisputed that the 1854 treaty established the Tribe as the legal titleholder to the land area within the Barrett Survey lines. This historical fact shows "previous possession or ownership" and is sufficient to raise a presumption of title in the Tribe under the statute and to place the burden of proof on the defendants. Contrary to the trial court's statement, applying the statutory burden of proof in this case does not decide the merits of the case since the fundamental issue still remains: Was there an alteration in the original boundary by reason of the marked movement of the Missouri River in the time periods involved? The defendants must bear the burden of proof that the boundary has been changed.

The early Indian Non-Intercourse Acts provided special treatment to Indian nations as the frontier was being settled. Section 194 was one of many special protective measures included in these Acts. The legislative history of the Act of June 30, 1834, 4 Stat. 729 (1846), of which § 194 was a part, clearly evidences a protectionist policy with regard to Indians.²⁰

The time has been when conciliation was sought; but the time is now passed when the fear of Indian hostility should be a leading feature of our Indian intercourse. Our relation to them is now that of the strong to the weak, and demands at our hands a more liberal policy, as well directed to promote their welfare as our political interests.

H.R.Rep.No.474, 23d Cong., 1st Sess. 10-11 (1834).

The practice of safeguarding Indians in special areas of legislation continues today. See, e. g., DeCoteau v. District County Court, 420 U.S. 425, 444, 95 S.Ct. 1082, 43 L.Ed.2d 300 (1975); Antoine v. Washington, 420 U.S. 194, 199-200, 95 S.Ct. 944, 43 L.Ed.2d 129 (1975).

Defendants urge that notwithstanding the failure of the court to apply § 194, the court, after placing the burden of persuasion on the defendants to establish their counterclaim, found that the defendants had in fact proven by the preponderance of evidence their title in the property.²¹ Although the trial court observed that it felt no presumption²² aided either party, the defendants' reasoning, as adopted by the trial court, erroneously focuses on the failure of the Tribe to carry a burden of proof to establish title to the land. In discussing the factual evidence, the court's opinion focuses almost entirely on the inability of the Tribe to prove that the movement of the thalweg was brought about by avulsion.²³

We find that the trial court improperly placed the burden of proof on the Indians in the instant case. Title to the Blackbird Bend area as depicted by the Barrett Survey was presumptively shown to be in the Tribe and therefore, notwithstanding the subsequent movement of the thalweg of the Missouri River, the non-Indian claimants were required to assume the burden of proof to show that the Indians no longer had lawful title to the reservation land in question.

We now proceed to an examination of the governing principles of law.

V. Law of Accretion and Avulsion.

It is fundamental that:

(W)here running streams are the boundaries between States, the same rule applies as between private proprietors, namely, that when the bed and channel are changed by the natural and gradual processes known as erosion and accretion, the boundary follows the varying course of the stream . . . .

Arkansas v. Tennessee, 246 U.S. 158, 173, 38 S.Ct. 301, 305, 62 L.Ed. 638 (1918).

See also Missouri v. Nebraska, 196 U.S. 23, 34-35, 25 S.Ct. 155, 49 L.Ed. 372 (1904); Nebraska v. Iowa, 143 U.S. at 360-61, 12 S.Ct. 396; Mayor, Aldermen & Inhabitants of New Orleans v. United States, 35 U.S. (10 Pet.) 662, 9 L.Ed. 573 (1836). Equally well settled is the proposition that

(i)f the stream from any cause, natural or artificial, suddenly leaves its old bed and forms a new one, by the process known as an avulsion, the resulting change of channel works no change of boundary, which remains in the middle of the old channel, although no water may be flowing in it, and irrespective of subsequent changes in the new channel.

Arkansas v. Tennessee, supra, 246 U.S. at 173, 38 S.Ct. at 304.

See also Missouri v. Nebraska, supra, 196 U.S. at 35, 25 S.Ct. 155; Nebraska v. Iowa, 143 U.S. at 361, 12 S.Ct. 396.

The trial court found that the eastern boundary of the Omaha Indian Reservation changed with the shifting river since the tribe had failed to show that the river had moved by avulsion. In reaching this result the trial court ruled that an avulsion occurs only where a sudden shift in a channel cuts off land "so that after the shift it remains identifiable as land which existed before the change of the channel and which never became a part of the river bed." 433 F.Supp. at 73. In doing so, the trial court rejected the plaintiffs' theory that the doctrine of avulsion is equally applicable when a sudden and perceptible shift of the thalweg occurs within the bed of the stream or over as well as around land in place. The government's evidence was that such a perceptible shift might occur when the river goes out of its bed and the land is submerged by a flood or freshet. We find the district court too narrowly focuses on identifiable land in place as the sole criterion of avulsion without giving proper weight to the plaintiffs' theory of their case and to the factual record presented.²⁴

The Supreme Court has defined accretion as "an addition to land coterminous with the water, which is formed so slowly that its progress cannot be perceived . . . ." Jefferis v. East Omaha Land Co., 134 U.S. 178, 193, 10 S.Ct. 518, 522, 33 L.Ed. 872 (1890).²⁵ In contrast, avulsion has been said to occur in various ways. One observation is that it occurs where there is a "sudden change of the banks of a stream such as occurs when a river forms a new course by going through a bend, the sudden abandonment by a stream of its old channel and the creation of a new one, or a sudden washing from one of its banks of a considerable quantity of land and its deposit on the opposite bank."²⁶ III American Law of Property § 15.26, at 855-56 (1952) (footnotes omitted).

A clear distinction between accretion and the sudden and perceptible movement associated with avulsion is, however, often obscured when applied to the actual movement of uncontrolled rivers. The Supreme Court emphasized the unpredictability of the Missouri River in Nebraska v. Iowa, 406 U.S. 117, 119, 92 S.Ct. 1379, 1381, 31 L.Ed.2d 733 (1972):

(E)xperience showed that "the fickle Missouri River . . . refused to be bound by the Supreme Court decree (of 1892). In the past thirty-five years the river has changed its course so often that it has proved impossible to apply the court decision in all cases, since it is difficult to determine whether the channel of the river has changed by 'the law of accretion' or 'that of avulsion.' " Eriksson, Boundaries of Iowa, 25 Iowa J. of Hist. and Pol. 163, 234 (1927).²⁷

The early decision in St. Louis v. Rutz, 138 U.S. 226, 11 S.Ct. 337, 34 L.Ed. 941 (1891), illustrates an attempt at more closely defining avulsion in light of actual river conditions. The Court found that violent erosion of shoreland along the Mississippi River between 1865 and 1875 was avulsive in nature, sustaining findings that "the caving in and washing away of the same was rapid and perceptible . . . (occurring) principally at the spring rises or floods of high water in the Mississippi. . . . " Id. at 231, 11 S.Ct. at 339.²⁸

Rapidity of erosion as the determinative factor in a finding of avulsion was, however, rejected in early dicta in Nebraska v. Iowa, 143 U.S. 359, 12 S.Ct. 396, 36 L.Ed. 186 (1892). See also Oklahoma v. Texas, 260 U.S. 606, 43 S.Ct. 221, 67 L.Ed. 428 (1923) (where the Court applied the rule of accretion, following Nebraska v. Iowa, to the Red River); Philadelphia Co. v. Stimson, 223 U.S. 605, 32 S.Ct. 340, 56 L.Ed. 570 (1912). Although the litigated facts of Nebraska v. Iowa appear to have dealt only with the movement of the Missouri River cutting across the neck of a U-shaped land formation commonly known as an ox-bow,²⁹ the Court expressed its view that the rapidity of the process of subtraction or addition did not prevent application of the rule of accretion.

In discussing the rules of accretion and avulsion the Supreme Court quoted, among others, Vattel, an early civil law authority. Vattel's formulation of avulsion held that "when the violence of the stream separates a considerable part from one piece of land and joins it to another, but in such manner that it can still be identified, the property of the soil so removed naturally continues vested in its former owner."³⁰ 143 U.S. at 366, 12 S.Ct. at 398.

It is obvious, however, when viewed in the context of the entire opinion, that the Court was not seeking to narrow the traditional scope of avulsion but merely to demonstrate that the rule of accretion, as traditionally defined, was equally applicable to the Missouri River. The Court, in defining avulsion, cited Gould on Waters, noting:

It is equally well settled, that where a stream, which is a boundary, from any cause suddenly abandons its old and seeks a new bed, such change of channel works no change of boundary; and that the boundary remains as it was, in the center of the old channel, although no water may be flowing therein. This sudden and rapid change of channel is termed, in the law, avulsion. In Gould on Waters, sec. 159, it is said: "But if the change is violent and visible, and arises from a known cause, such as a freshet, or a cut through which a new channel is formed, the original thread of the stream continues to mark the limits of the two estates." 2 Bl.Com. 262; Angell on Water Courses, § 60; Trustees of Hopkins' Academy v. Dickinson, 9 Cush. 544; Buttenuth v. St. Louis Bridge Co., 123 Illinois 535 (17 N.E. 439); Hagan v. Campbell, 8 Porter (Ala.) 9; Murry v. Sermon, 1 Hawks (8 N.C.) 56.

143 U.S. at 361, 12 S.Ct. at 397 (emphasis added).

After Nebraska v. Iowa only a few federal cases have addressed the scope of the avulsion rule in a context other than an ox-bow cut-off involving permanently emerged land in place.³¹ In Veatch v. White, 23 F.2d 69 (9th Cir. 1927), the facts revealed that:

Years ago, between 1859 and 1874, in the southern shore of Puget Island there was a slough running in a northwesterly direction from the Columbia river. The slough, although only used by fishing boats, had a channel that was shallow and more or less filled with snags. So much of the area of Puget Island as was separated from the mainland by this slough was called Coffee Island, which gradually became submerged. Some time before 1894 the water of the river began to bore out and enlarged the slough, and when freshet waters of 1894 came the slough was so enlarged that a channel formed, which after 1894 was used for navigation. After this new channel was created, shoals formed to some extent on the south, or Oregon, side of Coffee Island, and navigation on that side became unsafe for deep draft ships . . . .

Id. at 70 (emphasis added).

Relying on the definition of avulsion in Nebraska v. Iowa, the court held that:

(T)hough by erosion of Puget Island the river has widened and the center of the old channel has been changed somewhat, and has become more shallow than it was at the time of the fixing of the boundary of the state of Oregon, such changes are not to be confused with changes made by the creation of the slough channel, which was caused by sudden and known causes, not by accretion. The demarking line must therefore remain the center of the channel between Puget Island and Oregon before the avulsion.

Id. at 71 (emphasis added).

This court applied the same rationale in Uhlhorn v. U. S. Gypsum Co., 366 F.2d 211 (8th Cir. 1966), cert. denied, 385 U.S. 1026, 87 S.Ct. 753, 17 L.Ed.2d 674 (1967), where the end of a meander bend in the Mississippi River gradually became separated from the mainland area by a small channel. During a flood in 1938 the subsidiary channel was scoured out making it the main navigational channel following the flood. Relying upon Nebraska v. Iowa, this court, through Judges Vogel, Van Oosterhout and Mehaffy, held that, despite the fact that the bar separating the old and new channel was as much as four feet under water when the change occurred, the change was avulsive.³² Id. at 219-20. The court observed:

In most instances where a river changes by avultive processes, it has left intervening land above high water mark, but we do not think the elevation of the land mass between an old channel and a new one that is cut by avultive processes is a decisive criterion for a change in a state boundary. By all logic and reason, the boundary should not and does not change from the original thalweg except as the Supreme Court said in State of Arkansas v. State of Tennessee, supra, "by gradual process." Since there was admittedly nothing gradual here, we conclude and believe that State of Arkansas v. State of Tennessee, supra, commands that the boundary remains in the thalweg of the Bendway Channel subject to its erosion and accretions occurring prior to its stagnation and death.

Id. at 219 (emphasis added).

Several state cases have similarly recognized that the sudden, perceptible change of the channel, whether within or without the river's original bed, is a critical factor in defining an avulsion.³³

Our review of the foregoing authorities leads us to conclude that, although evidence of identifiable land in place may have some probative value that erosion has not occurred, the fact that intervening land may not be visible at the time a sudden flood or freshet occurs is not conclusive in itself.34 To reason otherwise would be to limit the rule to the rare situation involving only an obvious neck cut-off where intervening land is not submerged. The history of the rule, the case law developed under it, and the policy underlying the doctrine all support a broader application.³⁵

In Bonelli Cattle Co. v. Arizona, 414 U.S. 313, 327, 94 S.Ct. 517, 38 L.Ed.2d 526 (1973), overruled on other grounds, Oregon ex rel. State Land Board v. Corvallis Sand & Gravel Co., 429 U.S. 363, 97 S.Ct. 582, 50 L.Ed.2d 550 (1977), the Supreme Court explained:

The rationale for the doctrine of avulsion is a need to mitigate the hardship that a shift in title caused by a sudden movement of the river would cause the abutting landowners were the accretion principle to be applied.³⁶

Undisputed historical data relating to the early movements of the Missouri River make clear that the wild and uncontrolled movements of the river did not occur with mathematical precision or follow predictable paths. In fact, as the voluminous testimony and documentary evidence presented by both sides reveal, accretion and avulsion are interrelated phenomena often occurring together and in fact often acting as the motivating force for each other. Erosion and accretion, for example, may change the angle at which a river attacks a downstream bank, increasing the likelihood of an avulsive cut-through. Erosion may narrow the neck of a meander bend producing the necessary conditions for an ox-bow cut-off. Or, as the government asserts, an avulsion can produce river characteristics such as low river current energy areas which are favorable to rapid deposition.

When weighed with the significant policy considerations involved, we hold that, under governing principles, the critical determinant of avulsion is a sudden perceptible shift of the channel.³⁷ Only where the thalweg gradually moves through the intervening land as a direct consequence of erosion and the imperceptible process of accretion to the forming bank do the policies underlying the accretion and avulsion rules justify altering permanent land boundaries to conform with the gradually changing thalweg.

In the present case the plaintiffs claim that a sudden and unusual jump in the thalweg within the bed of a stream or over, as well as around, land (submerged or not) invokes the doctrine of avulsion and its corollary rule that the boundary does not change with the shift of the thalweg. The trial court in rejecting this theory held that a sudden and unusual (erratic) jump or movement of the thalweg without evidence of identifiable land in place falls within the historical rule of accretion. We find this ruling inconsistent with settled principles governing the rule of accretion and the broader parameters involving the doctrine of avulsion. We therefore conclude that it was error for the trial court to reject the plaintiffs' legal theory in its evaluation of the evidence.

We now turn to the factual findings of the district court.

VI. The 1875-1879 Movement of the Thalweg.

The basic finding essential to the defendants' case is the trial court's statement that "the original Omaha Indian reservation land within the 1867 Barrett Survey has subsequently been washed away by the Missouri River . . . and that at the same time new land was added to the Iowa riparian land . . . by the gradual process of deposition within the Blackbird Bend area . . . ." 433 F.Supp. at 88. In reviewing this finding our task is not made easier by the district court's verbatim adoption of the defendants' analysis of the evidence and proposed findings of fact including the defendants' credibility assessments of the witnesses.³⁸ We hold the trial court's conclusion to be clearly erroneous and not supported by substantial evidence.

The defendants' proof, and the trial court's conclusion that erosion and accretion produced the movement in the river between 1875 and 1879, rest essentially upon six factual premises. First, defendants assert that bar A (see Plate II) must have been of recent origin (not land in place) since it was situated in the area formerly occupied by the old channel and because willows were the only vegetation growing on the bar. Thus, they contend that the river must have eroded the meander lobe and through the process of accretion deposited the crescent shaped sand bar depicted as bar A during its westward movement. The defendants next point to expert testimony that the remnant channel between bar A and the easterly high bank is a "common phenomenon" associated with erosion and accretion. Such channels are produced, they assert, when a river gradually moves away from its previous channel by the process of erosion and accretion. The accretive deposition then closes the old channel at its upper end forming the remnant channel. Third, defendants' experts assert that bars B and D shown on the 1879 map could not have been identifiable land in place since they were barren of vegetation. Instead, they suggest that the bars were middle sand bars formed behind the southerly and westerly migration of the river. Defendants further contend that since no cottonwood trees, which grow only on land that is stabilized and not subject to frequent inundation, were shown to be growing on bar C, the bar must have been completely eroded away as the river moved. Defendants also find support for their accretion theory in the opinion of one of their experts that the parallel positioning of bars A, B, C and D was consistent with a gradual southwesterly movement of the river as a result of erosion of the meander lobe. Finally, the defendants introduced the experiments of Captain J. F. Friedkin³⁹ into evidence which, along with hydrologic experience, allegedly showed "that during high water flows, the river will flow and erode against the upper side of a point bar . . . ."⁴⁰

The court concluded on the basis of this evidence that the meander lobe was eroded away as the channel moved over the area where the lobe had existed. Thus, the court ruled that the shift in the course of the river was a consequence of progressive scour and deposition, that is by accretion. 433 F.Supp. at 77-78.

Our analysis of the record leads us to conclude that the evidence presented at trial as a matter of law was insufficient to satisfy the defendants' burden of proving by the preponderance of the evidence that erosion and accretion were responsible for the significant shifts of the river between 1875 and 1879.

A. Identifiable Land in Place.

The years from 1875 through 1879 were years of extremely high water flow on the Missouri River; no other four year period equaled or exceeded the maximum discharge for those years.⁴¹ Defendants' experts agreed that during this time the meander lobe was low, at times entirely under the surface of the moving river and extremely vulnerable. This is corroborated by Barrett, who in his 1867 survey described the eastern end of the meander lobe as a low sandy point.

Recognizing that identifiable land in place may in given circumstances have probative value in helping to distinguish between accretion and avulsion, that is, at least in the sense of determining whether intervening land has been completely eroded or not, little significance can be attached to its alleged absence under the evidence adduced in the present case. The defendants urge that absence of identifiable land in place provides the necessary inference of erosion of the original reservation land. However, the trial court's finding that in 1879 bar A was of recent origin and was not identifiable land in place does not afford a permissible inference that the original reservation land had been eroded since, as the trial court itself pointed out, at least part of bar A was located within the area of the old abandoned channel. No land could be eroded if it never existed in the first place. Under the circumstances it is obvious that bar A is nothing more than land formed by deposition after the channel was abandoned.

The evidence that bar D and part of bar B, lying to the west of bar A, and inside the Barrett Survey lines, were not identifiable land in place is equally inconclusive. It is conceded that the eastern end of the Barrett Survey was made up of sandy material. Thus, even if the river changed by avulsive movements through the end of the meander lobe, the land remaining in place would have been low and composed of sand.⁴²

The trial court also found that the land which had previously occupied the area shown as bar C on the 1879 map had been completely eroded away and that bar C had formed thereafter as a middle bar as the thalweg moved to the west. The court observed: "If bar 'C' were land-in-place which had existed prior to 1879, it would have supported the growth of cottonwoods or other vegetation more substantial than willows by 1890."⁴³ 433 F.Supp. at 77. Although it is possible that the land represented by bar C may have completely eroded, it is entirely speculative to say that that is what occurred. The record also supports the possibility that bar C, located on the eastern end of the lobe, was the same surface area described by Barrett in his notes and was not built up by accretive deposits. The record is insufficient to prove what actually occurred.

Under defendants' accretion theory bar C would of necessity have been comprised of relatively newly deposited soil since it was located close to the 1879 position of the thalweg. Nevertheless, the record shows that willows were growing on bar C in 1879 indicating, as Dr. McQuivey, a government witness, theorized, that the bar may well have been land in place.⁴⁴ The fact that cottonwoods were not also growing on the bar does not prove the contrary. Bar C, along with bars B and D, was located near the eastern end of the Barrett Survey which Barrett described as sandy soil and frequently inundated. Testimony in the record shows that cottonwoods did not thrive in areas subject to frequent inundation. We find the evidence concerning bar C to be highly conjectural and inconclusive as to whether it formed by accretion or was in fact identifiable land in place.

There exists another basic reason why we regard the evidence of the defendants as insubstantial. The opinion of the defendants' experts⁴⁵ that no identifiable land remained in place after the movement of the river sometime between 1875 and 1879 is essentially based upon inferences drawn from the 1879 map admittedly prepared in a 10-day period during the June rise of the Missouri River when the river was as much as five feet above its ordinary high water level. At the time the river was shown to be nearly 10,000 feet wide, whereas in 1875 the bed had been only approximately 800 feet across. Soundings taken at that time demonstrate that a substantial land area was immediately below the surface of the flood water. The defendants do not contend that the river bed permanently expanded to 10,000 feet as shown in 1879; it obviously would be much narrower upon subsidence. See, e. g., the 1890 Missouri River Commission Map, set out as Plate V, infra, in which the river is shown to be no more than 3,500 feet wide. The existence or nonexistence of identifiable land in place could not have been accurately assessed at a time when the river's flow was abnormally high during floods which completely inundated the adjacent land. Thus, any inferences drawn from the alleged land forms exhibited on the 1879 map appear to be highly conjectural. Substantial evidence cannot be based upon an inference drawn from facts which are uncertain or speculative and which raise only a conjecture or possibility.⁴⁶ See Polk v. Ford Motor Co., 529 F.2d 259, 271 (8th Cir.), cert. denied, 426 U.S. 907, 96 S.Ct. 2229, 48 L.Ed.2d 832 (1976); Wilson v. Volkswagen of America, Inc., 561 F.2d 494, 517 n. 65 (4th Cir. 1977); Padgett v. Buxton-Smith Mercantile Co., 262 F.2d 39, 41 (10th Cir. 1958); Gilbert v. Gulf Oil Corp., 175 F.2d 705, 709 (4th Cir. 1949).⁴⁷ As this court indicated in Uhlhorn v. U. S. Gypsum Co., 366 F.2d at 219-20, if land over which a channel changes during abnormal high water periods, inundating all intervening land masses, is identifiable as the same land mass upon subsidence of the high water, the boundary does not change even though the land's surface may be somewhat eroded.

Defendants' experts also relied upon inferences drawn from the existence of remnant channel formations, from the parallel positioning of bars A, B, C and D and their interpretation of applicable principles of hydrology. The record, in our judgment, requires us to give little or no probative effect to the ultimate conclusion reached from these factual premises.

B. Remnant Channels.

The defendants rely on evidence of remnant channels in the Blackbird Bend area as a "common phenomenon" associated with the progressive and gradual movement of a channel as a result of accretion. However, this evidence was proffered only as a possible alternative explanation to the plaintiffs' evidence that the remnant channel areas demonstrated avulsive changes in the thalweg.⁴⁸

The evidence further reflects that Dr. John F. Kennedy testified that, as the thalweg shifted to the west, the low energy level of the river in the former channel created by the movement would result in deposition there. The defendants conclude from this that the shift in the river was "a consequence of progressive scour and deposition." The testimony of defendants' expert, Dr. Kennedy, showed, however, that the shift of the thalweg is often the responsible agent for the "subsequent diminished sediment transport capacity of the water." Thus, the testimony is inconclusive as to whether the remnant channel was formed by accretion or avulsion since a remnant chute might also have been formed after the thalweg suddenly and perceptibly moved. In the latter case the deposition forming the remnant channel would be the effect of the low river energy in the area brought about by the sudden avulsive shift of the thalweg rather than a consequence of accretion. As the Supreme Court observed in Arkansas v. Tennessee, 246 U.S. at 175, 38 S.Ct. at 305,

if the stream leaves its former bed and establishes a new one as the result of an avulsion, the boundary remains in the middle of the former channel. An avulsion has this effect, whether it results in the drying up of the old channel or not. So long as that channel remains a running stream, the boundary marked by it is still subject to be changed by erosion and accretion; but when the water becomes stagnant, the effect of these processes is at an end; the boundary then becomes fixed in the middle of the channel as we have defined it, and the gradual filling up of the bed that ensues is not to be treated as an accretion to the shores but as an ultimate effect of the avulsion.

(Emphasis added).

None of the explanations for the remnant channels are, however, more than sheer conjecture and do not, under the factual circumstance shown here, constitute probative evidence of whether the movement occurred by either accretion or avulsion.⁴⁹

C. Bar Formation.

Just as the remnant channels may have formed as the effect of an avulsion rather than as the result of accretion, the parallel positioning of bars A, B, C and D, while perhaps characteristic of accretion, could have resulted from the accretion which followed as an effect of avulsion as well. Moreover, as we have discussed the actual surface positioning of those bars based on the 1879 map is conjectural since the contours were drawn at the high water stage which existed at that time.

D. Captain Friedkin's Experiments.

The final proofs which defendants and the trial court relied on to establish accretion as the cause of the river's movement were Captain Friedkin's experiments and general principles of hydrology. Both Friedkin's experiments and principles of hydrology, however, provide strong evidence that avulsive change may have produced the 1879 movement. Friedkin noted that when a meander bend reaches its limiting width,⁵⁰ as it is conceded Blackbird Bend had here, it does not stop caving its banks. Instead, "(t)he flow short-cuts over the convex bars of bends, chute channels form, and a new bend develops a little farther downstream." J. Friedkin, Meandering of Alluvial Rivers 14 (1945) (footnote omitted). Such chute channels⁵¹ are avulsive since the channel moves around or over, not imperceptibly through the interjacent land. One of the defendants' witnesses, Dr. George R. Hallberg, testified that it was quite possible that chutes similar to those described by Friedkin could have formed along the eastern edge of Blackbird Bend, although he felt the area was probably submerged when this occurred. Hallberg's testimony concurred with the government's expert, Dr. Paul McQuivey, a research hydrologist, who testified that, when a river is at high flow it tends to increase its radius, that is, it tends to take a more direct course rather than a meandering one.⁵² To do so, he continued, the thalweg moves to the inside of the bend, and erodes new chute channels⁵³ through the point bar. Eventually, the record shows, one of the chute channels becomes large enough to carry the main flow of the river, and the river abandons the old channel.⁵⁴ Cf. Veatch v. White, 23 F.2d at 70.

In addition to the evidence suggesting that the movement of the river in 1879 could have occurred through a series of chute channels, the evidence also supports the possibility that during this same time a cut-off could have occurred across the neck of Blackbird Bend.⁵⁵ Friedkin also described the conditions when a cut-off is likely:

Natural cut-offs occur when a meandering river develops and finally erodes through a narrow neck between the upper and lower arms of a bend. . . . In over 50 laboratory streams in uniform materials not a single cut-off of this type developed. This fact indicates that natural cut-offs result from local differences in the erodibility of bank materials.

With all bends in a meandering river migrating down the valley at the same rate, a cut-off cannot possibly develop. The upper arm of a bend never catches up with the lower arm. For a natural cut-off to develop, erosion on the downstream bank of the lower arm of a bend must be slower than along the upper arm. Generally, when a cut-off develops, erosion in the bend proper has taken place so that the flow in the lower arm of the bend has become directed up-valley . . . and a narrow neck has developed. It is, therefore, indicated that it is the local differences in erodibility of the bank materials in natural rivers which cause narrow necks to form and cut-offs to develop.

Friedkin, supra at 16.⁵⁶

NOTE: OPINION CONTAINS TABLE OR OTHER DATA THAT IS NOT VIEWABLE

There exists strong corroborative proof of such occurrences from Barrett's field notes made during his 1867 survey. He wrote:

Until very recently, appearances indicated that this point was increasing in size from the deposits and drift of the river; but, during the present season, the river, rising to a great height, partly worked a channel across it, which may, eventually, entirely detach it from the Nebraska shore, rendering it an island in the river.

Tribe exhibit 26E, at 6.

The evidence also demonstrated that the Iowa south bank of the Blackbird Bend area was composed of erosion resistant material which would have prevented the southerly movement of the meander bend and made a cut-off possible. Cf. Friedkin, supra at 16-17.⁵⁷ In addition, the record shows that the potential for breakthroughs in the 1875 through 1879 period was enhanced by high water flows during those years.⁵⁸

Based on the foregoing analysis we find the factual predicate, supporting defendants' theory as the causative reason for the river's movement, is in large part conjectural and the opinions drawn therefrom must be viewed as speculative. Under the circumstances we hold that the defendants have failed to meet their burden of proof that the significant and marked changes of the Missouri River between 1875 and 1879 were the result of erosion and gradual imperceptible accretion to the Iowa bank.

VII. The River Between 1879 and 1912.

In 1881 the highest flood waters of any time since reliable records have been kept occurred on the Missouri River. However, no maps were introduced to show the location of the river between 1879 and 1890. The next map available after 1879 is the 1890 Missouri River Commission map, see Plate V, which shows the thalweg to have moved north and somewhat to the east of its 1879 location. Significantly, the river is shown to occupy far less area than that shown on the 1879 map and the land to the east of the thalweg is shown as stabilized soil with permanent vegetation growing on it.

The trial court felt these facts "simply (show) the normal and logical progression of the accretion which was shown to be forming in 1879 . . . ." 433 F.Supp. at 79. There exists no factual predicate whatsoever to support this conclusion.⁵⁹

After 1890 the river moved in a northerly and easterly direction to a position shown as the northerly high bank in approximately 1912. See Plate III.

We now turn to the trial court's findings and the factual discussion involving the marked change in the course of the river between 1912 and 1923.

NOTE: OPINION CONTAINS TABLE OR OTHER DATA THAT IS NOT VIEWABLE

VIII. The 1912-1923 Movement of the Thalweg.

The trial court found, again relying upon the defendants' analysis of the evidence, that the 1912 through 1923 movement of the Missouri River was also a direct result of erosion and imperceptible accretion to the Iowa riparian land. The court concluded:

(T)he Court finds that there were no avulsions in the Blackbird Bend area between 1890 and 1923, and that the movements of the river during that period of time were erosive in nature so that accretion was being formed on the side of the river opposite the erosion. The Court finds that after 1890 the river moved erosively until it reached what is now the northerly high bank following which it commenced a southern migration throughout the Blackbird Bend area until it reached its 1923 position. This migration eroded almost all of the westerly end of the land as surveyed by Barrett in 1867 and the deposition which occurred during the southerly migration of the river was accretion to the northerly and easterly high banks and thereby became accretion to the Iowa riparian owners.

433 F.Supp. at 85.

The defendants contend that the river moved in a slow progressive movement south and westward to bring about the remarkable change in the thalweg between 1912 and 1923. Compare Plate III with Plate IV. The basic disagreement between the experts for both sides still exists. The defendants' experts Hallberg, Kennedy, and Raymond L. Huber testified that sometime around 1912 the river moved away from the northerly high bank and began to erode to the south depositing accretion materials to Iowa riparian land. It was their theory that all of the land in the path of the river was eroded away. On the other hand, the plaintiffs' experts varied in their appraisal of the river movement during this period. Elmer M. Clark, an aerial surveyor, believed that the river achieved its 1923 position by one or more sudden and noticeable movements of the channel. Plaintiffs' witness, Dr. Charles S. Robinson, a geologist, thought the southward movement occurred suddenly during one high water period in a matter of a few days or months. Dr. McQuivey, the government's expert, felt that the river moved as a result of several avulsive point bar cut-offs.

In reviewing the record, we cannot but echo the words of witness Huber, that it is again only an "educated guess" as to just how the river moved. The extremely speculative assessment of the reasons for the river's movement offered by the defendants is not sufficient to sustain their burden of proof.

The evidence relied upon by the defendants, and the court in reaching its conclusion that accretion caused the 1912-1923 river movement, falls essentially within four areas of discussion. First, the defendants' experts point to evidence of the absence of identifiable land in place. This evidence consisted of testimony from witnesses who had lived in the Blackbird Bend area at the time of the movement that the land on the Iowa side was "new accretion land." Defendants' witnesses also pointed out that there were no geologic or geomorphic formations evident that were typical of avulsive river movement. In addition, the defendants alleged that no trees could be found which predated the movement away from the northerly high bank.⁶⁰

Second, defendants' experts asserted that a change in the Missouri River above Blackbird Bend altered the angle of approach of the river into Blackbird Bend ultimately producing a southerly migration of the river. In support of this point the defendants introduced in evidence a 1912 survey showing a developing sand bar on the Iowa shore (referred to as the Fairchild sand bar) said to be consistent with a changed angle of entry. The defendants' witnesses also contended that hydrological principles would predict erosive changes in the river as a result of the change of the angle at which the river entered Blackbird Bend. Complimenting this proof were several Indian allotment letters which documented erosion in the northwestern part of the Blackbird Bend meander lobe at a point opposite the formation of the Fairchild sand bar.⁶¹

Third, topographic cross-sections prepared by Dr. Hallberg showed that the land surface gradient in the Blackbird Bend area sloped from northwest to southeast, and that the land formations in the area were progressively lower in elevation in the southeast. In his opinion, this gradient was compatible with a theory of bar growth on the northeast side of the river as it migrated to the southwest.

Finally, the defendants relied on soil analysis which allegedly revealed findings consistent with the southward and eastward accretive movement of the river.⁶² The government's expert, Dr. McQuivey, had testified that analysis of soil samples taken in the area produced data indicating that the soil becomes sandier as one moves westward in the Blackbird Bend area. Dr. Hallberg utilized this data to theorize that the sandier nature of the western edge of Blackbird Bend indicated that remnant channels had formed behind accretive point bars deposited as the river slowly moved to the southwest.⁶³

Very few facts relating to the actual river movement in the period between 1912 and 1923 are proven on the record. First, it is clear that the thalweg had moved substantially in a relatively short period of time; perhaps as few as three years,⁶⁴ but no more than 11 years. Second, as the trial court found, substantial high water periods occurred in 1905, 1906, 1912, 1913, 1915, 1916 and 1920. 433 F.Supp. at 83. Third, the angle of approach of the river had changed subjecting the adjacent land in place to at least surface erosion. Furthermore, substantial erosion was undeniably occurring along the Nebraska shore.⁶⁵ Finally, it is beyond dispute that remnant channel-like formations may be identified by soil samples and aerial photographs. These established facts do not prove that either accretion or avulsion caused the river's movement; the issue remains whether they may form a sufficient factual predicate for defendants' witnesses to conclude that the marked change of the thalweg was a gradual one directly caused by erosion and imperceptible deposition to the Iowa land. We hold the evidence too conjectural and the ultimate conclusion reached too speculative to sustain the defendants' burden of proof under § 194.

The expert opinions and the lay testimony indicating that land in place could not be identified in the area are not sufficient to prove that accretion was responsible for the 1912-1923 movement. It is well established on the record that after 1890 as the river moved in a northerly direction alluvion soil subject to frequent inundation was deposited throughout much of the area. Thereafter, when the river moved southwesterly away from the northerly high bank, either by accretion or as the result of avulsion, this sandy area would not reveal any conspicuous identifiable features. The fact that some erosive action occurred in the northwest corner of the Barrett Survey area does not support the inference that accretion was the primary cause for the movement. As we have noted earlier, erosion may readily occur along with avulsive movements of a river; the two phenomena may often take place together. Under the circumstances the absence of identifiable land in place has little probative value in determining whether erosion and accretion were in fact the responsible elements for the 1912 through 1923 movement of the river.⁶⁶

Aside from the inconclusive evidence relating to identifiable land in place, little can be found in the record that supports the defendants' position. The fact that the river changed its angle of approach does not in itself support an inference that accretion was responsible for the changed movement of the thalweg. Although the change may have altered the erosion patterns in the Blackbird Bend area, it is still a tenuous conclusion at best to infer from this that the thalweg moved imperceptibly. While reasoned deductions may be made from probative facts, the ultimate conclusion may not rest on mere guesswork. Similarly, as in the 1875-79 river movement, the sand bars and the gradient of the land could have just as easily occurred from deposition resulting from low river energy caused by avulsive movements of the river as by a gradual shift or movement of the thalweg.

The little solid scientific evidence in the record contradicts the defendants' theory of how the river moved. Soil samples taken in the area by government experts⁶⁷ corroborate Dr. McQuivey's testimony of the existence of four major channel remnants.⁶⁸ Aerial photographs made in 1925 also indicated the channel remnants in the area. Although the defendants presented an alternative theory of how the remnant channels might have formed, their existence is strongly probative of the government's theory that the river migrated from the northerly high bank to its 1923 position by a series of four point bar cut-offs.

We conclude on the basis of an overall review of the record that it is entirely speculative to determine when or how the thalweg moved to the position shown on the 1923 map.

IX. Conclusion.

The district court's ruling, adopting the defendants' theory of their case, depends on the assumption that the doctrine of avulsion is not applicable without evidence of identifiable land in place. On the record presented we deem this an erroneous legal assumption. When considered in the context of the broader parameters of avulsion we hold the defendants' case establishes only speculative inferences as to whether the thalweg moved by accretion or avulsion in the critical time periods involved. The essential inferences cannot be left to speculation or conjecture. Under the circumstances, we hold that the defendants have failed in sustaining their burden of proof under § 194.⁶⁹

We recognize that to require the defendants to prove the cause of the river's movement occurring some 100 years after the event is indeed an onerous burden. This may seem to be an injustice when one considers that the defendants or their predecessors have possessed and continuously farmed the land without protest for nearly 40 years. However, as the trial judge observed in a letter written to counsel after trial, divesting the Omaha Indian Tribe of their original reservation land promotes an equal injustice.

While burdening either side in this case with proving the movements of the river occurring many years ago may result in undesirable hardships, the clear policy of the federal government mandates that the interests of the Omaha Indian Tribe be given their historical and statutory protection. These important possessory land interests cannot be taken away on proof that is basically speculative and conjectural.

The judgment of the district court is ordered vacated; the cause is remanded with directions to enter judgment quieting title in the trust lands involved in this action⁷⁰ in the United States as trustee, and the Omaha Indian Tribe; the prior orders relating to escrow funds and accounting procedures governing the 2,900 acres within the original boundary of the Barrett Survey as originally ceded to the Tribe in the Treaty of 1854 are ordered dissolved.⁷¹