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Geological fluvial geomorphology CENTENNIAL ARTICLE

VICTOR R. BAKER Department of Geosciences, University of Arizona, Tucson, Arizona 85721

ABSTRACT disdain the approaches and/or problems of oth- phasis that Gilbert had placed on timeless, equi- ers. Moreover, there are fundamental dichoto- librium processes of genesis (Chorley The history of American fluvial geomor- mies in the basic assumptions made by individ- and Beckinsale, 1980; Ritter, 1988). phology over the past century is viewed as ual geomorphological researchers as they pursue There are parallels between the ways scien- one of conflict and crises. From 1888 to 1938, various studies. Views such as gradualism in tists organize their own programs of study and a controversy arose between (1) a rational process operation, randomness in , and the ways that historians may organize the anal- approach to understanding genesis dynamic equilibrium in landscape development yses of such programs through time. Thus, one and history, with its roots in , and may be held in personal preference to contrary obvious approach to the history of American (2) a spatial-analytical approach to landscape assumptions. geological fluvial geomorphology over the past classification and description, with its roots in A century ago, geomorphology was in its century might be an evolutionary one, perhaps . By the 1960s, geomorphology, golden age. It was a science filled with wonder punctuated with the occasional major change in led by fluvial studies, had changed its empha- and excitement. The source of scientific stimulus scientific program. Thus, Morisawa's (1985) his- sis from historical studies to process studies, was not the establishment of new methodologies tory recognizes a progressive increase in the use and the geology/geography dispute became for landscape study. Rather, it was the discovery of quantitative approaches to problems, punctu- irrelevant. Since the 1960s, a new conflict has of new phenomena in that seemed as ated by Horton's (1945) seminal paper on arisen between (1) problem-oriented studies bizarre and alien to the residents of humid- -basin analysis. Whether or not quanti- of landform genesis and (2) method-oriented temperate academia as the surfaces of other fication constituted a true scientific revolution studies. The latter emphasize useful predic- planets seem to most of today's terrestrial geo- for geomorphology, it certainly engendered a tions and a methodology that generates re- morphologists. For American geological geo- new program of effort based on quantitative spect from other scientific and engineering morphologists, the most important scientific measurements of processes, statistical treatment disciplines. In extreme cases, approach 2 may trinity was not structure, process, and stage, of data, and predictive models with practical bypass the understanding of phenomena in emerging from the heuristic synthesis of a Har- applications. As pointed out by Morisawa order to generate useful predictions of sys- vard scholar. Rather the critical trinity was Gil- (1985), much of the methodology for the new tems assumed to embody the behavior of bert, Powell, and Dutton, who were stimulated program was borrowed directly from engineer- those phenomena. In order to achieve its goal by studies of the arid western United States. ing disciplines, such as hydraulics and hydrol- of intellectually satisfying understanding of ogy, as as from basic physics, , The American character of geological fluvial phenomena, approach 1 may require the and mathematics. Moreover, the kinds of geo- geomorphology derives directly from the scien- stimulus of the occasional outrageous hy- morphological problems studied under this new tific example of and the or- pothesis, thereby posing a seeming anathema program tended to be those that were most eas- ganization of the United States Geological to an existing scientific program. The identifi- ily analyzed by the new methodology. Survey by John Wesley Powell. Considerable cation and explanation of anomalies is critical history has been written on this era of fluvial Perhaps even more substantive than mere to approach 1. Because of the inherent con- geomorphology (Chorley and Beckinsale, 1980; quantification has been the move toward a dy- flict in these approaches to fluvial geomor- Pyne, 1980; Tinkler, 1985), and so, rather than namical basis of geomorphology, inspired by phology, there is a need to balance opposing again describing its inspiration, let suffice Dut- Strahler (1952). It would be heartening to re- tendencies. ton's (1885) acknowledgment of his two col- cord the progressive march of geomorphology leagues. "If I were to attempt payment, I would toward understanding modern surficial INTRODUCTION be bankrupt" (p. 198). processes in a physical-quantitative fashion. As a Probably the only great revolutionary change geological science, however, geomorphology Geomorphology is one science divided by ar- that ever occurred in geomorphology was the must strive not only to understand modern bitrary classifications that contribute nothing to one that Hubbert (1967) recognized for all geol- Earth processes, but to place this understanding the understanding of landscapes but much to the ogy and which he termed "Huttonian-Lyellian- within the broader context of Earth history. As impediment of such understanding. Fluvial Darwinian." The Darwinian influence was stated by Bryan (1950): "the essence of geomor- geomorphologists are divided into paramount by the early 1900s, when Russell phology is the discrimination of the ancient from and by arbitrary academic convention, (1904) described geomorphology as a science the modern." Thus, another important theme is into process or historical geomorphologists by "vivified by evolution." As noted by Judson that of tension between historical and dynamical their emphasis on time scales of study, and into (1958), the scientific program established by emphases in geomorphological research (Ritter, rational or empirical geomorphologists by their merely followed in this 1988). scientific methodologies. Members of each trend. The Davisian emphasis on time-directed There are many sources of conflict in geo- group have their own sets of problems and may evolution of landscapes overshadowed the em- morphological research directions ( 1).

Geological Society of America Bulletin, v. 100, p. 1157-1167, 6 figs., 3 tables, August 1988.

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TABLE 1. SOME CONFLICTING RESEARCH DIRECTIONS OR PROGRAMS IN FLUVIAL CEOMORPHOLOGY geological and geographical geomorphologists his geological colleagues with statements such as turned their attention to process studies. that at his Presidential Address to the Geological

Geography Geology As stated by Thornes and Brunsden (1977): Society of America (Davis, 1912, p. 121): "all Process Historical "The current paradigm is one in which process geography belongs under geology, since geog- Empirical Rational Applied Basic studies prevail effected principally and increas- raphy is neither more nor less than the geology Experimental Field Quantitative Qualitative ingly by mathematical and stochastic models." of today." Indeed, fluvial geomorphology has been so in- Such statements did not reflect the main- fused by new research methods that those meth- stream of thinking in geography, where one Much has been written on these approaches to ods are determining the choice of appropriate could argue that empirical landscape description research by their adherents. Another area of geomorphological research problems. This has was preferable to hypothesizing genetic explana- conflict is the fundamental assumptions that un- resulted in the paradox described by Church tions. Questions of landform genesis can be con- derlie individual geomorphological investiga- (1980): "Contemporary process studies are of sidered irrelevant when concern is with the tions (Table 2). Whether termed "fundamental little worth in evaluating landscape evolution." human use of landscapes. Davis' explanatory concepts" (Thornbury, 1969), "philosophical The process studies most amenable to the new description was subjective and qualitative. By assumptions" (Twidale, 1977), "paradigms" method-dominated approach to geomorphology concentrating on objective, quantitative mea- (Oilier, 1981), or "basic postulates" (Pitty, may be largely irrelevant to the most important sures of slopes, spatial relationships, and so on, 1982), these ideas are the conventional wisdom scientific questions in problem-dominated ge- geomorphography could become more appro- for the science. Whereas the analysis of research netic geomorphology. The issues in this new cri- priate as a branch of geography. In being what directions must emphasize the backgrounds and sis for geomorphology are further complicated Cotton (1956) terms a "utilitarian art," geomor- methodologies of groups, the analysis of funda- by attempts by geomorphologists to make their phography would divorce itself from rational mental assumptions must emphasize the basic science more relevant in technical applications argument over landform genesis and concentrate philosophies of individuals. and more respectable in comparison to sister on an empirical approach that would be useful basic sciences. The resulting choices of research The view that science advances by the inter- for social purposes. It was this evolving view of direction (Table 1) and fundamental assump- action of incompatible alternative hypotheses is geomorphography that caused Douglas Johnson tions (Table 2) by the new method-dominated discussed at length in the book Against Method (1929) to conclude: "Geomorphology itself has geomorphologists reflect a new crisis of purpose (Feyeraband, 1975). In the view of Feyeraband suffered, and will continue to suffer, from at- that will be described in this review. (1975), it is the proliferation of mutually incon- tempts to include it in the geographic realm. In sistent theories that is most healthy for scientific the history of its development, in its methods, and in its affiliations it is a part of geology." advancement. In this spirit, therefore, my review GEOMORPHOGRAPHY OR will emphasize the role of problems and ques- GEOMORPHOGENY? Fortunately for terminology explosion, the tions. I will argue that several fundamental crises term "geomorphology" entered America from have developed during the past century of fluvial In reviewing the status of American geomor- Europe (Cotton, 1956), displacing both "geo- geomorphological research. Moreover, I believe phology to a Polish audience, John P. Miller morphogeny" and "physiography" about the that the issues in these crises transcend the sim- (1959) wrote: "One curious aspect of geomor- time of the 50th anniversary of the Geological ple classifications of Tables 1 and 2. phology in North America is its alliance with Society of America (Bryan, 1941). Fortunately From 1888 to 1938, a controversy evolved geology rather than geography, as is the case in for -geomorphologists, the empirical over the purpose for studies of terrestrial land- other parts of the world." Miller's Ph.D. advisor view of geomorphography did not prevail into forms. A rational approach to the genetic under- had been , who became Professor of the modern era. By the 1960s, geomorphology standing of landscapes developed from roots in Physiography at Harvard in 1943. Bryan pre- seemed to have finally accepted what Dury geology, but found its most eloquent expression ferred the term "geomorphology" to describe his (1972) termed "its somewhat ambivalent geo- in the writings of a geographer, William Morris scientific activity. This caused much dismay to graphic-geologic location as a research field." In Davis. More basic to its roots in geography was Bryan's predecessor at Harvard, William Morris part this was achieved by the shift in emphasis an empirical approach to as spatial Davis, who reportedly told him (Bryan, 1941, from the historical-based explanatory descrip- elements of the Earth's surface, where objective p. 6): "Bryan, I am afraid that you will always tion of Davis to modern process studies (Chor- measurement was more important than subjec- teach more Geomorphogeny than Geomorphog- ley, 1962). A new geography arose as both tive interpretations of genesis. This conflict dis- raphy." In its use of terminology to stand for human and physical geographers adapted appeared after World War II, when both complex ideas, this quote is typical of Davis, but Baconian scientific methods to their disciplines it also conveys the extreme irony of his argu- (Johnston, 1983). New tools such as statistical ment. Davis was not in the evolving mainstream treatment of data, spatial analysis, and systems

TABLE 2. SOME CONFLICTING FUNDAMENTAL ASSUMPTIONS of geography in his definition of "geomorphog- theory were found to be useful in both physical IN FLUVIAL GEOMORPHOLOGICAL RESEARCH raphy" as the explanatory description of the and . land. Explanation, in terms of genesis, was the The American concerns over geomorphogeny Randomness or indeterminacy Causality purpose of "geomorphogeny," as originally de- Gradualism and geomorphography were best expressed by fined by Lawson (1894). Davis believed that a successive Harvard geomorphologists: William Disorder Order genetic description of landforms was more un- Complexity Simplicity Morris Davis, Kirk Bryan, and John P. Miller. derstandable and heuristically preferable to an These giants of our science inspired successive Dominance of present-day Importance of ancient conditions for empirical one. This view made Davis a cher- processes relict landscapes generations of geomorphologists, but ultimately ished member of the geological community, Youthfulness of Antiquity of relict they seem to have inspired neither their geo- who regarded his geographical assertions as Morphoclimatic zonation of Azonal landforms controlled by graphical nor their geological colleagues. Geo- landscapes structure mere idiosyncrasy (Bryan, 1941). Davis pleased morphology was abolished during the 1960s as

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an academic enterprise at Harvard, and that ex- graded segment, and some, perhaps, in investiga- cist or a chemist or a statistician or an engineer, is not ample of arbitrary definition has been followed tion of the slope or height of waterfalls, there cannot living up to his contract. A verse keeps running by other universities that purport to cover the possibly be any profit in analyzing a slope that aver- through my head: ages these two unlike types of slope. Indeed, the aver- subject matter of the earth sciences in their cur- aging of these basically different types of slopes is I wonder what the vinters buy, ricula. Such decisions, in effect, constitute value certain to defeat any attempt to understand either of one half so precious as the stuff they sell. judgments on geomorphology and/or geomor- them. phologists. Because these value judgments have In the Leopold and Langbein (1963) paper, been made and continue to be made by others, Thus, Mackin clearly distinguished two as- progress in science is viewed as a transition there is a need for geomorphologists themselves pects of slope in relation to the operation of from qualitative description to quantitative to assess the basic values of their discipline. : (1) a timeless aspect in which equilibrium prediction: adjustments prevailed and (2) a timebound as- RATIONAL OR EMPIRICAL pect in which time, the history of the system, A continued interest in classification, during the first GEOMORPHOLOGY was of paramount importance. The relationship third of the present century, took the form of assigning names to features of the landscape. Streams were de- of time to fluvial analysis was subsequently signated as subsequent, superimposed, etc., and each The Fiftieth Anniversary Volume of the Geo- stated more explicitly by Schumm and Lichty such designation carried with it appropriate inference logical Society of America contained a single (1965) and elaborated upon in extenso by about both operative processes and historical se- address exploring the issue of geomorphogeny Thornes and Brunsden (1977). quence. Little attention was paid to the study of pro- cess, which, looking back at the record, now appears versus geomorphography (Bryan, 1941). The Mackin's concern, however, was not merely to have led to a neglect of field studies as the founda- 75th anniversary volume, entitled The Fabric of with timeless versus timebound geomorphology. tion of geomorphic science. As a result, the subject Geology, contained two papers, both relying on Rather, he made it clear that the appropriate became one of decreasing interest to other workers in fluvial geomorphological examples, which ex- goal was the understanding of fluvial systems. geology. An important aspect of this growing disinter- est was that geomorphology, as practiced, seemed to plored a new dichotomy in the field. The papers, His worry was that an emphasis on method, lose its inherent usefulness. one by J. Hoover Mackin (1963), and the other specifically the empirical studies that appeared by Luna B, Leopold and Walter B. Langbein in the 1950s, would overshadow this goal. He wrote (Mackin, 1963, p. 148-149): In science usefulness is measured in part by ability to (1963), are generally assumed to represent a de- forecast, i.e., to predict relations postulated by reason- bate over methodology in fluvial process studies ing about associations and subsequently subject to (Thornes, 1979). I shall argue that these papers If this empirical approach—this blind probing—were verification by experiment or field study. With this in presaged the predominant conflict for the most the only way of quantifying geology, we would have mind, it is apparent that preoccupation with descrip- tion could lead to decreasing usefulness because classi- recent generation of fluvial geomorphologists. to be content with it. But it is not; the quantitative approach is associated with the empirical approach, fication and description are usually insufficient bases Mackin's (1963) paper was derived from an but it is not wedded to it. If you will list mentally the for extrapolation and thus for prediction. oral address given at a banquet of the Branner best papers in your own field, you will discover that Club during the meeting of the Cordilleran Sec- most of them are quantitative and rational. In the Note that the emphasis is on usefulness. Leo- tion of the Geological Society of America in Los study of rivers I think of Gilbert's field and laboratory studies of Sierra Nevada mining debris (1914, 1917), pold and Langbein (1963) describe a revitaliza- Angeles, April 17, 1962. In an unpublished and Rubey's analysis of the force required to move tion of geomorphology through its concentration review of this after-dinner talk, Mackin included particles on a stream bed (1938). These geologists, and on process studies, increased use of quantitative several examples of "shotgun empiricism" that many others that come to mind, have (or had) the data, and mathematical expression. In addition, did not survive editing into the 1963 paper. He happy faculty of dealing with numbers without being given this new emphasis on prediction, Leopold specifically analyzed a geomorphological study carried away by them—of quantifying without, in the same measure, taking leave of their senses. and Lanbein (1963) also foresaw the that related channel slope to bed-material size, of stochastic principles as a dominating theme in width-depth ratios, and drainage areas. Scatter fluvial geomorphology. Somewhat ironically, Mackin emphasized the use of rational scien- diagrams of these parameters illustrated interest- however, at the end of their paper, Leopold and tific thinking because that thinking sometimes ing trends. Analyzed without concern for Langbein (1963, p. 192), like Mackin (1963), became clouded in the use of certain new inves- individual data points, however, these trends concluded that problems in fluvial geomorphol- tigative tools that streamlined analysis. Despite also concealed an important distinction de- ogy are more important than methods: his misgivings, however, Mackin clearly re- scribed by Mackin as follows: spected the new methodologies, as long as they had what he considered to be a geological pur- The measure of a research man is the kind of question in any graded segment of a river, the channel is shaped pose. He concluded the unpublished version of he poses. So, also, the vitality of a branch of science is by the river itself in alluvial materials; the outstanding a reflection of the magnitude or importance of the characteristic of this self-modeled channel is that the his talk as follows: questions on which its students are applying their ef- slope is adjusted—it is precisely that slope which pro- fort. Geomorphology is an example of a field of in- vides the transporting power required to move the I am not sure that I have made these points clear, and I quiry rejuvenated not so much by new methods as by load with the available , and with the prevail- think that I will be damned by some in the groups on recognition of the great and interesting questions that ing channel characteristics, whatever these may be. both sides. . . . But if this talk starts some discussion— confront the This equilibrium, or steady-state condition, is timeless; I mean, of course, rational discussion—it will have the graded condition is maintained without change as served its purpose. There are many more things to be long as controlling conditions remain the same. . .. said for my position, and there are surely other points Because both of the Fabric of Geology papers The slope of a rapid or waterfall, on the other hand, is of view that are just as valid or perhaps more valid cited above ultimately espoused geomorphog- a function of (a) erodibility, which depends on than mine. The things that I am sure of are that geol- eny, both were seriously attempting to resolve a resistance of the rock to , spacing and orienta- ogy is a science, with different sorts of problems and major conflict that was emerging in their tion of joints, and so on; (b) discharge—how big the methods, but not in any sense inferior to, or less ma- science. Other fluvial investigators, however, river is; and (c) time—how long the river has been ture than, any other science; and that anyone who operating at that place.... I suggest that while there hires out as a geologist, whether in practice, or in have exacerbated the issues in this conflict is much profit in further investigation of the slope of a research, or in teaching, and then thinks like a physi- beyond the simple divisions of rational and em-

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TABLE 3. CONTRAST BETWEEN EXTREME SCIENTIFIC APPROACHES IN pirical, qualitative and quantitative, or pure and FLUVIAL GEOMORPHOTECHNICS AND GEOMORPHOGENY applied.

Geomorphotechnics Geomorphogeny GEOMORPHOGENY OR Emphasis Use of scientific and engineering Study of landscape origins, development, GEOMORPHOTECHNICS? methodology (method dominated) and changes (problem dominated)

Theme Utility of answers Quality of questions

To streamline the discussion of the modern Goal Prediction Understanding

crises in fluvial geomorphology, I will resurrect Measure of success Objective tests of predictive capability Intellectual satisfaction (multiple working hypotheses)

Lawson's (1894) old term "geomorphogeny." Quantification Essential in all cases Desirable where appropriate to problem

This will be defined as the study of the origin, Optimum scales of study Small Large development, and changes in the landscapes and (temporal and spatial) landforms of Earth and the Earth-like planets. It Process studies Measure modern processes Reconstruct ancient processes will be contrasted with a hypothetical subdisci- Causality Indeterminate or irrelevant Deterministic by assumption pline, "geomorphotechnics," defined as the use Examples of appropriate development on a hillslope Origin of pediments problems for study transport in alluvial channels Origin of the Channeled Scabland of scientific and engineering methodology to ac- Origin of channels and valleys on

quire, interpret, and apply knowledge of the Landmark papers Horton, 1945 Bretz and others, 1956 (a hydrologist introducing a quantitative, predictive (geologists using the method of multiple working Earth's landscape and the processes operating theory to the study of common fluvial landscapes) hypotheses and the principle of uniformity to upon it. The emphasis of geomorphotechnics is understand an anomalous fluvial landscape) on methodology and usefulness of results in the conduct of geomorphological research. The em- phasis of geomorphologeny is on identifying crit- Sparks (1971) observed that classifications esting issues of conflict. Figure 3 makes some of ical questions that lead to scientific understand- are merely arbitrary constructions, designed to the relevant points using the systems-termi- ing. It is my belief that the recent growth of the facilitate the discussion of diverse phenomena at nology so in vogue among geomorphotechni- geomorphotechnical approach to landform the risk of some distortion of the truth. This cians. Because engineering prediction must be study has produced an imbalance of emphases in undoubtedly applies to my arbitrary division of achieved, associations and analogies are extrap- modern fluvial geomorphological research. The modern fluvial geomorphologists. Nevertheless, olated from observation, often with the aid of arbitrary device of defining subdisciplines is in- the distinction will serve to illustrate some inter- mathematical "short cuts." Science, however, tended to facilitate discussion of this imbalance, not to introduce new terminology. In their extreme forms, geomorphogeny and geomorphotechnics have numerous distinctive elements (Table 3). Their most divisive aspect, however, is in the views with which extremists in each camp hold the extremists of the opposite camp. Extremist geomorphogenists are viewed as prone to qualitative generalization, deductive reasoning, and emphasis on the "big picture" rather than the detailed evidence (Fig. 1). Ex- tremist geomorphotechnicians, on the other hand, are viewed either as so immersed in pre- dictive mathematical modeling that nature is ig- nored in order to simulate, or so tied to detailed measurement of processes that their inductive methodology ignores the relevance of their mea- surements to the genesis of landforms and land- scapes (Fig. 2). The infusion of mathematical rigor into geo- morphotechnics may be viewed as both a bless- ing and a curse. Similar trends are apparent in modern , where, as noted by Klemes (1987) "paradoxically, it has become almost ax- iomatic that to be a good hydrologist means to learn how to be a mediocre mathematician or statistician." By concentrating on mathematical modeling, facilitated by the "computer revolu- tion," it has become easier to bypass understand- ing to achieve elegant quantitative predictions. Klemes (1986) warns that an overemphasis on Figure 1. Uncomplimentary view of a geomorphogenist studying an outcrop of fluvial such models has the danger of transforming . Alternative genetic hypotheses for the sediments are envisioned simplistically as a hydrology from a science into a type of mountain environment of braided streams (A) or as a lowland environment of a meandering dilettantism. river (B).

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views were those of Johnson (1932), who hy- pothesized lateral planation by streams; Lawson (1915) and Rich (1935), who hypothesized the parallel retreat of slopes; and Bryan (1922), Gilluly (1937), and Sharp (1940), who hy- pothesized complex combinations of plana- tion, , and wash in pedimentation processes. In his last paper, published posthumously, Mackin (1970) reflected on the conflict that arose over the geomorphology of pediments. He noted the existence of two end members in an isomorphous series: corrasion (lateral planation) pediments and weathering-washing (sheet wash) pediments. In reflecting on the controversy over pediment genesis, Mackin (1970, p. 85) stated:

much of the controversy in the United States regarding pediments has arisen from the fact that people working in different places have seen different things. If a man is familiar with pediments of only one origin, and thinks that all pediments are the same in origin, he is likely to disagree with those who have worked with pediments elsewhere. Many of our problems are of this nature; the disagreements between different schools of thought in the United States, over the years, would have been greatly reduced had the men exchanged visits in the field.

When new field studies turn up phenomena inconsistent with prevailing views, one has Figure 2. Uncomplimentary view of a geomorphotechnician studying same sediments as in anomalies. These introduce conflict in the exist- Figure 1. Quantitative-engineering methodology results in many useful predictive relation- ing scientific program. In the above case, it has ships, but their relevance to this field problem is unclear. become obvious that the same geomorphic form (the pediment) can be arrived at by multiple genetic paths. Moreover, many pediments may involves loops so that temporary un- Mountains of Utah, there are slopes across be relict forms, on which the presently active derstandings (hypotheses) can be tested by their relatively weak sedimentary rocks. These are processes are irrelevant for their genesis. Here implications (predictions). Prediction for both veneered with cap rocks of resting on then is a geomorphogenetic problem that is par- science and engineering is a tool, not a goal. In surfaces that truncate the rock structure. The ticularly unsuited to geomorphotechnics. In- science it serves to test hypotheses in order to gravel caps are fluvial in origin but only several deed, Schumm (1985) lists the phenomenon of generate a more satisfactory understanding. This meters thick. Gilbert termed these mountain- different processes or causes yielding similar ef- is an endless process with a Utopian goal (truth). bounding surfaces "slopes of planation." McGee fects, which he termed "convergence" or "equi- In engineering, prediction serves a utilitarian (1897) subsequently provided the inevitable finality," as one of seven reasons for geologic purpose. It must be achieved quickly in order to descriptive term for such landforms, "pedi- uncertainty for extrapolation in geomorphology. control critical systems important to humankind. ments," which are common geomorphological He views extrapolation as based on the use of A well-known hydrologist recently told me, features in arid and semiarid regions (Fig. 4). analogy and the reliance on the concept of geo- "one does not do science unless all of the rele- This review cannot do full justice to the pro- logical uniformity. vant equations can be written down and pro- longed debate over the origin of pediments and Extrapolation can be abused in either geo- grammed into a computer." Such an attitude related concerns over the role of stream morphogeny or geomorphotechnics. King might serve well in geomorphotechnical studies, processes. At one extreme, Keyes (1912) argued (1953) generalized concepts of parallel slope re- but it would not be much use in relation to a that pediments were produced by . treat into a model of regional pedimentation problem identified by Gilbert (1877). Surround- This extravagant hypothesis was simply incon- producing globally correlated planation surfaces. ing the diorite porphyry intrusions of the Henry sistent with the field evidence. More rational Because the model was inconsistent with abun- dant evidence that planation surfaces formed by other mechanisms, the persistence of its author in holding to it can only be considered an ex- travagance. Similarly, a computer simulation Figure 3. Systems diagram il- model, despite its mathematical elegance, is no lustrating some differences be- more than an intellectual game if it fails to be tween scientific and engineering consistent with detailed evidence in the field. methodologies (after Dooge, A good geomorphotechnical extrapolation 1986). must have the respect of those who will use it.

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This means that phenomena must be predicted according to certain standards and that the rea- soning employed in the analysis must have general acceptance in the scientific community. Of itself this is merely a path to applying existing knowledge, not a means of discovery that will lead to new understanding. If the goal is discov- ery, then it is necessary to focus on anomalies, the failures of extrapolations, thereby bringing into question the prevailing understanding of the phenomenon under investigation. Because such questions are so vital to science, researchers may even employ in their analysis reasoning or methods that are not respectable to many contemporaries.

OUTRAGEOUS OR EXTRAVAGANT HYPOTHESES

In describing what he perceived to be a lack of scientific excitement at the meetings of the Geological Society of America, William Morris Davis (1926) wrote: "We shall be indeed fortu- A nate if geology is so marvelously enlarged in the next thirty years as physics has been in the last thirty. But to make such progress violence must be done to our accepted principles." In this view, it is not respectable new methodologies that will advance geomorphology, but rather advancement will come from outrageous hy- potheses that eventually are proven correct. There is no more sacred principle in geomor- phology than that of gradualism. Its antithesis, that of cataclysms, epitomizes disruptive activity in both science and its history. Cataclysmic geomorphological processes are events of un- usual suddenness and magnitude that generate ex- ceptional change in the landscapes of a . The study of such processes follows in a long tradition of somewhat disreputable scien- tific activity. This lack of respect from other derives from centuries of mistaken views as to what constituted proper scientific pursuits. Through the 17th and 18th centuries, it was common scientific practice to try to recon- cile the surface features of the Earth with cata- clysmic events, such as the flood (Davies, 1969). By the 19th century, the efforts of , John Playfair, and Charles Lyell had replaced the biblical-catastrophist view of Earth history with a concept of gradual- ism. The new dogma held that fluvial landform Figure 4. Contrasting pediments in arid environments. (A) Dissected pediment surfaces of development, like science itself, proceeded probable lateral planation origin south of the James Ranges in the Amadeus Basin in central slowly and with order. Catastrophist views came Australia. The lateritic weathering profiles developed on the pediment gravel indicate that into disrepute. these surfaces probably formed during a Tertiary period of tropical weathering long before dissection during the modern arid climatic regime. (B) Exhumed rock pediment surface (right A great misconception among many earth center) developed on granite west of the Catalina Mountains of south-central Arizona. Late scientists is that the above transition had some- Tertiary fan gravel at left probably correlates to the former that once overlaid this thing to do with . As reviewed ancient landform. (Photograph by Peter Kresan.) by Albritton (1967), Gould (1965), Hubbert

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(1967), and Shea (1982), uniformitarianism in modern holds merely that among competing hypotheses, the simple hypothesis often tends to prevail. This principle, also known as "Occam's razor," leads to hypotheses such as the following: the basic laws of nature remain invariant with time (or at least over the time period of interest). Uniformitarianism in its 20th century form has absolutely nothing to do with whether or not a process is catastrophic. Rather, it has everything to do with whether a hypothesized cataclysm obeys the laws of phys- ics and is consistent with the field evidence. One of the greatest of geological controver- sies arose in the 1920s and 1930s because of the absolutely erroneous belief that hypotheses involving cataclysmic origins of features could be rejected merely because catastrophic proc- esses were inconsistent with uniformitarianism. J Harlen Bretz, in a series of a dozen papers, doc- umented the cataclysmic flood origin of the Channeled Scabland in the finest tradition of uniformitarianism. In their righteous defense of an anachronistic, Victorian concept of scientific dignity, it was Bretz's critics who were the nonuniformitarians. Despite this legacy, there remain vestiges of concern that the immense power and energy of extraordinary floods are something to be down- played. How are such processes to be reconciled with the orderly, slow progression of landscape change? In science such paradoxes are known as anomalies, and it is in the study of such anoma- lies that major advances in knowledge can occur (Kuhn, 1962). If the "Great Scablands Debate," as it was dubbed by Gould (1978), did not concern uni- formity, why was it so significant for geological fluvial geomorphology? Bretz (1928, p. 701) provided the answer at the conclusion of his detailed descriptive paper on scabland bars:

Ideas without precedent are generally looked on with disfavor and men are shocked if their conceptions of an orderly world are challenged. A hypothesis earn- estly defended begets emotional reaction which may cloud the protagonist's view, but if such hypotheses outrage prevailing modes of thought the view of an- tagonists may also become fogged. B

On the other hand, geology is plagued with extrava- gant ideas which spring from faulty observation and Figure 5. in the Channeled Scabland of eastern Washington. The ripples misinterpretation. They are worse than "outrageous are composed of gravel and boulders. Their size proved to be incontrovertible evidence hypotheses," for they lead nowhere. The writer's Spo- kane Flood hypothesis may belong to the latter class, consistent only with the cataclysmic flood hypothesis for the origin of the Channeled Scabland but it cannot be placed there unless errors of observa- (Bretz and others, 1956). (A) Gravel bar adjacent to modern Snake River immediately down- tion and direct inference are demonstrated. The writer stream of junction with Palouse River (top center). Spacing of giant current ripples averages insists that until then it should not be judged by the about 60 m. Note railway bridge for scale. (B) Giant current ripples on divide between Crab principles applicable to formation, for the scab- land phenomena are the product of river channel me- Creek (top left) and Canniwai Creek, Washington. Ripples with a spacing of about 60 m chanics. If this is in error, inherent disharmonies developed beneath flood that innundated both valleys and spilled over divides between should establish the fact, and without adequate ac- them.

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quaintance with the region, this is the logical field for pothesis; rather, the investigator must test the esses operating and as more is learned about the critics. rival hypotheses. If the hypotheses are too factors involved, the range of uncertainty will de- closely identified with the hypothesizer, then this crease, but it never will be entirely removed. When Bretz and others (1956) documented may be viewed as a regrettable, even an offen- In essence, the orderliness and causality of the cataclysmic flood origin of the Channeled sive, way to proceed. Hypotheses (models) that nature are matters of faith. This is no better illus- Scabland, they used meticulous field evidence to survive tests while their rivals are disproven are trated than in the classic exchange between Al- destroy the hypotheses of those who had dis- never fully established. They merely begin to bert Einstein and Niels Bohr. Paraphrasing its puted Bretz's outrageous hypothesis (Fig. 5). In seem more probable than other explanations. At recounting by Bohr (1949), Einstein's question essence the concept of the outrageous hypothesis some point, a model may begin to abstract from was, "Do you really believe that God plays espoused by Davis (1926) was made respecta- raw data the facts that its inventor perceives to dice?" Bohr's reply was, in effect, "It is pre- ble. The methods employed by Bretz in his scab- be fundamental and controlling, placing these in sumptious of us to say what God does." Heisen- land studies were those dictated by what was relation to each other in ways that were not berg's famous "uncertainty principle" was ap- important to achieve fundamental geomorpho- understood before, and thereby generating pre- plied to the indeterminancy of specifying the logical understanding. Moreover, those methods dictions of surprising new facts (Judson, 1980). position and momentum of electrons (Heisen- had to be adapted from their original intended At this point, the model has the qualities of a berg, 1958). Bohr extended that principle to a uses and modified to be geomorphological tools. theory. True theories bind diverse consequences philosophical one: "There is no such thing as an This point was made most clearly by J. Hoover together in such an elegant manner that they electron with definite position and momentum." Mackin, who was trained both as an engineer compel belief by the scientific community. To this, Einstein's rational mind rebelled. For and geologist. Mackin is quoted by Bretz and Geomorphology has little in the way of true him the uncertainty principle was not an inher- others (1956, p. 960) as stating, "to understand scientific theories as defined in this manner. Its ent feature of reality, but rather it was merely a the scablands one must throw away textbook recent activity has largely consisted of the devel- shortcoming of the current theory for reality. treatments of river work." opment of models (hypotheses) that move from The Einstein-Bohr debate was never resolved. one level of analogic reasoning to another. A new debate, in many ways comparable to Indeed it may be the ultimate dilemma of all that over the origin of the Channeled Scabland, Note that there are elements of the above science. The need to predict certain phenomena has recently arisen with the discovery of chan- process, such as surprise, elegance, and belief, often requires assumptions of randomness to nels and valleys on Mars (Fig. 6). Despite the that do not program well into a computer. If predict at least probability distributions of large current consensus about an aqueous origin for geomorphology is to develop scientific theories, populations of those phenomena. This expe- Martian channels (Mars Channel Working it must cultivate these elements. It must continu- dient, however, has also been termed "the philo- Group, 1983), it is fascinating that in the scien- ally question its basic tenets, even causality itself. sophy of scientific desperation." Sometimes it is tific literature nearly every conceivable fluid has the individual phenomena that require scrutiny. been invoked to explain the Martian channels. RANDOMNESS OR CAUSALITY? Many scientists might rebel at this view that The list includes low-viscosity turbulent-flow causality and determinism are matters of faith. , wind, glacial , liquefaction of crustal The complexity of operation of fluvial sys- Adherents of Bridgman's (1936, 1959) logical materials, debris flow, and water. Some fluids tems has for centuries been a source of frustra- positivism would hold that a proposition has were proposed without reasonable analogs to tion for engineers and one of fascination for scientific meaning only if it can be tested for their geomorphic effects (for example, liquid al- scientists. Albert Einstein, who published on validity by accepted scientific principles. Smart kanes and liquid CO2). Some models achieved river meandering, is said to have been impressed (1979), for example, concluded that claims of theoretical elegance (for example, the eolian hy- with the difficulties in explaining fluvial either inherent macroscopic randomness or de- pothesis of Cutts and Blasius, 1981) but failed in phenomena. One manifestation of this complex- terminism for are both proposi- their consistency with the available evidence, ity has been termed "complex response" tions without scientific content because neither argued, not in the field, but from imagery of the (Schumm, 1977). Complex response appears in can be adequately tested. planetary surface. river terraces (Womack and Schumm, 1977), A pragmatic view of scientific understanding, The rapid pace of hypothesis formulation to which otherwise might be presumed to have cer- one that is testable, is that it is achieved when explain Martian channels illustrates the fine line tain genetic significance. the properties of the system under study can be that exists between the outrageous hypothesis The concept of complexity is also central to predicted to a satisfactory level of accuracy. that goes beyond the bounds of existing theory arguments about the statistical (random) or de- There is no question that empirical geomorpho- to explain startling new facts, and the extrava- terministic (causal) nature of fluvial phenomena. logical studies, such as those of drainage net- gant hypothesis that ignores important facts For example, Leopold and Langbein (1963) works or river-channel hydraulic geometry, are merely to present speculation as a startling new argue for a basic indeterminancy of fluvial made immensely more useful when fitted to theory. The former can serve as a stimulating phenomena: predictive models. Indeed, Shreve (1979) ar- source of scientific advancement, as in the gued that such models constitute an appropriate famous Spokane Flood Debate over the origin Where a large number of interacting factors are in- goal for modern fluvial geomorphology. Models of the Channeled Scabland. The latter, however, volved in a large number of individual cases or exam- can be based on randomness, as is the probabi- tends to suppress facts that are inconsistent with ples, the possibilities of combination are so great that listic-topologic approach to drainage-basin geo- the favored hypothesis. physical laws governing forces and motions are not morphology (Shreve, 1975), or they can be sufficient to determine the outcome of these interac- Clearly one may need to throw out the text- tions in an individual case. The physical laws may be deterministic, as are diffusion-equation-based books to advance scientific understanding, but completely fulfilled by a variety of combinations of the models of (Kirby, 1971). The one cannot throw out the necessity of testing interrelated factors. The remaining statements are sto- quality of such studies is that they provide pre- chastic in nature rather than physical. These stochastic hypotheses against the field data. To establish a dictions of phenomena that are useful in many statements differ from deterministic physical laws in applications. hypothesis, the investigator cannot simply test that the former carry with them the idea of an irre- the analogies (or models) that relate to that hy- ducible uncertainty. As more is known about the proc- Success at prediction is certainly a goal that is

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/100/8/1157/3380275/i0016-7606-100-8-1157.pdf by guest on 28 September 2021 Figure 6. Geomorphological map (right) prepared from Viking Spacecraft images 3A11, 3A12, 3A13, 3A14, 3AI5, and 3A16 (left) showing a portion of Ares Vallis, a large channel system on Mars. The anastomosing pattern of channelized zones (CHg) indicates now to the north (from lower right to upper left). The large crater at the bottom center (named "Shawnee") acted as an obstacle lo large-scale fluid flows, resulting in preservation of the terraced upland (T) on its downstream margin. Streamlined (SH) arc uplands that were modified by erosion in the large-scale fluid flows. Scarps bounding these uplands are up to a few hundred meters high. Relatively fresh craters are designated C,, and craters modified by fluid flows are designated PC2- Wind streaks (A) show local effects of blowing from north (top) to south (bottom).

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considered paramount to many clients of scien- have chosen a theme of conflict to provoke bert might be considered ironic in view of the tific knowledge. Fluvial geomorphology will thought rather than offense. In the first half of conflicts described in this paper. Gilbert's focus exhibit soundness and prestige through its quan- this century, geomorphology split into one camp on equilibrium emphasized the timeless over the itative predictions. Although we scientists must that held explanatory genetic description to be timebound aspects of geomorphology. He used concern ourselves with this public perception of all important and another camp that argued for physical principles in analyzing geomorphologi- scientific success, we must not let the scientific empirical description and objective analysis that cal processes. I think that what most impresses image conflict with the scientific process. was geographically useful. The geography/geol- geologists, however, is that Gilbert carried the Kuhn (1962, 1978) argued that laboratory ogy dichotomy of the past has now been re- principle of balance into his scientific philos- measurements in science generally refine placed by another dichotomy, more subtle yet ophy. His purpose was always clearly geomor- principles that are presupposed by the prevailing more divisive. One activity seeks to satisfy the phogenetic, and he chose the geomoiphotechni- consensus of "normal science," that is, the para- rational mind by searching for ultimate origins cal approach that was most appropriate to the digm. In geology and hydrology, the "labora- or causes, while the other uses objective criteria, task. It is true that he worked in a simpler time, tory" is often the Earth itself, but the principle including tests and predictability to wed techno- before the advent of computers, , remains that the quantitative regularity sought is logical advances into a geomorphology that is and simulation modeling. Nevertheless, these conditioned by the regularity that is expected. both useful and respectable. These are both developments merely make the need today even Stated another way, Kuhn's argument holds that worthy goals, but the advantages and limitations more acute for the type of philosophical balance prediction with "loaded dice" is far more prev- of each must be kept in mind by their exemplified by Gilbert's scientific work. alent in science than frustrating attempts to practitioners. In a very perceptive review on how much fathom the unknown. Thus, one can demon- Consistent with the view of fluvial geomor- has contributed to the un- strate that the predictive capabilities of many phology argued in this paper, one might define a derstanding of rivers, J. F. Kennedy (1983) models arise because the tests of those models turning point of study, one based on a change of found that the history of the subject illustrated are severely constrained. view related to geomorphological problems the operation of a nonphysical conservation law. A story about Alexander the Great may illus- rather than methods. This change need not have The law states that the anguish of the river re- trate the choice that must be made. King Gor- affected the majority of geomorphologists, but it searcher over the status of his subject is balanced dius of Phrygia supposedly tied an immensely must carry the essential element of anomaly that only by his joy that so much remains to be elu- intricate knot and stated that the knot could be creates conflict and drives a science toward de- cidated and reliably formulated. undone only by the future ruler of Asia. Faced veloping its own methodologies to achieve un- with the knot's complexity, Alexander summar- derstanding. For this reason, I do not view the ACKNOWLEDGMENTS ily cut it with his sword. critical turning point in the history of fluvial There are also shortcuts in science. Some geomorphological thought to be defined by the I thank William L. Graf, Jim E. O'Connor, especially powerful methodologies can achieve paper of a hydrologist (Horton, 1945). Horton Stanley A. Schumm, and C. R. Twidale for re- useful results, but in doing so, they may bypass (1945) introduced very significant quantitative view comments and discussions. This paper was the fundamental understanding of the natural approaches to principles of stream junctions, completed while the author was Visiting Re- world. Faced with the complexity of the geolog- slopes, and divides that were already appre- search Fellow, Department of Geology and ical record, many geologists have tried com- ciated, at least in part, by earlier masters of met- , The University of Adelaide, South promise on this issue through a rational method aphorical description such as William Morris Australia. of working hypotheses (Gilbert, 1886; Cham- Davis. Nor would I pick papers by geographers, berlin, 1897). Gilbert (1886) even tried to avoid introducing the rigor of spatial statistical treat- the pitfalls of causality by conceiving of "an- ment of the extant landscape. Nor do I propose tecedent and consequent" relations constituting that the important contributions of regime the- REFERENCES CITED ory or sediment-transport hydraulics, the two a "plexus" that pervades nature. Hypotheses are Albritton, C. C., 1967, Uniformity, the ambiguous principle, in Albritton, C. C., used to penetrate this plexus, but it is not their conflicting approaches in ed., Uniformity and simplicity: Geological Society of America Special Paper 89, p. 1-2. predictive ability that the must seek. (Leliavsky, 1955), are the critical inputs. In- Bohr, N., 1949, Discussion with Einstein on epistemological problems in stead, I propose that geological fluvial geomor- atomic physics, in Schilpp, P. A., ed., Albert Einstein: Philosopher- Rather it is the points at which models (hypoth- scientist: London, England, Cambridge University Press, p. 199-241. eses) fail to predict accurately. Science will phology has been and will continue to be most Bretz, J H., 1928, Bars of the Channeled Scabland: Geological Society of America Bulletin, v. 39, p. 643-702. progress only by concern with the failings of its enriched by the demonstration by a geologist Bretz, J H., Smith, H.T.U., and Neff, G. E, 1956, Channeled Scabland of that his outrageous hypothesis for the cataclys- Washington: New data and interpretations: Geological Society of own accomplishments. Fluvial geomorphology America Bulletin, v. 67, p. 957-1049. is fated to this same dilemma. mic flood origin of a landscape was indeed the Bridgman, P. W., 1936, The nature of physical theory: Princeton, New Jersey, Princeton University Press. appropriate route to understanding. Published 1959, The way things are: Cambridge, Massachusetts, Harvard Univer- after his last season of field work in the Chan- sity Press. CONCLUSIONS Bryan, Kirk, 1922, Erosion and sedimentation in the Papago Country, Arizona: neled Scabland, J Harlen Bretz's detailed refuta- U.S. Bulletin 730, p. 19-90. tion of all criticisms of his cataclysmic flood 1941, Physiography, in Geology, 1888-1938, Fiftieth Anniversary Vol- Niels Bohr believed that there were two kinds ume: New York, Geological Society of America, p. 1-15. hypothesis (Bretz and others, 1956) is meticu- 1950, The place of geomorphology in the geographic sciences: Annals of scientific truth: trivialities, where opposites of the Association of American Geographers, v. 40, p. 196-208. lous on detail but profound in its lasting lesson Chamberlin, T. C., 1897, The method of multiple working hypotheses: Journal are obviously absurd, and profound truths, rec- of Geology, v. 5, p. 837-848. of how to pursue fluvial studies as a geologist. Chorley, R. J., 1962, Geomorphology and general : U.S. Geolog- ognized by the fact that the opposite is also a ical Survey Professional paper 500-B, 10 p. profound truth. There is much good to be said of The reverence with which geological fluvial Chorley, R. J., and Beckinsale, R. P., 1980, G. K. Gilbert's geomorphology, in Yochelson, E. L., ed., The scientific ideas of G. K. Gilbert: Geological both geomorphogeny and geomorphotechnics. I geomorphologists hold the work of G. K. Gil- Society of America Special Paper 183, p. 129-142.

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Church, M., 1980, Records of recent geomorphologicai events, in Cullingford, Sciences Transactions, ser. II, v. 20, p. 305-315. Pyne, S. J., 1980, Grove Karl Gilbert: A great engine of research: Austin, Texas, R. A., Davidson, D. A., and Lewin, J., eds., Timescales in geomorphol- Kennedy, J. F., 1983, Reflections on rivers, research, and Rouse: American University of Texas Press, 306 p. ogy: New York, John Wiley, p. 13-29, Society of Civil Engineers, Journal of Hydrological Engineering, v. 109, Rich, J. L., 1935, Origin and evolution of rock fans and pediments: Geological Cotton, C. A., 1956, Geomorphology, geomorphography, geomorphogeny and p, 1258-1260. Society of America Bulletin, v. 46, p. 999-1024. geography: New Zealand Geographer, v. 12, p. 89-90. Keyes, C. R., 1912, Deflative systems of the geographical cycle in an arid Ritter, D. F., 1988, Landscape analysis and the search for geomorphic unity: Cutis, J. A., and Blasius, K, R„ 1981, Origin of Martian outflow channels: : Geological Society of America Bulletin, v. 23, p. 537-562. Geological Society of America Bulletin, v. 100, p. 160-171. The eolian hypothesis: Journal of Geophysical Research, v. 86, King, L. C., 1953, Canons of landscape evolution; Geological Society of Amer- Rubey, W. W., 1938, The force required to move particles on a stream bed: p. 5075-5102. ica Bulletin, v. 64, p. 721-752. U.S. Geological Survey Professional Paper 189-E, p. 120-140. Davies, G. L., 1969, The Earth in decay: London, England, MacMillan. Kirby, M. J., 1971, Hillslope process-response models based on the continuity Russell, I. C., 1904, Physiographic problems of today: Journal of Geology, Davis, W. M., 1912, Relation of geography to geology: Geological Society of equation, in Brunsden, D., ed., Slopes: Form and process: Institute of v. 12, p. 524-550. America Bulletin, v. 23, p. 93-124. British Geographers Special Publication 3, p. 15-30. Schumm, S. A., 1977, The fluvial system: New York, Wiley, 338 p. 1926, The value of outrageous geological hypotheses: Science, v. 63, KlemeS, V., 1986, Dilettantism in hydrology: Transition or destiny?: Water 1985, Explanation and extrapolation in geomorphology: Seven reasons p. 463-468. Resources Research, v. 22, p. 177S-188S. for geologic uncertainty: Japanese Geomorphologicai Union, Transac- Dooge, J.C.I., 1986, Looking for hydrologic laws: Water Resources Research, 1987, Hydrological and engineering relevance of flood frequency analy- tions, v. 6, p. 1-18. v. 22, p. 46S-58S. sis, in Singh, V. P., ed., Hydrologic frequency modeling: Boston, Massa- Schumm, S. A., and Lichty, R, W., 1965, Time, space, and causality in geo- Dury, G. HL, 1972, Some current trends in geomorphology: Earth-Science chusetts, Dordrecht, p. 1-18. morphology: American Journal of Science, v. 263, p. 110-119. Reviews, v. 8, p. 45-72. Kuhn, T. S., 1962, The structure of scientific revolutions: Chicago, Illinois, Sharp, R. P., 1940, Geomorphology of the Rubey-East Humbolt Range, Dutton, C. E„ 1885, Mount Taylor and the Zuni : U.S. Geological University of Chicago Press, 172 p. Nevada: Geological Society of America Bulletin, v. 51, p, 337-372. Survey Annual Report, no. 6. p. 113-198. 1978, The essential tension: Chicago, Illinois, University of Chicago Shea, J. H., 1982, Twelve fallacies of uniformitarianism: Geology, v. 10, Fenneman, N. M., 1939, The rise of physiography: Geological Society of Amer- Press, 366 p. p. 455-460. ica Bulletin, v. 50, p. 349-360. Lawson, A. C„ 1894, Geomorphogeny of the coast of northern California: Shreve, R. L., 1975, The probabilistic-topologic approach to drainage-basin Feyeraband, P., 1975, Against method: London, England, NLB, 339 p. University of California Publications, Bulletin of the Department of geomorphology: Geology, v. 3, p. 527-529. Gilbert, G. K., 1877, Geology of the Henry Mountains: Washington, D.C., U.S. Geology, v. l,p. 241-272. 1979, Models for prediction in fluvial geomorphology: Mathematical Geological and Geographical Survey, 160 p. — 1915, The epigene profiles of the desert: University of California Publi- Geology, v. 11, p. 165-174. 1886, The inculcation of scientific method by example: American Jour- cations, Bulletin of the Department of Geology, v. 9, p. 23-48. Smart, J. S., 1979, Determinism and randomness in fluvial geomorphology: nal of Science (3rd ser.), v. 31, p. 284-299. Leliavsky, Serge, 1955, An introduction to fluvial hydraulics: London. England, EOS (American Geophysical Union Transactions), v. 60, p. 651-655. 1914, The transportation of debris by running water: U.S. Geological Constable and Company, 257 p. Sparks, B. W., 1971, Rocks and relief: London, England, Longman, 404 p. Survey Professional Paper 86, 263 p. Leopold, L. B., and Langbein, W. B., 1963, Association and indeterminancy in Strahler, A. N., 1952, Dynamic basis of geomorphology: Geological Society of 1917, Hydraulic-mining debris in the Sierra Nevada: U.S. Geological geomorphology, in Albritton, C. C., ed.. The fabric of geology: Reading, America Bulletin, v. 63, p. 923-938. Survey Professional Paper 105,154 p. Massachusetts, Addison-Wesley, p. 184-192. Thornbury, W. D., 1969, Principles of geomorphology: New York, Wiley, Gilluly, James, 1937, Physiography of the Ajo region, Arizona: Geological Leopold, L. B., Wolman, M. G., and Miller, J. P., 1964, Fluvial processes in 594 p. Society of America Bulletin, v. 48, p. 323-348. geomorphology: San Francisco, California, Freeman, 522 p, Thornes, J. B,, 1979, Fluvial processes, in Embleton, C., and Thornes, J., eds., Gould, S. J., 1965, Is uniformatarianism necessary?: American Journal of Mackin, J. H., 1963, Rational and empirical methods of investigation in geol- Process in geomorphology: New York, Wiley, p. 213-271. Science, v. 263, p. 223-228. ogy, in Albritton, C. C., ed.. The fabric of geology: Reading, Massachu- Thornes, J. B., and Brunsden, Denys, 1977, Geomorphology and time: London, 1978, The great scablands debate: Natural History, v. 87, no, 7, setts, Addison-Wesley, p. 135-163. England, Methuen, 208 p. p. 12-18, 1970, Origin of pediments in the western United States, in Problems of Tinkler, K. J., 1985, A short history of geomorphology: London, England, Heisenberg, W., 1958, Physics and philosophy: New York, Harper, 206 p. relief planation: Studies in Hungarian geography, Volume 8: Budapest, Croom Helm, 317 p. Horton, R. E., 1945, Erosional development of streams and their drainage Hungary, Akademia Kiado, p. 85-105. Twidale, C. R., 1977, Fragile foundations: Some methodological problems in basins: Hydrophysical approach to quantitative morphology: Geological Mars Channel Working Group, 1983, Channels and valleys on Mars: Geologi- geomorphologicai research: Revue de Geomorphologie Dynamique, Society of America Bulletin, v. 56, p. 275-370. cal Socicty of America Bulletin, v. 94, p. 1035-1054. v. 26, p. 81-95. Hubbert, M. K., 1967, Critique of the principle of uniformity, in Albritton, McGee, W. J., 1897, Sheetflood erosion: Geological Society of America Bul- Womack, W. R., and Schumm, S. A., 1977, Terraces of Douglas Creek, C. C., ed., Uniformity and simplicity: Geological Society of America letin, v. 8, p. 87-112. northwestern Colorado: An example of episodic erosion: Geology, v. 5, Special paper 89, p. 3-33. Miller, J. P., 1959, Geomorphology in North America: Przeglad Geograficzny p. 72-76. Johnson, D. W., 1929, The geographic prospect: Association of American (Polish Geographical Review), v. 31, p. 567-587. Geographers Annals, v. 19, p. 168-231. Morisawa, M., 1985, Development of quantitative geomorphology, in Drake, 1932, Rock fans of arid regions: American Journal of Science, 5th ser., E. T., and Jordan, W. M., eds., Geologists and ideas: A history of v. 23, p. 389-416. North American geology: Geological Society of America, The Geology Johnston, R. J., 1983, Geography and geographers: Anglo-American human of North America, Centennial Special Volume 1, p. 79-107. geography since 1945: London, England, Edward Arnold, 264 p. Ollier, C, D., 1981, and landforms: London, England, Longman, Judson, H. F., 1980, The search for solutions: New York, Holt, Rinehart and 324 p. MANUSCRIPT RECEIVED BY THE SOCIETY DECEMBER 17,1987 Winston, 212 p. Pitty, A. F., 1982, The nature of geomorphology: London, England, Methuen, REVISED MANUSCRIPT RECEIVED APRIL 18,1988 Judson, Shelton, 1958, Geomorphology and geology: New York Academy of 161 p. MANUSCRIPT ACCEPTED APRIL 19, 1988

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