The Art of Scientific Precision: River Research in the United States Army Corps of Engineers to 1945

In river engineering, all objectives of the engineering process are subordinated to one factor: control. The aim is not to use knowledge of natural forces to develop new technological devices such as airplane wings or computer chips but to control the forces themselves. ¹ But the science is inadequate. We still do not fully understand the dynamics of river flow, and complex natural systems exceed our ability to mimic them in laboratories. Consequently, engineers must fall back on art, intuition, and close empirical study. River engineering remains in many ways experimental and tentative.

The problems are daunting. Viewed holistically and over a long period of time, rivers exist in a state of equilibrium; changes occur within a limited range and tend to offset one another. The rare period of readjustment—a sudden shift in the channel, for instance—will eventually lead to a new dynamic equilibrium. One author has suggested that the process is analogous to a soldier’s career: 98 percent boredom and 2 percent terror, with “most of the significant work accomplished during moments of terror.” ² But from year to year a river’s physical features hardly seem static. Sediment load, morphology, discharge, and even location can change. There is perpetual adjustment of the five variables that influence river flow: velocity, channel width, channel depth, gradient, and bed “roughness” (the resistance of a bed to flow). Heraclitus neatly summed up the quandary: “No one can step twice into the same river.”

The technologies to control river flow have not changed fundamentally for ages. They include dams, levees and floodwalls, bank revetment, jetties, channel stabilization, and dredging. The emphasis is on the effective application of existing technologies; the innovation usually is in the details. In the last two and a half centuries engineers have applied mathematical rationalization to structural design, allowing each unique design to respond to the particular combination of variables affecting flow in a given stretch of river over time. The challenge is somewhat analogous to designing suits for a customer who is both demanding in his needs and discontented with his shape, constantly indulging in fad diets and binge eating. Even experts may wonder how to design a suit—or dam, revetment, or levee—for a constantly changing profile. The answer, of course, is to design within a range of anticipated parameters. Still, neither the tailor nor the river engineer will sanguinely predict success. In the case of river engineering, humility is especially called for when the river’s discharge is known to vary widely or human activity modifies the floodplain.

This article analyzes the evolving relationship between river engineering and science by focusing on the largest river engineering organization in the world: the U.S. Army Corps of Engineers, an agency presently composed of some 37,000 civilians, 300 officers, and 200 enlisted personnel. ³ Since its permanent establishment as a small officer corps in 1802, the Corps of Engineers has contributed to science and applied scientific knowledge to practical problems. Its engineers have occasionally advanced theoretical science, but its research efforts have largely been empirical and inductive, reflecting an organizational culture and sociopolitical context that have often decisively influenced laboratory and field investigations. The major difference between nineteenth- and twentieth-century army engineers is not in their approach but in their self-confidence; today, army engineers appreciate better the challenges of unlocking the secrets of river behavior. An examination of the Corps’s river research, emphasizing the agency’s laboratory program at the Waterways Experiment Station during the New Deal, illuminates the limitations of scientific analysis—and the necessity of engineering art—in the complex world of fluvial hydraulics.

Empiricism, Mathematics, and Theory

Although many nineteenth-century army engineers thought of themselves as scientists as well as engineers, they subordinated their desire to discover nature’s laws to the practical need for navigable and safe rivers. Following the precepts of the Common Sense philosophers of the Scottish Enlightenment, they suspected any theory not thoroughly verified empirically. Precise and repetitive measurements, not the search for universal truth, characterized...