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Abstract

Luna B. Leopold was a hydrologist and fluvial geomorphologist who headed the Water Resource Division of the U.S. Geological Survey from 1957 to 1966 and was one of the leaders of the postwar quantitative revolution in geomorphology. Like other quantitative geomorphologists of his generation, he turned to numbers partly to strengthen his professional authority in policy debates, particularly those concerning a looming ‘}water crisis{’ in the United States. This paper traces the traces the evolution of Leopold's thought from the 1950s to the 1970s, when he turned from seeking universal empirical regularities in river processes to arguing that fluvial systems were inherently indeterminate and unpredictable. While this position was largely rejected by Leopold's scientific colleagues, it was embraced by members of the emerging environmental movement, for whom Leopold's stochastic understanding of rivers provided a seemingly authoritative rationale for the position that complete control and prediction of river systems would always remain out of reach. More broadly, this case shows how quantitative imprecision and uncertainty can sometimes be advantageous for experts seeking to establish authority in a contested policy domain.