FLOODING AND THE DISTRIBUTION OF SELECTED METALS IN FLOODPLAIN SEDIMENTS IN ST. MARIES, IDAHO GRAHAM A. TOBIN 1∗ , ROBERT BRINKMANN 1 and BURRELL E. MONTZ 2 1 Department of Geography, University of South Florida, Tampa, Florida, USA 2 Department of Geography, Binghamton University, Binghamton, New York, USA ( ∗ author for correspondence, e-mail: gtobin@chumal.cas.usf.edu; fax: 813-974-4808) Received 10 February 1999; accepted in revised form 30 June 2000 Abstract. The link between sediment contamination and flooding is not well established, since flooding may exacerbate problems by spreading pollutants throughout the floodplain, or alternatively may dilute contaminants in source areas. To determine the substance of such relationships, the pattern of sediment contamination was examined in a small Idaho town following flooding in 1996. Four heavy metals were tested, nickel, chromium, zinc and copper, in 97 soil samples obtained from sites across the floodplain of the St. Joe River. Flood history and land-uses at each sample site were noted. Results showed that contamination levels generally were not high, with flood areas having lower concentrations than non-flood areas. A stronger relationship could be argued for land-use, with higher concentrations of contamination associated with some industrial sites. High levels of contamination were also found in several samples taken from recreational areas. Further research looking at the potential sources of contamination in relation to characteristics of the flood hydrology would seem pertinent. Key words: flood hazard, heavy metals, Idaho, USA 1. Introduction There are many, potentially adverse, environmental impacts associated with the oc- currence of natural disasters, and attempts have been made to provide a systematic framework for analysis (Montz and Tobin, 1997, 1998). Impacts can include the dispersal of hazardous substances into ground and surface waters, contamination of soils with different chemicals, and the pollution of public water supply sources. Flooding can present an added dimension in that toxic materials can be picked up and transported by the hazard medium, thus disseminating possible pollutants over a wider area (Tobin and Montz, 1994, 1997; Federal Emergency Management Agency, 1997). While it is recognised that the nature of environmental impacts relates to land uses, few baseline data exist, and, as a result, previous work has been unable to establish a clear relationship. In an attempt to establish such a relationship and, thus, to further our understanding of potential impacts from flooding, this paper examines the pattern of metal contamination in floodplain soils to determine (1) the extent to which particular land-uses affect the spatial distribution of metals Environmental Geochemistry and Health 22: 219–232, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands.