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INTERBIOME ANALYSIS OF STREAM MEANDERING. James H. Thorp and Robert W. Bosserman, Water Resources Laboratory and Biology Department, University of Louisville, Louisville, KY 40292, U.S.A. Knowledge of North American rivers is based primarily on ecological studies of many small headwater streams and a few mid-order rivers, with little attention paid to large rivers or inter-regional comparisons. Consequently, our understanding of the structure and functioning of river networks is weak and our ability to manage these ecosystems is thereby restricted. One management tactic which has been applied to many rivers is the straightening, or channelization, of the river channel. Models of stream meandering generally assume that the tendency of a channel to meander is not influenced by stream order or geographic region. In order to test these assumptions and prior to examining the ecological effects of stream meandering, we analyzed the geomorphic complexity of various stream orders in 15 rivers spread through 5 biomes of the United States. Rivers were selected from the following biomes: eastern deciduous forest, southeast evergreen (coastal plain), grassland, desert shrub, and mixed montane woodland-brush and northern desert shrub (Rocky Mountain streams). Meandering, or stream complexity, was quantified using fractal geometric analyses of streams that had been digitized from U.S. Geological Survey maps. We tested for significant differences in fractal dimensions as influenced by biome, geologic region, slope, stream order, and intrabiome river network. Despite common assumptions of constancy among and within rivers, we found significant differences in meandering that were related to many of these factors, especially to the type of biome. Intrabiome differences in river complexity were generally less pronounced than interbiome comparisons. Results will be discussed in light of current ecosystem models of regulated rivers. HISTORICAL CHANGES IN THE SOLA RIVER PATTERN AS A RESULT OF CATCHMENT MANAGEMENT. Jolanta Grocholska, Polish Academy of Sciences, Nature and Natural Resources Protection Research Center, Cracow, Poland. The Sola River is a gravel-bed stream draining northern slopes of the Western Carpathians. Great variability of discharge and occurrence of heavy floods during summertime characterize the hydrologic regime of the river. These features result from the low retention potential of flysch bedrock, high relief energy (extreme elevations 1557 - 225 m a. s. 1.), and heavy rainfall received by the basin during frontal downpours. Changes in the channel pattern of the Sola River, accomplished during the last few centuries, are reconstructed on the basis of analysis of paleochannels of known age. The time framework for the changes is provided by cartographic data. Within them, the data on channel location in 1563 are of unique importance as they allow determination of alterations in extent within the valley floor of fluvial reworking of sediments since that time. Initially, the Sola flow diverged into two channels on the Carpathians foreland, within the settlement area occupying the middle part of the valley floor between these channels since the Middle Ages. One of these channels must have been plugged and abandoned before 180. At that date, the river was of multi-thalweg-type, within numerous vegetated islands and gravel bars between braids. A wide zone of Carr forest then developed along the river. Progressive clearance of the riparian vegetation due to putting riverain terrains under cultivation have necessitated narrowing the zone of river migration. Therefore, river bands were lined with stones, some braids were artificially cut-off, and the river course was straightened; all the works having resulted in the present-day channelized river. 13