ABSTRACT
This chapter focuses on the South River basin of Iowa, which possesses characteristics that favor generalization of the conclusions to broader environments. The South River basin’s well-integrated stream network is carved into a loess-mantled Kansan glaciation drift plain. The boundaries of valleys in the South River basin were interpreted from USGS topographic maps of varying scales, dates of publication, and levels of accuracy. The South River main stem, Otter Creek, and South River’s two major branches, Squaw Creek and Coal Creek, were streams whose valleys were mapped. Variations in valley width exist in every valley which is not straight-jacketed by intransigent rock walls or concrete. The “Valleys of Iowa” model of stream valley form for “normal” humid environment or effluent streams proposes a fairly constant decline or decay in width upstream from the mouth of the basin. The valley of the South River main stem belies the notion that there is a threshold of tributary importance associated with valley widening.
