BANKFULL REGIONAL CURVES FOR THE INNER AND OUTER BLUEGRASS REGIONS OF KENTUCKY 1 Ruth R. Brockman, Carmen T. Agouridis, Stephen R. Workman, Lindell E. Ormsbee, and Alex W. Fogle 2 ABSTRACT: Bankfull regional curves that relate channel dimensions and discharge to watershed drainage area are useful tools for assisting in the correct identification of bankfull elevation and in stream restoration and reconstruction. This study assessed 28 stable streams located in two physiographic regions of Kentucky: the Inner Bluegrass and the Outer Bluegrass. Bankfull channel dimensions, discharge, and return period as well as average channel slope, median bed material size, sinuosity, Rosgen stream classification, and percent impervious area were determined. Significant relationships were found between drainage area and the bankfull characteris- tics of cross-sectional area, width, mean depth, and discharge for both the Inner Bluegrass and Outer Bluegrass regions (a = 0.05). It was also found that the percent impervious area in a watershed had minimal effect on bankfull dimensions, which is attributed to the well-vegetated nature of the streambanks, cohesive streambank materials, and bedrock control. No significant differences between any of the Inner Bluegrass and Outer Blue- grass regional curves were found (a = 0.05). Comparisons were made between the Inner Bluegrass and Outer Bluegrass curves and others developed in karst-influenced areas in the Eastern United States. Although few significant differences were found between the regional curves for bankfull discharge and width, a number of the curves differed with regards to bankfull cross-sectional area and mean depth. (KEY TERMS: regional curves; fluvial geomorphology; stream restoration; surface water ⁄ groundwater interac- tions; rivers ⁄ streams; watersheds.) Brockman, Ruth R., Carmen T. Agouridis, Stephen R. Workman, Lindell E. Ormsbee, and Alex W. Fogle, 2012. Bankfull Regional Curves for the Inner and Outer Bluegrass Regions of Kentucky. Journal of the American Water Resources Association (JAWRA) 48(2): 391-406. DOI: 10.1111 ⁄ j.1752-1688.2011.00621.x INTRODUCTION Stream restoration refers to efforts to ameliorate previous activities that have diminished, impaired, or destroyed the structure and function of stream sys- tems. Restoration generally involves the conversion of an unstable, altered or degraded channel to its natu- ral or pre-disturbance state while considering present and future watershed conditions (NRC, 1992). The process consists of restoring the stream’s morphologic features in an effort to achieve dynamic equilibrium, 1 Paper No. JAWRA-11-0004-P of the Journal of the American Water Resources Association (JAWRA). Received January 21, 2011; accepted October 19, 2011. ª 2012 American Water Resources Association. Discussions are open until six months from print publication. 2 Respectively, Graduate Research Assistant, Biosystems and Agricultural Engineering Department, University of Kentucky, Lexington, Kentucky; Assistant Professor, University of Kentucky, Biosystems and Agricultural Engineering Department, 128 C.E. Barnhart Bldg., Lex- ington, Kentucky 40546; Assistant Dean for Research and Associate Director of the Agricultural Experiment Station, Agriculture Science Center North, Lexington, Kentucky; Professor, Civil Engineering Department, Lexington, Kentucky; and Kentucky Geological Survey ⁄ Biosystems and Agricultural Engineering Department, University of Kentucky, Lexington, Kentucky (E-Mail ⁄ Agouridis: carmen. agouridis@uky.edu). JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 391 JAWRA JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION Vol. 48, No. 2 AMERICAN WATER RESOURCES ASSOCIATION April 2012