This work examines the relationship between imperviousness, climate, and the Richards-Baker (R-B) index, a measure of ow variability. Regression equations to predict the R-B index are developed for annual, cool, and warm seasons. The re- gression equations developed, are calibrated using stream ow data from 1970-2000 for 29 USGS streamgages throughout Maryland. Regression equations for the R-B ashiness index are developed as a function of imperviousness, precipitation char- acteristics, and drainage area. The relationship is used to estimate stream quality conditions throughout Maryland for present and future land use and climate. The regression equations are used to calculate the future stream ow variability by pro- jecting the R-B index predictors to re ect the following conditions: (1) Increasing imperviousness only, (2) Climate change only, and (3) Jointly changing impervious- ness and climate. Finally, the relationship between R-B index and stream quality is studied.