Stream channel incision in the Piedmont of the southeastern US has resulted in a loss of stream and floodplain functions. Reduced flood frequency and lowered water tables typify incised low-order streams of the region. The objective of this study was to determine if a quantifiable shift in riparian vegetation community structure exists along a gradient of channel incision. Stream channel incision was described using bank height ratio (BHR), defined as the ratio of streambank height to bankfull depth. Ten low-order streams in the Alabama Piedmont were selected across a gradient of BHR values (1.0–5.2). Stream incision is strongly correlated with a shift of community type in the ground flora stratum, from wetland-adapted species at low degrees of incision to plants typical of upland settings at incised sites. Based on Nonmetric Multidimensional Scaling (NMDS) ordinations, functional composition of the ground flora layer was significantly related to median groundwater depth and BHR. These results suggest strong linkages between channel incision, subsequent lowered water table levels and decreased soil moisture, and herbaceous/ground flora composition in floodplains of the Alabama Piedmont.