Tamarix ramosissima has caused dramatic morphological changes to riparian ecosystems and their bank structures over the last century throughout the southwestern United States. Growing as either small trees or dense stands of shoots, Tamarix species displace or actively outcompete native species of willow (Salix exigua) and cottonwood (Populus deltoides) on the Arkansas River in Colorado. Under normal conditions for colonization by native species, Tamarix seedlings are at a great competitive disadvantage due to slow above ground biomass accumulation. However, damming and the resulting altered disturbance regime may give Tamarix an advantage over native species. Damming on the Arkansas River, Colorado, dramatically reduces the intensity and recurrence interval of downstream flooding. Using two dams in eastern Colorado as proxies for flood control, we assessed physiological, demographic and abiotic factors in order to understand how flooding and damming might influence riparian community dynamics. Our study demonstrates that drought and salinity stress may influence native species recruitment and survival in areas with reduced flooding. Moreover, Tamarix water-use may be quite plastic in drought conditions, suggesting that it conserves water at below dam sites.