Social vulnerability indicators seek to identify populations susceptible to hazards based on aggregated sociodemographic data. Vulnerability indices are rarely validated with disaster outcome data at broad spatial scales, making it difficult to develop effective national scale strategies to mitigate loss for vulnerable populations. This paper validates social vulnerability indicators using two flood outcomes: death and damage. Regression models identify sociodemographic factors explaining variation in outcomes from 11,629 non-coastal flood events in the USA (2008-2012), controlling for flood intensity using stream gauge data. We compare models with i) socioeconomic variables, ii) the composite social vulnerability index (SoVI), and iii) flood intensity variables only. The SoVI explains more variance in death (AIC = 2829) and damage (R2=0.125) than flood intensity alone (death-AIC = 2894 ;damage-R2=0.089), and models with individual sociodemographic factors perform best (death-AIC = 2696; damage- R2=0.229). Socioeconomic variables correlated with death (rural counties with a high proportion of elderly and young) differ from those related to property damage (rural counties with high percentage of both Black, Hispanic, and Native American populations in poverty). Future validation studies should examine other flood outcomes, such as evacuation, migration, and health, across scales.