Hosted by: Bob McGraw

Long duration floods cause substantial damage and prolonged interruptions to water resource facilities, critical infrastructure, and regional economic development. We present a novel physics-based model for inference of such floods with a deeper understanding of dynamically integrated nexus of land surface wetness, effective atmospheric blocking/circulation, and moisture transport/release mechanism. Diagnostic results indicate that the flood duration is varying in proportion to the antecedent flow condition which itself is a function of the available moisture in the air, the persistency in atmospheric pressure blocking, convergence of water vapor, and the effectiveness of divergent wind to condense the aforesaid atmospheric water vapor into liquid precipitation. A physics-based Bayesian inference model is developed that considers the complex interactions between moisture transport, synoptic-to-large-scale atmospheric blocking/circulation pattern, and the antecedent wetness condition in the basin. We explain more than 80% variations in flood duration with a high success rate on the occurrence of long duration floods. Our findings underline that the synergy between a large persistent low-pressure blocking system and a higher rate of divergent wind often triggers a long duration flood, even in the presence of moderate moisture supply in the atmosphere. This condition in turn causes an extremely long duration flood if the basin-wide surface wetness prior to the flood event was already high.