Increasing flood hazard in the Lower Mississippi River due to extreme storm clustering.

Although major floods in the Lower Mississippi River Basin (LMRB) are primarily driven by clusters of extreme storms rather than isolated events, the role of storm clustering in LMRB flood hazard remains underexplored. We show that floods driven by compound space-time storm clustering have higher peaks, volumes, and durations compared to those from isolated storms or single-mode clustering. Under future climate conditions (2070 to 2100; SSP3-7.0 scenario), projections indicate a 26% rise in the number of extreme storms, an 8% increase in average storm precipitation, and a 17% reduction in dry intervals preceding flood peaks. The dominant flood type is projected to shift from those produced by isolated storms (38%) to ones produced by compound storm clustering (49%)-the type of floods that have been responsible for catastrophic floods historically. These findings highlight the need to incorporate storm clustering and its changes into design flood analysis and management strategies for the LMRB.