Low-lying and densely populated coastal and estuarine cities are highly vulnerable to extreme coastal high tide, storm surge, precipitation, and high river discharge. In recent decades, there has been a rise in the frequency and intensity of pluvial-coastal compound flood (CF) events due to the increased frequency of intense precipitation and storm surge events. However, in estuarine and deltaic regions, the CF characteristics depend mainly on the storm tide and river flow interaction. Understanding how the sensitivity of fluvial-coastal CF may respond to changes to watershed and estuarine characteristics is essential for future CF hazard prediction. This study examined two critical processes: 1) the interplay between the potential antecedent soil moisture conditions and peak river discharge, and 2) how sea-level rise’s (SLR) impact on storm surge and river flood distribution alter the CF in complex estuaries. As the study area, we selected Delaware Bay and River (DBR), a shallow and convergent estuarine system in the US Mid-Atlantic region – where flood hazards during a CF can become more significant than the surge and river flood processes occurring in isolation. For the focal event for the study, we selected Hurricane Irene (2011) because it reportedly produced the most extreme CF over the past two decades in the same region. The study revealed that the flood depth in DBR is extremely sensitive to the watershed’s antecedent soil moisture condition and SLR. Studies that focus on large-scale future compound flooding hazard assessment need to adequately address the interacting watershed-coastal processes.