Variable Flood Discharge Constrains Autochthonous Organic Carbon Preservation in Deltas: Insights From Physical Experiments

Abstract Many global and regional climate models predict shifts in the frequency and magnitude of precipitation events. It is unclear how this transition will influence delta and wetland development. We address this knowledge gap via two reduced‐scale physical delta experiments: one with constant discharge and the other with variable discharge. Floods with a peak discharge equal to three times the baseflow reduce the mean total delta‐top area by a factor of two and a half and increase slopes by a factor of two. Enhanced channel mobility increases delta top slopes and limits large‐scale shoreline movement, which reduce wetland planform. There is a 108% difference in the volume of preserved organic material in the subsurface between the variable and constant discharge conditions. Morphometric differences between systems constructed under constant versus variable discharge highlight the potential impact on ecologically sensitive and economically important coastal wetlands, with implications for the ability to sequester carbon.