Repeat LiDAR Reveals Patterns of Island Accretion in a Rapidly Growing River Delta

River deltas are losing land where accretion fails to keep pace with subsidence and sea‐level rise. However, it remains challenging to quantify the accretion rate on deltas and understand its spatial and temporal variability. Here, we leveraged five repeat airborne laser mapping (lidar) to quantify accretion rates across Wax Lake Delta (WLD), Louisiana, USA, a growing branch of the Mississippi‐Atchafalaya system. We removed water and low‐lying vegetation returns, applied vertical co‐registration, and used a local accretion monitoring station to parse LiDAR elevation change into shallow subsidence and sediment accretion. Accretion and elevation‐change rates between 2009 and 2020 averaged 4.1 ± 3.7 cm/yr and 1.2 ± 1.3 cm/yr, respectively, which exceeded the rate of relative sea‐level rise (1.2 ± 0.83 cm/yr) and corresponded with a sediment trapping efficiency of ∼22%. Accretion was concentrated near island edges where the land surface was within the intertidal zone, with lower accretion rates toward island interiors. While flattening of the downstream delta gradient was apparent between 2009 and 2013, possibly due to the 2011 major flood, the gradient increased back to 1.1 × 10 −4 m/m in 2020, similar to the 2009 value, suggesting a recovery toward an equilibrium gradient set by the flood surface water profile. Our findings imply that delta‐scale accretion patterns are set by feedback between elevation and flood‐water inundation frequency that controls local sediment supply, whereas vegetation and island morphology cause local variations in accretion by modulating sediment trapping.