Architecture and evolution of crevasse splay in Po River Delta: implications for nature-based wetland restoration

Crevasse splays generated by natural levee breaches are key geomorphodynamic mechanisms through which rivers deliver sediment to adjacent floodplains and lagoons, promoting land building and wetland development. In heavily engineered deltaic systems, such features provide valuable natural analogues for nature-based solutions (NbS) aimed at restoring sediment connectivity and enhancing coastal resilience. This study investigates the recent morphodynamic evolution of a crevasse splay in the Batteria Island, Po River Delta, formed due to a natural levee breach, with the aim of quantifying rates of splay growth, surface accretion, and channel-network dynamics.

The evolution of the splay between 2015 and 2024 was reconstructed using Sentinel-2 Satellite Imagery. Changes in vegetation cover, tidal-flat extent, and distributary channel patterns were mapped from true- and false-colour composites, while rates of splay-front progradation were quantified using DSAS. High-resolution surface morphology was further constrained using two drone-based LiDAR surveys (2024 and 2025), complemented by a bathymetric survey.

Sedimentological data from approximately 30 shallow sediment cores distributed across the splay were used to constrain vertical and lateral variability within the deposit and to generate a three-dimensional subsurface model of the splay’s internal architecture.

Results show self-sustained growth of the crevasse splay into the lagoon, accompanied by a gradual expansion of vegetated salt-marsh surfaces and net positive vertical accretion. Progradation rates decrease slowly over time due to geometric spreading of sediment across the widening splay lobes. The distributary channel network exhibits distinct dynamics: three main channels remain consistently open, whereas secondary channels are frequently abandoned after becoming blocked by plant debris. These abandoned channels are subsequently colonized by vegetation, promoting sediment trapping and stabilizing the splay surface. In the northern part of the splay, newly formed lobes are beginning to be colonized by vegetation, but the process remains slow, indicating a lag between sediment deposition and ecological succession.

The Batteria Lagoon crevasse splay demonstrates how naturally occurring levee breaches can rapidly create and stabilize new wetland surfaces in a tide-influenced delta. These findings highlight the geomorphic effectiveness of levee-breach-driven sediment delivery and provide quantitative insights relevant to the design and assessment of NbS-based wetland restoration strategies in deltaic environments.