Hydrological restoration of coastal wetlands: optimizing site selection and implementation strategies

Abstract Introduction Coastal wetlands, despite their importance in providing ecosystem services like carbon sequestration, water quality improvement, and coastal protection, have suffered extensive degradation and loss in the past two centuries. Hydrological restoration of these degraded ecosystems presents an emerging opportunity for mitigating and adapting to climate change, along with restoring the ecosystem services they provide. Objectives This study evaluates economies of scale and variations in restoration effectiveness, measured as inundation extent and tidal depth, when land parcels are consolidated based on tidal flow paths (sub‐catchment scale) compared to restoring individual land parcels. Methods Using hydrodynamic modeling, we simulated the removal and creation of bund walls to restore tidal flows to land currently used for sugarcane production in the lower Herbert River region, Wet Tropics, Australia, while maintaining zero spill to neighboring land parcels. The extent of the earthworks required to achieve restoration of tidal flows and limit flooding on adjacent land was used as a proxy for the cost of the restoration project. Results Results showed that sub‐catchment‐scale restoration was more cost‐effective and achieved greater restoration effectiveness than land parcel‐by‐land parcel approaches. Pre‐clear intertidal ecosystem mapping and historical satellite imagery were useful for identifying potential restoration sites and demonstrated that modeled restoration of tidal inundation could exceed pre‐clear wetland vegetation extents. Conclusions Restoring whole sub‐catchments rather than individual land parcels is a more cost‐effective strategy because of lower levels of earthworks required to protect adjacent land parcels from unintended inundation.