Can Restoring Tidal Wetlands Reduce Estuarine Nuisance Flooding of Coasts Under Future Sea-Level Rise?
Wetland restoration is an increasingly popular nature-based method for reducing flooding impacts in coastal communities. In regions with steep topography such as Coos Bay, Oregon, wetland restoration reduces flooding by modulating the tidal signal through increased tidal prism. This study modeled the potential reductions in future flooding events, which will impact both transportation and physical infrastructure, in Coos Bay under a range of sea-level rise (SLR) and wetland restoration scenarios. These scenarios were co-developed through a stakeholder engagement climate adaptation planning effort which includes tidal wetland restoration. We found that restoration can reduce future peak water surface elevations (pWSE) by up to 10 cm dependent on the wetland location and future SLR scenario. Wetland restoration had minimal impact on reducing pWSE within 5 km of the estuary mouth, but led to greater reduction in pWSE inland where wetland tidal storage volume constitutes a larger proportion of the tidal prism. Restoration was effective at reducing pWSE in all SLR scenarios through 2050 and reduced pWSE under the median SLR scenario by half. The reduction in pWSE under the lower SLR scenarios and higher wetland restoration scenarios can significantly reduce the number of hours that a major transportation artery is closed due to tidal flooding. By 2100, the benefit of restoration was reduced under the median SLR scenario and completely eliminated under the high SLR scenario because the increase in tidal prism overwhelms any potential increase in tidal storage volume provided by wetland restoration.