HGS RESEARCH HIGHLIGHT – Storm Surges and Coastal Salinization/Saltwater Intrusion
This week’s research highlight introduces two papers by Dr. Holly Michael’s research group at the University of Delaware – papers which bring attention to the impact of storm surges on coastal salinization/saltwater intrusion under a changing climate, and on the subsequent impact of saltwater flooding on crop-yields in adjacent agricultural lands.
Dr. Holly Michael (hmichael@udel.edu) is corresponding author for both papers.
Paper #1: Effects of Marsh Migration on Flooding, Saltwater Intrusion, and Crop Yield in Coastal Agricultural Land Subject to Storm Surge Inundation
AUTHORS: Julia A. Guimond and Holly A. Michael
Abstract:
Low-lying coastlines are vulnerable to sea-level rise and storm surge salinization, threatening the sustainability of coastal farmland. Most crops are intolerant of salinity, and minimization of saltwater intrusion is critical to crop preservation. Coastal wetlands provide numerous ecosystem services, including attenuation of storm surges. However, most research studying coastal protection by marshes neglects consideration of subsurface salinization. Here, we use two-dimensional, variabledensity, coupled surface-subsurface hydrological models to explore how coastal wetlands affect surface and subsurface salinization due to storm surges. We evaluate how marsh width, surge height, and upland slope impact the magnitude of saltwater intrusion and the effect of marsh migration into farmland on crop yield. Results suggest that along topographically low coastlines subject to storm surges, marsh migration into agricultural fields prolongs the use of fields landward of the marsh while also protecting groundwater quality. Under a storm surge height of 3.0 m above mean sea level or higher and terrestrial slope of 0.1%, marsh migration of 200 and 400 m protects agricultural yield landward of the marshfarmland interface compared to scenarios without migration, despite the loss of arable land. Economic calculations show that the maintained yields with 200 m of marsh migration may benefit farmers financially. However, yields are not maintained with migration widths over 400 m or surge height under 3.0 m above mean sea level. Results highlight the environmental and economic benefits of marsh migration and the need for more robust compensation programs for landowners incorporating coastal wetland development as a management strategy.
Paper #2: Storm Surges Cause Simultaneous Salinization and Freshening of Coastal Aquifers, Exacerbated by Climate Change
AUTHORS: Anner Paldor and Holly A. Michael
CLICK HERE TO READ THE PAPER #2
Abstract:
Ocean surge events are known to threaten coastal aquifers through vertical infiltration, with the degree of salinization depending on hydrogeologic factors. Another salinization process in coastal aquifers is lateral saltwater intrusion, which may also be affected during surges as the inundation alters the aquifer hydraulic heads. While these processes have been considered individually, here we consider the interplay between them and the longer-term impact of climate change, which is projected to increase the frequency of surges in the future. Using numerical modeling, the location of the lateral freshwater-saltwater interface and the total salt storage are calculated for single and repetitive surge events with different recurrence times to predict the long-term effect of surges. Results point to two novel mechanisms: (1) Following a single overwash event, salt storage in the aquifer peaks due to vertical salinization, and a second, lower peak occurs on a longer time scale. This second peak is due to the surge-induced rebound motion (seaward and then landward) of the interface. (2) The projected increase in surge frequency due to climate change can potentially induce long-term migration of the interface seaward, independent of a change in sea level, depending on the aquifer permeability. Together with this freshening effect, the total salt load in the aquifer increases due to repetitive vertical salinization. Thus, we show for the first time the combined effect of storm surges and climate change on both vertical and horizontal movement of salt in coastal aquifers, with important implications for water management along global coastlines.