Future inundation of coastal on-site wastewater treatment systems in a region with pronounced sea-level rise

Threndyle, Ryan Edward; Jamieson, Rob; Kennedy, Gavin W.; Lake, Craig B.; Kurylyk, Barret L.

doi:10.1016/j.jhydrol.2022.128548

Cited by 8 publications

(4 citation statements)

References 47 publications

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“…Also, the relative sensitivity of an island or coastal aquifer to changing recharge would differ along the global coastline as some coastal areas have historic trends or future projections that generally indicate increased precipitation (e.g., Curtis, 2019). Depending on the coincident changes in evapotranspiration, potential increases in recharge arising from increased precipitation could help combat SWI due to SLR (e.g., Threndyle et al., 2022).…”

Section: Discussionmentioning

confidence: 99%

Saltwater Intrusion Into a Confined Island Aquifer Driven by Erosion, Changing Recharge, Sea‐Level Rise, and Coastal Flooding

Stanic,

LeRoux,

Paldor

et al. 2024

Water Resources Research

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Aquifers on small islands are at risk of salinization due to low elevations and limited adaptive capacity, and present risks will be exacerbated by climate change. Most studies addressing small‐island saltwater intrusion (SWI) have focused on homogeneous sandy islands and one or two hydraulic disturbances. We herein investigate SWI dynamics in a layered, confined island aquifer in response to multiple environmental perturbations related to climate change, with two considered in tandem. Our field and modeling work is based on an island aquifer that provides the drinking water supply for an Indigenous community in Atlantic Canada. Observation well data and electrical resistivity profiles were used to calibrate a numerical model (HydroGeoSphere) of coupled groundwater flow and salt transport. The calibrated model was used to simulate the impacts of climate change including sea‐level rise (SLR), storm surge overtopping, changing aquifer recharge, and erosion. Simulated aquifer conditions were resilient to surges because the confining layer prevented deeper saltwater leaching. However, reduced recharge and erosion resulted in saltwater wedge migration of 170 and 110 m, respectively when considered individually, and up to 295 m (i.e., into the wellfield) when considered together. Despite the confining conditions, SLR resulted in wedge migration up to 55 m as the confining pressures were not sufficient to resist wedge movement. This is the first study to harness an integrated, surface‐subsurface hydrologic model to assess effects of coastal erosion and other hydroclimatic stressors on island aquifers, highlighting that climate change can drive extensive salinization of critical groundwater resources.

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Section: Discussionmentioning

confidence: 99%

Saltwater Intrusion Into a Confined Island Aquifer Driven by Erosion, Changing Recharge, Sea‐Level Rise, and Coastal Flooding

Stanic,

LeRoux,

Paldor

et al. 2024

Water Resources Research

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“…Sediment‐ocean and atmosphere‐ocean interactions play an essential role in marine ecosystems and contribute to biological productivity (e.g., Santos et al., 2021). Sediment loading from erosion and high saline SGD rates following storms may impact contaminant fate and transport (e.g., Threndyle et al., 2022; Wong et al., 2015). Such processes can impact nearshore water quality and disturb biogeochemical processes, ecosystems, and aquaculture operations (Chambers et al., 2013; Rakhimbekova et al., 2023).…”

Section: Resultsmentioning

confidence: 99%

Interrelated Coastal Flooding, Erosion, and Groundwater Salinization on a Barrier Island During Hurricane Fiona

Cantelon,

LeRoux,

Mulligan

et al. 2024

JGR Earth Surface

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Coastal flooding transforms barrier island morphology and rapidly salinizes freshwater lenses that support island populations and ecosystems. Climate change is expected to increase coastal flood risks, and understanding future island vulnerability requires understanding erosion and salinization processes and their feedbacks. This study investigates how island morphology and groundwater salinity distributions on Hog Island, Prince Edward Island, Canada, responded to high water levels during post‐tropical storm Fiona (24 September 2022), the costliest hurricane to make landfall in Canadian history. Island morphology was monitored with drone‐based LiDAR, and beach groundwater dynamics were investigated with frequency‐domain electromagnetic geophysics surveys and monitoring wells. Comparing pre‐storm and post‐disturbance data revealed high dune scarping that thinned the ocean‐side foredune by 12.3 m on average and reduced the total island volume by 12%. Beach groundwater levels and electrical conductivity increased by up to 2 m and 19 mS cm−1, respectively, and the freshwater lens was lost under the eroded foredune. Measurements 9 months after the storm revealed early‐stage recovery of the foredune; however, high dune scarping prolonged recovery, and the island volume only increased by 1%. Without a stable ocean‐side foredune, the landward extent of recurring coastal flooding increased and limited freshwater flushing and aquifer recovery. Results indicate that rapid erosion from extreme coastal storms shifts coastal boundaries, salinizes formerly freshwater resources, and limits freshwater recovery. These findings emphasize the importance of understanding the often‐overlooked interconnections between coastal flooding, erosion, and groundwater salinization to effectively manage coastal resources in an age of environmental change.

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“…The field data yielded useful insights into the local basin and aquifer properties, ocean and aquifer interactions, and processes influencing SWI. The geophysics survey highlighted how highly dynamic the deep intertidal region is during spring high tides (Figure 4c), how these dynamics create the brackish USP, and how the deeper confined aquifer conditions “push” the salt wedge offshore as observed elsewhere along Nova Scotia's coastline (e.g., Threndyle et al., 2022). Several numerical modeling studies have simulated USP dynamics (Robinson et al., 2018; Xiao, Li, et al., 2019; Xiao, Wang, et al., 2019; Yu et al., 2019), but field observations are less common (Geng & Boufadel, 2017).…”

Section: Resultsmentioning

confidence: 99%

Mega‐Tidal and Surface Flooding Controls on Coastal Groundwater and Saltwater Intrusion Within Agricultural Dikelands

LeRoux,

Frey,

Lapen

et al. 2023

Water Resources Research

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Climate change will increase sea levels, driving saltwater into coastal aquifers and impacting coastal communities and land use viability. Coastal aquifers are also impacted by tides that control groundwater‐ocean interactions and maintain an “upper saline plume” (USP) of brackish groundwater. Coastal dikes are designed to limit the surface impacts of high‐amplitude tides, but, due to ongoing sea‐level rise (SLR), low‐lying dikelands and underlying aquifers are becoming increasingly vulnerable to flooding from high tides and storm surges. This study combines field observations with numerical modeling to investigate ocean‐aquifer mixing and future saltwater intrusion dynamics in a mega‐tidal (tidal range >8 m) dikeland along the Bay of Fundy in Atlantic Canada. Field data revealed strong connectivity between the ocean and coastal aquifer, as evidenced by pronounced tidal oscillations in deeper groundwater heads and an order of magnitude intra‐tidal change in subsurface electrical resistivity. Numerical model results indicate that SLR and surges will force the migration of the USP landward, amplifying salinization of freshwater resources. Simulated storm surges can overtop the dike, contaminating agricultural soils. The presence of dikes decreased salinization under low surge scenarios, but increased salinization under larger overtopping scenarios due to landward ponding of seawater behind the dike. Mega‐tidal conditions maintain a large USP and impact aquifer freshening rates. Results highlight the vulnerability of terrestrial soil landscapes and freshwater resources to climate change and suggest that the subsurface impacts of dike management decisions should be considered in addition to protection measures associated with surface saltwater intrusion processes.

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Future inundation of coastal on-site wastewater treatment systems in a region with pronounced sea-level rise

Cited by 8 publications

References 47 publications

Saltwater Intrusion Into a Confined Island Aquifer Driven by Erosion, Changing Recharge, Sea‐Level Rise, and Coastal Flooding

Saltwater Intrusion Into a Confined Island Aquifer Driven by Erosion, Changing Recharge, Sea‐Level Rise, and Coastal Flooding

Interrelated Coastal Flooding, Erosion, and Groundwater Salinization on a Barrier Island During Hurricane Fiona

Mega‐Tidal and Surface Flooding Controls on Coastal Groundwater and Saltwater Intrusion Within Agricultural Dikelands

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