Impact of Coastal Marsh Eco‐Geomorphologic Change on Saltwater Intrusion Under Future Sea Level Rise

Journal Article · 24 May 2022 · Water Resources Research

DOI: https://doi.org/10.1029/2021WR030333 · OSTI ID:1870046

Zhang, Yu  ^[1]; Svyatsky, Daniil ^[2]; Rowland, Joel C.  ^[1]; Moulton, J. David ^[2]; Cao, Zhendong  ^[3]; Wolfram, Phillip J. ^[4]; Xu, Chonggang ^[1]; Pasqualini, Donatella ^[5]

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1. Earth and Environmental Sciences Division, Los Alamos National Laboratory Los Alamos NM USA
2. Theoretical Division Los Alamos National Laboratory Los Alamos NM USA
3. Theoretical Division Los Alamos National Laboratory Los Alamos NM USA, Center for Applied Coastal Research University of Delaware Newark DE USA
4. Advanced Engineering Analysis Los Alamos National Laboratory Los Alamos NM USA
5. Analytics, Intelligence &, Technology Division Los Alamos National Laboratory Los Alamos NM USA

Abstract Coastal saltwater intrusion (SWI) is one key factor that affects the hydrology, ecology, and biogeochemistry of coastal ecosystems. Future climate change, especially intensified sea level rise (SLR), is expected to trigger SWI to encroach on coastal freshwater aquifers more intensively. Numerous studies have investigated decadal/century scale SWI under SLR by assuming a static coastal landscape topography. However, coastal landscapes are highly dynamic in response to SLR, and the impact of coastal landscape evolution on SWI has received very little attention. Thus, this study used a coastal marsh landscape as an example and investigated how coastal marsh evolution affects future SWI with a physically‐based coastal hydro‐eco‐geomorphologic model, Advanced Terrestrial Simulator. Our numerical experiments showed that it is very likely that the marsh elevation increases with future SLR due to sediment deposition, and a depression zone is formed due to different marsh accretion rates between the ocean boundary and the inland. We found that marsh accretion may significantly reduce the surface saltwater inflow at the ocean boundary, and the evolved topographic depression zone may prolong the residence time of surface ponded saltwater, affecting subsurface salinity distribution differently. We also predicted that marshlands may become more sensitive to upland freshwater supply under future SLR, compared with previous predictions without marsh evolution. This study demonstrates the importance of coastal evolution to coastal freshwater‐saltwater interaction. The eco‐geomorphologic effect may not be ignored when evaluating coastal SWI under SLR at decadal or century scales.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE; USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 1870046
• Report Number(s): LA-UR-21-24288; e2021WR030333
• Journal Information: Water Resources Research, Journal Name: Water Resources Research Journal Issue: 5 Vol. 58; ISSN 0043-1397
• Publisher: American Geophysical Union (AGU)Copyright Statement
• Country of Publication: United States
• Language: English