Stanford University
Research
The Nearshore
The nearshore region, the boundary between land and open ocean, dramatically impacts our rapidly growing coastal population centers and vulnerable infrastructure. This region has increasingly degraded water quality, and coastal hazards are being further magnified by a changing climate. It is critical to understand how complex processes spanning the nearshore environment impact public safety, economic activity, and fragile ecosystems.
The nearshore is comprised of several distinct regions, each influenced by a unique set of processes. In the swash zone, oscillatory motions from waves running up and down the beach face reshapes the morphology and can cause coastal inundation or overwash during storm events. In the surf zone, waves break due to depth limitations and transform shoreward as a bore, often driving strong circulation patterns and suspending sediment into the water column. In the inner shelf, overlapping wind- and wave-driven circulation on the continental shelf transports material, such as larvae, phytoplankton, and nutrients.
We are broadly interested in dynamics within the nearshore environment and their impact on material transport, beach shape, and other coastal hazards. Topics of interest and tools we use to study them are described below.
What processes drive material Mixing and transport within the nearshore?
Waves and currents transport and disperse pollutants, terrestrial runoff, heat, larvae, and other particles within the nearshore environment, altering water quality and ecosystem health.
Surf-zone Circulation
Mean circulation patterns, such as alongshore currents driven by oblique waves, transport material along the surf zone. However, surf-zone eddies, horizontal rotational motion or vertical vortices, have been observed to significantly enhance material mixing and dispersion within the surf zone. Once generated by shear instabilities or forced by alongshore-varying wave breaking patterns, surf-zone eddies can interact with other eddies and transfer energy across scales. Surf-zone eddy behavior is highly variable across space and time and can change dramatically with environmental conditions, much of which remains poorly understood. We explore the fundamental physical processes generating eddies and how they evolve within the surf zone. Topics of interest include:
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How does wave breaking along finite regions inject vorticity into the water column? Once generated, how do these eddies evolve?
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How well does two-dimensional turbulence describe eddy evolution within the surf zone?
A force associated with breaking waves injects vorticity into the water column. These rotational flows are important for surf-zone mixing and cross-shore exchange.
Surf-Shelf Exchange
Rip currents, narrow and concentrated seaward-directed flows, are a primary mechanism leading to surf-shelf material exchange. There are several rip current types that form due to varying wave breaking patterns, each with differing implications for material transport and beach safety. For example, bathymetric rip currents form due to waves breaking over alongshore varying bathymetry, such as a channeled sandbar, while transient rip currents are solely driven by hydrodynamics when wave energy is spread in many directions. We aim to improve predictions of surf-shelf material exchange by elucidating the dynamics leading to enhanced rip current activity. Topics of interest include:
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What are the dominant mechanisms driving surf-shelf exchange in varying field environments? What are the resident timescales?
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How do rip current circulation patterns and vertical structure alter net cross-shore material exchange?
A transient rip current ejects from the surf zone in large-scale wave basin experiments.
Relevant Publications
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Baker, C. M., Moulton, M., Raubenheimer, B., Elgar, S., & Kumar, N. (2021). Modeled Three‐Dimensional Currents and Eddies on an Alongshore‐Variable Barred Beach. Journal of Geophysical Research: Oceans, 126(7), e2020JC016899. https://doi.org/10.1029/2020JC016899. [PDF]
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Baker, C. M., Moulton, M., Palmsten, M. L., Brodie, K., Nuss, E., & Chickadel, C. C. (2023). Remotely sensed short-crested breaking waves in a laboratory directional wave basin. Coastal Engineering, 183, 104327. https://doi.org/10.1016/j.coastaleng.2023.104327. [PDF]
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Baker, C.M., Moulton, M., Chickadel, C.C., Nuss, E.S., Palmsten, M., & Brodie, K. (2023), Two-dimensional inverse energy cascade in a laboratory surf zone for varying wave directional spread. Physics of Fluids, 35 (12): 125140. https://doi.org/10.1063/5.0169895 [PDF]
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Nuss, E., Moulton, M., Suanda, S., & Baker, C.M. (In Review). Modeled surf-zone eddies on a laboratory scale barred beach with varying wave conditions.
How do waves shape our coastlines?
Waves arriving at our coastlines transform and dissipate in shallow waters, dramatically transforming the landscape over timescales of individual storm events (hours to days) to more extended time periods (years to decades).
Infragravity waves
Infragravity waves, long ocean surface waves with periods of 25 to 250 sec, often dominate wave energy within the inner surf zone. Infragravity waves that reach the shoreline are generated locally (bound or breakpoint mechanisms) or remotely (propagating from deep water as free waves). The interaction of short and long waves in the shoaling zone and across the surf can alter sediment suspension and transport. Once reaching the shoreline, infragravity waves can erode the beach face, increase runup and overtopping of structures, and reflect energy seaward. These infragravity-wave-driven impacts can be particularly severe during storm events. Our research examines the influence of coupled short and long wave dynamics on sediment transport and beach face erosional processes to inform numerical model parameterizations. Topics of interest include:
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What are the relative contributions of short and long waves to sediment suspension and transport in the shoaling zone?
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How do infragravity waves transform across the surf zone and lead to beach erosion?
A large wave event in the Outer Banks, NC. Long waves often dominate wave energy in the inner surf zone.
Extreme events
Coastal storms are a major source of episodic morphological change, driving beach erosion, cliff failure, and damage to coastal infrastructure. During storms, sediment is rapidly transported seaward. Post-storm beach recovery duration varies with environmental conditions, with rapid recovery over weeks to months in some instances, while others may take several years. Storm impacts can exhibit signficant alongshore variability associated with local beach morphology, hard infrastructure, or the cumulative effects of marine and continental processes. Our research investigates the impacts of coupled hydrodynamic and morphodynamic processes during individual extreme events, as well as longer term beach recovery. Topics of interest include:
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What is the role of infragravity waves on dune slumping during extreme events?
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During extreme events, how does alongshore variability of localized impacts alter beach recovery?
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We deployed cameras at Masonboro Island Research to study beach evolution over seasonal timescales.
Relevant Publications
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van Wiechen, P., Rutten, J., de Vries, S., Tissier, M., Mieras, R., Anarde, K., Baker, C.M., Reniers, A., Mol, J.W. (Accepted). Measurements of dune erosion processes during the RealDune/REFLEX experiments. Scientific Data.
Funded project
Derakhti, M., Hegermiller, C.A., Wilson, G., Baker, C.M., Moulton, M., Chickadel, C.C. Sediment Transport Over the Nearshore Environment (STONE): Linking nonlinear wave effects across the shoaling and breaking zone. U.S. Coastal Research Program, 2023 RFP. (2023 - 2027)
How can we support safer, resilient coastlines in a changing climate?
We rely on our coastlines for recreation, commerce, and ecosystem resources as well as protection from coastal hazards and rising sea levels.
Informed coastal management
Coastal hazards, such as rip currents, degraded water quality, and coastal erosion, pose direct risks to beach users, marine ecosystems, and coastal communities. Climate change thrusts many of these issues into immediate focus. The capacity for communities to adapt is contingent on a combination of hazard exposure and socioeconomic factors, which often disproportionally affects those with fewer resources. Furthermore, warming waters and human-induced water quality deterioration can inflict direct harm to coastal ecosystems.
Our lab seeks to improve scientific knowledge that can help inform sustainable coastal management. We value engaging with community members and policy makers and aspire to build collaborative partnerships as the lab grows.
A condemned house on the Outer Banks due to shoreline erosion and sea level rise.
Relevant Publications
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Casper, A., Nuss, E.S., Baker, C.M., Moulton, M., & Dusek, G. (2024). Assessing NOAA Rip-Current Hazard Likelihood Predictions: Comparison of an Operational Model with Lifeguard Observations in the Context of Rip-Current Types. Weather and Forecasting. https://doi.org/10.1175/WAF-D-23-0181.1.
Recording of Baker's UW Engage Program: Town Hall Research Talk (Apr. 2021)
Scientific Tools
We use a diverse set of methods to address science questions. Our work integrates laboratory experimentation with numerical modeling and remotely sensed field observations.
