Low Inflow Estuarine Response to Extreme Events: Storms and El Nino as Indicators of Future Conditions in Urban SoCal Estuaries

Focus Areas > Current Projects > Indicators of Future Conditions in Urban SoCal Estuaries
Sarah Giddings, Scripps Institution of Oceanography, UCSD
Eugene Pawlak, UCSD School of Engineering

Scroll down for 2016 project updates

Project Overview:

Many estuaries with small amounts of freshwater inflow, called low inflow estuaries, - once prevalent along the Southern California coast - have been removed or heavily modified by development. It is unclear if these estuaries can maintain their vital roles contributing to habitat, carbon storage, and coastal protection. One critical gap in knowledge is their capacity to deal with future changes in sea level rise and extreme storm events. Prior research has shown that impacts of extreme storms can be drastic, altering the benthic zone and landscape (morphodynamic) and movement of water (hydrodynamic). Understanding how estuaries might change in the future will enable planners to make informed choices for their management and sustainable development.

This project will:                                                                                                          Los Peñasquitos Lagoon. Credit: Sarah N Giddings Lab

  • Assess hydrodynamic and morphodynamic impacts from storms and El Nino conditions on low inflow estuaries, as well as the physics of how these estuarine systems respond.        
  • Determine if more natural estuarine systems will adapt and be more resilient to extreme events than engineered estuarine systems.
  • Based on this research, make predictions about how low inflow estuaries may respond and change with future conditions including sea level rise and enhanced storminess.

The researchers will work in three Southern California estuaries and employ a variety of research techniques including detailed measurements of currents and water depth, transect surveys, and time-lapse imagery. This project is led by Sarah Giddings, Assistant Professor at Scripps Institution of Oceanography, who specializes in environmental fluid mechanics, and Eugene R. Pawlak, Associate Professor of Mechanical and Aerospace Engineering at the Jacobs School of Engineering at UCSD. 

Read the summary project proposal. Visit the Giddings Lab website.

2016 Research Updates:

The project has found that wave, stream flow, and tidal energy play major roles in driving morphodynamic alterations in small Southern California estuaries by affecting sand bar movement and mouth closure, although not always acting in concert. Large offshore waves carry sediment into the lagoon through a combination of bed load and suspended transport. The sediment can form a sill near the mouth and ultimately disrupt the estuarine exchange flow. Large flows (either due to strong spring tides or heavy rainfall) are able breach the sill, reopening the lagoon to estuarine exchange.

Analysis of the imagery has shown that large-scale sediment changes can take place over the course of a single wave event. This single storm event (~1-2 days) can close the lagoon altering the longer-term (~weeks) circulation of the lagoon. Some preliminary results show morphodynamic alterations in the Tijuana River Estuary do occur and can modify the hydrodynamics, but to a lesser degree than in Los Peñasquitos Lagoon. Likely this is because the morphodynamic changes are less severe and do not typically lead to closures because the lagoon mouth can migrate much more substantially; more data collection and analysis hopefully will prove this.

Photos show researchers in the field and impacts at Los Peñasquitos Lagoon, courtesy of Sarah N Giddings Lab:


























For more information about the project, contact Phyllis Grifman, Associate Director

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  • USC Sea Grant
  • 3454 Trousdale Pkwy, CAS 200
  • Los Angeles, CA 90089-0373
  • (213) 740 - 1961
  • seagrant@usc.edu