UC GIS Week

Evaluating Harmful Algal Blooms and Sediment Plumes on the South Florida Coast using Satellite-Based Remote Sensing to Inform Management and Conservation Efforts

Harmful algal blooms (HABs) are common occurrences on the South Florida coast and lead to environmental repercussions which harm the local ecosystem. HABs in Florida Bay, the shallow lagoonal estuary between Florida’s peninsula and the Florida Keys, are commonly caused by Synechococcus, a prominent unicellular cyanobacterium. To address local community concerns regarding the increasing occurrences of HABs, this study utilized satellite remote sensing data from the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) Ocean Color Instrument (OCI), the Sentinel-3-derived Cyanobacteria Assessment Network (CyAN), as well as collections from Sentinel-2 and the Harmonized Landsat and Sentinel-2 (HLS) project. Using these datasets, we calculated common water quality indices (Normalized Difference Chlorophyll Index and Normalized Difference Turbidity Index) to identify areas of HAB and sediment plume conditions. Both indices were found to have similar seasonality between 2019–2025, with the highest values concentrated in the western part of Florida Bay during the summer. We combined CyAN and the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5) data from 2016–2025 to provide monthly cyanobacteria forecasts with three modeling approaches: an autoregressive integrated moving average (ARIMA) model, ARIMA with exogenous variables (ARIMAX), and integrated nested Laplace approximations (INLA). ARIMA and ARIMAX provided temporal forecasts which showed moderate bloom activity for July 2025, while the INLA method produced spatiotemporal forecasts which predicted high cyanobacteria activity concentrated in the north-central region of Florida Bay for the same month. These forecasts will be used to inform future in-situ monitoring and protection of marine species in partnership with the Florida Fish and Wildlife Conservation Commission and the Bonefish and Tarpon Trust. This project was conducted as part of NASA's DEVELOP program in the summer of 2025.

Dune restoration enhances coastal resilience on an urban beach

Coastal dunes are globally recognized as natural features that can enhance coastal resilience and protection from wave events, storm surges, coastal flooding, and sea level rise. We evaluated a pilot restoration of coastal dunes on an intensively groomed urban beach in southern California (Santa Monica Beach, Los Angeles County) after grooming was discontinued. Restoration actions were minimal and included installation of three sides of perimeter sand fencing, cessation of mechanical grooming, and the addition of native dune plant seeds. Sediment accretion, elevation, and geomorphic complexity increased over time in the restoration site, largely in association with sand fencing and dune vegetation. A foredune ridge (maximum elevation increase of 0.9 m) and vegetated hummocks developed, along with a general increase in elevation across the restoration site (0.3 m). After six years, an estimated total volume of approximately 1,730 m3 of sand had accreted in the restoration site and 540 m3 of sand had accreted in the foredune ridge. Over the same period, more than a meter of sediment (vertical elevation change) accumulated along the perimeter sand fencing. Groomed control areas remained flat and uniform. The total cover of vegetation in the restoration site increased over time to a maximum of 7% cover. Following an extreme wave event in December 2023, we compared the performance of the dune restoration to the adjacent groomed control site. We used total water level (wave setup, tide, wave runup) as a proxy for flooding potential. The average wave runup distance was 13.6 m farther inland on the groomed control site compared to the restoration site. Our results demonstrated the potential for restored dunes to enhance flood protection and the potential for increasing coastal resilience using nature-based solutions on urban beaches and provided new insights on the opportunities for restoring dunes as nature-based solutions for climate adaptation.

Dynamic Cities, Dynamic Housing Policy: How BuildSD broke down SB79

This lightning talk would be an overview of the work I do with BuildSD (buildsd.org), specifically our project to combine open-source transportation data (GTFS) with housing production and zoning data to understand 2025's SB 79. SB 79 mandates upzoning near major transit stops, allowing for increased housing production across California, but only in narrow cases so as to not disrupt local control. The talk would discuss some of the challenges inherent in understanding and integrating GTFS, zoning, historical, etc... data from a variety of transit agencies and municipalities, and our work to create a single comprehensive SB 79 upzoning map for San Diego County, where dozens of transit stops are potentially eligible.