UC GIS Week

Mapping Coastal Cliff Erosion along the California Coast Using Statewide LiDAR Datasets

Coastal cliffs are widespread along the California shoreline, providing habitats for coastal vegetation and wildlife while supporting critical socio-economic infrastructure such as housing, roads, and utilities. Although cliff erosion poses substantial geohazard risks to coastal communities, the eroded material also offers a sediment source to adjacent beaches and the nearshore zone. However, accurate statewide monitoring of cliff change has been limited by 1) the scarcity of repeated, high-resolution datasets, 2) the intensive processing requirements for large geospatial data volumes, and 3) challenges in estimating elevation beneath vegetated areas. To address these limitations, we analyzed statewide, high-resolution (30 pts/m²) airborne LiDAR data collected in 2023, together with the previous 2016 LiDAR survey (15 pts/m²) acquired by NOAA. We developed an automated workflow to delineate cliff boundaries, estimate cliff geometry, and quantify volumetric cliff changes. Importantly, our approach integrates a ground-filtering technique to estimate elevation beneath vegetation, facilitating consistent, statewide quantification of cliff dynamics. Our results show clear northward trends in cliff height, width, and retreat rates, with maximum sediment losses and mean cliff retreat rates respectively exceeding 1150 m³ m⁻¹ yr⁻¹ and 0.1 m/yr in high-erosion Northern California (e.g., Humboldt, San Francisco, and San Mateo Counties). The results also show that steeper and narrower beaches are often associated with enhanced cliff erosion, whereas taller cliffs tend to retreat more slowly. This study demonstrates that combining high-density LiDAR data, ground-filtering techniques, and automated approaches provides an advanced framework for statewide cliff change monitoring and improved understanding of coastal hazard risks and landscape evolution across diverse coastal settings.

Producing Vegetation Burn Severity Data for California

Seven of the ten largest fires in the State of California’s history have burned in the last five years. While large areas of high vegetation burn severity can be devastating to a forested ecosystem, low to moderate severity fire can restore forest resilience and reduce fire hazard. Understanding where fires were beneficial or damaging to eco-systems is crucial for post-fire planning and management. As required by Senate Bill 1101, CAL FIRE's Fire and Resource Assessment Program has been tasked with producing vegetation burn severity data for all large fires in California. This presentation will describe the methods currently used to produce the data, what data is currently available and how to access it, the various challenges faced as the program moves forward, and what is coming next.

Reforesting California using GIS

California is a tinder box, and it's only going to get worse. Reforesting our vast, burned landscapes with limited resources requires careful planning with an adaptation mindset. Last year, we presented the data sources and GIS methods for a cone collection site selection protocol for "triaging" the highest-priority places to collect seeds for reforestation, according to each species' place-based climate exposure, fire risk, and seed supply/demand. This year, we present the application of that protocol in a GIS-based website, as well as its integration with other reforestation tools and examples of how land management agencies and private industry are using our findings.