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Research about Santa Monica Mountains

Source-linked reports with geographic coverage including Santa Monica Mountains.

5 recordsLinked to original sources
USGS2025

Post-wildfire sediment fluxes and turbidity plumes in a coastal-draining watershed

Coastal watersheds impacted by wildfires experience higher erosion resulting in increased sediment delivery to the ocean that alters limiting factors (i.e., light) for marine organisms. With increasing wildfire magnitude and severity, it is critical to explore changes in riverine discharges to the ocean to assess cascading hazards associated with wildfires. In situ data, remotely sensed turbidity data, and hydrological model (Soil and Water Assessment Tool “SWAT”) simulations have been adapted to capture and investigate fire-related land use change impacts on Malibu Creek, California, USA. Modifying SWAT land cover inputs using burn severity data had minimal impact on simulations, requiring additional parameterization for acceptable model performance. Remotely sensed turbidity, in situ discharge, rating curve sediment loads, and SWAT simulated discharge and sediment loads increased following the Woolsey Fire. When compared to in situ and rating curve data in similar non-fire water years, the 2019 Woolsey Fire water year in situ discharge was 1.8 times higher, SWAT simulated discharges were 1.4–1.7 times higher, and rating curve sediment load was 1.3 times higher. However, the SWAT simulated sediment loads were slightly lower (0.8–0.9 times) than rating curve sediment loads in similar non-fire water years. Mean coastal turbidity increased to 18.2 Formazin Nephelometric Unit (FNU) during the first storm post-fire (mean background value of 4.3 FNU). Synergies between methods demonstrated rapid coastal sediment exports (remote sensing) and ongoing erosion post-fire (SWAT). These data are essential to understanding fire-related marine ecological changes and implementing effective management and conservation initiatives.

California↗
USGS1986

Demographic patterns of the shrub Ceanothus megacarpus in an old stand of chaparral in the Santa Monica Mountains

Wildfires have had a major influence on the structural and functional adaptations that have evolved in Mediterranean-type ecosystems. Some chaparral shrubs sprout after fires while others produce serotinous cones or seeds refractory to germination until they are cued by a fire. Ceanothus megacarpus is a sclerophylous shrub commonly found in California in either pure of mixed stands which does not survive fires but whose seeds germinate following a fire. Because in recent decades man-made fires have become frequent, few older stands remain, and they have been described as "decadent" or "senescent." Since data on older chaparral stands are scarce, a stand of chaparral in the Santa Monica Mountains of southern California, which last burned in 1929 was studied in an effort to elucidate the survivorship patterns and community structure of Ceanothus megacarpus as it ages. Ceanothus is responsible for 68 percent of the basal coverage at this mixed stand, and one-eighth of the Ceanothus were found to be dead. Over 130 such dead individuals were cut at ground level and aged by ring counts to establish the survivorship curve for this species in this chaparral community in the absence of fires.

California↗
USGS1984

Post-fire recovery of California coastal sage scrub

Postfire regeneration of the shrub and herb vegetation on eight coastal slopes of California coastal sage scrub was studied in the first two growing seasons after fire. All shrub species resprouted with the exception of the suffrutescent Lotus scoparius , though it is not known if this species was alive prior to the fire. It was estimated that 70% of the prefire shrub populations resprouted and these sprouts covered one third of the ground surface by the end of the second season. In contrast to chaparral, seedling establishment from soil-stored seed was low (∼ 102-103/ha) in the 1st postfire year. Resprouts of most major species ( Artemisia californica , Encelia californica , Haplopappus squarrosus , Eriogonum cinereum ) flowered and set seed in the 1st year. Seedling densities were ∼ 104-106/ha in the 2nd year. Herbs dominated the first postfire season vegetation in number of species, cover and biomass. The magnitude of the postfire herb flora was comparable to that in chaparral after fire and included many of the same species. On several slopes, "pyrophyte endemic" annuals ( Lupinus succulentus , Lotus salsuginosus , Phacelia parryi ) dominated the first season and were rare or absent in the 2nd year. One major distinction between these coastal sage sites and chaparral was that resprouting perennial herbs dominated some slopes in the first postfire season and most slopes in the second season in coastal sage. Seedling recruitment of perennial herbs was rare; 26 of the 28 species were present only as resprouts. Total herb cover was markedly lower in the 2nd year despite the fact that it was a wetter year. Between the 1st and 2nd years, shrub cover ∼ doubled, largely from resprouts, annual herb cover declined markedly and perennial herb cover remained relatively constant. The perennial bunchgrass Stipa lepida was an important component of the herb flora on all slopes and was the only species (herb or shrub) to exceed 1/m2 on all eight slopes.

California↗
USGS1977

Catalog of earthquakes in the Santa Monica Mountains area for the period February 21, 1973 to December 31, 1973

The Seismological Laboratory of the California Institute of Technology(CALTECH) has reported instrumentally recorded earthquakes throughout southern California since 1932. Allen and others (1965) analyzed results from the Caltech seismograph network, and related earthquake data for the period from 1934 to 1963 to the regional geologic structures in southern California. A magnitude 6.0 earthquake occurred near Point Mugu, California, approximately 15 km southeast of Oxnard, on February 21, 1973. Within 20 hours of the main shock the U.S. Geological Survey (USGS) and the California Institute of Technology, Pasadena(CALTECH) began operation of temporary portable seismograph stations to study the aftershock sequence of the earthquake (Ellsworth and others, 1973). The temporary network of stations was replaced by an enlarged, permanent seismograph network beginning in June 1973. This catalog contains the fundamental parameters for earthquakes located within and adjacent to the seismograph network operated in the western Santa Monica Mountain region by the National Center for Earthquake Research (NCER), U. S. Geological Survey, during the period from February 21, 1973 to December 31, 1973 covering the main shock and aftershocks of the Pt. Mugu earthquake. The basic data contained in this catalog provides a foundation for further study of active tectonic processes in the western Santa Monica Mountains and adjacent areas.

California↗