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Research about Santa Cruz County, California

Source-linked reports with geographic coverage including Santa Cruz County, California.

At least 19 recordsLinked to original sources
USGS2026

Morphodynamic controls on the performance of dune-based coastal flood mitigation under sea-level rise

Dune-based adaptation is increasingly used as a nature-based solution for coastal flood mitigation, yet many assessments rely on hydrodynamic-only approaches that treat beach and dune morphology as static, neglecting storm-driven erosion that can degrade dune performance during extreme events. This study develops a process-based modeling framework coupling extreme value analysis of regional wave climate with XBeach surfbeat simulations to evaluate coastal flooding, erosion, and dune performance across three time horizons (2025, 2055, 2085) and four storm return periods (5, 20, 50, and 100 years) at two contrasting sites in Santa Cruz County, California. At Santa Cruz Beach, flood extent increases at an accelerating rate with sea-level rise (SLR) for a given return period, while higher return period storms exhibit diminishing incremental increases under fixed SLR conditions. Storm-scale morphodynamic feedbacks reduce predicted flood extent by up to 32.4% through profile adjustment and nearshore bar formation. Dune effectiveness is strongly regime-dependent, reducing flooding by up to 60% under collision-regime conditions but declining rapidly as the system transitions toward overwash and inundation under stronger storms and late-century SLR. Comparison of static and erodible dune representations shows that flood estimates are not consistently conservative, with differences reaching up to 54.3% depending on storm intensity and time horizon. At Capitola Beach, limited accommodation space and water-level-dominated dynamics collectively constrain morphodynamic adjustment, render the site near its inundation capacity under present-day conditions, and result in near-complete dune collapse and limited flood mitigation across all scenarios. These findings highlight the importance of site-specific regime evaluation, process-based morphodynamic modeling, and adaptive management when assessing dune-based adaptation under rising sea levels.

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USGS2021

Acute mortality in California tiger salamander (Ambystoma californiense) and Santa Cruz long-toed salamander (Ambystoma macrodactylum croceum) caused by Ribeiroia ondatrae (Class: Trematoda)

In early September 2019, a morbidity and mortality event affecting California tiger salamanders ( Ambystoma californiense ) and Santa Cruz long-toed salamanders ( Ambystoma macrodactylum croceum ) in late stages of metamorphosis was reported at a National Wildlife Refuge in Santa Cruz County, California, U.S.A. During the postmortem disease investigation, severe integumentary metacercarial (Class: Trematoda) infection, associated with widespread skin lesions, was observed. Planorbid snails collected from the ponds of the refuge within seven days of the mortality event were infected with Ribeiroia ondatrae, a digenetic trematode that can cause malformation and death in some amphibians. We suggest sustained seasonal high-water levels due to active habitat management along with several years of increased rainfall led to increased bird visitation, increased over-wintering of snails, and prolonged salamander metamorphosis, resulting in a confluence of conditions and cascading of host-parasite dynamics to create a hyper-parasitized state.

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USGS2007

High-resolution topographic, bathymetric, and oceanographic data for the Pleasure Point area, Santa Cruz County, California: 2005-2007

The County of Santa Cruz Department of Public Works and the County of Santa Cruz Redevelopment Agency requested the U.S. Geological Survey (USGS) Western Coastal and Marine Geology Team (WCMG) to provide baseline geologic and oceanographic information on the coast and inner shelf at Pleasure Point, Santa Cruz County, California. The rationale for this proposed work is a need to better understand the environmental consequences of a proposed bluff stabilization project on the beach, the nearshore and the surf at Pleasure Point, Santa Cruz County, California. To meet these information needs, the USGS-WCMG Team collected baseline scientific information on the morphology and waves at Pleasure Point. This study provided high-resolution topography of the coastal bluffs and bathymetry of the inner shelf off East Cliff Drive between 32nd Avenue and 41st Avenue. The spatial and temporal variation in waves and their breaking patterns at the study site were documented. Although this project did not actively investigate the impacts of the proposed bluff stabilization project, these data provide the baseline information required for future studies directed toward predicting the impacts of stabilization on the sea cliffs, beach and nearshore sediment profiles, natural rock reef structures, and offshore habitats and resources. They also provide a basis for calculating potential changes to wave transformations into the shore at Pleasure Point.

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USGS2002

Flow and sediment suspension events on the inner shelf of central California

The US Geological Survey conducted a field experiment in the late spring and early summer of 1998 off northern Santa Cruz County, California, to study sediment fluxes along the central California shelf. As part of this study, a bottom-mounted instrument package was deployed in a sediment-filled paleo-stream channel (h=12 m) off a pocket beach to measure waves, currents, suspended-sediment concentration, temperature, salinity, and seabed-level changes. The observations of suspended-sediment concentration revealed intermittent, intense periods of sediment suspension near the bed that were associated with the passage of individual large waves or wave groups. We used an ensemble averaging technique to characterize the temporal structure of near-bed sediment suspension events (SSEs) defined as when the near-bed instantaneous concentration exceeded the mean by three standard deviations. During the 800 h of deployment, over 9500 SSEs occurred. The 3917 SSEs that began under onshore flow were found to have a different temporal structure than the 5650 events that began during offshore flow. The longer mean duration of the onshore flow events caused an average of 83% of the sediment suspended during the course of the events to be carried offshore after the reversal of flow. All of the sediment suspended during the offshore events was carried offshore due to the shorter mean duration of these events. SSEs are shown to contribute 12% on average and up to 95% of the total sediment suspended by mass, demonstrating the importance of these events to sediment transport in this type of environment. Suspended-sediment transport models developed for the shelf, which use the product of the mean current and the mean suspended-sediment concentration, cannot accurately model the magnitude and direction of suspended-sediment transport on this energetic inner shelf due to the lack of information regarding the instantaneous coupling between fluid flow and sediment suspension. We conclude that time-variant models must be used to accurately model suspended-sediment transport in this type of environment.

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USGS2000

Storage capacity and sedimentation of Loch Lomond Reservoir, Santa Cruz County, California, 1998

In 1998, a bathymetric survey was done to determine the storage capacity and the loss of capacity owing to sedimentation of Loch Lomond Reservoir in Santa Cruz County, California. Results of the survey indicate that the maximum capacity of the reservoir is 8,991 acre-feet in November 1998. The results of previous investigations indicate that storage capacity of the reservoir is less than 8,991 acre-feet. The storage capacity determined from those investigations probably were underestimated because of limitations of the methods and the equipment used. The volume of sedimentation in a reservoir is considered equal to the decrease in storage capacity. To determine sedimentation in Loch Lomond Reservoir, change in storage capacity was estimated for an upstream reach of the reservoir. The change in storage capacity was determined by comparing a 1998 thalweg profile (valley floor) of the reservoir with thalweg profiles from previous investigations; results of the comparison indicate that sedimentation is occurring in the upstream reach. Cross sections for 1998 and 1982 were compared to determine the magnitude of sedimentation in the upstream reach of the reservoir. Results of the comparison, which were determined from changes in the cross-sectional areas, indicate that the capacity of the reservoir decreased by 55 acre-feet.

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USGS1985

Capacity and sedimentation of Loch Lomond Reservoir, Santa Cruz County, California

A sedimentation study of Loch Lomond Reservoir in Santa Cruz County, California, was begun in 1982 to determine reservoir storage capacity and to establish permanent ranges for future studies. Results of a reservoir survey indicated a total storage capacity of 8,824 acre-ft in 1982. Comparison of thalweg profiles from this survey and a survey done prior to dam construction in 1960 shows that deposition has occurred in the lower reach of the reservoir due to landsliding and in the upper reach due to sediment inflow from Newell Creek.

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USGS1981

Approximate ground-water-level contours, April 1981, for the Soquel-Aptos area, Santa Cruz County, California

Ground-water levels in selected wells were measured in the Soquel-Aptos, Calif., area in April 1981. On the basis of these measurements approximate ground-water-level contours were constructed. The general direction of ground-water movement in the Soquell-Aptos area is from the ridges in the northern part of the area, toward the adjacent canyons, and then southward toward the ocean. Ground-water pumping has caused ground-water levels to decline below sea level in the Capitola area, in the area just to the west and northwest of aptos, and in isolated local areas southwest of Rio Del Mar. Ground-water levels in the northern part of the area away from the seacoast have not declined much over time. (USGS)

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USGS1981

late Pleistocene and Holocene pollen record from Laguna de las Trancas, northern coastal Santa Cruz County, California

A 2.1-m core from Laguna de las Trancas, a marsh atop a landslide in northern Santa Cruz County, California, has yielded a pollen record for the period between about 30,000 B. P. and roughly 5000 B. P. Three pollen zones are recognized. The earliest is characterized by high frequencies of pine pollen and is correlated with a mid-Wisconsinan interstade of the mid-continent. The middle zone contains high frequencies of both pine and fir (Abies, probably A. grandis) pollen and is correlated with the last full glacial interval (upper Wisconsinan). The upper zone is dominated by redwood (Sequoia) pollen and represents latest Pleistocene to middle Holocene. The past few thousand years are not represented in the core. The pollen evidence indicates that during the full glacial period the mean annual temperature at the site was about 2°C to 3°C lower than it is today. We attribute this small difference to the stabilizing effect of marine upwelling on the temperature regime in the immediate vicinity of the coast. Precipitation may have been about 20 percent higher as a result of longer winter wet seasons.

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USGS1980

Geology and ground water in north-central Santa Cruz County, California

North-central Santa Cruz County is underlain mainly by folded sedimentary rocks of Tertiary and Cretaceous age that have been highly fractured by movements in the San Andreas fault system. Ground water is stored in fractures within shale and mudstone formations and in intergranular pore spaces within fine- to very fine-grained sandstone and siltstone formations. Fewer than 10% of the wells yield more than 15 gallons of water per minute. The water in most wells is moderately hard to very hard, is generally of a sodium bicarbonate or calcium bicarbonate type, and commonly has excessive concentrations of iron or manganese. Of the many geologic units in the study area, only the Purisima Formation of Pliocene age has the potential to sustain well yields greater than 100 gallons per minute. (USGS)

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USGS1980

Seawater intrusion and potential yield of aquifers in the Soquel-Aptos area, Santa Cruz County, California

Seawater has intruded the Purisima Formation in the interval 0-100 feet below sea level in the Soquel-Aptos area. It occurs in the central part of the area and extends inland about half a mile. The potential yields of the two principal aquifers in the Soquel-Aptos area are 4,400 acre-feet per year from the Purisima Formation and 1,500 acre-feet per year from the Aromas Sand. Pumping from the Purisima Formation, averaging about 5,400 acre-feet per year since 1970, has caused water levels along the coast to decline below sea level and has allowed seawater to enter the aquifer. Seawater intrusion and ground-water storage could be monitored in all depth zones by expanding the observation-well network to include a number of shallow wells, one deep well inland from the coast, and three deep wells along the coast.

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USGS1979

A Late Pleistocene and Holocene pollen record from Laguna de las Trancas, northern coastal Santa Cruz County, California

A 2.1-m core from Laguna de las Trancas, a marsh atop a landslide in northern Santa Cruz County, Calif., has yielded a pollen record for the period between about 30,000 B.P. and roughly 5,000 B.P. Three pollen zones are recognized; the earliest is characterized by high frequencies of pine pollen and is correlated with a mid-Wisconsinan interstade of the mid-continent. The middle zone contains high frequencies of both pine and fir (Abies, probably A. grandis) pollen and is correlated with the last full glacial interval (upper Wisconsinan). The upper zone is dominated by redwood (Sequoia) pollen and represents latest Pleistocene to middle Holocene. The past few thousand years are not represented in the core. The pollen evidence indicates that during the full glacial period the mean annual temperature at the site was about 2 ° C to 3 ° C lower than it is today. We attribute this small difference to the stabilizing effect of marine upwelling on the temperature regime in the immediate vicinity of the coast. Precipitation may have been about 20 percent higher as a result of longer winter wet seasons.

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USGS1978

Stream quality in the San Lorenzo River Basin, Santa Cruz County, California

Stream quality in the San Lorenzo River basin, Calif., was studied from November 1973 through June 1975 to determine areal and temporal variations in water quality, problem areas and times of water quality degradation, and compliance with State and local water-quality objectives. Sampling from November 1973 through July 1974 was done at five stations in the Zayante Creek drainage basin and at one station on the San Lorenzo River at Big Trees. Sampling from August 1974 through June 1975 was done at 15 stations in the San Lorenzo River basin, including one station in the Zayante Creek subbasin. Properties and constituents measured were water temperature, specific conductance, pH, alkalinity, dissolved oxygen, turbidity, fecal-coliform and fecal-streptococcal bacteria, major dissolved ions, nutrients (nitrogen and phosphorus), chemical and biochemical oxygen demand, and trace elements. Benthic invertebrates were collected during autumn 1974 and spring 1975 at two stations. Results show that the water in most streams in the basin can be classified as calcium bicarbonate, but based on the dissolved-ion concentrations the basin can be divided into three water-quality areas that correspond generally to three geologic areas. The most pronounced change in water quality occurs during storms when streamflow, turbidity, and total Kjeldahl-nitrogen, total-phosphorus, dissolved-potassium, and fecal-coliform concentrations increase, while concentrations of most dissolved ions decrease owing to dilution of the nonstorm part of the flow. Late winter and early spring nonstorm flows yield water of the best quality because the concentrations of most dissolved ions and fecal-coliform and fecal-streptococcal bacteria are relatively low, whereas turbidity values are the same as, or not appreciably greater than, during the summer low-flow period. Dissolved-ion concentrations exceeded objectives at stations on east-side streams north of the Zayante fault, probably because of lower-than-normal streamflows during water year 1975. Total-nitrogen and fecal-coliform concentrations exceeded objectives in the Zayante Creek and Branciforte Creek drainage basins, probably because of domestic sewage from improperly operating septic-tank systems. The high total-nitrogen and fecal-coliform concentrations in the Zayante Creek basin might also result from the primary-treated effluent discharged by the city of Scotts Valley into an old sand pit. Results of diel studies (intensive sampling for a 24-hour period) made at two stations on the San Lorenzo River indicate that residential areas between the stations do not contribute sufficient quantities of oxygen-demanding wastes to the river during low streamflow to cause appreciable dissolved-oxygen depletion. Greater streamflows and residential development seem to be responsible for unstable streambed substrates and reduced diversity of benthic invertebrates during the spring at a station downstream of most of the residential areas in the San Lorenzo River valley.

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USGS1977

Geology and ground-water in western Santa Cruz County, California, with particular emphasis on the Santa Margarita Sandstone

The water-bearing potential of the geologic formations in the western part of Santa Cruz County, Calif., is evaluated. Most of the sedimentary formations in this area are fine-grained rocks of Tertiary age that have been folded and faulted. These rocks, in general, yield supplies of water sufficient only for individual domestic supplies. The Lompico and Santa Margarita Sandstones, however, are coarser grained and have the potential to yield moderate quantities of water (50-100 gallons per minute). Areas where the Lompico Sandstone might warrant explorations are (1) near and on the west side of the Ben Lomond fault, (2) near and south of the outcrop of the Lompico Sandstone between Ben Lomond and Felton, and (3) in the area near Bald Mountain School. The Santa Margarita Sandstone should be explored by test drilling in the area between Davenport and Bonnie Doon. The quality of ground water is generally good, although saline water occurs in the San Lorenzo Formation near Redwood Grove and Riverside Grove. (Woodard-USGS)

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USGS1974

Faults and their potential hazards in Santa Cruz County, California

This report and map area designed to provide Santa Cruz County with basic data on the location, pattern, recency of movement, potential for future surface rupture, and anticipated earthquake magnitudes and recurrence intervals for several of the faults located there for consideration in the county's land-use planning program and the preparation of its seismic safety element. This report does not consider other seismic hazards such as ground shaking, seismically induced ground failure, or tsunamis (seismically generated sea waves) that can accompany offshore earthquakes of large magnitude.

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USGS1973

Erosion processes, fluvial sediment transport, and reservoir sedimentation in a part of the Newell and Zayante Creek basins, Santa Cruz County, California

The drainage basins upstream from Loch Lomond, a water-supply reservoir on Newell Creek, and a proposed reservoir site on Zayante Creek were investigated for their characteristics with respect to the erosion, transportation, and deposition of sediment. The study area is underlain predominantly by sandstone, siltstone, and shale of Tertiary age that decompose readily into moderately deep soils, friable colluvium, and easily transported sediment particles. The Rices Mudstone and Twobar, Shale Members of the San Lorenzo Formation of Brabb (1964) underlie steep dip slopes in the study area, and probably are the most highly erodible of the several geologic units present there. However, nearly all of the geologic units have shown a propensity for accelerated erosion accompanying the disturbance of the land surface by the roadbuilding practices that predominate over other types of sediment-producing land-use activities in the study area. Sediment transport in the study area was estimated from (1) a reservoir survey of Loch Lomond in 1971 that was compared with a preconstruction survey of 1960, and (2) sampling of sediment transported in suspension by Zayante Creek during the 1970 and 1971 water years. At least 46 acre-feet of sediment accumulated in Loch Lomond in a 10-year period, and an unmeasured quantity of very fine sediment in the form of a thin layer over much of the reservoir bottom was observed. The measured quantity of deposited sediment in a 10-year period represented a sediment yield of about 1,100 tons annually per square mile of drainage basin upstream from the reservoir arms where the major deposition occurred. This sediment occupied less than i percent of the original capacity of Loch Lomond, but the volume of measured sediment deposition is probably conservative in view of the unmeasured deposits observed and a reservoir trap efficiency of about 95 percent. Sediment sampling on Zayante Creek indicated suspended-sediment yields of about 4,570 and 570 tons per square mile for the 1970 and 1971 water years. These values were considered excessive with respect to the relatively low flows during which they were measured, and probably reflect the intensive and current roadbuilding practices in the central and upstream parts of the Zayante Creek drainage in the study area.

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