Curt Storlazzi

Sediment traps are commonly used as standard tools for monitoring "sedimentation" in coral reef environments. In much of the literature where sediment traps were used to measure the effects of "sedimentation" on corals, it is clear from deployment descriptions and interpretations of the resulting data that information derived from sediment traps has frequently been misinterpreted or misapplied. Despite their widespread use in this setting, sediment traps do not provide quantitative information about "sedimentation" on coral surfaces. Traps can provide useful information about the relative magnitude of sediment dynamics if trap deployment standards are used. This conclusion is based first on a brief review of the state of knowledge of sediment trap dynamics, which has primarily focused on traps deployed high above the seabed in relatively deep water, followed by our understanding of near-bed sediment dynamics in shallow-water environments that characterize coral reefs. This overview is followed by the first synthesis of near-bed sediment trap data collected with concurrent hydrodynamic information in coral reef environments. This collective information is utilized to develop nine protocols for using sediment traps in coral reef environments, which focus on trap parameters that researchers can control such as trap height ( H), trap mouth diameter ( D), the height of the trap mouth above the substrate ( z o ), and the spacing between traps. The hydrodynamic behavior of sediment traps and the limitations of data derived from these traps should be forefront when interpreting sediment trap data to infer sediment transport processes in coral reef environments.

Recent work to the east of Pt. Barrow on the North Slope of Alaska’s Arctic coast and along the Beaufort Sea coast has shown staggering rates of bluff recession. Bluff recession is also prevalent on the Chukchi Sea coast to the west of Pt. Barrow, but current knowledge suggests that the recession rates are smaller than those on the Beaufort coast. It has been suggested that the bluffs on the Beaufort Sea are ‘melting’ away while bluff erosion on the Chukchi Sea coast is driven by storm events. Although hypothesis have been put forward as to the underlying reason for the variation in the recession rates, detailed knowledge of the forcing and resisting mechanisms responsible for bluff erosion on the Chukchi coast has not been investigated closely. In this study we investigate various processes driving bluff erosion on the Chukchi coast of northwestern Alaska with the goal of identifying the dominant forcing mechanisms. During a field study conducted in late-summer 2009, three Arctic coastal bluff failure modes were inferred from observations and ground-based lidar along a 10-km stretch of the Chukchi Sea. The three failure modes can be summarized as (1) thaw-slump of originally ice-bonded clay and sand resulting in a downward-driven failure block, (2) cantilever beam failure of ice-bonded peat and clay tundra blocks bounded by ice-wedges, and (3) retrogressive landslides of thawed sand-rich sediment layers resulting in steeply inclined bluff faces. Comparison of bluff edge lines from historical aerial photographs indicate that recession rates between 1955 and 1997 were approximately 60% greater for the section of coast dominated by ice wedges and undergoing cantilever beam failure (type-2 failure mode). The type-2 failure is believed to be the dominant mechanism by which bluffs erode on the Beaufort coast. The type-2 failure mechanism is driven by thermal niching, whereby warm air or seawater melts the permafrost at the base of the bluff leaving an overhang and an impending cantilever beam. On the Chukchi coast within the study area, the type-2 cantilever beam failure mode appears to be associated with surficial deposits of marine sand while the majority of the study area consists of marine beach deposits that are eroding by thaw-slump and retrogressive bluff failures. Based on visual observations, historical temperatures, time-lapse photography, and nearshore wave climate measurements made during ice free conditions, thaw-slump and retrogressive bluff failures appear to be driven by both thermal niching and mechanical erosion due to wave impact at the base of the bluffs. In order to better identify the presence and relative importance of these processes on bluffs undergoing thaw-slump and retrogressive failures, measured temperature gradients of bluff material and sea water along with inferred wave impact at the base of the bluff are evaluated. Measured wave conditions and water elevations are used as boundary inputs to calculate wave run-up heights, storm-surge levels, and infer impact with the base of the bluff.

Wave energy is imparted to sea cliffs in discrete, concentrated bundles every 4-25 seconds. While the resulting episodic sea cliff failure occurs when internal strength of sea cliff material is exceeded by forces associated with waves, the detailed mechanics of sea cliff failure processes are poorly understood. Failure events are difficult to predict and challenging to instrument. Ground motions associated with nearshore wave energy, microseisms, directly measure the response of sea cliffs to assailing waves. Through several microseismic field deployments from 2000 - 2003, we documented both the high-frequency shaking of sea cliffs, an instantaneous ringing response to the strike of waves against the sea cliff face, and a low-frequency (10 to 20 sec period) swaying of sea cliffs. This latter signal we interpret to reflect ground motion associated with water from the broken wave bore loading the wave cut platform that fronts the sea cliff face. We integrate microseismic velocities to...

Wind and wave patterns affect many aspects of continental shelf and shoreline evolution. While our understanding of the processes controlling sediment suspension on the continental shelf has improved over the past decade, our ability to predict sediment mobility over large spatial and temporal scales remains limited. The deployment of robust operational buoys in the early 1980's provides large quantities of high-resolution oceanographic and meteorologic data. By 2005, these data sets were long enough in duration to clearly identify long-term trends and compute statistically significant probability estimates of wave and wind behavior during seasonal, annual and inter-annual (i.e., El Nino and La Nina) climatic cycles. Wave-induced sediment mobility on the shelf and upper slope off central California was modeled using synthesized oceanographic and meteorologic data as boundary input for the Delft SWAN model, grain size data provided by the usSEABED database and regional bathymetry...

Wave heights, periods, and directions were forecast for 2081–2100 using output from four coupled atmosphere–ocean global climate models for representative concentration pathway scenarios RCP4.5 and RCP8.5. Global climate model wind fields were used to drive the global WAVEWATCH-III wave model to generate hourly time-series of bulk wave parameters for 25 islands in the mid to western tropical Pacific. December–February 95 th percentile extreme significant wave heights under both climate scenarios decreased by 2100 compared to 1976–2010 historical values. Trends under both scenarios were similar, with the higher-emission RCP8.5 scenario displaying a greater decrease in extreme significant wave heights than where emissions are reduced in the RCP4.5 scenario. Central equatorial Pacific Islands displayed the greatest departure from historical values; significant wave heights decreased there by as much as 0.32 m during December–February and associated wave directions rotated approximately...

Seafloor sediment mobilization on the inner Northwest Iberian continental shelf is caused largely by ocean surface waves. The temporal and spatial variability in the wave height, wave period, and wave direction has a profound effect on local sediment mobilization, leading to distinct sediment mobilization scenarios. Six grain-size specific sediment mobilization scenarios, representing seasonal average and storm conditions, were simulated with a physics-based numerical model. Model inputs included meteorological and oceanographic data in conjunction with seafloor grain-size and the shelf bathymetric data. The results show distinct seasonal variations, most importantly in wave height, leading to sediment mobilization, specifically on the inner shelf shallower than 30 m water depth where up to 49% of the shelf area is mobilized. Medium to severe storm events are modeled to mobilize up to 89% of the shelf area above 150 m water depth. The frequency of each of these seasonal and storm-re...

ABSTRACT Nearshore currents are driven by a number of components including tides, waves winds and even internal tides. To adequately simulate transport of sand and other constituents, the realistic behavior of the dominant current-generating phenomena should be resolved. This often requires sufficient observations and calibration/validation efforts to achieve realistic modeling results. The work explores the capabilities of modeling the currents along West Maui. The West Maui coast has a propagating tide where the observed peak tidal currents, which are directed parallel to the coast, occur very closely to the peak tidal water levels. In 2003, the USGS collected an extensive set of current observations along West Maui, Hawaii, with the goal of better understanding transport mechanisms of sediment, larvae, pollutants and other particles in coral reef settings. The observations included vessel mounted ADCP surveys and an array seafloor instruments at the 10m isobath along the coast. A simple 2DH model of West Maui using Delft3D shows good comparison of the modeled and observed currents. Nearshore currents driven by waves and winds are also considered. During the data collection period a significant erosion event occurred within the study domain at Kaanapali Beach. This event undermined several trees on the shoreline and threatened resort infrastructure. In modeling the nearshore currents of this region we hope to determine the potential for sand transport and shoreline change to hindcast this event.

Two hydrographic surveys produced high-resolution images of the inner shelf of northern Monterey Bay, Santa Cruz County, CA. Interferometric side-scan swath bathymetric sonar data were combined with sub-bottom seismic profiles, aerial imagery, high-resolution topography, and local geology to better understand how coastal geomorphology, lithology, and tectonics influence the distribution and transport of littoral sediment in the nearshore and inner shelf

Recent work to the east of Pt. Barrow on the North Slope of Alaska's Arctic coast and along the Beaufort Sea coast has shown staggering rates of bluff recession. Bluff recession is also prevalent on the Chukchi Sea coast to the west of Pt. Barrow, but current knowledge suggests that the recession rates are smaller than those on the Beaufort

Abstract: United States Geological Survey, Pacific Science Center. Chief Scientist: Curt Storlazzi. Sidescan Sonar data (navigation) of field activity P-1-05-MB in Monterey Bay, Central California from 10/11/2005 to 10/20/2005,< http://walrus. wr. usgs. gov/infobank/p/ ...

Abstract: United States Geological Survey, Pacific Science Center. Chief Scientist: Curt Storlazzi. Collect field data data of field activity A-3-10-OA in Maunalua Bay, southern Oahu, Hawaii from 09/13/2010 to 09/14/2010,< http://walrus. wr. usgs. gov/infobank/a/a310oa/ ...

... http://slo.org/lo/pdf/vol_55/issue_3/1105.pdf> <br /> Knee, Karen, Street, Joseph, Grossman, Eric, and Paytan, Adina, 2008. ... infobank@octopus.wr.usgs.gov <mailto:infobank@octopus.wr. usgs.gov> Data_Set_Credit: Eric Grossman (Chief Scientist, USGS); Curt Storlazzi (Co ...