scholarly journals FIELD MEASUREMENTS AND SWASH PARAMETERIZATION ON BEACHES

2018 ◽  
pp. 23
Author(s):  
Paula Gomes Da Silva ◽  
Raúl Medina ◽  
Mauricio González ◽  
Roland Garnier
Keyword(s):  
Environmental Parameters ◽  
Field Measurements ◽  
Wave Runup ◽  
Wave Processes ◽  
Site Specific ◽  
Erosion Risk ◽  
Sediment Size ◽  
Water Edge ◽  
Offshore Wave ◽  
Empirical Approaches

The wave runup, defined as the vertical oscillation of the water edge at the coast, is commonly used as criterion for coastal design projects and flooding/erosion risk analysis. Due to the complexity of nearshore wave processes, most runup studies are based on empirical approaches which directly relate these oscillations to the beach and offshore wave characteristics. However, there is still considerable debate about just how runup is related to these environmental parameters, as well as about the range of application of empirical models due to site specific conditions. Recent works emphasized the importance of including site specific conditions to reduce the scatter in available parameterizations. Parameters related to beach characteristics like the sediment size, the amount of reflection, wave spectral shape and morphodynamic beach state may improve runup predictions (Poate et al., 2016, Guza and Feddersen, 2012).

Is more better? Sediment production, weathering, and erosion inferred from multiple geochemical proxies and comprehensive field measurements in mountain catchments

2020 ◽  
Author(s):  
Clifford S. Riebe ◽  
Leonard S. Sklar ◽  
Claire E. Lukens
Keyword(s):  
Field Measurements ◽  
Cosmogenic Nuclides ◽  
Spatial Variations ◽  
Residence Times ◽  
Size Distributions ◽  
Erosion Rates ◽  
Cosmogenic Nuclide ◽  
Sediment Production ◽  
Sediment Size ◽  
Geochemical Proxies

<p>Weathering in mountain landscapes produces sediment with size distributions that evolve as particles are transported down hillslopes, delivered to channels, and carried downstream. The evolving sizes influence rates of river incision into bedrock, which in turn set sediment residence times on hillslopes, with implications for the sizes of sediment produced by weathering. Hence, variations in sediment size are central to feedbacks that link climate, tectonics, and erosion in mountain landscape evolution. However, few studies have quantified how sediment sizes evolve during transport across catchments, focusing instead on rates of erosion and weathering. Yet recent modeling suggests that spatial variations in sediment size can lead to bias in erosion rates from conventional techniques, further highlighting the importance of understanding how sediment size evolves across landscapes.</p><p>Here we show how a more complete and unbiased picture of sediment production, weathering, and erosion can be obtained by combining field measurements of sediment size together with conventional geochemical proxies in an integrative model that accounts for spatial variations in erosion, weathering, and sediment mixing, while incorporating effects of both abrasion and fragmentation during transport in channels. Our measurements, from a catchment draining the steep eastern Sierra Nevada, California, include particle size distributions of sediment from widely distributed locations. These measurements represent sediment that is produced on hillslopes and delivered to channels, reflecting the combined effects of the initial sediment size distribution (set by bedrock fracture spacing) and subsequent weathering on slopes. Our measurements also include cosmogenic nuclide concentrations and apatite-helium ages in 11 size classes, from sand to boulders, sampled from the creek. The cosmogenic nuclides reveal residence times of sediment in the catchment, while the apatite-helium ages reveal source elevations of sediment eroded into the stream. When combined together, the cosmogenic nuclide and apatite-helium data can be used to quantify altitudinal variations in erosion rates and sediment size distributions.</p><p>Our measurements from catchment slopes indicate that hillslope sediment size decreases with decreasing elevation, reflecting altitudinal trends in physical, chemical, and biological weathering and producing downvalley fining in hillslope sediment supply. Cosmogenic nuclides in stream sediment decrease by two-fold with increasing particle size, indicating that erosion rates calculated using traditional techniques are sensitive to the size sampled from the creek. Apatite-helium ages suggest that the smallest and largest sizes sediment sizes in the stream originate from lower elevations, where slopes are gentler and soil-mantled. In contrast, coarse gravel and cobbles appear to originate from higher in the catchment, where slopes are steeper and bare bedrock is exposed. The differences in altitudinal trends in sediment size implied by the apatite-helium data and the direct observations from catchment slopes can be reconciled by accounting for particle fragmentation and abrasion during transport from hillslope sources to the sampling point in the creek. Our analysis indicates that each of the unique sources of information in our study are necessary for a complete and unbiased understanding of spatial variations in the production of sediment across the full range of sizes and their evolution during transport across the catchment.</p>

Analysis of Impact Loads on a Self-Elevating Unit During Jacking Operation

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Jonas W. Ringsberg ◽  
Viktor Daun ◽  
Fredrik Olsson
Keyword(s):  
Simulation Model ◽  
Deformation Behavior ◽  
Environmental Parameters ◽  
Time Domain Analysis ◽  
Offshore Wind ◽  
Soil Deformation ◽  
Site Specific ◽  
Impact Forces ◽  
Capacity Theory ◽  
Vessel Motion

A method is presented that enables the analysis of weather window assessments for the installation and retrieval phases of a self-elevating unit (SEU). The method takes site-specific parameters, defined as soil type and water depth, into account in addition to vessel-specific and environmental parameters. The inclusion of site-specific parameters is the novel contribution compared to assessment methodologies used today. A simulation model is presented that incorporates a coupled nonlinear time-domain analysis of vessel motion and soil–structure interaction. Soil deformation behavior during impact is described by resistance curves based on a bearing capacity theory. A structural evaluation criterion against which impact forces are compared is used for weather window assessments. The simulation model is applied on a case study utilizing different soil types to study impact forces and the capacity of the structure for withstanding such impacts and eventually performing a weather window assessment. The results show that the jacking operation can be divided into two phases when it comes to loads on the spudcan: a phase dominated by vertical forces followed by a phase dominated by horizontal forces. It is found that including soil deformation behavior is of paramount importance to the magnitude of the resulting impact forces and that class-recommended practice does indeed produce rather large force estimates. Thus, assessments where site-specific parameters are incorporated could definitely increase the operable weather window for SEUs, and, consequently, increase the economic competitiveness of, for example, the offshore wind industry.

scholarly journals Two- and three-dimensional computation of solitary wave runup on non-plane beach

2008 ◽  
Vol 15 (3) ◽  
pp. 489-502 ◽  
Author(s):  
B. H. Choi ◽  
E. Pelinovsky ◽  
D. C. Kim ◽  
I. Didenkulova ◽  
S.-B. Woo
Keyword(s):  
Solitary Wave ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Wave Runup ◽  
Water Displacement ◽  
Wave Processes ◽  
Field Surveys ◽  
Nonlinear Shallow Water Theory ◽  
Slope Channel

Abstract. Solitary wave runup on a non-plane beach is studied analytically and numerically. For the theoretical approach, nonlinear shallow-water theory is applied to obtain the analytical solution for the simplified bottom geometry, such as an inclined channel whose cross-slope shape is parabolic. It generalizes Carrier-Greenspan approach for long wave runup on the inclined plane beach that is currently used now. For the numerical study, the Reynolds Averaged Navier-Stokes (RANS) system is applied to study soliton runup on an inclined beach and the detailed characteristics of the wave processes (water displacement, velocity field, turbulent kinetic energy, energy dissipation) are analyzed. In this study, it is theoretically and numerically proved that the existence of a parabolic cross-slope channel on the plane beach causes runup intensification, which is often observed in post-tsunami field surveys.

scholarly journals ESTIMATION OF TIDAL EXCURSION LENGTH ALONG THE SHATT AL-ARAB ESTUARY, SOUTHERN IRAQ

2021 ◽  
Vol 59 (1) ◽  
pp. 79
Author(s):  
Ali Lafta
Keyword(s):  
Water Level ◽  
Neap Tide ◽  
Spring Tide ◽  
Field Measurements ◽  
Site Specific ◽  
Estuary Mouth ◽  
Tidal Excursion ◽  
Mathematical Relation ◽  
Southern Iraq

The tidal excursion length along the Shatt Al-Arab estuary was estimated based on the mathematical relation proposed by Parsa and Shahidi (2010). The field measurements of water level, bathymetry, and discharges were conducted to fulfill the objective of the study. The results revealed that the tidal excursion length is site-specific and depends on the characteristics of location which include tidal phases, bathymetry, and geometry. However, the results indicated that there are pronounced differences in tidal excursions lengths between the spring and neap tide phases in all studies stations. The spring tide coincided with the maximum tidal excursion lengths in Shatt Al-Arab estuary with 16.537, 16.187, 11.122, and 9.139 km in the estuary mouth, Faw, Siba, and Abo Flous stations respectively. While the neap tidal excursion lengths were 12.298, 9.254, and 7.269 km in Faw, Siba, and Abo Flous stations respectively.

scholarly journals Low-Input Estimation of Site-Specific Lime Demand Based on Apparent Soil Electrical Conductivity and In Situ Determined Topsoil pH

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5280
Author(s):  
Moritz von Cossel ◽  
Harm Druecker ◽  
Eberhard Hartung
Keyword(s):  
Electrical Conductivity ◽  
Field Measurements ◽  
Ex Situ ◽  
Soil Electrical Conductivity ◽  
Standard Equipment ◽  
Site Specific ◽  
Input Estimation ◽  
Low Input ◽  
North Germany

Site-specific liming helps increase efficiency in agricultural production. For adequate determination of the lime demand, a combination of apparent soil electrical conductivity (ECa) and topsoil pH can be used. Here, it was hypothesized that this can also be done at low-input level. Field measurements using the EM38 MK I (Geonics, Canada) were conducted on three experimental sites in north Germany in 2011. The topsoil pH was measured based on two approaches: on the field using a handheld pH meter (Spectrum-Technologies Ltd., Bridgend, UK) with a flat electrode (in situ), and in the lab using standard equipment (ex situ). Both soil ECa (0.4–35.9 mS m−1) and pH (5.13–7.41) were heterogeneously distributed across the sites. The same was true of the lime demand (−1.35–4.18 Mg ha−1). There was a significant correlation between in situ and ex situ determined topsoil pH (r = 0.89; p < 0.0001). This correlation was further improved through non-linear regression (r = 0.92; p < 0.0001). Thus, in situ topsoil pH was found suitable for map-overlay with ECa to determine the site-specific lime demand. Consequently, the hypothesis could be confirmed: The combined use of data from EM38 and handheld pH meters is a promising low-input approach that may help implement site-specific liming in developing countries.

scholarly journals Seasonal Variation of Soil Respiration in the Mongolian Oak (Quercus mongolica Fisch. Ex Ledeb.) Forests at the Cool Temperate Zone in Korea

Forests ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 984
Author(s):  
Gyung Soon Kim ◽  
Seung Jin Joo ◽  
Chang Seok Lee
Keyword(s):  
Soil Respiration ◽  
Environmental Parameters ◽  
Field Measurements ◽  
Temperate Zone ◽  
Short Time Scale ◽  
Strongly Correlated ◽  
Quercus Mongolica ◽  
Cool Temperate ◽  
Mongolian Oak ◽  
Short Time

To investigate the variation in seasonal soil respiration (SR) as a function of soil temperature (Ts) and soil water content (SWC) in Mongolian oak (Quercus mongolica) forests in urban (Mt. Nam) and well-reserved (Mt. Jeombong) areas in South Korea, we conducted continuous field measurements of SR and other environmental parameters (Ts and SWC) using an automated chamber system. Overall, the SR rates in both stands were strongly correlated with the Ts variable during all seasons. However, abrupt fluctuations in SR were significantly related to episodic increases in SWC on a short time scale during the growing season. The integrated optimal regression models for SR using Ts at a depth of 5 cm and SWC at a depth of 15 cm yielded the following: the SR rate in Mt. Nam = SR(Ts) + ΔSR(Ts) = 104.87 exp(0.1108Ts) − 10.09(SWC)2 + 604.2(SWC) − 8627.7 for Ts ≥ 0 °C, and the SR rate in Mt. Jeombong = SR(Ts) + ΔSR(Ts) = 95.608 exp(0.1304Ts) − 33.086(SWC)2 + 1949.2(SWC) − 28499 for Ts ≥ 0 °C. In both cases, SR = 0 for Ts < 0 °C. As per these equations, the estimated annual total SRs were 1339.4 g C m−2 for Mt. Nam and 1003.0 g C m−2 for Mt. Jeombong. These values were quite similar to the measured values in field. Our results demonstrate that the improved empirical equation is an effective tool for estimating and predicting SR variability and provide evidence that the SR of Q. mongolica forests in the cool temperate zone of Korean Peninsula depends on Ts and SWC variables.

scholarly journals Numerical simulation of a tsunami event during the 1996 volcanic eruption in Karymskoye lake, Kamchatka, Russia

2010 ◽  
Vol 10 (11) ◽  
pp. 2359-2369 ◽  
Author(s):  
T. Torsvik ◽  
R. Paris ◽  
I. Didenkulova ◽  
E. Pelinovsky ◽  
A. Belousov ◽  
...  
Keyword(s):  
Wave Speed ◽  
Field Measurements ◽  
Wave Model ◽  
Tsunami Source ◽  
Wave Runup ◽  
Underwater Explosions ◽  
North Shore ◽  
The North ◽  
Order Of Magnitude ◽  
South Shore

Abstract. Karymskoye caldera lake is a nearly circular body of water with a diameter of approximately 4 km and a depth of up to 60 m. The sublacustrine, Surtseyan-type eruption in the lake on 2–3 January 1996 included a series of underwater explosions. A field survey conducted the following summer showed signs of tsunami wave runup around the entire coastline of the lake, with a maximum of 29 m runup at the north shore near the source of the eruption, and 2–5 m runup at locations on the east and south shore far away from the source. The tsunami has been simulated using the numerical long wave model COULWAVE, with input from reconstructed realistic pre-eruption bathymetry. The tsunami source was chosen as suggested by Le Mehaute (1971) and Mirchina and Pelinovsky (1988). The initial wave was prescribed by a parabolic shape depression with a radius of R=200 m, and a height of 23 m at the rim of the parabola. Simulations were conducted to show principle directions for wave propagation, wave speed and arrival time for the leading wave group at the shore, and the distribution of wave height throughout the lake. Estimated result for wave runup are of the same order of magnitude as field measurements, except near the source of the eruption and at a few locations where analysis show significant wave breaking.

The effect of climate on the photosynthesis of Picea mariana at the subarctic tree line. 1. Field measurements

1975 ◽  
Vol 53 (7) ◽  
pp. 604-620 ◽  
Author(s):  
T. Vowinckel ◽  
W. C. Oechel ◽  
W. G. Boll
Keyword(s):  
Picea Mariana ◽  
Dark Respiration ◽  
Environmental Parameters ◽  
Field Measurements ◽  
Dry Weight ◽  
Gas Analysis ◽  
Tree Line ◽  
Stevenson Screen ◽  
Analysis System ◽  
June July

Field measurements of the diurnal rates of photosynthesis of Picea mariana, the dominant tree species at the subarctic tree line, were made during the summers of 1972 and 1973 at Schefferville, Quebec (latitude 55° N). All relevant plant physiological and environmental parameters were also monitored. Photosynthesis was measured with an open gas analysis system with temperature-controlled cuvettes. Maximum daily rates were 2.0–3.5 mg CO2 g−1 dry weight h−1. Daily totals were between 15 and 30 mg CO2 g−1 dry weight. Temperature was unimportant in affecting daily photosynthesis totals during the summer months. The photosynthesis vs. needle temperature curve had an optimum of 15C. Dark respiration rates were 0.2–0.4 mg CO2 g−1 dry weight h−1 at 15C. The photosynthesis vs. light intensity curve was saturated at 0.8 ly min−1 (1.0 μE cm−2 s−1 PhAR.). As a result, heavy cloud cover considerably reduced daily photosynthesis. No seasonal variations in photosynthesis over June, July, and August were observed. No differences in maximum rates occurred between the three experimental sites. Needle temperatures within the cuvettes were 2–4C above air temperature under full sunlight (1.2 ly min−1). Needle temperatures under natural conditions were up to 7C above Stevenson screen temperatures and fluctuated rapidly with changes in turbulence.

scholarly journals Reproducing Field Measurements Using Scaled-Down Hydraulic Model Studies in a Laboratory

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Seung Oh Lee ◽  
Seung Ho Hong
Keyword(s):  
Three Dimensional ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Physical Models ◽  
Laboratory Model ◽  
Scour Depth ◽  
Model Studies ◽  
Sediment Size ◽  
Laboratory Results ◽  
Scale Ratio

Little efforts have been made to the value of laboratory model study in closing the gap between results from idealized laboratory experiments and those from field data. Thus, at first, three bridge sites were selected and equipped with fathometers to find the bed elevation change in the vicinity of bridge pier over time. After and during the flooding, the stream flow variables and their bathymetry were measured using current viable technologies at the field. Then, to develop and suggest a laboratory modeling techniques, full three-dimensional physical models including measured river bathymetry and bridge geometry were designed and fabricated in a laboratory based on the scale ratio except for the sediment size, and the laboratory results were compared with the field measurements. Size of uniform sediment was carefully selected and used in the laboratory to explore the scale effect caused by sediment size scaling. The comparisons between laboratory results and field measurements show that the physical models successfully reproduced the flow characteristics and the scour depth around bridge foundations. With respect to the location of the maximum scour depth, they are not consistent with the results as in the previous research. Instead of occurring at the nose of each pier, the maximum scour depths are located further downstream of each pier column in several experimental runs because of the combination of complex pier bent geometry and river bathymetry, and the resulting unique flow motions around the pier bent.

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