scholarly journals EVALUATION OF OVERALL ENTRANCE STABILITY OF TIDAL ENTRANCES

1974 ◽  
Vol 1 (14) ◽  
pp. 91 ◽  
Author(s):  
P. Bruun ◽  
F. Gerritsen ◽  
N.P. Bhakta
Keyword(s):  
Sediment Transport ◽  
Spring Tide ◽  
Tidal Prism ◽  
Material Transport ◽  
Tidal Inlets ◽  
Littoral Drift ◽  
Overall Stability ◽  
The Mean ◽  
Two Parameters

This paper is written in continuation of earlier published material (2, 4, 5) dealing with stability of tidal inlets on littoral drift shores. The experience available at that time was responsible for the introduction of two parameters: .vmean max/ defined as the mean max. velocity in the gorge at spring tide and the K/M-tot ratio (tidal prism at spring tide divided by material transport to the entrance from the adjoining shores) as the most pertinent parameters for description of overall stability. A more detailed justification for this choice is given in this paper, based on computation of the relative sediment transport at various tidal phases. Examples of earlier date (4) and twelve new examples from India are given.

scholarly journals INLETS/ESTUARIES DISCHARGING INTO SHELTERED WATERS

1980 ◽  
Vol 1 (17) ◽  
pp. 151 ◽  
Author(s):  
H.P. Riedel ◽  
M.R. Gourlay
Keyword(s):  
Maximum Velocity ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Tidal Prism ◽  
The South ◽  
Tidal Inlets ◽  
Littoral Drift ◽  
Cross Sectional ◽  
Tidal Estuaries ◽  
The Mean

Tidal prism - cross sectional area relationships and tidal velocities have been measured for inlet entrances and along the length of the estuary for four creeks entering the sheltered waters on the South East Queensland coast, Australia. It has been found that the inlet entrance tidal prism - cross-sectional area relationship is controlled by the magnitude of littoral drift. The tidal prism - cross-sectional area relationship along the estuary is believed to be common to all tidal estuaries landward of the region where littoral drift has an influence. For tidal inlets on sheltered coasts with tidal prisms of the order of 10 n~, the mean maximum velocity entrance is about 0.3 to 0.4 m/s.

Sediment transport and shoreline shifts in response to climate change at the tidal inlets of Chilika, India

2018 ◽  
Vol 233 (1) ◽  
pp. 372-387 ◽  
Author(s):  
B Gopikrishna ◽  
MC Deo
Keyword(s):  
Climate Change ◽  
Sediment Transport ◽  
Climate Model ◽  
Regional Climate ◽  
Shoreline Change ◽  
Tidal Inlets ◽  
Littoral Drift ◽  
The Past ◽  
Longshore Sediment Transport ◽  
Other Information

The shoreline adjoining Chilika Lake, situated along India’s east coast, has multiple tidal inlets which connect the lake with Bay of Bengal. The shoreline behavior near such inlets is generally studied with the help of a suitable numerical model. Such models are run on the basis of historical data of waves and other information. However, the waves in future may show different strength and pattern than the past as a result of the climate change induced by global warming. It is thus necessary that the model input should correspond to future or projected data of wind and waves. In this work, we have used the wind information from a state-of-the-art regional climate model, CORDEX RegCM-4, of future 25 years in order to run a shoreline evolution model and have derived the longshore sediment transport rate as well as the shoreline change rate around Chilika inlets. These future values are compared with corresponding ones of the past 25 years. It is found that at the given location, mean wind might go up by 20%, and this could raise the mean significant wave height strongly by 32%. The direction and frequency of occurrence of waves would also change, and this in turn will cause an increase in the net littoral drift by 41% and net accumulated drift over the entire cross-shore width by 84%. Interestingly, the present site where accretion was prevalent in the past may see erosion in future at the rate of about 1 m per year.

scholarly journals Managing Tidal Inlets

2019 ◽  
Vol 1 (2) ◽  
Author(s):  
Jonathan Akin French
Keyword(s):  
Dynamic Equilibrium ◽  
River Mouth ◽  
Tidal Prism ◽  
Tidal Inlets ◽  
Littoral Drift ◽  
Flow Area ◽  
Cross Sectional ◽  
Storm Flow ◽  
Tidal Flows ◽  
Runoff Events

Sandy inlets are in a dynamic equilibrium between wave-driven littoral drift acting to close them, and tidal flows keeping them open. Their beds are in a continual state of suspension and deposition, so their bathymetry and even location are always in flux. Even so, a nearly linear relationship between an inlet’s cross-sectional flow area and the inshore tidal prism is maintained - except when major wind and/or runoff events act to close or widen an inlet. Inlet location can be stabilized by jetties, but dredging may still be necessary to maintain a navigable channel. Armoring with rock large enough to resist erosion can protect an inlet bed or river mouth from excessive storm flow erosion.  Armoring can also be used as a stratagem to close inlets.

scholarly journals Wind and Tide-Induced Hydrodynamics and Sedimentation of Two Tidal Inlets in Western Greece

2018 ◽  
Author(s):  
Nikolaos Th. Fourniotis ◽  
Georgios M. Horsch ◽  
Georgios A. Leftheriotis
Keyword(s):  
Sediment Transport ◽  
Simulation Models ◽  
Google Earth ◽  
Tidal Inlets ◽  
Horizontal Structure ◽  
Numerical Predictions ◽  
Combined Action ◽  
Mean Water Level ◽  
The Mean ◽  
Induced Currents

To quantify the detailed mechanisms that cause sedimentation at the tidal inlets in the Messolonghi-Aetoliko lagoonal system, the MIKE 21 FM (HD & ST) numerical simulation models were applied. The study focuses on the hydrodynamic circulation in the vicinity of the tidal inlets and the associated wind and tide-induced currents, as well as sediment transport, bed level evolution and total sediment load accumulation, with emphasis on the vicinity of two tidal inlets, where the problem is more acute. Based on the numerical predictions, which have been qualitatively corroborated via satellite images from Google Earth, it is shown that under the prevailing winds and tidal action, sandbars are formed in front or behind the tidal inlets depending on the wind direction, resulting in a gradual decrease of the mean water level at the mouths. Under the combined action of the tide and the wind the characteristic horizontal structure of the flow includes cyclonic and anti-cyclonic eddies that form at the near tip area of the jetties, which are associated with sediment transport mechanisms.

scholarly journals Managing Tidal Inlets

2019 ◽  
Vol 1 (2) ◽  
Author(s):  
Jonathan Akin French
Keyword(s):  
Dynamic Equilibrium ◽  
River Mouth ◽  
Tidal Prism ◽  
Tidal Inlets ◽  
Littoral Drift ◽  
Flow Area ◽  
Cross Sectional ◽  
Storm Flow ◽  
Tidal Flows ◽  
Runoff Events

Sandy inlets are in a dynamic equilibrium between wave-driven littoral drift acting to close them, and tidal flows keeping them open. Their beds are in a continual state of suspension and deposition, so their bathymetry and even location are always in flux. Even so, a nearly linear relationship between an inlet’s cross-sectional flow area and the inshore tidal prism is maintained - except when major wind and/or runoff events act to close or widen an inlet. Inlet location can be stabilized by jetties, but dredging may still be necessary to maintain a navigable channel. Armoring with rock large enough to resist erosion can protect an inlet bed or river mouth from excessive storm flow erosion.  Armoring can also be used as a stratagem to close inlets.

scholarly journals EQUILIBRIUM FLOW AREAS OF TIDAL INLETS ON SANDY COASTS

1966 ◽  
Vol 1 (10) ◽  
pp. 38 ◽  
Author(s):  
Morrough P. O'Brien
Keyword(s):  
Pacific Coast ◽  
The United States ◽  
Beach Erosion ◽  
Equilibrium Flow ◽  
Tidal Prism ◽  
Tidal Inlets ◽  
Littoral Drift ◽  
Flow Area ◽  
The Pacific ◽  
Unique Relationship

The flow area of inlets on sandy coasts is a unique function of the tidal prism when equilibrium has been achieved. The size of material, the presence or absence of jetties, and the magnitude of general littoral drift does not appear to affect this equilibrium flow area within the accuracy of the data available. In the summer of 1929, the writer made a reconnaissance of the beaches and harbors of the Pacific Coast of the United States for the predecessor organization of the U. S. Beach Erosion Board. In tiie years preceding this study, many tidal inlets on the Worth Pacific Coast had been improved for navigation by constructing jetties, and the progress of these inlets towards stabilization was being followed through frequent hydrographic surveys, which were available for study. The obvious fact that large inlets were found at large bays and small inlets at small bays suggested the possibility that there might be a unique relationship between entrance area and tidal prism.

Photo-electric Hβ and uvby photometry

1966 ◽  
Vol 24 ◽  
pp. 170-180
Author(s):  
D. L. Crawford
Keyword(s):  
Narrow Band ◽  
Line Strength ◽  
Interference Filter ◽  
B Stars ◽  
Relative Line ◽  
The Mean ◽  
F Stars ◽  
Two Parameters ◽  
Filter Photometry ◽  
The Continuum

Early in the 1950's Strömgren (1, 2, 3, 4, 5) introduced medium to narrow-band interference filter photometry at the McDonald Observatory. He used six interference filters to obtain two parameters of astrophysical interest. These parameters he calledlandc, for line and continuum hydrogen absorption. The first measured empirically the absorption line strength of Hβby means of a filter of half width 35Å centered on Hβand compared to the mean of two filters situated in the continuum near Hβ. The second index measured empirically the Balmer discontinuity by means of a filter situated below the Balmer discontinuity and two above it. He showed that these two indices could accurately predict the spectral type and luminosity of both B stars and A and F stars. He later derived (6) an indexmfrom the same filters. This index was a measure of the relative line blanketing near 4100Å compared to two filters above 4500Å. These three indices confirmed earlier work by many people, including Lindblad and Becker. References to this earlier work and to the systems discussed today can be found in Strömgren's article inBasic Astronomical Data(7).

Essai d'application de modèles météorologiques au calcul du moment d'apparition de deux phases phénologiques | Application of Meteorological Models for the Calculation of the Beginning of Two Phenological Phases

2000 ◽  
Vol 151 (10) ◽  
pp. 385-397
Author(s):  
Bernard Primault
Keyword(s):  
Sunshine Duration ◽  
Fruit Trees ◽  
Swiss Alps ◽  
Winter Solstice ◽  
Phenological Data ◽  
Thermal Thresholds ◽  
The Mean ◽  
Two Parameters ◽  
Meteorological Models ◽  
Phenological Phases

Many years ago, a model was elaborated to calculate the«beginning of the vegetation's period», based on temperatures only (7 days with +5 °C temperature or more). The results were correlated with phenological data: the beginning of shoots with regard to spruce and larch. The results were not satisfying, therefore, the value of the two parameters of the first model were modified without changing the second one. The result, however, was again not satisfying. Research then focused on the influence of cumulated temperatures over thermal thresholds. Nevertheless, the results were still not satisfying. The blossoming of fruit trees is influenced by the mean temperature of a given period before the winter solstice. Based on this knowledge, the study evaluated whether forest trees could also be influenced by temperature or sunshine duration of a given period in the rear autumn. The investigation was carried through from the first of January on as well as from the date of snow melt of the following year. In agricultural meteorology, the temperature sums are often interrelated with the sunshine duration, precipitation or both. However,the results were disappointing. All these calculations were made for three stations situated between 570 and 1560 m above sea-level. This allowed to draw curves of variation of the two first parameters (number of days and temperature) separately for each species observed. It was finally possible to specify the thus determined curves with data of three other stations situated between the first ones. This allows to calculate the flushing of the two tree species, if direct phenological observation is lacking. This method, however, is only applicable for the northern part of the Swiss Alps.

scholarly journals Relationship between large-scale ionospheric field-aligned currents and electron/ion precipitations: DMSP observations

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Chao Xiong ◽  
Claudia Stolle ◽  
Patrick Alken ◽  
Jan Rauberg
Keyword(s):  
Time Distribution ◽  
Large Scale ◽  
Particle Flux ◽  
Particle Energy ◽  
Lower Latitude ◽  
Particle Precipitation ◽  
Data Set ◽  
The Mean ◽  
Two Parameters ◽  
Meteorological Satellite

Abstract In this study, we have derived field-aligned currents (FACs) from magnetometers onboard the Defense Meteorological Satellite Project (DMSP) satellites. The magnetic latitude versus local time distribution of FACs from DMSP shows comparable dependences with previous findings on the intensity and orientation of interplanetary magnetic field (IMF) By and Bz components, which confirms the reliability of DMSP FAC data set. With simultaneous measurements of precipitating particles from DMSP, we further investigate the relation between large-scale FACs and precipitating particles. Our result shows that precipitation electron and ion fluxes both increase in magnitude and extend to lower latitude for enhanced southward IMF Bz, which is similar to the behavior of FACs. Under weak northward and southward Bz conditions, the locations of the R2 current maxima, at both dusk and dawn sides and in both hemispheres, are found to be close to the maxima of the particle energy fluxes; while for the same IMF conditions, R1 currents are displaced further to the respective particle flux peaks. Largest displacement (about 3.5°) is found between the downward R1 current and ion flux peak at the dawn side. Our results suggest that there exists systematic differences in locations of electron/ion precipitation and large-scale upward/downward FACs. As outlined by the statistical mean of these two parameters, the FAC peaks enclose the particle energy flux peaks in an auroral band at both dusk and dawn sides. Our comparisons also found that particle precipitation at dawn and dusk and in both hemispheres maximizes near the mean R2 current peaks. The particle precipitation flux maxima closer to the R1 current peaks are lower in magnitude. This is opposite to the known feature that R1 currents are on average stronger than R2 currents.

Stability of micro-tidal inlets along coastlines dominated by littoral drift

2017 ◽  
Vol 21 (6) ◽  
pp. 789-801 ◽  
Author(s):  
R. Senthilkumar ◽  
K. Murali ◽  
V. Sundar
Keyword(s):  
Tidal Inlets ◽  
Littoral Drift
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