scholarly journals A SURVEY OF MAN-MADE TIDAL SWIMMING POOLS ALONG THE SOUTH AFRICAN COAST

1982 ◽  
Vol 1 (18) ◽  
pp. 151
Author(s):  
D.E. Bosman ◽  
D.J.P. Scholtz
Keyword(s):  
South African ◽  
Spring Tide ◽  
High Water ◽  
Swimming Pools ◽  
The South ◽  
Recreational Facilities ◽  
African Coast ◽  
Shark Attacks ◽  
Rocky Coast ◽  
Tidal Pools

A large number of man-made tidal swimming pools (two examples are shown in Figure 1) exist along the South African coast. They are usually situated on rocky outcrops in the close vicinity of popular sandy bathing beaches to provide protected bathing conditions in these areas mainly for children and elderly people. Some tidal pools, especially along rocky coast, provide the only safe bathing facilities. Besides affording protection against waves and surfzone currents the pools provide protection from sharks. A large number of tidal pools were built during the early 1950s along the Natal South Coast after the occurrence of a relatively large number of shark attacks on bathers on that coast. The semi-diurnal tide with a range of about 1,5 m along the South African coast makes it possible for pools to be built such that water replenishment can occur during every high-water (approximately every 12 hours) during both neap and spring tide periods. Presently, there exists a great need for more tidal pools as part of the demand for more recreational facilities along the South African coast. However, no information on design criteria could be found in the literature.

scholarly journals Role of intertidal wetlands for tidal and storm tide attenuation along a confined estuary: a model study

2015 ◽  
Vol 3 (5) ◽  
pp. 3181-3224 ◽  
Author(s):  
S. Smolders ◽  
Y. Plancke ◽  
S. Ides ◽  
P. Meire ◽  
S. Temmerman
Keyword(s):  
Surface Area ◽  
Wave Attenuation ◽  
Spring Tide ◽  
Storm Surges ◽  
High Water ◽  
Water Levels ◽  
Storm Tide ◽  
Flood Risks ◽  
Model Study

Abstract. Coastal lowlands and estuaries are subjected to increasing flood risks during storm surges due to global and regional changes. Tidal wetlands are increasingly valued as effective natural buffers for storm surges by dissipating wave energy and providing flood water storage. While previous studies focused on flood wave attenuation within and behind wetlands, this study focuses on the effects of estuarine wetland properties on the attenuation of a storm tide that propagates along the length of an estuary. Wetland properties including elevation, surface area, and location within the estuary were investigated using a numerical model of the Scheldt estuary (Belgium, SW Netherlands). For a spring tide lower wetland elevations result in more attenuation of high water levels along the estuary, while for a higher storm tide higher elevations provide more attenuation compared to lower wetland elevations. For spring and storm tide a arger wetland surface area results in a better attenuation along the estuary up to a threshold wetland size for which larger wetlands do not further contribute to more attenuation. Finally a wetland of the same size and elevation, but located more upstream in the estuary, can store a larger proportion of the local flood volume and therefore has a larger attenuating effect on upstream high water levels. With this paper we aim to contribute towards a better understanding and wider implementation of ecosystem-based adaptation to increasing estuarine flood risks associated with storms.

scholarly journals Comparison of empirical models with intensively observed data for prediction salt intrusion in the Sumjin River estuary, Korea

2009 ◽  
Vol 6 (2) ◽  
pp. 1879-1905 ◽  
Author(s):  
D. C. Shaha ◽  
Y.-K. Cho
Keyword(s):  
River Discharge ◽  
Neap Tide ◽  
Spring Tide ◽  
River Estuary ◽  
High Water ◽  
Empirical Models ◽  
Length Scale ◽  
Salt Intrusion ◽  
Salinity Data ◽  
Comparative Results

Abstract. Intensive measurements of salt intrusion in the Sumjin River estuary were taken at high and low waters during both spring and neap tides in each season from August 2004 to April 2007. The estuary demonstrated partially- and well-mixed characteristics during the spring tide and stratified condition during the neap tide. The salt intrusion at high water varied from about 13.39 km in summer 2005 to 25.62 km in autumn 2006. The salt intrusion depended primarily on the freshwater discharges rather than those of spring-neap tidal oscillations. Analysis of three years of observed salinity data indicated that the salt intrusion length scale in the Sumjin River estuary was proportional to the river discharge to the −1/5 power. Five empirical models were applied to the Sumjin River estuary to explore the most suitable as an easy-to-use tool for prediction of the salt intrusion length as functions of the geometry, river discharge and tide. Comparative results showed that the Nguyen and Savenije (2006) model developed under both partially- and well-mixed estuaries yielded the most satisfactory results of all the models studied for computing the salt intrusion length in the Sumjin River estuary. Our study suggests that the model can generate reasonable results for stratified conditions also.

A Note on the Habits and Nutrition of Solemya parkinsoni (Protobranchia: Bivalvia)

1961 ◽  
Vol s3-102 (57) ◽  
pp. 15-21
Author(s):  
G. OWEN
Keyword(s):  
Organic Material ◽  
Alimentary Canal ◽  
Spring Tide ◽  
Muscular Activity ◽  
Mantle Cavity ◽  
Animal Burrows ◽  
Water Spring

Adult specimens of Solemya parkinsoni Smith, embedded in mud at a depth of 50 cm or more, were collected near low water (spring tide). The animal burrows with the anterior end downwards and does not maintain an opening to the surface. An inhalant current is drawn into the mantle cavity anteriorly on each side of the foot, while an exhalant current leaves by the single, posteriorly situated aperture. This is probably a respiratory current, bottom material entering the mantle cavity as a result of the muscular activity of the mantle and foot. The course of the alimentary canal is described, and the problem of feeding and nutrition correlated with the extreme reduction of the gut exhibited by S.parkinsoni discussed. It is suggested that an initial breakdown of organic material may take place in the mantle cavity.

scholarly journals Modelling Study of Transport Time Scales for a Hyper-Tidal Estuary

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2434
Author(s):  
Guanghai Gao ◽  
Junqiang Xia ◽  
Roger A. Falconer ◽  
Yingying Wang
Keyword(s):  
Numerical Model ◽  
Water Level ◽  
Residence Time ◽  
Exposure Time ◽  
Neap Tide ◽  
Spring Tide ◽  
High Water ◽  
Residence Times ◽  
Severn Estuary ◽  
Release Times

This paper presents a study of two transport timescales (TTS), i.e., the residence time and exposure time, of a hyper-tidal estuary using a widely used numerical model. The numerical model was calibrated against field measured data for various tidal conditions. The model simulated current speeds and directions generally agreed well with the field data. The model was then further developed and applied to study the two transport timescales, namely the exposure time and residence time for the hyper-tidal Severn Estuary. The numerical model predictions showed that the inflow from the River Severn under high flow conditions reduced the residence and exposure times by 1.5 to 3.5% for different tidal ranges and tracer release times. For spring tide conditions, releasing a tracer at high water reduced the residence time and exposure time by 49.0% and 11.9%, respectively, compared to releasing the tracer at low water. For neap tide conditions, releasing at high water reduced the residence time and exposure time by 31.6% and 8.0%, respectively, compared to releasing the tracer at low water level. The return coefficient was found to be vary between 0.75 and 0.88 for the different tidal conditions, which indicates that the returning water effects for different tidal ranges and release times are all relatively high. For all flow and tide conditions, the exposure times were significantly greater than the residence times, which demonstrated that there was a high possibility for water and/or pollutants to re-enter the Severn Estuary after leaving it on an ebb tide. The fractions of water and/or pollutants re-entering the estuary for spring and neap tide conditions were found to be very high, giving 0.75–0.81 for neap tides, and 0.79–0.88 for spring tides. For both the spring and neap tides, the residence and exposure times were lower for high water level release. Spring tide conditions gave significantly lower residence and exposure times. The spatial distribution of exposure and residence times showed that the flow from the River Severn only had a local effect on the upstream part of the estuary, for both the residence and exposure time.

scholarly journals Present-day Special Features of the Don River Basin Rivers Spring Tide

2013 ◽  
pp. 60-76
Author(s):  
Keyword(s):  
River Basin ◽  
Water Regime ◽  
Spring Tide ◽  
High Water ◽  
Annual Runoff ◽  
Water Runoff ◽  
Regime Changes ◽  
Flow Duration ◽  
High Water Period ◽  
Don River

The article is devoted to present-day specific features of the Don River basin rivers spring tide. On the basis of the recent data on the rivers’ water regime changes of maximal water flow, duration of high water period, high water runoff fractions in the annual runoff and hydrograph forms have been shown. It has been demonstrated that the spring tide character change is closely linked with the other phases of rivers’ water regime change.

Tree-climbing behaviour of Cerithidea decollata, a western Indian Ocean mangrove gastropod (Mollusca: Potamididae)

2006 ◽  
Vol 86 (6) ◽  
pp. 1429-1436 ◽  
Author(s):  
Marco Vannini ◽  
Rocco Rorandelli ◽  
Outi Lähteenoja ◽  
Elisha Mrabu ◽  
Sara Fratini
Keyword(s):  
Indian Ocean ◽  
Neap Tide ◽  
High Tide ◽  
Spring Tide ◽  
Western Indian Ocean ◽  
High Water ◽  
Avicennia Marina ◽  
Single Individual ◽  
Night Time ◽  
Mangrove Tree

The behaviour of Cerithidea decollata, a common western Indian Ocean mangrove tree climbing gastropod, was studied in Mida Creek, Kenya. At the study site, this snail mainly lived in Avicennia marina dominated areas, i.e. in the mangrove belt between high water spring tide and high water neap tide levels. Not a single individual was found on the less common mangrove tree Lumnitzera racemosa, living just above the A. marina level (together with terrestrial grass), and was very rarely recorded on the common Rhizophora mucronata, bordering the seaward side of the A. marina belt. No significant gradient of C. decollata density was found within the whole 150–200 m wide belt. The majority of C. decollata rested on tree trunks during high tide, creeping on the mud flat below the tree for part of low tide, and returning on the trunks well before being reached by the water. This migratory pattern was more evident at spring than at neap tide, at day than at night time and it was strongly influenced by the shore level of the mangrove zone in which animals resided. While C. decollata from lower shore levels neatly massively migrated twice a day, individuals from upper levels showed a more continuous and irregular activity, sometimes crawling on the mud even at high water of spring tide, when they experience just a few centimetres of water for no more than one to two hours.

scholarly journals SALINITY INTRUSION IN THE GUAPIMIRIM ESTUARY, RIO DE JANEIRO STATE, BRAZIL

2014 ◽  
Vol 32 (1) ◽  
pp. 161 ◽  
Author(s):  
Gustavo Vaz de Melo ◽  
José Antonio Baptista Neto ◽  
Susana Beatriz Vinzón ◽  
Allan Sandez de Oliveira ◽  
Michel Arthur Faria Vicente ◽  
...  
Keyword(s):  
Water Column ◽  
Residence Time ◽  
Neap Tide ◽  
Spring Tide ◽  
High Water ◽  
Freshwater Discharge ◽  
Salinity Intrusion ◽  
Rainy Period ◽  
Meandering Channel ◽  
Column Structure

ABSTRACT. This work was conducted in the Guapimirim estuary, the main tributary of the Guanabara Bay. This system is located in a preserved area in the catchmentbasin of the bay, inside the Guapimirim Environmental Protection Area. The estuary presents a meandering channel with 3 meters mean depth. The aim of thiswork is to evaluate the salinity intrusion dynamics in response to the tide and freshwater discharge, as well as its effects on the water column structure and residencetime. Surveys were performed to assess the salinity structure along the estuary main channel under different freshwater discharges (dry and rainy period) and tide (neapand spring). The results showed significant differences in the water column structure, presenting high stratification in neap tide and conditions homogeneous in springtide. The salinity front (SF) showed a bigger displacement in the spring tide. Under highly stratified conditions, in neap tide, its displacement was bigger with smallertidal amplitude. The location of SF inside of the estuary, in the high water, was influenced manly by freshwater discharge. The residence time in the Guapimirim estuarywas longer in neap tide and dry period, presenting a good relationship with freshwater discharge.Keywords: Guapimirim estuary, salinity intrusion, residence time. RESUMO. Este trabalho foi desenvolvido no estuário de Guapimirim, principal tributário da Baía de Guanabara. Este sistema se localiza em uma área ainda preservadana bacia de drenagemda baía, dentro da Área de Proteção Ambiental de Guapimirim. O estuário apresenta um canal meandrante com uma profundidade média de 3 metros. O objetivo deste trabalho consiste em avaliar a dinâmica da intrusão salina em resposta a atuação dos processos físicos como a vazão fluvial e a maré, assimcomo, sua consequência na estrutura da coluna d’água e tempo de residência. Foram realizados levantamentos sobre a estrutura salina ao longo do canal principal doestuário em diferentes condições de vazão fluvial (período seco e chuvoso) e maré (quadratura e sizígia). Os resultados mostraram diferenças marcantes na estrutura dacoluna d’´agua sendo estratificado em maré de quadratura e mais homogêneo em maré de sizígia. A frente salina apresentou um maior deslocamento em maré de sizígia.Em condições de alta estratificação, em maré de quadratura, o maior deslocamento da frente salina esteve associado a uma menor amplitude da maré. A vazão fluvial foio principal processo físico que atuou no alcance máximo da frente salina. O tempo de residência de uma parcela de água dentro do estuário de Guapimirim foi maiorem condição de maré de quadratura e em período seco, apresentando boa relação com a vazão fluvial.Palavras-chave: estuário de Guapimirim, intrusão salina, tempo de residência.

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