الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
Abstract
Stability of tidal inlets has two essential parts: (1) stability of tidal inlets versus migration; and (2) stability of tidal inlets cross-sections against closure. Factors controlling the stability of tidal inlets cross-sections were discussed. These factors were analyzed dimensionally considering hydraulic and geometrical parameters. From this analysis, series dimensionless fimctions were developed concerning inlet channel velocity, bay tidal amplitude and flushing capacity of tidal inlet In order to transform these fimctions to applicable curves and equations, a munerica1 model was developed and checked with field data. This model is used to calculate inlet channel velocity, discharge, tidal prism, bay water level, sediment transport through inlet channe~ flushing capacity and Keulegan’s coefficient The sediment transport is calculated using equations of Engelund-Hansen and Vim-Rijn. The nwnerica1 model is also used to explain the behavior of the dimensionless parameters in the developed fimctions. This model was run, not only for stable tidal inlets but also for all probable inlet cases to obtain two families of curves describing the behavior of different parameters controlling the inlet velocity and bay tidal amplitude. By means of multi regression method and using the results of 2550 model runs for stable tidal inlet, a relationship for tidal inlet flushing capacity in tenns of maximwn mean inlet discharge, inlet Froude nwnber, relative channel length and relative grain size was obtained. The results of flushing capacity equation were compared to field data and a good agreement was found. Also, a relationship between stable cross-section area and tidal prism was developed and compared to other famous equations. From comparison, it was noticed that the developed equation gives a very good results. The effect of tidal amplitude, tidal period and length of inlet channel on inlet cross-section area and flushing capacity were examined. The critical cross-section area was also determined as a boundary between the stable and unstable areas according to Escoffier’s (1940) principal.
Another program was developed to predict the wave characteristics at breaking zone and to calculate the longshore sediment transport, which was compared to the flushing capacity in the cases of study.
Finally, a design approach consisting of series curves and equations was developed to design stable tidal inlet or check the stability of an existing inlet. This approach was used to check the stability of tidal inlets at El-Bardawil lagoon and used to propose stable inlets for this lagoon and for Rosetta branch inlet From this study, the main results are: (1) the stable cross-section area and flushing capacity incr~e with the increase of lagoon/bay surface area, tidal amplitude and
decrease with the increase of tidal period and length of channel; (2) the critical inlet cross¬section area and also the maximum flushing capacity takes place when Keulegan’s coefficient is between 0.6 and 0.82; (3) a greater depth for inlet channel is preferable, because it gives higher velocities, higher flushing capacities and larger trapping depth; (4) small cross-section areas are more susceptible to storm closure than larger area; and (5) larger cross-section area enhances the circulation inside lagoon/bay, where it gives large tidal prism.