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Long period waterlevel variations, from 14 d to 1 yr, are examined for Hamanako, a tidal inlet on the Pacific coast of Honshu, Japan. Eleven years of records, prior to the regulation of the entrance to the inlet, are analyzed. At all the frequencies examined there were substantial fluctuations, some periodic and some irregular. Dominant features were abrupt changes in mean waterlevel and tidal range, and regular 14 d and 28 d cycles in most years. These cycles have been related to the role of the entrance constriction in generating spring-tidal pumping (STP). The rapid changes in tidal amplitude and mean waterlevel are explained in terms of changes in the hydraulic resistance of the entrance and have been correlated with outflows from the tidal lagoon caused by typhoons and catchment runoff. An annual cycle of amplitude 12.5 cm has been explained in terms of the annual cycle of the Kuroshio. Novel features of this study are the extensions to conventional time series analysis, and showing that the 14 d periodic fluctuations were caused by STP and that this process also contributed to the 28 d fluctuations. STP is invariably present in estuaries with a shallow inlet but is rarely identified; this paper shows methods to evaluate it and other long period components of the waterlevel record.

Hamanako is an economically and culturally important tidal lake on the Pacific coast of Honshu, Japan. Between 1954 and 1973, entrance works were constructed to regulate the channel to the lake. In a previous paper, the tidal records from Maisaka just inside the lake, prior to regulation, were analyzed to explain the responses of the lake to the ocean tide and other water level changes. The present paper compares water level responses with those following regulation of the entrance. The principal differences are that at Maisaka the tidal range increased up to 1965, following the first stages of regulation, but it has been constant since then. In the inner part of the lake, regulation has increased the tidal range but reduced its variability and has reduced the mean water level in the lake. The southern sand shoal divides the lake into two tidal basins, with Maisaka lying in the smaller outer basin. Studies of the inner basin have shown that its tidal range continues to increase. A hydrodynamic model has been used to show that this increase is primarily due to scouring of the inner channel through the southern shoal. The model has also shown that the constancy of the Maisaka tidal amplitude since 1965 is not a static equilibrium, but is a balance between the effects of the outer entrance channel scouring and increasing the Maisaka tide, offset by the inner channel scouring and reducing the Maisaka tide.

Tidal inlets are an ecologically sensitive and significant constituent of the coastal environment, where an opening along the shoreline permits the free exchange of fresh and seawater. Predominant longshore currents along the shore result in the formation of sandbars, spits and shoals. Frequent occurrence of such sediment depositions acts as barriers, preventing the ingress of tidal flow. Conventionally training walls are constructed at the inlet to prevent sandbar and spit formations. The volume of water exchanged at the inlet mouth and ebb tidal currents primarily govern the inlet dimensions and the rate of littoral transport, respectively. The case study of a trained micro-tidal inlet at Karaikal (10${}^{\circ }54^{\prime }$52${}^{\prime \prime }$N; 79${}^{\circ }51^{\prime }09^{\prime \prime }$E), India is discussed in this paper. A numerical model using the finite volume method is applied to estimate the siltation rate and distribution within the study domain, driven by tide-induced currents and riverine discharge. A revetment structure is proposed to combat siltation within the inlet to facilitate smooth navigation. The study highlights the notable changes in the presence and absence of the proposed revetment.

Four inlets (Johns Pass and Blind Pass; and New Pass and Big Sarasota Pass) in two multi-inlet systems along the West-central Florida coast were studied. Johns Pass, New Pass, and Blind Pass are dredged every 4-9 years, whereas Big Sarasota Pass has never been dredged. The goal of this study was to investigate the morphodynamics of the four inlets and the influences of channel dredging on the flow patterns over the ebb tidal delta and sediment bypassing. Time-series aerial photographs and bathymetric maps starting from the 1920s were analyzed to assess the pathways of sand bypassing and morphodynamics at the inlets. The Coastal Modeling System (CMS), computing wave, current, sediment transport, and morphology change of tidal inlets, was applied and reproduced the observed medium-term morphology changes. CMS is then used to investigate influences of channel dredging on inlet morphodynamics.

Numerical simulations of hydrodynamics and sediment transport were conducted for Sebastian Inlet, FL, using the Coastal Modeling System (CMS). The study is aimed at determining changes in morphology under the existing topography and configuration as compared with two proposed modification scenarios: 1) an extension of the south jetty and 2) dredging of the outer section of the ebb shoal. The analysis time period encompasses short term (storm vents), as well as long term (seasonal). Overall, the predicted morphology changes were in good agreement with measured data. Model calculations of littoral sand transport under the existing configuration indicated an overall sand transport to the south over the long term, as well as reversal approximately 2km south of the inlet. The model also successfully reproduced the variability in littoral transport due to the different storms, especially the reversal in the drift direction.