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Chan, M.C., 2023. Sizing a small tidal inlet for restoration. Journal of Coastal Research, 39(4), 610–624. Charlotte (North Carolina), ISSN 0749-0208. Coastal inlets located on active shorelines can be vulnerable to shoaling and closure. It is not uncommon for some of these inlets to fall under the category of small tidal inlets with cross-sectional areas <100 m2 and to be transitional in stability characteristics such that neither the classic large-inlet O'Brien-Jarrett equilibrium formulas nor the small-inlet Byrne stability criteria apply fully. The Flax Pond inlet, a dual-jettied small inlet located on the south shore of Long Island Sound, New York, is an example of this class of inlets. The inlet, which connects Flax Pond, a degraded tidal marsh embayment, to Long Island Sound, was analyzed to support a proposed plan to reconstruct the twin jetties and restore the pond's tidal prism to its conditions in the early 1970s to prevent further loss of wetland and ecosystem diversity. The lack of directly suitable stability criteria presented a challenge because an extrapolative use of unsuitable criteria could entail unacceptable risks. The issue necessitated a comprehensive, process-driven analysis of the littoral and inlet conditions to frame a solution. An approach involving multiple stability criteria was followed to determine the inlet dimensions needed to achieve the restoration objectives. It was demonstrated that, with a process-based understanding and informed assumptions, a transitional small inlet can be sized with reasonable confidence.

This research was funded by the Agencia Estatal de Investigación (AEI) of the Spanish Ministry of Science and Innovation through the national research project TED2021-132098B-C22 (“Better understanding of stormwater interception and clogging dynamics of surface drainage systems”, CLOGGING—INLETS), within the call for projects focused on the ecological transition and the digital transition of the State Plan for Scientific, Technical, and Innovation Research 2021–2023.

Roadside bio-retention (RBR) facilities are low impact development practices, which control urban runoff primarily from road pavements. Using hydrologic models, such as the US EPA Storm Water Management Model (SWMM), RBR are typically designed with some fundamental assumptions, including where runoff completely enters the facilities and fully utilizes the whole surface area for percolation, detention, filtration, and infiltration to the surrounding soils. This paper highlights the importance of inlet hydraulics and the spatial distribution of inflow along a RBR, and proposes an integrated hydraulic and hydrologic modelling approach to simulate its overall runoff control performance. The integrated hydraulic/hydrologic modelling approach consists of three components: (1) A dual drainage hydrologic model to simulate runoff generation, runoff hydrographs entering and bypassing a storm inlet, and the outflow hydrograph from a fully utilized RBR; (2) a computational fluid dynamic model to determine the inflow distribution along a RBR; and (3) an overall runoff control performance analysis of RBR by considering the inlet efficiency, and the partially and fully utilized RBR during a storm event. A case study of an underground RBR in the City of Toronto was used to demonstrate the integrated modelling approach. It is concluded that; (1) inlet efficiency of a RBR will determine the overall runoff control performance; and (2) the inflow distribution will dictate the effective length of a RBR, which may affect the overall runoff control performance.

Green infrastructure (GI) is a decentralized stormwater management strategy that can simultaneously enhance the resilience of the urban landscape to weather-related stressors. The effectiveness of individual GI facilities is determined by the physical characteristics of the tributary area and inlet, including factors such as slope and geometry, apron configuration, roughness, and clogging, all of which have been inadequately studied. In this paper, we construct, calibrate, and validate a computational fluid dynamics (CFD) model using field survey data collected at a Bronx, NY GI facility. The validated CFD model is used to evaluate how inlet clogging and flow rate affect GI inlet performance. Seven flow rates ranging from 0.00044 to 0.00755 CMS were simulated. As the flow rate increased, the inlet efficiency dropped from 100% to 60% at one location (the SW inlet) and from 100% to 25% at another location (the NW inlet). At a fixed flow rate, the inlet efficiency dropped from 100% efficient (with no clogging) to 0% (with the inlet fully clogged). The stage-discharge relationship for the inlet based on the simulated field conditions deviated from that assumed based on normative flow and was revised. We suggest that GI facilities installed on mild- slope, or rough streets be fitted with non-clogging inlets to maintain free outfall conditions.

The impact of opening a new inlet to connect the Delaware Bay with adjacent wetlands is described. A hydraulic and stability analysis of the new inlet is presented. The growth of the ebb tidal shoal is identified as the primary cause of beach erosion updrift and downdrift of the new inlet. An estimate of the expected erosion along adjacent beaches is made and compared with erosion occurring during the period between 1994 and 2006.

The Coorong is an elongated coastal lagoon system in southern Australia whose major freshwater input occurs through a series of barrages separating it from an adjacent lake. The connectedness of the lagoon to the sea continuously evolves as its Mouth channel is scoured by sustained outflows associated with barrage discharges or is infilled with sand during times of zero flows. A key driver of the Coorong dynamics is oceanic water-level fluctuations propagating into the lagoon, and the representation of the continuously changing transmission properties of the Mouth channel for these fluctuations is a necessary requirement for the successful modelling of these dynamics. This paper applies a methodology for estimating the effective bed elevation and width of the Mouth channel by considering how oceanic water-level fluctuations propagate into the Coorong. The analysis applied to 22 years of measurements shows how the effective depth of the Mouth channel has been highly dynamic, varying between more than 5 m to less than 0.5 m depending on barrage flows. A simple algorithm is developed that well represents the time series of effective bed elevations as a function of Mouth channel outflow. This algorithm enables the hydrodynamic modelling of the Coorong to be undertaken to assess the impact on the lagoon of alternative barrage release strategies.

The need for a cautious interpretation of results from an analytic method for an analysis of the stability of tidal inlets is illustrated by comparing theory with data from St. Andrew Bay in Florida's panhandle. Historically this bay was connected to the Gulf of Mexico by East Pass at the eastern end of the bay. However, following the opening of St. Andrew Bay Entrance in 1934 at the western end to serve Panama City, the flow cross-section of this channel increased while East Pass contracted gradually and eventually closed in 1998. In December 2001 East Pass was reopened by dredging a small flow-relief channel. These events provided the opportunity to apply the stability analysis to the newly-formed two-inlet one-bay system. Interpretation of the results in terms of observed inlet stability versus prediction is shown to be contingent upon knowledge of the history of channel maintenance and the morphodynamics of the bay. The illustration underscores the need to apply the method in pre-project engineering investigations of the long-term impact of opening a second inlet in a bay.

After completion of a new south jetty at Barnegat Inlet, New Jersey, data collection was initiated in 1993 by the U.S. Army Corps of Engineers to evaluate the performance of this project. Long-term (34 days) and short-term (13 and 25 hours) velocity measurements were made with Acoustic Doppler Current Profilers. Tide measurements were made at able for the duration of the study. From the data it was found that tidal prism and bay tide amplitudes increased as the inlet system became more efficient with the new south jetty in place. It was found that flood predominance exists for spring tide conditions and ebb predominance can exist for some neap tides. In addition, over a given tidal cycle, locally flood-dominant and ebb-dominant channels exist. Overall the inlet is flood dominant in terms of current and sediment transport.

Tidal motion and inlet processes were investigated in Ponce de Leon (Ponce) Inlet, Florida and its bay channels through a 10-week data-collection campaign and two-dimensional numerical simulation modeling. Water level and current were measured at six locations spanning the ebb shoal, inlet, and bay channels. Measurements revealed that the inlet was flood dominated during the data-collection period. The flood dominance may have been enhanced by a net influx of water during the measurement period, which was captured at two measurement stations in the bay channels located 5 km away from the inlet. Scour, erosion, and sedimentation are problems faced at Ponce Inlet, and calculations suggest tide-related circulation patterns contribute to problematic hot spots. Scour along the north jetty may be most active on the ebb tide, when the strongest flows oriented parallel to the jetty are present. Erosion on the north interior spit owes to a bend in the inlet that forces the strong flood current to impinge on the spit shoreline. Progradation of the south spit into the inlet is a product of the curvature of the spit that creates a region of relatively weak current in the southern portion of the inlet. Deposition may therefore occur on both flood and ebb tidal cycles. Tidal attenuation was calculated along a 7 km transect from the ebb shoal, through the inlet, and south along the Indian River North. Attenuation of the M2tide (water level) was estimated to be 1.1 cm/km along the unimpeded reach of the transect extending south from the ebb shoal to just north of a bridge. At the bridge, the attenuation was increased to 55 cm/km, a decay that is 50 times greater than in the unimpeded channel. The bridge was found to contribute to 56% of the tidal-amplitude reduction between the ebb shoal and the bridge.

The conceptual designs of cooling channels can be quickly obtained by the Darcy flow based topology optimization within a cheap computational cost. However, a long standing issue of this approach is that the hydraulic pressure loss of the optimized flow is difficult to control due to the model simplification of neglecting the fluidic inertial force. This paper presents an ad-hoc algorithm to effectively control the pressure loss such that the optimized fluid meets the practical design requirement of the allowable pumping pressure under a given flow rate. A Darcy flow based topology optimization approach is employed to design 2D cooling channels together with the inlets and outlets. The optimized topologies are further translated into 3D cooling plates with smooth geometry boundaries and the fluidic performances is evaluated using the full-blown turbulence model. Based on the difference with the actual pressure loss of the optimized design and the target requirement, the inlet pressure is adjusted and the channel is redesigned. Numerical examples show that an optimized 3D cooling channel topology that matching the allowable pressure drop can be obtained efficiently within a few design cycles.