Bay Water Levels Research Articles

Modeling the hydrodynamics of a tidal inlet during bay-side storms

Bay-side storms, defined here as storms with tracks on the landward side of barrier islands, may disturb the hydrodynamics of inner bays to a larger extent than on the ocean side. These storms are common in large-scale O(>100,000 m) estuarine systems and have the potential to modify the circulation in bays and within tidal inlets. Here, we provide an overview of the hydrodynamic response of a tidal inlet under forcings caused by bay-side storms and explore the role of waves in modulating the release of storm surge from the back-barrier regions into the ocean. A two-dimensional horizontal numerical model including wave-current interactions is calibrated and validated against field observations of water levels and depth-averaged velocities at Oregon Inlet, NC. The model is then used to investigate the effect of synthetic bay-side storms with varying wave conditions and water levels based on those generated by Hurricane Irene (2011), which is the strongest bay-side storm to hit the Outer Banks of North Carolina in the last two decades. Effect of timing of the peak storm surge during the ebb and flood phases of the tide is also explored.Results from synthetic storms indicate that, during bay-side storms, the water level gradient along the inlet favors ebbing flows regardless of the timing of the storms relative to tidal phase. These results suggest that waves might be responsible for any influx of volume to the bay during high bay-side surge events. Wave blocking effects were found to be stronger along the ebb shoal and only reached the flood delta when bay water levels were nearly the same as the ocean water levels. Reduction of currents by waves in the inlet have the potential to extend the duration of the inundation period in the back barrier region. Bay-side storms also caused flux enhancement over inlet shoals and channels in the flood delta, which could have implications for circulation patterns as well as the morphodynamics of the system.

Episodic complexity and the emergence of a coastal kingdom: Climate, cooperation, and coercion in Southwest Florida

At European contact, the Calusa of southwestern Florida were the most complex society in Florida. For staple sustenance they relied not on agriculture, but on aquatic resources harvested mainly from shallow inshore bays. We summarize recently discovered physical evidence on Mound Key of mound-building, monumental architecture, large-scale food processing, watercourt construction and use, and the sixteenth-century Spanish fort and mission of San Antón de Carlos. We fold these findings into regional paleoenvironmental, archaeological, and historical knowledge, refining our understanding of Calusa history by examining it at smaller time increments. Following a diminished fishery during a significant drop in bay water levels near the end of the cool Vandal Minimum episode, the Medieval Warm Period reversed the situation and increased the productivity of the shallow waters, which provided food surpluses and new opportunities. After ca. AD 950, long-established cooperative heterarchical relations among coastal and inland polities gave way to coercive hierarchical relations. During the succeeding Little Ice Age, they intensified food production by engineering and maintaining “watercourts” that functioned as fish traps and short-term fish storage areas. Periods of overall prosperity were dampened by times of uncertainty, characterized by short-term, lowered water levels with reduced fisheries and renewed cooperative, heterarchical relations.

Wetland Dynamics Inferred from Spectral Analyses of Hydro-Meteorological Signals and Landsat Derived Vegetation Indices

The dynamic response of coastal wetlands (CWs) to hydro-meteorological signals is a key indicator for understanding climate driven variations in wetland ecosystems. This study explored the response of CW dynamics to hydro-meteorological signals using time series of Landsat-derived normalized difference vegetation index (NDVI) values at six locations and hydro-meteorological time-series from 1984 to 2015 in Apalachicola Bay, Florida. Spectral analysis revealed more persistence in NDVI values for forested wetlands in the annual frequency domain, compared to scrub and emergent wetlands. This behavior reversed in the decadal frequency domain, where scrub and emergent wetlands had a more persistent NDVI than forested wetlands. The wetland dynamics were found to be driven mostly by the Apalachicola Bay water level and precipitation. Cross-spectral analysis indicated a maximum time-lag of 2.7 months between temperature and NDVI, whereas NDVI lagged water level by a maximum of 2.2 months. The quantification of persistent behavior and subsequent understanding that CW dynamics are mostly driven by water level and precipitation suggests that the severity of droughts, floods, and storm surges will be a driving factor in the future sustainability of CW ecosystems.

Morphodynamic modeling of the response of two barrier islands to Atlantic hurricane forcing

The accurate prediction of a barrier island response to storms is challenging because of the complex interaction between hydro- and morphodynamic processes that changes at different stages during an event. Assessment of the predictive skill is further complicated because of uncertainty in the hydraulic forcing, initial conditions, and the parameterization of processes. To evaluate these uncertainties, we investigated the morphological change that occurred during two Atlantic hurricane events on two barrier islands at Matanzas (Florida) and Fire Island (New York) with differing topographies and forcing conditions.We used the morphodynamic model XBeach with hydrodynamic forcing extracted from a regional coupled D-Flow FM/SWAN model. The XBeach model was initialized with a spatially varying roughness map derived from a land cover classification map generated with supervised conditional-random-field classification. The model was supplemented with a dynamic roughness module recognizing that, under extreme conditions, vegetation can be washed away or buried by sediment.For the Fire Island case, the modeled spatial extent of roughness reduction as a proxy for vegetation removal during the storm was accurate. For both the Fire Island and Matanzas cases, the model predicted erosion and deposition volumes and dune-crest lowering well. The occurrence of breach formation was also predicted by the model, but the exact location of these breaches did not match observations. Variations of 10% in boundary conditions (surge, wave direction, significant wave height, and bay water levels) produced regime shifts in modeled barrier island response. These results not only stress the critical role of boundary conditions in morphodynamic model skill, but also show the limitations of single deterministic model runs in forecasting impact.

A Tool for Rapid Assessment of Hydrological Connectivity Patterns in Texas Coastal Wetlands: Linkages between Tidal Creeks and Coastal Ponds

Coastal salt marshes are heterogeneous, spatially complex ecosystems. The degree of hydrological connectivity in these systems can be a significant driver in the flux of energy, organisms, and nutrients across the marsh landscape. In tidally driven systems, the frequency and magnitude of hydrological connection events results in the creation of a matrix of intermittently connected coastal wetland habitats, some of which may be hydrologically isolated or partially drained at any given time. Previous approaches to understanding landscape-level hydrologic connectivity patterns have required either intensive long-term monitoring or spatially explicit modeling. In this paper, we first describe a 13-month field study in the Guadalupe Estuary of the Texas Gulf Coast that linked hydrological connectivity patterns between a saltwater pond to water levels in an adjacent tidal creek and nearby San Antonio Bay. We next describe the integration of these field data with high-resolution digital elevation models and environmental parameters to develop a spatially explicit model that is a Simulation of Landscape-level Oscillations in Salt Marsh Hydroperiod (SLOSH). We evaluated the ability of SLOSH to simulate trends in landscape-level patterns of hydrological connectivity between a tidal creek and an inland marsh pond. Magnitude and periodicity of simulated and observed water-level fluctuations in the pond were similar. Highest creek water levels, resulting in high frequency and duration of hydrological connectivity with the pond, corresponded with the highest bay water levels, which occurred during September and October. Lowest creek water levels, resulting in low frequency and duration of hydrological connectivity, corresponded with the lowest bay water levels, which occurred during December through February. By simulating the pulsing structure of salt marsh hydrology, SLOSH creates the foundation on which to assess how additional drivers (precipitation, wind, freshwater inflows, etc.) can influence coastal marsh hydrology and overall ecology. Citation: Swannack TM, Wozniak JR, Grant WE, Davis SE III. 2019. A tool for rapid assessment of hydrological connectivity patterns in Texas coastal wetlands: linkages between tidal creeks and coastal ponds. Texas Water Journal. 10(1):46-59. Available from: https://doi.org/10.21423/twj.v10i1.7073.

A SEMI-ANALYTIC MODEL OF TIDAL INLETS AND THEIR EVOLUTION

The water exchange between the sea and a lagoon or bay through an inlet due to tides is a classical topic that has been investigated in a large number of studies (Keulegan, 1967; O’Brien and Dean, 1972; O’Brien and Clark, 1974; Escoffier, 1977). In this paper, a simple semi-analytic model of the flow induced by tides through an inlet connecting the sea to a lagoon or bay is developed. The model is employed to derive explicit expressions for key parameters associated with inlet flows such as bay water level amplitude, tidal prism, maximum inlet velocity, and mixing (retention) time. Also, the inlet flow model is combined with a sediment transport model to determine the conditions for equilibrium as well as the evolution of the inlet cross-sectional area towards equilibrium or closure.

ADAPTATION PATHWAY FOR A BARRIER ISLAND TO FUTURE HURRICANES

The numerical model XBeach is used to simulate hydrodynamics and morphological change of Bay Head, NJ, which is located on a developed barrier island. Bay Head is fronted with a seawall buried beneath its dunes, and the seawall has been shown to mitigate damage due to storm surge and waves during Hurricane Sandy (2012). The objective of this study is to re-evaluate the effectiveness of the seawall in mitigating damage from a synthetic storm and sea level rise, and refine an adaptation pathway previously created for Bay Head. Utilizing the wave and surge data generated from the North Atlantic Coast Comprehensive Study, synthetic Storm 391 is simulated using XBeach. Model results show the seawall is overtopped by storm surge and waves, causing overwash and reducing dune heights. As sea levels rise, the backbarrier region of the barrier island is severely eroded and the seawall acts as a barrier preventing elevated bay water levels from freely flowing across the island and into the ocean, exacerbating sediment transport on the backbarrier. To fully evaluate the capabilities and limitations of the seawall in mitigating storm damage, additional synthetic storms need to be simulated and the results re-evaluated. This will, in turn, lead to a comprehensive, more robust adaptation pathway for Bay Head.

A simplified physically-based model for coastal dike and barrier breaching by overtopping flow and waves

The simplified physically-based breach model, DLBreach, has been developed to simulate the overtopping breaching of coastal dikes and barriers, which can occur either from the sea side or the bay side. The breaching process is divided into two stages: intensive breaching and general inlet evolution, in which the flows are calculated using the weir flow equation and the Keulegan equation, respectively. The Keulegan equation is a simplified energy equation for steady nonuniform flow with local head loss due to channel contraction and expansion, revised herein by adding the wind driving force. Empirical formulas are adopted to calculate phase-averaged wave overtopping discharge, wave setup, and wind setup/setdown. The wave overtopping discharge is combined with the surge overflow discharge, and the wave setup and wind setup/setdown are added to the sea and bay water levels for the hydrodynamic and sediment routing. Alongshore sediment is considered as a source boundary condition for the non-equilibrium sediment transport model at the breach. The model has been tested using the 94’ field experiment of sea dike breaching by overflow in the Zwin Channel Estuary, a laboratory experiment of sea dike breaching initiated by wave overtopping, and a field observation of the eight-day breaching and closure event of the Mecox Inlet at eastern Long Island of New York during Sept. 10–18, 1985. The model results agree generally well with the measurements.

Observations and a linear model of water level in an interconnected inlet‐bay system

AbstractA system of barrier islands and back‐barrier bays occurs along southern Long Island, New York, and in many coastal areas worldwide. Characterizing the bay physical response to water level fluctuations is needed to understand flooding during extreme events and evaluate their relation to geomorphological changes. Offshore sea level is one of the main drivers of water level fluctuations in semienclosed back‐barrier bays. We analyzed observed water levels (October 2007 to November 2015) and developed analytical models to better understand bay water level along southern Long Island. An increase (∼0.02 m change in 0.17 m amplitude) in the dominant M2 tidal amplitude (containing the largest fraction of the variability) was observed in Great South Bay during mid‐2014. The observed changes in both tidal amplitude and bay water level transfer from offshore were related to the dredging of nearby inlets and possibly the changing size of a breach across Fire Island caused by Hurricane Sandy (after December 2012). The bay response was independent of the magnitude of the fluctuations (e.g., storms) at a specific frequency. An analytical model that incorporates bay and inlet dimensions reproduced the observed transfer function in Great South Bay and surrounding areas. The model predicts the transfer function in Moriches and Shinnecock bays where long‐term observations were not available. The model is a simplified tool to investigate changes in bay water level and enables the evaluation of future conditions and alternative geomorphological settings.

Morphological response of a sandy barrier island with a buried seawall during Hurricane Sandy

Coastal populations continue to increase globally, causing potential damage costs of coastal hazards to rise and community resiliency to become a worldwide priority. Recently, Hurricane Sandy (2012) devastated areas of New York and New Jersey and caused overwash and breaching of several urbanized barrier islands along the U.S. eastern seaboard. This study focuses on the morphological response of Bay Head, NJ, a township on a barrier island fronted with a buried seawall. The hydrodynamics and morphology of Bay Head during Hurricane Sandy are simulated with XBeach, a numerical model designed to study these processes during storm events. From the simulations, the seawall protected Bay Head by effectively dissipating wave energy during the peak of the storm and from rapidly increasing bay water levels that flood the backbarrier region of the island. When the seawall is removed from the simulation, dune heights are lowered, allowing bay side flooding to cause a devastating erosive event that completely destroys the remaining dune system. XBeach indicates severe erosion seaward of oceanfront buildings in the absence of a seawall (vertical erosion under the dune peak about 15m more than in the presence of the seawall), and wave energy propagates further inland even after the storm has passed. However, with the seawall present, wave attack is reduced on the island by a factor of 1.7 and prevents bay side flooding from causing significant morphological change on the island. Therefore, the seawall increased resiliency of the Bay Head community during and after peak Hurricane Sandy forcing by preserving the dune system.

Impacts of Large-Scale Stormwater Green Infrastructure Implementation and Climate Variability on Receiving Water Response in the Salt Lake City Area

This study evaluated impacts of Green Infrastructure (GI) as a stormwater management practice on return flows and the further Implications of climate variability. The goal was to create a model to explore the impacts that bioretention and Rainwater Harvesting (RWH) representing GI had using goldsim and Stormwater Management Modeling (SWMM) software. The software was used to represent impacts that climate variability individually and combined, may have on downstream stakeholders and receiving water systems in Salt Lake city, Utah, USA. Primary stakeholders included downstream water rights users, Farmington Bay waterfowl management area and the migratory birds that rely on Farmington Bay and the advocates that represent them. The steps to reach this goal were broken down incrementally to: (1) Characterize daily inflows to Farmington Bay, (2) Provide daily inflows from natural and urban runoff to the Jordan river, (3) Create a daily water balance model of Farmington Bay, (4) Demonstrate the model with and without stormwater GI and climate variability scenarios and (5) Determine trends of inflow to the Jordan River, duck clubs and Farmington Bay under various scenarios. The simulation results demonstrated that bioretention and RWH individually and combined had minimal impact on downstream water users, Jordan River flows and ultimately Farmington Bay water levels. Bioretention reduced the flow in the Jordan River minimally, with reductions primarily during peak flow. RWH actually kept more water in the natural system on average because less water was needed from the water treatment facilities when outdoor irrigation was supplemented with rainwater. The user reliability did not differ for any of the bioretention and RWH scenarios. The climate variability scenario had the greatest impact to Jordan River flows, Farmington Bay water levels and user reliability. When analyzed without GI implementation, the climate variability induced reduction in tributary flows and precipitation led to an average decrease of 11% in the Jordan River streamflow when compared to average baseline scenario over a 25 year simulation. The user reliability decreased by 5% and most importantly there was found to be an average of 36% decrease in the water levels in Farmington Bay. The resultant of the decrease in Farmington Bay water level is a loss of up to 61 square kilometers (15,000 acres) of open bay that would impact bird habitat, brine shrimp grounds, recreationalists, bird watchers, hunters and more. For this case study the implications of climate variability on the water system are much greater than implementing GI.

Temporal variability of freshwater and pore water recirculation components of submarine groundwater discharges at Baffin Bay, Texas

Submarine groundwater discharges (SGDs) are an important source of freshwater as well as nutrients and other chemicals to bays and estuaries. SGDs are particularly important for coastal bodies in arid and semi-arid regions that are not fed by perennial streams. The Baffin Bay, TX is a shallow coastal water body that is weakly connected to the Gulf of Mexico and has no major rivers or streams draining into it. A year-long submarine groundwater discharge measurement study was carried out at the Loyola Beach of the Baffin Bay during the months of July 2005–June 2006. A total of 23 synoptic SGD sampling events were carried out with most events collecting SGD data continuously over a period of 24 h at a 1-min temporal resolution using an ultrasonic seepage meter. The median SGD was noted to be 3.83 cm/d with an inter-quartile range (IQR) of 11.36 cm/d. Four sampling events had anomalously high SGD values (~27–48 cm/d) which are hypothesized to be due to the geologic heterogeneity of the sea bed and meteorological effects. Eight of the 23 sampling events had a negative average SGD flux indicating landward flow. The short-term diurnal variability of SGD was comparable or sometimes higher than the longer-term and between-events variability. No long-term trend could be inferred. In the short-term, SGD measurements showed considerable persistence and the effective sample size analysis indicated each sampling event (consisting of over 1,000 samples) yielded only a handful of statistically independent measurements of SGD. The measured SGD values exhibited both negative (hydraulically controlled) and positive (wave set-up controlled) correlations with the bay water levels. Marine controls appeared to be the most significant SGD drivers and are in turn controlled by prevailing aeolian forcings. The salinity of the SGDs were estimated from measured sonic velocities and used in conjunction with the end-member mixing models to estimate fresh (meteoric) and re-circulated pore-water fractions. The freshwater fraction of the SGD was estimated to vary between nearly 4 and 89 % with a median value of 9.96 % and an IQR of 7.16 %. Three events were noted to have abnormally high freshwater fractions (~28, 50 and 84 %) which are likely artifacts caused by bay water freshening from rainfall and plausible thermal expansion. The meteoric and pore-water partitioning was sensitive to the assumed end-member concentrations. This study provides preliminary estimates for SGDs along the South Texas coast line and is useful for calibrating groundwater flow models and understanding the relative importance of terrestrial and marine controls on SGD. However, the heterogeneous nature of the sedimentary geology of the Texas Gulf Coast implies the SGD fluxes are likely to exhibit considerable spatial variation that has not been characterized yet. Therefore, the study provides useful insights for such future data collection and monitoring activities. The measured SGD values at Baffin Bay, TX are comparable to those reported at other parts of the Gulf of Mexico.

Did Port Phillip Bay nearly dry up between ∼2800 and 1000 cal. yr BP? Bay floor channelling evidence, seismic and core dating

Imagery of meandering river-like channel features up to 5 m deep and 100 m wide on the floor of Port Phillip Bay have been revealed by recent multibeam surveys. They are in water depths to −22 m below the present bay water level. This young channelling overlies older infilled Pleistocene–early Holocene channels considered to be cut by the Yarra and Werribee rivers during the last glacial or previous low stand minima >10 000 cal. yr BP and infilled during the Holocene transgression. Vibrocoring data indicate the young channels incise shelly mud. Twelve 14C shell dates in vibrocores from bay floor to 3.5 m are in two units—a lower unit range between 2880 cal. yr BP at 0.7 m to 9491 cal. yr BP at 3.5 m, and an upper unit ∼0.5 to 0.7 m thick <869 cal. yr BP forming the present bay floor. Seismic and vibrocore evidence suggests the post-869 cal. yr BP upper unit also covers the base of the young channels. This evidence implies that Port Phillip dried out to −22 m between ∼2800 and ∼1000 cal. yr BP at a time of stable present day sea-levels. The most likely cause is a sand blockage to the Port Phillip Bay channel entrances, coupled with high evaporation rates. Palynological and foraminiferal evidence suggests variable salinities occurred immediately prior to the sedimentary hiatus, with restoration of marine conditions after. The results have wide implications on Port Phillip's water balance, salinity, pre-European climatic events and Aboriginal occupation.

Storm-Wave Flow through Tidal Inlets and Its Influence on Bay Flooding

Offshore wave setup generated by wave breaking during coastal storms can create significant flow through tidal inlets and increase bay flooding. However, these flow contributions are not always considered when determining coastal flooding risk for engineering studies. This paper describes the wave-driven flow process at tidal inlets and demonstrates its impact on bay flooding on Long Island, New York. Numerical simulations using a coupled hydrodynamic and wave model are presented to show contributions to bay water level by wave-driven flow with respect to those by wind surge. These simulations include two major historical coastal storms and a small nor’easter in 2003, during which the model was validated using field measurements of water level. Finally, an approach is introduced for estimating wave-induced flow contributions to bay flooding as a function of inlet and storm characteristics, including tidal prism and wave conditions. The findings of this study indicate that wave-induced flow contributions m...

Simulation of storm-induced barrier island morphodynamics and flooding

Prediction of coupled storm hydrodynamics and morphodynamics is essential for accurately designing coastal flood protection measures. A numerical simulation methodology was developed and implemented to evaluate and assess engineering design solutions for storm damage reduction along the south shore of Long Island, New York, USA. This simulation methodology was applied to compute bay water levels for two major coastal storms taking into account contributions from storm surge, waves, wind, and barrier island overwash and breaching. Simulation results for breaching and bay flooding compare well to historically documented barrier island morphological change and bay high water marks.

Evaluation of a small beach nourishment project to enhance habitat suitability for horseshoe crabs

This field study evaluates the effect of nourishing an estuarine beach with gravel to enhance spawning rates by horseshoe crabs. A total of 564 m 3 of coarse sand and gravel were emplaced in two 90 m-long treatment segments at Bowers Beach, Delaware, USA from 9 to 11 April 2002. Field data were gathered between 6 April and 24 May 2002 to characterize the two fill segments and the un-nourished segments between them as well as two control segments at the adjacent Ted Harvey Beach. Sediment samples were taken from the foreshore surface and at depth before and after the nourishment. Bay water levels, wave heights, and beach ground water characteristics were monitored over a 12-hour tidal cycle at one of the nourished (15 May 2002) and the unnourished segment (16 May 2002) at Bowers Beach and at one of the control segments at Ted Harvey Beach (21 May 2002) using piezometers and pressure transducers inserted in wells. The beaches were cored to estimate the density of horseshoe crab eggs deposited during the spawning season. Horseshoe crab eggs were buried in pouches at 0.15 to 0.20 m depth for 30 to 40 days to evaluate their survival in developing into embryo or larval stage. Bulk sediment samples were taken to evaluate moisture characteristics near locations where egg pouches were buried. Density of spawning females at Bowers Beach was 1.04 m − 2 in 2001 and 1.20 m − 2 in 2002. These rates are lower than at Ted Harvey Beach but reveal an increase in spawning while Ted Harvey Beach underwent a considerable decrease (2.63 m − 2 to 1.35 m − 2 ). Sediments low on the foreshore remained nearly saturated throughout the tidal cycle at both beaches. The average hydraulic conductivity on the upper foreshore at the non-treatment section at Bowers Beach (0.19 cm s − 1 ) was less than at Ted Harvey Beach (0.27 cm s − 1 ), and the finer, better sorted sediments at depth at Bowers Beach resulted in a higher porosity, creating greater moisture retention potential. Egg development was greatest at mid foreshore at all sites. Eggs at the lower foreshore elevation remained viable, but did not develop to the embryo stage. Between-beach differences were limited to high elevations where higher mortality occurred at Ted Harvey Beach due to desiccation. Adding small amounts of gravel to a sand beach may change the appearance of the surface but may not appreciably increase mean grain size and sorting at depth or the hydraulic conductivity over the spawning season. The pebble fraction may be important for site selection, but finer sizes may be more important for egg survival because of moisture retention.

Linear systems analysis approach to inlet–bay systems

Fluctuating water levels in tidal inlet-bay systems are investigated by comparison of bay water levels resulting from a linearization of the combined continuity and integrated equation of motion to bay water levels from a numerical model with the complete non-linear equation terms. In this approach a linearized friction factor is computed using results from the non-linear model. The present paper addresses the possibility of utilizing this alternate approach to assessment of water level elevation changes in the bay for realistic tides consisting of a number of harmonic components.

Cardiff Bay Barrage: planning and design

In 1986 Mr Peter Walker, Secretary of State for Wales, accepted the view that the Cardiff Bay area was in urgent need of urban renewal. The government, with support from the Vale of Glamorgan, the county of South Glamorgan and the City of Cardiff, created the Cardiff Bay Development Corporation (CBDC). Its remit was to regenerate some 1100 ha in this area of south Cardiff. The keystone to this strategy was the construction of the Cardiff Bay Barrage, to impound the estuaries of the rivers Taff and Ely, creating a 200 ha fresh water lake and about 12 km of attractive waterfront. Works of this magnitude and scope on tidal waters at that time required an Act of Parliament. The 1100 m long barrage includes sluices, locks, an outer harbour, fish pass, embankment and bridges. The sluices have a capacity of 2300 m3/s, to discharge combined flood flows from the Taff and Ely. The gates close to exclude the highest tides, allowing bay water levels to be controlled even in extreme conditions. A large fish pass allows migratory fish to move easily between the rivers and the sea. The paper describes the overall objectives of the Cardiff Bay Barrage, and the design of the barrage.

Cardiff Bay Barrage: planning and design

In 1986 Mr Peter Walker, Secretary of State for Wales, accepted the view that the Cardiff Bay area was in urgent need of urban renewal. The government, with support from the Vale of Glamorgan, the county of South Glamorgan and the City of Cardiff, created the Cardiff Bay Development Corporation (CBDC). Its remit was to regenerate some 1100 ha in this area of south Cardiff. The keystone to this strategy was the construction of the Cardiff Bay Barrage, to impound the estuaries of the rivers Taff and Ely, creating a 200 ha fresh water lake and about 12 km of attractive waterfront. Works of this magnitude and scope on tidal waters at that time required an Act of Parliament. The 1100 m long barrage includes sluices, locks, an outer harbour, fish pass, embankment and bridges. The sluices have a capacity of 2300 m3/s, to discharge combined flood flows from the Taff and Ely. The gates close to exclude the highest tides, allowing bay water levels to be controlled even in extreme conditions. A large fish pass allows migratory fish to move easily between the rivers and the sea. The paper describes the overall objectives of the Cardiff Bay Barrage, and the design of the barrage.

Cardiff Bay Barrage: planning and design

In 1986 Mr Peter Walker, Secretary of State for Wales, accepted the view that the Cardiff Bay area was in urgent need of urban renewal. The government, with support from the Vale of Glamorgan, the county of South Glamorgan and the City of Cardiff, created the Cardiff Bay Development Corporation (CBDC). Its remit was to regenerate some 1100 ha in this area of south Cardiff. The keystone to this strategy was the construction of the Cardiff Bay Barrage, to impound the estuaries of the rivers Taff and Ely, creating a 200 ha fresh water lake and about 12 km of attractive waterfront. Works of this magnitude and scope on tidal waters at that time required an Act of Parliament. The 1100 m long barrage includes sluices, locks, an outer harbour, fish pass, embankment and bridges. The sluices have a capacity of 2300 m3/s, to discharge combined flood flows from the Taff and Ely. The gates close to exclude the highest tides, allowing bay water levels to be controlled even in extreme conditions. A large fish pass allows migratory fish to move easily between the rivers and the sea. The paper describes the overall objectives of the Cardiff Bay Barrage, and the design of the barrage.