Tidal Prism Research Articles

Generating meshes for tidal wetland modeling using light detection and ranging (LiDAR) data

A high resolution model mesh was required to numerically simulate sediment transport in tidal marshes. The timing of flooding is dependent on the tidal marsh ground elevation, which requires accurate topographic elevation data. The tidal prism of the marsh is determined by the volume provided by tidal channels in the system. Hence, their location and bathymetry needed to be represented adequately. Due to the high spatial variability and inaccessibility of marshes, remote sensing techniques such as light detection and ranging (LiDAR) are a significant resource for elevation data. LiDAR measures the highest elevation of elements. To determine the bare ground elevation, filter techniques exist but are often inadequate to eliminate elevation errors that are introduced by the vegetation of marshes. We introduce a simple method to remove remaining vertical elevation errors in high resolution digital terrain models (DTMs) of vegetated marshes and present an approach to determine the bathymetry of tidal channels based on a limited number of cross-sectional measurements. Forcing polygons for mesh generation were extracted from the DTMs to assure an accurate spatial representation of the marsh. DTMs (2 × 2 m/1 × 1 m) derived from LiDAR data from the Blackbird Creek Reserve and Bombay Hook National Wildlife Refuge in Delaware, USA, were used.

東日本大震災津波後の名取川河口地形回復と課題

Morphological changes and recovery process at the Natori River mouth were evaluated by using the aerial photography and the observed cross-sectional data. The river mouth morphology has changed completely due to the 2011 Tohoku Tsunami. Since then, there is in the process of recovery. The result of the analysis shows that the morphological changes of the river mouth become stable condition. Furthermore, the relationship between tidal prism and inlet cross-sectional area was used to determine the current state of the Natori River mouth. It indicates that the river mouth condition has been returned to the past state before the 2011 Tohoku Tsunami. This study presents the influences of the river mouth structure in analyzing morphological changes and recovery process. It is also considered the practical problems in this area.

Rapid Evolution of a Flood Tidal Deltaic Island in the River Murray Estuary, South Australia: A Canary in the Cage of River Management

James, K.F.; Bourman, R.P., and Harvey, N., 2015. Rapid evolution of a flood tidal deltaic island in the River Murray estuary, South Australia: A canary in the cage of river management.Bird Island, at the oceanic outlet of Australia's largest exoreic river system, the Murray-Darling, did not exist before 1940. Originally, flood tidal sediments were moulded by tides, waves, wind, and river flows in the back-barrier lagoon, landward of the migrating River Murray Mouth. The estuary was fluvially dominated, and the terminal lakes were mainly fresh. Following more than a century of European settlement and freshwater abstraction, salinity levels increased, prompting the construction of barrages (completed in 1940) near the Murray Mouth to restore the former predominantly freshwater character of the estuary. Further reduced river flows, a restricted tidal prism, and management strategies produced irreversible changes in the dynamics of the River Murray Mouth. These are archived in the landforms and vegetation of Bird Island. By the mid-1950s, sand shoals were enlarging and a small patch of vegetation was established, forming the core of an incipient island. Progressively, dunes and salt marshes were established, reflecting intimate associations between landform evolution, vegetation colonisation, and island stability. As the mouth migrated to the NW, so did the flood tidal shoals, the sources for newer generations of dunes, thereby developing a clockwise establishment of dunes on the expanding island. Approximately 1 km in diameter and carrying more than 80 plant species, Bird Island assisted mouth closure in 1981. During the 2002–10 drought, dredging maintained the mouth and improved lagoonal water quality. Subsequent healthy river flows cleared the mouth, highlighting the important role of river flows in maintaining oceanic access, and sediment removal, while flushing the river system. The evolution of Bird Island as documented in this study demonstrates how anthropogenic activities can cause rapid and irrevocable changes to coastal–estuarine environments.

Hydrodynamic Impact on Pearl River Estuary from HZM Bridge

The HZM(Hongkong-Zhuhai-Macao) bridge connects Hongkong, Zhuhai and Macao district, and it strctchs across the Pearl River estuary. A lot of piers and three large artifical islands would have some impact on the hydrodynamic environment in the Pear River estuary. In this paper, a 2D tidal current numerical model is introduced to simulate the hydrodynamic impact from the HZM brdige. The simulated results show that the Hydrodynamic influence is concentrated on the 5.0 km range from downstream to upstream nearby the navigation zone and the 1.0 km range of bridge site in not-navigation zone, and the tidal range reduction is limited 0.03m and the tidal prism reduction is not more than 1% in the Lingding Sea after the HZM bridge constructed. Therefore, the HZM bridge has little influence on the distribution of hydrodynamic environment in the Pearl River estuary.

Scale-dependent characteristics of equilibrium morphology of tidal basins along the Dutch–German North Sea Coast

Tidal basins can be characterized by two major morphological elements: tidal channels and tidal flats. Some scale-dependent empirical relations have been suggested based on observations in tidal basins of the Dutch and German coast. Thus, the dimensional parameters of channel area and volume are proportional to the 1.5 power of the basin area and tidal prism, respectively, whereas the dimensionless parameters of relative channel area and the ratio between channel volume and tidal prism are both proportional to the square root of basin area (Ab). The values of the coefficients before the power in these relations are of the order of 10− 5. In order to provide physical explanations for these relations, a theoretical model and a two-dimensional horizontal numerical model are developed. Based on the concept of uniform equilibrium channel velocity, the channel cross-sectional area is directly proportional to Ab and, when integrating the cross-sectional area in the flow direction, a 1.5 power relationship between the channel volume and Ab is obtained. Due to the parameters expressing the characteristic basin depth and the ratio of channel depth to the characteristic depth, which are confirmed to be scale-insensitive in both the numerical model and in field observations, the channel area is also proportional to Ab1.5. Theoretical expressions suggest the same order for the coefficients before the power as found in empirical studies. In the numerical model, the same type of scaling relations are illustrated, and the morphological response of changing grain size and tidal amplitude can be successfully predicted by the theoretical model.

Morphological evolution of an ephemeral tidal inlet from opening to closure: The Albufeira inlet, Portugal

Like other similar coastal systems, the Albufeira lagoon is artificially opened every year to promote water renewal and closes naturally within a few months. The evolution of the Albufeira Lagoon Inlet from its opening in April 2010 to its closure 8 months later is qualitatively and quantitatively analyzed through a combination of monthly field surveys and the application of a process-based morphodynamic model. Field data alone would not cover the whole space–time domain of the morphology of the inlet during its life time, whereas the morphodynamic model alone cannot reliably simulate the morphological development. Using a nudging technique introduced herein, this problem is overcome and a reliable and complete data set is generated for describing the morphological development of the tidal inlet. The new technique is shown to be a good alternative to extensive model calibration, as it can drastically improve the model performance. Results reveal that the lagoon imported sediments during its life span. However, the whole system (lagoon plus littoral barrier) actually lost sediments to the sea. This behavior is partly attributed to the modulation of tidal asymmetry by the spring–neap cycle, which reduces flood dominance on spring tides. Results also allowed the assessment of the relationship between the spring tidal prism and the cross-section of tidal inlets (the PA relationship). While this relationship is well established from empirical, theoretical and numerical evidences, its validity in inlets that are small or away from equilibrium was unclear. Results for the Albufeira lagoon reveal an excellent match between the new data and the empirical PA relationship derived for larger inlets and equilibrium conditions, supporting the validity of the relationship beyond its original scope.

Coastal saltmarsh managed realignment drives rapid breach inlet and external creek evolution, Freiston Shore (UK)

The creation of saltmarsh through the managed realignment of sea defences, implemented in NW Europe as a sustainable coastal defence option, represents a substantial hydrodynamic perturbation to the local coastal system. The impact of a significantly increased tidal prism on hydromorphological features was investigated at Freiston Shore, Lincolnshire UK. Local tidal conditions and inadequate drainage at this realignment trial contributed to significant channel erosion due to the establishment of water surface slopes and pooling between the newly realigned site and the adjacent intertidal zone. Very high spatial resolution aerial photography and blimp photography were used to monitor inlet evolution from breaching in August 2002 to March 2008, showing a highly non-linear response with breach channels increasing in width by up to 960% within 2.5months. Airborne laser scanning/LiDAR and terrestrial laser scanning quantified breach channel volume increases, showing a similar pattern. Breach channel evolution did not follow established tidal prism–channel width/cross-sectional area relationships that are often used to guide realignment design. Pre- and post-breach rates of external creek morphology change between 1999 and 2006 were also quantified, with intertidal creeks attached to the breach channels increasing significantly after realignment in both width and depth. This study highlights the physical processes affected by managed realignment, and the importance of understanding the causes of complex water surface slopes at multiple scales.

Investigation of hydraulics transport time scales within the Arvand River estuary, Iran

Transport time scales are key parameters for understanding the hydrodynamic and biochemical processes within estuaries. In this study, the flushing and residence times within the Arvand River estuary have been estimated using a two-dimensional hydrodynamic model called CE-QUAL-W2. The model has been calibrated and verified by two different sets of field data and using the k-ε vertical eddy diffusivity scheme. Flushing time has been estimated using different methods such as the tidal prism and fraction of freshwater methods. Moreover, residence times have been investigated using pulse residence time, estuarine residence time and remnant function approaches. The results have shown that different methods yield different time scales, and freshwater inflow has the greatest impact upon estimation of residence time, whereas tidal circulation hardly contributes to residence time at all. It has also been shown that the neap-spring circulation and start phase of simulations have negligible effects on the Arvand's time scales. The investigation of bathymetry showed that two sills of the estuary tend to significantly increase residence time. Understanding the applicability of these time scales and their estimation approaches helps us to evaluate the water quality management of estuaries. Copyright © 2013 John Wiley & Sons, Ltd.

Flow routing in mangrove forests: A field study in Trang province, Thailand

Flow routing in mangrove forests has great implications for the transport and distribution of sediments and nutrients and hence for mangroves' development and persistence. Whereas previous studies were limited to the creeks, supposedly feeding the surrounding mangroves, this study demonstrates the contribution of biogeophysical impacts on flow routing through estuarine mangroves. We present the results of a field campaign covering three pristine mangrove sites in two estuaries in Trang province, Thailand. The sites range from a mangrove forest elevated above mean sea level with steep cliffs and incised by tidal creeks, to smoothly inclining mangroves fronted by extensive mudflats and showing a clear vegetation zonation starting below mean sea level. It is shown how flow routing through estuarine mangroves is impacted by biogeophysical factors; elevation, exposure and vegetation. Within the higher elevated mangroves, creek flow prevails when water levels remain below a dense vegetation layer at the mangrove fringe bordering the estuary. Sheet flow prevails when this threshold is exceeded and direct water exchange takes place. The low-lying sites do not feature creeks and tidal flows are typically sheet flows, being susceptible to forcing by river discharges. With decreasing water depths and/or increasing vegetation densities, the effects of this forcing are reduced and flow velocities follow the vegetation induced cross-shore water level gradients. Flow velocities within the creeks are up to an order of magnitude greater than those within the vegetation, where velocities decrease progressively with increasing vegetation densities. Particular vegetation and elevation characteristics cause irregular velocity variations along the vertical, within the vegetation as well as in the creeks. Tentative tidal flux calculations demonstrate the significant contribution of creek flow to the total tidal prism in higher elevated mangroves. By explicitly quantifying and mapping flow routing through mangrove forests, this study provides observational evidence for flow routing phenomena that have been postulated in previous studies.

A New Look at Barrier-Inlet Morphodynamics

Davis, R.A., 2013. A New Look at Barrier-Inlet Morphodynamics.Coastal morphodynamics is dependent on the interaction of multiple variables. An earlier publication demonstrated that the comparative influence of waves and tides was the fundamental relationship in coastal morphology. The discussion in this paper adds the important variables of tidal prism, sediment abundance, and sea-level change to the equation. Tidal prism is critical in that it can be the primary factor in morphodynamics if both wave and tidal climate are held constant. Abundant or scarce sediment availability can produce coastal morphology that would not develop otherwise. Because of the extremely slow rate of sea-level change, its impact is less prominent than the other variables and we see less evidence of its influence than the others, except in certain coastal reaches.

Unusual Barrier/Inlet Behaviour Associated with Active Coastal Progradation and River-Dominated Estuaries

ABSTRACT Green, A.; Cooper, J.A.G., and LeVieux, A., 2013. Unusual barrier/inlet behaviour associated with active coastal progradation and river-dominated estuaries. The mesoscale behaviour of unusual barrier inlets on the east coast of South Africa is described. The inlets are associated with river-dominated estuaries and are consequently subject to periodic closure during low river flow. They are also located on a prograding barrier coast. Deflection of the estuary channel of a small river in the direction of longshore transport by 1230 m resulted in its capture by the estuarine channel of a larger river. The larger catchment river was not deflected by coastal progradation but maintained its position by periodic breaching of a channel through the barrier during floods. Flood breaches reseal by landward reworking of ephemeral deltas and may undergo limited migration. A tidal inlet at the northern end of the barrier is maintained by a small tidal prism and has a flood-tidal delta. It exhibits limited late...

Model Study of the Water Exchange in a Shallow Bay

Both the tidal prism and the water exchange duration can be used as the index of examining the residence time of the pollutants in a semi-enclosed bay, and it is significant to predict the long-term variation of water quality. A 3-dimensional coastal circulation model is used to reproduce the tidal regime in the Shenhu Bay. Simulated tidal currents are examined first, and the then the tidal prism is also compared to observations. Based on the validated simulations, the water exchange duration is further estimated by means of the numerical experiment. The simulations show that the half-exchange and 80%-exchange time are about 14 and 30 d, respectively.

Changes in surfzone morphodynamics driven by multi-decadal contraction of a large ebb-tidal delta

The impact of multi-decadal, large-scale deflation (76 million m3 of sediment loss) and contraction (~ 1 km) of a 150 km2 ebb-tidal delta on hydrodynamics and sediment transport at adjacent Ocean Beach in San Francisco, CA (USA), is examined using a coupled wave and circulation model. The model is forced with representative wave and tidal conditions using recent (2005) and historic (1956) ebb-tidal delta bathymetry data sets. Comparison of the simulations indicates that along north/south trending Ocean Beach the contraction and deflation of the ebb-tidal delta have resulted in significant differences in the flow and sediment dynamics. Between 1956 and 2005 the transverse bar (the shallow attachment point of the ebb-tidal delta to the shoreline) migrated northward ~ 1 km toward the inlet while a persistent alongshore flow and transport divergence point migrated south by ~ 500 m such that these features now overlap. A reduction in tidal prism and sediment supply over the last century has resulted in a net decrease in offshore tidal current-generated sediment transport at the mouth of San Francisco Bay, and a relative increase in onshore-directed wave-driven transport toward the inlet, accounting for the observed contraction of the ebb-tidal delta. Alongshore migration of the transverse bar and alongshore flow divergence have resulted in an increasing proportion of onshore migrating sediment from the ebb-tidal delta to be transported north along the beach in 2005 versus south in 1956. The northerly migrating sediment is then trapped by Pt. Lobos, a rocky headland at the northern extreme of the beach, consistent with the observed shoreline accretion in this area. Conversely, alongshore migration of the transverse bar and divergence point has decreased the sediment supply to southern Ocean Beach, consistent with the observed erosion of the shoreline in this area. This study illustrates the utility of applying a high-resolution coupled circulation-wave model for understanding coastal response to large-scale bathymetric changes over multi-decadal timescales, common to many coastal systems adjacent to urbanized estuaries and watersheds worldwide.

Shifts in depositional environments as a natural response to anthropogenic alterations: Nakdong Estuary, South Korea

Abstract The Nakdong Estuary, located within the coastal zone of Busan, South Korea, has been subjected to a series of engineered alterations typical of many eastern Asian estuaries. The construction of two estuarine dams (1934 and 1983) and numerous seawalls associated with land reclamation projects has altered the timing and flux of sediment, and resulted in three contrasting discharge energy regimes. Additionally, the impoundments have appreciably reduced the tidal prism by at least 50%. Consequently, vast geomorphologic changes have occurred including the development of five new barrier islands. In order to assess the impacts of these modifications, 19 vibracores were obtained throughout the estuary. The dispersal and accumulation of sediment was evaluated utilizing 210 Pb and 137 Cs radioisotope geochronology of 6 cores. Average sediment accumulation rates range from 2.19 cm yr − 1 adjacent to the first constructed dam to as high as 6.55 cm yr − 1 in the middle region of the estuary. These high rates are further supported by comparison of bathymetric survey data from 1985 to 2009. Laser diffraction grain size analyses and X-radiographs revealed distinctive changes associated with dam construction, and correlation of events between cores conveys the episodic sedimentation corresponding to floodgate releases. Ultimately, anthropogenic alterations have resulted in a shift from a tide-dominated to a wave-dominated estuary. The increase in sediment trapping efficiency that has ensued resulting from extensive coastal construction provides the basis for reevaluating traditional facies models for estuaries. A conceptual model is developed here to characterize the alterations in sediment depositional patterns according to relative discharge energy of the adjacent floodgate.

Characterising the distribution and morphology of creeks and pans on salt marshes in England and Wales using Google Earth

By using Google Earth images and simple morphometric analyses, pan and creek characteristics of salt marshes across England and Wales have been mapped and related to key environmental variables, including tidal range, sea level change, coastal configuration, sediment type and erosion state. Pan density was found to be higher on the west coast or where there is a moderate tidal range and low sea level change. Pan density is also higher on back barrier and drowned valley marshes and when creek density is low. Maximum pan size is partly controlled by pan density. Creek density and sinuosity showed great variability between areas with marshes in the south having a higher creek density. Creek density is related to tidal prism and marshes undergoing high rates of sea level change usually have higher creek densities. Marshes with an upstream configuration (embayment, drowned valley and back barrier) have lower creek densities due to a lower tidal prism. Sediment type also plays a role with lower creek densities found on coarser sediment types. Creek sinuosity seems to be largely controlled by tidal range with higher sinuosities on meso- or macro-tidal marshes. This large-scale, Google Earth-based, analysis of the distribution and likely environmental controls on salt marsh morphometry illustrates the utility of Digital Globes as sources of freely-available, high resolution imagery for geomorphological research.

Salinity variations in the Venice Lagoon, Italy: Results from the SIOSED Project, May 2005–February 2007

As a component of the Scripps Institution of Oceanography Sediment Research Project (SIOSED) in the Venice Lagoon, we studied the variability of the salinity regime with time at three principal locations in the south-central part of the Lagoon. We carried out measurements of salinity near the bottom of the Lagoon at these stations, as well as measurements of the chloride concentrations of the sedimentary pore fluids with depth into the sediments. The principal aim of these combined studies was to examine the relationship between the chloride contents of the overlying waters with those in the pore fluids. Salinity variations were measured several times over month-long periods during the SIOSED program. Occasionally these measurements overlapped with the taking of sediment cores from which pore fluids were extracted for studies of interstitial water chemistry.Generally chloride concentrations in the upper 2–4cm of the sediments reflected the average chlorides in the overlying water column, estimated from average salinities measured over the sites of the cores, notwithstanding the short-term variability of the salinities as a function of tidal currents. Chloride concentration-depth profiles are interpreted in terms of exchange with overlying waters as well as in terms of potential influences of underlying aquifers. Though cores were taken at a higher frequency than the salinity measurements, we feel justified to use this data set together with the pore fluid data in recording the time change in chlorides of the near-bottom waters of two major SIOSED sites from May 2005 through February 2007.Results provide a better understanding of the salinity dynamics of the Venice Lagoon, and revealed that deep pore water gradients in salinity likely reflect diffusive exchange with underlying freshwater aquifers. These findings highlight the need for additional long cores, and will guide subsequent geochemical investigations of the Lagoon. Indications of the influences of aquifers on pore waters will help prevent misinterpretation of pore water trends as indications of gradual changes in the salinity of the tidal prism over time.

Exchange Between an Estuary and an Intertidal Marsh and Slough

The hydrodynamic characteristics of small, intertidal perimeter habitats make flushing and residence times in these environments difficult to quantify using conventional approaches. The flooding and draining of intertidal shallows surrounding small perimeter sloughs result in large volume changes relative to total system volume during each tidal cycle. In such environments, an Eulerian framework of flushing and residence time may not be the best approach for quantifying tidal exchange; thus, alternative approaches should be considered in analyzing hydrodynamic exchange in small perimeter habitats. In this study, the results of applying such an approach to a small intertidal perimeter slough in South San Francisco Bay are presented. Previous work has shown that hydrodynamic exchange in an estuarine system can be analyzed by making Eulerian measurements of hydrodynamic fluxes and binning them according to salinity and temperature classes, thus providing a quasi-Lagrangian method of analyzing exchange and transport in an estuarine system. We apply a method which uses this approach to estimate the volumetric exchange ratio M, which is used to estimate the tidal exchange within an estuary during each tidal cycle. We find that the estimation of volumetric exchange ratios and the calculation of hydrodynamic residence times in estuarine systems can be complicated by mixing conditions associated with very strong tidal forcing, particularly in small-volume systems such as small perimeter sloughs, where the tidal prism can be on the scale of or greater than the total system volume.

Groundwater–surface water exchange in a mangrove tidal creek: Evidence from natural geochemical tracers and implications for nutrient budgets

Assessing submarine groundwater discharge (SGD) in mangroves can be challenging due to the complex, heterogeneous nature of sediments and temporally dynamic water flows. Here, we use natural tracers (i.e., radon and radium isotopes) to quantify groundwater–surface water exchange in a mangrove tidal creek at the ecosystem scale, and to assess whether SGD was a source of dissolved inorganic and organic nutrients to the nearby estuary. Hourly sampling for over 27h in the winter and 30h in the summer revealed clear tidal trends for 222Rn, 224Ra, 223Ra, 226Ra, dissolved oxygen, ammonium, and dissolved organic nitrogen (DON) in a mangrove tidal creek with no upstream freshwater inputs (Kangaroo Island, Southern Moreton Bay, Australia). Nitrate, phosphate and dissolved organic phosphorus (DOP) did not show a clear tidal trend. A mass balance revealed that 5–12% of the tidal prism volume infiltrated the sediments and drained back to the creek at low tide. Groundwater exchange accounted for nearly all the ammonium and about 30% of the DON exported by the creek. Crab burrows were a major factor influencing groundwater exchange in this tidal creek. A detectable 226Ra (half-life of 1600years) enrichment in the creek at low tide could only be explained by the construction of new crab burrows during each tidal cycle exposing old sediments. Overall, the concentration of groundwater tracers and nutrients was higher in the summer most likely due to increased crab activity and organic matter degradation in the warmer months. Respiration of belowground organic matter apparently released nitrogen to groundwater seeping out from the creek bank at low tide and increased N:P ratios of surface water draining from mangroves. Therefore, we hypothesize that outwelling from mangroves with high SGD may influence the composition of downstream biological communities by altering estuarine N or P limitation conditions.

Experimental and numerical study of the hydrodynamics of the western sector of Ria Formosa

Jacob, J., Cardeira, S., Rodrigues, M., Bruneau, N., Azevedo, A., Fortunato, A.B., Rosa, M. and Cravo, A., 2013. Experimental and numerical study of the hydrodynamics of the western sector of Ria Formosa.The western sector of Ria Formosa, a lagoon system in the south of Portugal, represents approximately 90% of the total tidal prism of the lagoon and includes three inlets. Two sets of field campaigns to characterize the hydrodynamics of this sector in neap and spring tide conditions were conducted in the autumn of 2011 and spring 2012. The main findings related to the inlets hydrodynamics and water exchanges between the lagoon and the ocean along semi-diurnal tidal cycles are presented. To estimate the relative contribution of the three inlets to the water exchanges between Ria Formosa and the ocean, discharges were evaluated hourly along complete neap and spring semi-diurnal tidal cycles and the tidal prisms computed. In addition, two sea level time series measured in Faro-Olhão inlet and Faro commercial pier were harmonically analyzed. The results were compared with previous studies and used to validate the ELCIRC hydrodynamic model. This model provided additional information about the circulation and tidal prisms and distortion inside the western Ria Formosa. This study confirmed the Faro-Olhão inlet as the main inlet in terms of contribution for the total tidal prism. It is shown that the Ancão inlet lost hydraulic efficiency, contributing less than 6% to the total tidal prism in all situations and the Armona inlet gained efficiency in spring tide and lost efficiency in neap tide. Moreover, the Faro-Olhão inlet exhibits flood prisms higher than ebb prisms under neap and spring tides, suggesting a residual circulation towards the Ancão and Armona inlets.

Influence of morphological changes in a lagoon flooding extension: case study of Ria de Aveiro (Portugal)

Lopes, C.L., Plecha, S., Silva, P.A., and Dias, J.M., 2013. Influence of morphological changes in a lagoon flooding extension: case study of Ria de Aveiro (Portugal) In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)Coastal lagoons are interface zones where land, water and atmosphere interact in a dynamic balance that is constantly being changed by natural and human influence. The hydrodynamics and morphology of these coastal systems continuously adapt to changes in the forcing agents and show a complex interconnection. Worldwide studies show that tidal propagation is strongly dependent on local morphologic features. Attending to these concerns, the present study aims to assess the changes in flooding extension at Ria de Aveiro, as well as in the tidal prism, induced by local morphological modifications. The analysis of the topo-hydrography available for the Ria de Aveiro, comprising two general surveys carried out in 1987/88 and 2011 and two updates of the inlet bathymetry performed in 2001 and 2012, shows the deepening of the lagoon main channels and of the inlet evolving region. A flooding assessment of the lagoon margins and the determination of the tidal prism were performed applying the hydrodynamic model ELCIRC considering the four morphologic configurations described and different tidal conditions. The numerical results show the importance of lagoon morphological changes, which induce an increase of about 16% between 1987/88 and 2012 in the lagoon flooded area for spring tide. The new flooded regions correspond to the margins of S.Jacinto channel head and lagoon central areas. Additionally, the tidal prism results evidence a redistribution of the water volume flowing into the lagoon among their main channels during the period under analysis.