Surge Interaction Research Articles

A framework for holistic designs of power line systems based on lessons learned from Super Typhoon Haiyan

Climate Change results in possible less frequent but more intensified storm events that include so called “super typhoons”. To ensure the resilience of the energy power delivery systems, this paper offers lessons learned from forensic investigations of the damaged power delivery systems from the Philippines after the 2013 Super Typhoon Haiyan. The objective is to investigate new strategies to design the power delivery systems, especially in the coastal regions, to defend against the intensified storm events brought on by climate change. A critical review of current power line system design approach, especially load design based on ASCE 7–10, is conducted. The review along with extreme loading calculations revealed limitations in current design philosophies. A design framework using a holistic approach that includes a strong backbone line system is suggested. The strong backbone line system is to be designed for extreme loading scenario with additional considerations including debris loading, wind-storm surge interactions and local geospatial condition with multiple wind directions. Preliminary design of a strong backbone system for McClellanville, South Carolina, power supply scenario is presented as a case study and is shown to be economically viable.

Simulation of Typhoon-Induced Storm Tides and Wind Waves for the Northeastern Coast of Taiwan Using a Tide–Surge–Wave Coupled Model

The storm tide is a combination of the astronomical tide and storm surge, which is the actual sea water level leading to flooding in low-lying coastal areas. A full coupled modeling system (Semi-implicit Eulerian-Lagrangian Finite-Element model coupled with Wind Wave Model II, SELFE-WWM-II) for simulating the interaction of tide, surge and waves based on an unstructured grid is applied to simulate the storm tide and wind waves for the northeastern coast of Taiwan. The coupled model was driven by the astronomical tide and consisted of main eight tidal constituents and the meteorological forcings (air pressure and wind stress) of typhoons. SELFE computes the depth-averaged current and water surface elevation passed to WWM-II, while WWM-II passes the radiation stress to SELFE by solving the wave action equation. Hindcasts of wind waves and storm tides for five typhoon events were developed to validate the coupled model. The detailed comparisons generally show good agreement between the simulations and measurements. The contributions of surge induced by wave and meteorological forcings to the storm tide were investigated for Typhoon Soudelor (2015) at three tide gauge stations. The results reveal that the surge contributed by wave radiation stress was 0.55 m at Suao Port due to the giant offshore wind wave (exceeding 16.0 m) caused by Typhoon Soudelor (2015) and the steep sea-bottom slope. The air pressure resulted in a 0.6 m surge at Hualien Port because of an inverted barometer effect. The wind stress effect was only slightly significant at Keelung Port, contributing 0.22 m to the storm tide. We conclude that wind waves should not be neglected when modeling typhoon-induced storm tides, especially in regions with steep sea-bottom slopes. In addition, accurate tidal and meteorological forces are also required for storm tide modeling.

Coastal Inundation Research:An overview of the Process

Coastal inundation is the flooding of coastal zone resulting from increased river discharge, spring tides, severe storms, or generation of powerful waves from tectonic activity (tsunami). This article discusses the critical factors that contribute to coastal inundation. Among the probable factors that cause coastal flooding and destruction, storm surge is the most frequent, and hence this article provides a detailed evaluation of the progress made in storm inundation research. Recent advances in coastal inundation modelling include efforts to understand the nonlinear dynamic interaction of near-shore waves, wind and atmospheric pressure with still water sea level and coastal currents, and their combined effects on storm surge along the coast and interaction with coastal morphology. An advanced storm-surge model comprises different modules, viz. an atmospheric component, and two ocean components for surge and wave simulations; these modules are coupled with each other. The nesting of regional coastal model with an ocean-wide model captures the far-field boundary forcing of extreme events that usually originate from the warm open ocean. Even though significant advancements reported on the efficiency and accuracy of storm surge and inundation prediction, further studies are required to understand the nonlinear interaction of storm surge with coastal landforms and their vegetation (land cover). In the context of rising sea level, increased tropical cyclone activity and rapid shoreline change, it is pertinent to evaluate the future flooding risk associated with landfall of tropical cyclones in densely populated coastal cities.

Impact of the interaction of surge, wave and tide on a storm surge on the north coast of Vietnam

In the present paper, the interaction of surge, wave and tide on the north coast of Vietnamis assessed using a coupled model of surge, wave and tide. A series of storm surge simulations for Typhoons Frankie (1996) andWashi (2005) are carried out, considering the effects of the tide and the wave that combines a wave dependent drag and wave-induced radiation stress to find out a predominant factor in the storm surge generation. Typhoon Frankieis landfalled at the low tide while TyphoonWashi landfalled at the high tide. The results indicate that the effect of the wave is crucial to the storm surge simulation. In particular, the wave induced-surge improves the accuracy of the storm surge level up to 30 %. It also shows that the surge induced by wave radiation stress is dependant with the space resolution, and the finest resolution is improved and in close agreement with the observation. On the other hand, the influence of the tide is ignorable for the case of Typhoon Frankie and considerable in the case of Typhoon Washi.

Characteristics of river flood and storm surge interactions in a tidal river in Rhode Island, USA

During a hurricane event, heavy rainfall can cause storm runoff and river flood. In tidal rivers, hurricane induced storm surge can increase the river downstream boundary water levels. The interactions of storm-induced rainfall runoff and storm surge in tidal rivers may cause more severe flood during hurricane events. In this study, hydrodynamic model simulations were conducted to characterize the interactions of rainfall runoff and storm surge in a tidal river in Rhode Island, USA. River floods under scenarios with and without storm surge were compared.

Dynamics of wave–current–surge interactions in Lake Michigan: A model comparison

Wave, storm surge dynamics, and wave–current–surge interactions (WCSI) were investigated by applying a pair of unstructured-grid-based models to Lake Michigan under two strong wind events. The effects of wind field sources, wind drag coefficient bulk formula, and parameterizations of the bottom friction term were explored to understand lake dynamics. Two wave models were calibrated by using alternative wave physics settings under the 2011 northeasterly wind event. Forced by the southwesterly wind event in 2013, the calibrated models using the atmosphere–ocean fully coupled Climate Forecast System Version 2 wind field were further validated. It is found that the northwesterly winds induced 0.57m setup near the southwestern coast, whereas the southwesterly winds produced 0.28m setup and –0.43m setdown near the northern and southwestern coasts, respectively. The WCSI mostly influence waves and storm surge in shallow-water areas near coasts and islands through depth-induced breaking, current-induced frequency shift and refraction, and wave-induced setup/setdown through wave radiation stress. Owing to the adoption of different discretization algorithms and bottom friction formulations, the modeled storm surge and waves exhibit some variation between the paired models. Even though the storm surge difference with and without WCSI is smaller than that between the two WCSI-coupled models, both circulation models adopt WCSI considering their consistent improvement on model accuracy under both wind events. The analysis of water transport indicates that wind speed, direction, and coastal geometry and bathymetry are also important factors in storm surge.

Assessment of Storm Surge along the Coast of Central Vietnam

ABSTRACT Thuy, N.B.; Kim, S.; Chien, D.D.; Dang, V.H.; Cuong, H.D.; Wettre, C., and Hole, L.R., 2017. Assessment of storm surge along the coast of central Vietnam. In the present paper, the interaction of surge, wave, and tide along the coast of central Vietnam is assessed using a coupled model of surge, wave, and tide. A series of storm surge simulations for Typhoons Xangsane (2006), Ketsana (2009), and Nary (2013) are carried out, considering the effects of tides and waves that combines wave-dependent drag and wave-induced radiation stress to find a predominant factor in storm surge generation. The results indicate that the surge–wave interaction is crucial to the storm surge simulation in this area. In particular, the wave-dependent drag improves an accuracy of the storm surge level up to 30%. In addition, the radiation stress contributes up to 15%. However, the tide–surge interaction is negligible because there is less than 2% difference in results with and without the tide. A series of coupled surge ...

In this issue of Weather

The October 2016 issue of Weather begins on p. 241 with ‘A test of visibility sensors at Hong Kong International Airport’ by Pak-Wai Chan. Visibility is one of three observed features of weather that are significant to aviation, so the choice of a reliable accurate sensor, able to reproduce visibility as observed by humans – at least when obscurity removes our ability to see objects 10km or less away – is essential. There has been much development in both transmissometers and forward-scatter meters to measure visibility in recent years and this paper provides useful insight into relative performance that can be applied in many situations. On p. 247, we take our annual look at the duration of snow patches on English and Welsh mountains in 2016. Iain Cameron demonstrates that the mild weather of last winter meant that most snow in these countries disappeared relatively quickly. The factors that affect school attendance in sub-Saharan Africa are complex and manifold. Weather and its variability are key elements, as shown by Joseph Adejuwon in ‘Effect of climate variability on school attendance: a case study of Zamfara State in the semi-arid zone of Nigeria’ on p. 248. Next, we move on to an examination of ‘Tide–surge interaction in the Persian Gulf, Strait of Hormuz and the Gulf of Oman’. These interactions, associated with areas of low pressure, have a significant effect on shipping through the narrow Strait of Hormuz, used by a wide range of shipping, not least tankers carrying oil and gas from the oil fields of the Middle East. On p. 262, Sulafa Hag-elsafi and Manahil El-Tayib examine the inter-annual variability of the rainfall of Saudi Arabia in ‘Spatial and statistical analysis of rainfall in the Kingdom of Saudi Arabia from 1979 to 2008’. Their study shows no clear pattern in the distribution of rainfall, although much of the country receives and average of more than 150mm yr–1 and the highest values are usually found in the mountainous southwest. Ending a bumper issue, our last paper looks at ‘A train of cloud heads associated with multiple cold fronts’ on 5 and 6 February 2016. This short paper by David Smart and Keith Browning provides good revision of this form of mid-latitude weather system and its significance on p. 267.

A shallow water model for computing water level due to tide and surge along the coast of Bangladesh using nested numerical schemes

A vertically integrated shallow water model is developed for computing water levels due to the nonlinear interaction of tide and surge associated with some storms that hit the coast of Bangladesh. Emphasis is given on the investigation of tide generating forces for the purpose of increasing accuracy in water levels due to a storm. Offshore islands of the whole coastal belt along with the complex land–sea interface is modeled via stair step because of the application of a rectangular grid. Nested numerical schemes are exercised in this study to save computational cost. Appropriate tidal regime over the model domain is generated by forcing the sea level to be oscillatory with the constituent M2 along the southern open boundary of the parent model omitting wind stress and tide generating forces. The previously generated tidal regime is introduced as the initial state of the sea for the nonlinear interaction of tide and surge. The model is applied to estimate water levels at different coastal and island locations of Bangladesh associated with the two recent storms AILA and SIDR that hit the coast of Bangladesh. The results simulated by the model are found to be satisfactory with observed data and reported results obtained through various investigations.

Development of Tide–Surge Interaction Model for the Coastal Region of Bangladesh

In this paper, a two-dimensional, vertically integrated hydrodynamic model is developed taking into account entrained air bubbles during storm surges as well as incorporating inverted barometer, and river and land dynamics. The model is specifically designed for the coastal region of Bangladesh. A nested scheme method with a fine mesh scheme (FMS), capable of incorporating the complex coastline and all major offshore islands accurately, nested into a coarse mesh scheme (CMS) covering up to 15° N latitude in the Bay of Bengal is used. To incorporate the small and big offshore islands in the Meghna estuarine region with its complex coastline accurately, a very fine mesh scheme (VFMS) is again nested into the FMS. Along the northeast corner of the VFMS, the Meghna river discharge is taken into account. The coastal and island boundaries are approximated through proper stair steps. The model equations are solved by a semi-implicit finite difference technique using a staggered C-grid. A stable appropriate tidal condition over the model domain is generated by applying tidal forcing with the four major tidal constituents M2, S2, K1, and O1 along the southern open boundary of the CMS. This tidal regime is introduced as the initial state of the sea for nonlinear interaction of tide and surge. The model is applied to simulate water levels due to the interaction of tide and surge associated with the cyclones April 1991 and Aila at different coastal and island locations along the coast of Bangladesh. The results are found to be quite satisfactory with root mean square error of ∼0.50 m as calculated for both the storm events. Tests of sensitivities on water levels are carried out for air bubbles, offshore islands, river discharge, inverse barometer, and grid resolution. The presence of air bubbles increases simulated water levels a little bit in our model, and the contribution of air bubbles in increasing water level is found around 2 %. Further, water levels are found to be influenced by offshore islands, river discharge, inverse barometer as well as grid resolution.

Study on the storm surges induced by cold waves in the Northern East China Sea

Cold wave, a kind of severe weather system, can bring strong wind and induce significant sea level rise to the Northern East China Sea. Based on CFSR data, the study shows the monthly distributions of invaded days and the spatiotemporal distributions of cold-wave wind direction and wind speed. A three-dimensional numerical model (ROMS) was developed to study storm surges induced by cold waves. The role of wind direction, wind speed, wind duration, extratropical cyclone and tide–surge interaction is investigated by conducting different sensitivity experiments. The results indicate that storm surges mainly happen at the coasts perpendicular to the wind directions. Surge range and time lag are related to the geometry of the basin and the continental shelf. The response of the sea-level fluctuations to cold wave indicates that there is a positive correlation between crests and wind speed, a negative correlation between troughs and wind speed, but no obvious correlations to wind duration. Coupled weather cold waves, which yield a larger range and a multi-peak structure of surges, can be classified according to cold wave tracks and extratropical cyclones. The tide–surge interaction has an obvious and different effect on the magnitudes and phases of storm surges for different tidal stages.

Determination of extreme sea levels along the Iberian Atlantic coast

Extreme sea levels along the Atlantic Iberian coast are determined through the development and application of a numerical model for tides and surges, followed by a statistical analysis of the model results. A recent statistical method is assessed using 131 years of data from the Brest tide gauge, and the number of years of data required for an accurate statistical analysis is estimated. The statistical method is extended to consider tide–surge interactions, but they are shown to be small in the study region. The model covers a large portion of the NE Atlantic, with a 250m resolution in the Portuguese shelf. In the Iberian shelf, root mean square errors of tides are of the order of 5cm, and extreme sea levels are underestimated by about 10cm. Differences between sea level statistics obtained from model output and observations are of the order of 5cm in the study region. Simulation of tides and surges between 1980 and 2010, followed by a statistical analysis of the results, provide the extreme levels along the Iberian Atlantic coast for different return periods. Results reveal the increase of extreme sea levels from south to north and the importance of local effects.

Analyzing the physics of non-tidal barotropic sea level anomaly events using multi-scale numerical modelling in Singapore regional waters

The hydrodynamic flows in the Singapore regional waters (SRW) are the result of a complex mix of tide, seasonal and meteorological effects. The study of non-tidal effects or sea level anomalies (SLA) in this region has shown that it is possible to model some of these anomalies. The present study addresses the non-tidal barotropic water levels and currents in the Singapore region in detail. This analysis includes a multi-scale approach, and addresses amongst others hydrodynamic model grid resolution and the importance of resolving non-linear tide–surge interaction. The results show that the water level and current anomalies phenomena in a complex region like SRW can be effectively modelled using an approach combining non-tidal barotropic and multi-scale numerical modelling. A detailed investigation of the levels of non-linear tide–surge interaction is carried out by simulating SLA events in the Singapore regional waters during North-East (positive SLA) and South-West (negative SLA) monsoons based on ECMWF numerical weather forcing conditions. The results of combining both approaches suggest that the finer grid resolution improves the accuracy of water level and current anomalies simulations. Furthermore, the results also indicate that for the simulations of non-tidal barotropic flows in this area, non-linear tide–surge interaction is important and should be taken into account. Finally, the behaviour of the non-tidal barotropic flow in the region and its changes with tidal variation in the shallow region of the Singapore Strait is now much better understood. Therefore, for reliable operational forecast of sea level, the inclusion of non-linear tide–surge interaction should be required in numerical models to reproduce both tides and surges with improved accuracy in this region.

Rangia cuneata clam decline in Lake Pontchartrain from 2001 to 2014 due to an El Niño Southern Oscillation shift coupled with a period of high hurricane intensity and frequency

The clam, Rangia cuneata, occurs in low salinity zones of Atlantic and Gulf of Mexico estuaries. Prior to 2001, it was abundant in Lake Pontchartrain, a large and shallow oligohaline estuary, located north of New Orleans. However, density abruptly decreased by 96% after an extreme drought from an El Nino Southern Oscillation (ENSO) shift (1998—2000). Stable higher salinities resulted in the establishment of higher salinity communities. The hooked mussel, Ischadium recurvum, increased abruptly and colonized live R. cuneata. Competition from I. recurvum and the R. cuneata decline occurred at the end of the drought, despite a decrease in salinity. After the drought, there was a period of high hurricane intensity and frequency which stifled clam recovery. Their densities remained relatively low due to declines from hurricane disturbances in 2005, 2008 and 2012. In 2014, after two years without severe hurricane effects, density and biomass recovered to baseline years (1954 and 1997). Barrier island erosion caused by Hurricane Georges in 1998 and adverse effects of the ENSO drought on wetlands may have set the stage for increased effects of subsequent hurricanes. High relative sea level rise, wetland loss and erosion of barrier islands, which occurred with each successive storm, potentially increased the size of surges. Surges resuspended sediments which buried clams and abruptly increased salinity and lowered dissolved oxygen. Salinity stratification persisted after storms and caused hypoxia in bottom waters. Storm surge interactions with discharges from the Bonnet Carre Spillway, a Mississippi River flood diversion structure, and the MRGO, a ship channel, also exacerbated hurricane effects.

Applying POT methods to the Revised Joint Probability Method for determining extreme sea levels

Newly exposed concepts of POT declustering (Bernardara et al., 2014) within the GPD-Poisson model are applied to the joint probability of tide and surge for determining extreme sea levels, as a variation of the Revised Joint Probability Method (RJPM, Tawn and Vassie, 1989). A mixture model is proposed for the meteorological residual (surge) component with a non-parametric (empirical) density for the bulk values and parametric models for both the lower and upper tails. In particular, a distinction is made between values observed at regular time steps, called sequential values, and the clusters of extreme values, or events, on which the statistical extrapolations are performed. The sea level distribution is obtained by convolution of the tide and surge density functions. Confidence intervals are also proposed. This model is applied to the case study of Brest, France using both hourly and high water values. Two methods for handling tide–surge interaction are presented and discussed and a comparison with a direct approach is made.

Implementation of method of lines to predict water levels due to a storm along the coastal region of Bangladesh

In this study, the method of lines (MOL) has been applied to solve two-dimensional vertically integrated shallow water equations in Cartesian coordinates for the prediction of water levels due to a storm surge along the coast of Bangladesh. In doing so, the partial derivatives with respect to the space variables were discretized by the finite difference (central) method to obtain a system of ordinary differential equations (ODEs) with time as independent variable. The classical fourth-order Runge–Kutta method was used to solve the obtained system of the ODEs. We used a nested finite difference scheme, where a high resolution fine grid model (FGM) capable of incorporating all major islands along the coastal region of Bangladesh was nested into a coarse grid model (CGM) covering up to 15°N latitude of the Bay of Bengal. The boundaries of the coast and islands were approximated through proper stair step. Appropriate tidal condition over the model domain was generated by forcing the sea level to be oscillatory with the constituent M 2 along the southern open boundary of the CGM omitting wind stress. Along the northeast corner of the FGM, the Meghna River discharge was taken into account. The developed model was applied to estimate water levels along the coast of Bangladesh due to the interaction of tide and surge associated with the April 1991 storm. We also computed our results employing the standard finite difference method (FDM). Simulated results show the MOL performs well in comparison with the FDM with regard to CPU time and stability, and ensures conformity with observations.

Investigating River–Surge Interaction in Idealised Estuaries

Maskell, J.; Horsburgh, K.; Lewis, M., and Bates, P., 2014. Investigating river–surge interaction in idealised estuaries.A finite volume model (FVCOM) was used to investigate the combined influence of storm surge and river flow on floodplain inundation on the basis of idealized estuary test cases. The combined influence of storm surge and river discharge typical of extremes in estuary systems in Britain (up to 2 m and 1500 m3 s−1) was found to induce interactions that lead to increases in the nontidal residual elevation of up to 0.35 m. However, the extent of the inundation was found to be mainly controlled by the surge elevation. Exceeding the threshold of the up-estuary channel capacity was found to cause a nonlinear increase in the area of the nontidal inundation for any given peak river discharge, after which the rate of increase in inundation area as the surge height increases declines and is determined by the slope of the floodplain. This threshold is determined by the surge elevation with exception of the highest peak river discharges, where the surge elevation threshold is lowered. It was also found that the extent of the interactions and inundation were highly dependent on the geometry of the estuary and the timing of the surge with respect to peak river discharge, in particular the slope of the floodplain and at such times where the river discharge was similar in magnitude to that of the surge and the tide. After calibration an idealized estuary based in the LISFLOOD-FP code, using a simplified form of the two-dimensional (2D) shallow-water equations, was found to simulate the area of maximum inundation to a similar extent as the FVCOM model (based on the full 2D shallow-water equations) with a much reduced computation time. This paper highlights the potential advantages that simplified 2D inundation models may have for simulating estuarine flooding due to combined surge and river discharge, where surge–river interaction due to momentum exchange is insignificant in determining the flood extent and simplified equations capture the dominant hydrological drivers of coastal inundation.

Bay of Bengal cyclone extreme water level estimate uncertainty

Accurate estimates of storm surge magnitude and frequency are essential to coastal flood risk studies. Much research has focused on tide–surge interaction and joint probability techniques to combine multiple cyclone characteristics. In the Bay of Bengal, extreme water levels are derived from numerical storm surge models based on an idealised cyclone event; however, uncertainty within such calculations for this region is poorly understood, especially when propagated through to the flood hazard. We use the IBTrACs data set to estimate natural variability in four key parameters used to describe an idealised cyclone and create a set of idealised but equally likely “1 in 50 year” recurrence interval cyclone events. Each idealised cyclone is then used to force a storm surge model to give predicted peak water levels along the northern Bay of Bengal coast. Finally, extreme water level uncertainty is propagated through an inundation model to predict flood extent and depth over inland coastal floodplains. The descriptive parameters of 18 cyclone events (between 1990 and 2008) appear to show no statistically significant variation (at the 5 % level) due to landfall location, which allows us to pool characteristics for the entire Bay of Bengal. We find that the natural variability of cyclone parameters translates into large uncertainty both for storm surge height (of the order of metres) and for coastal inundation (hundreds of km2). Using the variability estimates for a 1-in-50-year cyclone event making landfall at the 2007 Sidr location, cyclone central pressure drop uncertainty had the greatest effect upon simulated storm surge magnitude. However, uncertainty within cyclone track characteristics (track speed, landfall and genesis location) has greater influence on subsequent inundation extent. Storm surge hazard uncertainty due to cyclone parameter variability was found to be comparable to the inundation difference simulated when the peak surge coincided with either a mean spring high or low water. Our research indicates the importance of improving extreme water level estimates along the Bay of Bengal coastline for robust flood hazard management decisions in the Bay of Bengal.

Storm surge and tidal interaction in the Tjeldsund channel, northern Norway

The aim of this study is to investigate tide–surge interaction in narrow channels with complex and relatively shallow topography. A high-resolution depth-integrated tidal and storm surge model has been implemented for the Tjeldsund channel which is an important sailing lane in northern Norway. A horizontal grid resolution down to 50 m is applied in order to represent the complex bottom topography and the formation of jets and small-scale eddies. Two typically storm surge events in December 2004 have been examined in detail. The tide–surge interaction is found to influence the generation of higher harmonics and the formation of eddies in the current field. In some cases, the magnitude of storm surge currents may reach the same magnitude as the tidal currents enhancing the formation of jets and eddies.

Improved water-level forecasting for the Northwest European Shelf and North Sea through direct modelling of tide, surge and non-linear interaction

In real-time operational coastal forecasting systems for the northwest European shelf, the representation accuracy of tide–surge models commonly suffers from insufficiently accurate tidal representation, especially in shallow near-shore areas with complex bathymetry and geometry. Therefore, in conventional operational systems, the surge component from numerical model simulations is used, while the harmonically predicted tide, accurately known from harmonic analysis of tide gauge measurements, is added to forecast the full water-level signal at tide gauge locations. Although there are errors associated with this so-called astronomical correction (e.g. because of the assumption of linearity of tide and surge), for current operational models, astronomical correction has nevertheless been shown to increase the representation accuracy of the full water-level signal. The simulated modulation of the surge through non-linear tide–surge interaction is affected by the poor representation of the tide signal in the tide–surge model, which astronomical correction does not improve. Furthermore, astronomical correction can only be applied to locations where the astronomic tide is known through a harmonic analysis of in situ measurements at tide gauge stations. This provides a strong motivation to improve both tide and surge representation of numerical models used in forecasting. In the present paper, we propose a new generation tide–surge model for the northwest European Shelf (DCSMv6). This is the first application on this scale in which the tidal representation is such that astronomical correction no longer improves the accuracy of the total water-level representation and where, consequently, the straightforward direct model forecasting of total water levels is better. The methodology applied to improve both tide and surge representation of the model is discussed, with emphasis on the use of satellite altimeter data and data assimilation techniques for reducing parameter uncertainty. Historic DCSMv6 model simulations are compared against shelf wide observations for a full calendar year. For a selection of stations, these results are compared to those with astronomical correction, which confirms that the tide representation in coastal regions has sufficient accuracy, and that forecasting total water levels directly yields superior results.