scholarly journals MODELING SURGE-DEPENDENT VEGETATION EFFECTS ON HURRICANE-GENERATED WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 67 ◽  
Author(s):  
Qin Chen ◽  
Haihong Zhao ◽  
Don Liu
Keyword(s):  
Energy Dissipation ◽  
Storm Surge ◽  
Reduction Rate ◽  
Wave Model ◽  
Water Levels ◽  
Marsh Vegetation ◽  
Vegetation Effects ◽  
Vegetation Height ◽  
The Impact ◽  
Surge Height

The study utilizes a coupled wave-surge-vegetation modeling system to quantify the effects of salt marsh vegetation on hurricane-generated waves. The wave model incorporates the energy dissipation model of Chen and Zhao (2012) for random waves over vegetation. The storm surge model incorporates the vegetal drag for both rigid and flexible types of vegetation. The surge and wave models with the vegetation effects are coupled, allowing the spatially and temporally varying vegetation heights, water levels and depth-averaged currents from the storm surge model to be fed into the wave model. Numerical experiments have revealed that vegetation can change the surge height and a storm surge can change the vegetation height. Both control the wave reduction rate in flooded wetlands. The impact of vegetation on hurricane-generated waves consists of indirect and direct effects. The former is caused by the changes in surge height due to vegetation. The latter comes from the direct interaction between vegetation and the oscillatory motion of surface waves. It has been found that flexible marsh vegetation deflects under the hydrodynamic force produced by a hurricane. The deflected height not only reduces the flow resistance in the surge model, but also decreases the energy dissipation caused by vegetation in the wave model. Consequently, neglecting plant flexibility may lead to overestimates of vegetation effects and exaggeration of wetland potential for flood risk reduction.

Wave Effects on the Storm Surge Simulation: A Case Study of Typhoon Khanun

2016 ◽  
Vol 11 (5) ◽  
pp. 964-972 ◽  
Author(s):  
Fuchun Lai ◽  
◽  
Luying Liu ◽  
Haijiang Liu ◽  
◽  
...  
Keyword(s):  
Storm Surge ◽  
Flow Model ◽  
Coupled Model ◽  
Wave Model ◽  
Model Tests ◽  
Storm Events ◽  
Wave Effects ◽  
Near Shore ◽  
Wave Induced ◽  
Surge Height

To study wave effects on storm surge, a depth-averaged 2D numerical model based on the Delft3D-FLOW model was utilized to simulate near-shore hydrodynamic responses to Typhoon Khanun. The Delft3D-WAVE model is coupled dynamically with the FLOW model and the enhanced vertical mixing, mass flux and wave set-up were considered as wave-current interaction in the coupled model. After verifying storm surge wind and pressure formulae of storm surge and optimizing calibration parameters, three numerical tests with different control variables were conducted. Model tests show that wave effects must be considered in numerical simulation. Simulating the flow-wave coupled model showed that wave-induced surge height could be as large as 0.4 m in near-shore areas for Typhoon Khanun. Comparing to its contribution to the peak surge height, wave-induced surge plays a more significant role to total surge height with respect to the time-averaged surge height in storm events. Wave-induced surge (wave setup) is in advance of typhoon propagation and becomes significant even before the typhoon landfall. Model tests demonstrate that the wave effects are driven predominantly by the storm wave, while the boundary wave contribution is rather limited.

scholarly journals INVESTIGATION OF WAVE INDUCED STORM SURGE WITHIN A LARGE COASTAL EMBAYMENT - MORETON BAY (AUSTRALIA)

2011 ◽  
Vol 1 (32) ◽  
pp. 22 ◽  
Author(s):  
Philip Treloar ◽  
David Taylor ◽  
Paul Prenzler
Keyword(s):  
Water Level ◽  
Tropical Cyclones ◽  
Storm Surge ◽  
Wave Model ◽  
Water Levels ◽  
Residual Water ◽  
Storm Tide ◽  
Moreton Bay ◽  
Coastal Embayment ◽  
Set Up

Moreton Bay is a large coastal embayment on the south-east Queensland coast which is surrounded by the urbanised areas of greater Brisbane on its western and southern shorelines. It is protected from the open coast by a number of islands, including South Stradbroke, North Stradbroke and Moreton Islands. Tropical cyclones occasionally track far enough south to cause significant damage to south-east Queensland due to flooding, winds, waves and elevated ocean water levels. Distant tropical cyclones which may be several hundred kilometres north of Moreton Bay have been known to cause storm surge, high waves and erosion inside Moreton Bay. These events generally do not generate gale force winds within Moreton Bay, but can generate large ocean swell waves. It has been identified that the wave conditions generated from distant cyclones can cause a variation in water levels inside Moreton Bay. A detailed study was undertaken to investigate the regional wave set-up process which affects Moreton Bay. The simulation of the residual water levels within Moreton Bay using a coupled hydrodynamic and wave model system developed for this study is considerably more accurate than applying a hydrodynamic model alone and explains water level anomalies that have a tidal frequency. The paper discusses the physical process of regional wave set-up inside a large embayment, analysis of observed residual water level and also the modelling study undertaken to quantify the influence of waves on storm tide levels inside Moreton Bay. The storm tide hazard study for the Moreton Bay Councils included the effects of regional wave set-up in the specification of design water levels.

scholarly journals Impact Assessment of a Major River Basin in Bangladesh on Storm Surge Simulation

2018 ◽  
Vol 6 (3) ◽  
pp. 99
Author(s):  
Md. Abdul Al Mohit ◽  
Masaru Yamashiro ◽  
Noriaki Hashimoto ◽  
Md. Bodruddoza Mia ◽  
Yoshihiko Ide ◽  
...  
Keyword(s):  
River System ◽  
Water Levels ◽  
Open Boundary ◽  
Sea Levels ◽  
Junction Area ◽  
Coupled Numerical Model ◽  
Tidal Condition ◽  
Major River ◽  
The Impact ◽  
Surge Height

A two-dimensional bay and river coupled numerical model in Cartesian coordinates was developed to find the impact of the river on the simulated water levels associated with a storm along the coast of Bangladesh. The shallow water models developed for both the bay and river were discretized by the finite difference method with forward in time and central in space. The boundaries for the coast and islands were approximated through proper stair steps representation and solved by a conditionally stable semi-implicit manner on a staggered Arakawa C-grid. A one-way nested scheme technique was used in the bay model to include coastal complexities as well as to save computational costs. A stable tidal condition was made by forcing the sea levels with the most energetic tidal constituent, M2, along with the southern open boundary of the bay model omitting wind stress. The developed model was then applied to foresee the sea-surface elevation associated with the catastrophic cyclone of 1991 and cyclone MORA. A comparative study of the water levels associated with a storm was made through model simulations with and without the inclusion of the river system. We found that the surge height in the bay-river junction area decreased by 20% and the surge height reduced by about 3–8% outside the junction area from this study. The obtained results were found to have a satisfactory similarity with some of the observed data.

scholarly journals Storm surge and wave simulations in the Gulf of Mexico using a consistent drag relation for atmospheric and storm surge models

2012 ◽  
Vol 12 (7) ◽  
pp. 2399-2410 ◽  
Author(s):  
D. Vatvani ◽  
N. C. Zweers ◽  
M. van Ormondt ◽  
A. J. Smale ◽  
H. de Vries ◽  
...  
Keyword(s):  
Wind Speed ◽  
Gulf Of Mexico ◽  
Drag Coefficient ◽  
Storm Surge ◽  
Weather Prediction ◽  
Surface Wind ◽  
Wave Model ◽  
Water Levels ◽  
Observation Data ◽  
Wave Effects

Abstract. To simulate winds and water levels, numerical weather prediction (NWP) and storm surge models generally use the traditional bulk relation for wind stress, which is characterized by a wind drag coefficient. A still commonly used drag coefficient in those models, some of them were developed in the past, is based on a relation, according to which the magnitude of the coefficient is either constant or increases monotonically with increasing surface wind speed (Bender, 2007; Kim et al., 2008; Kohno and Higaki, 2006). The NWP and surge models are often tuned independently from each other in order to obtain good results. Observations have indicated that the magnitude of the drag coefficient levels off at a wind speed of about 30 m s−1, and then decreases with further increase of the wind speed. Above a wind speed of approximately 30 m s−1, the stress above the air-sea interface starts to saturate. To represent the reducing and levelling off of the drag coefficient, the original Charnock drag formulation has been extended with a correction term. In line with the above, the Delft3D storm surge model is tested using both Charnock's and improved Makin's wind drag parameterization to evaluate the improvements on the storm surge model results, with and without inclusion of the wave effects. The effect of waves on storm surge is included by simultaneously simulating waves with the SWAN model on identical model grids in a coupled mode. However, the results presented here will focus on the storm surge results that include the wave effects. The runs were carried out in the Gulf of Mexico for Katrina and Ivan hurricane events. The storm surge model was initially forced with H*wind data (Powell et al., 2010) to test the effect of the Makin's wind drag parameterization on the storm surge model separately. The computed wind, water levels and waves are subsequently compared with observation data. Based on the good results obtained, we conclude that, for a good reproduction of the storm surges under hurricane conditions, Makin's new drag parameterization is favourable above the traditional Charnock relation. Furthermore, we are encouraged by these results to continue the studies and establish the effect of improved Makin's wind drag parameterization in the wave model. The results from this study will be used to evaluate the relevance of extending the present towards implementation of a similar wind drag parameterization in the SWAN wave model, in line with our aim to apply a consistent wind drag formulation throughout the entire storm surge modelling approach.

The impact of sea level rise on storm surge water levels in the northern part of the German Bight

2015 ◽  
Vol 96 ◽  
pp. 118-131 ◽  
Author(s):  
A. Arns ◽  
T. Wahl ◽  
S. Dangendorf ◽  
J. Jensen
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
German Bight ◽  
Water Levels ◽  
The Impact

scholarly journals Forecasting Storm Surge and Inundation: Model Validation

2017 ◽  
Vol 32 (6) ◽  
pp. 2045-2063 ◽  
Author(s):  
Jayaram Veeramony ◽  
Andrew Condon ◽  
Maarten van Ormondt
Keyword(s):  
Storm Surge ◽  
Stress Gradient ◽  
Forecast Model ◽  
High Water ◽  
Water Levels ◽  
Ocean Dynamics ◽  
Radiation Stress ◽  
Near Shore ◽  
The Impact ◽  
Inundation Model

Abstract Coastal regions are increasingly vulnerable to damage from storm surge and inundation. Delft3D is used by the Naval Oceanographic Office to model the ocean dynamics in the near shore. In this study, the performance of Delft3D in predicting the surge and inundation during Hurricane Ike, which impacted the northern Gulf of Mexico in September 2008, is examined. Wave height, water level, and high-water mark comparisons with a number of observations confirm that the model does well in predicting the surge and inundation during extreme events. The impact of using forecast winds based on the best-track data as opposed to hindcast winds is also investigated, and it is found that the extent of inundation is represented reasonably well with the forecast winds. In Delft3D, waves can be coupled to the hydrodynamic component using the radiation stress gradient method or the dissipation method. Comparing the results of using the two shows that for low-resolution grids such as that needed for a forecast model the dissipation method works better at reproducing the water levels and inundation.

scholarly journals Sea-State-Dependent Momentum Fluxes for Ocean Modeling

2007 ◽  
Vol 37 (11) ◽  
pp. 2714-2725 ◽  
Author(s):  
Øyvind Saetra ◽  
Jon Albretsen ◽  
Peter A. E. M. Janssen
Keyword(s):  
Sea Level ◽  
Storm Surge ◽  
Ocean Circulation ◽  
Circulation Model ◽  
Wave Model ◽  
Sea State ◽  
Surface Stresses ◽  
State Dependent ◽  
Momentum Fluxes ◽  
The Impact

Abstract The impact of wave-dependent surface stress on the ocean circulation has been studied using surface stresses calculated from a numerical wave model. The main questions to be investigated were what the effect would be on the Ekman currents in the upper ocean and what the impact would be on storm surge predictions. To answer the first question, the response of wave-dependent forcing on an Ekman type of model was studied. Here, the wave forcing was provided by a one-gridpoint version of the wave model. Second, the impact of the waves was studied with a three-dimensional ocean circulation model for the North Sea. Three different experiments were performed for a period of 1 yr. To test the effect on the storm surge signal, the results have been compared with sea level observations from 22 stations along the Norwegian and Dutch coasts. One of the main findings is that calculating stresses in the wave model, thereby introducing sea-state-dependent momentum fluxes, has a strong positive impact on the storm surge modeling compared with applying a traditional parameterization of surface stresses from the 10-m wind speed. When all cases with sea level deviation from the mean of less than 0.5 m were removed, the root-mean-square error for 1 yr averaged over all stations was reduced by approximately 6 cm. Splitting the momentum budget into an Eulerian and a wave part (Stokes drift) has only a negligible effect on the modeling of the sea surface elevation but increases the angular turning of the Eulerian surface drift to the right of the wind direction with an angle of about 4°.

scholarly journals EFFECTS OF STORM SURGE ON WATER LEVELS OF THE LAGOON SYSTEM OF JACAREPAGUÁ – RIO DE JANEIRO, BRAZIL

2018 ◽  
pp. 16
Author(s):  
Monica F.Y. Buckmann ◽  
Laura Aguilera ◽  
Paulo Cesar C. Rosman
Keyword(s):  
Sea Level ◽  
Storm Surge ◽  
Water Levels ◽  
Time Lags ◽  
Tidal Prism ◽  
Lagoon System ◽  
Maximum Elevation ◽  
Maximum Water ◽  
Water Elevations ◽  
The Impact

The Lagoon System of Jacarepaguá is the most vulnerable coastal area of Brazil due to its high population density and important economic activities. Severe meteorological conditions due to climate changes are more likely to affect the lagoon system in the future, increasing the exposure of the area and the probability of flooding of the low-lying surrounding areas. To determine the vulnerability of the area to diverse agents, this work addressed the impact of different combinations of sea level rise, heavy rainfall and storm surges. The study cases considered two different bathymetry conditions, the actual silting bathymetry, and the resulting bathymetry after a planned dredging project. Tidal prism, the maximum water elevations and the time of occurrence were analyzed. The main results showed that storm surge has the most impact on the maximum water elevations, overcoming the impact of an increase in the sea level, river flow and changes in bathymetry. The results of time lags comparing the time of occurrence of maximum elevation recorded at the open sea and the time of occurrence of maximum elevation on the north margin, the most populated area, of the lagoon system showed a time lag of 13-17h. The benefits of the planned dredging project would be mostly to allow a better water renovation in the lagoons, due to a higher tidal prism.

scholarly journals Sea level rise and its impact on storm surge and tide in Shanghai

MAUSAM ◽  
2021 ◽  
Vol 48 (4) ◽  
pp. 541-554
Author(s):  
ZENGHAO QIN
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Dynamic Models ◽  
Spring Tide ◽  
Water Levels ◽  
Ground Subsidence ◽  
Past Century ◽  
The Mean ◽  
The Impact

Based on both the historical tidal gauge and ground subsidence records for the seven stations in Shanghai region, a non-linear statistical model fitting the variation of the mean annual eustatic sea level (ESL) is established to reveal the characteristics of the ESL in the past century and to estimate the mean annual relative sea level (RSL) in the next five decades by the model extrapolation for Shanghai region. The estimated values of the sea level rises are assessed to be fairly reasonable. The impact of the estimated sea level rise in the coming decades on the storm surges and tides in Shanghai region is numerically computed by using the two-dimensional nonlinear storm surge and tide dynamic models. In addition, on the basis of numerical integration of the same dynamic model, the probable maximum water levels resulting from the RSL in the coming decades are also estimated by the probable optimal combination of the track, intensity, landfall site, incident angle of tropical cyclone and spring tide.  

Tidal Management: Consequences for the Salt-Marsh Vegetation1

1984 ◽  
Vol 16 (1-2) ◽  
pp. 79-86 ◽  
Author(s):  
A M Groenendijk
Keyword(s):  
Salt Marsh ◽  
Seed Germination ◽  
Storm Surge ◽  
Plant Species ◽  
High Water ◽  
Water Levels ◽  
Complete Control ◽  
Tolerant Species ◽  
Negative Effect ◽  
The Impact

The construction of a storm-surge barrier in the mouth of the Eastern Scheldt will allow complete control of the tidal conditions in the estuary. In order to indicate the limiting conditions for tidal management for the plant species, a number (10) of the most prominent salt-marsh angiosperms were tested for their tolerance against elongated inundation times of 2, 4 and 8 days. Criteria such as: die back, regrowth, generative development and seed germination were measured. The results indicate that for the majority of salt-marsh angiosperms a prolonged inundation is not likely to cause immediate die back. Only the species from the higher reaches of the marsh are severely affected by the impact of the barrier closure at high water levels. All species involved show a decreasing immersion tolerance with increasing water temperatures, with a subsequent die back of the less tolerant species. In contrast with the vegetative parts of the species, the inflorescences suffer an overall severe negative effect from prolonged immersions. This leads to the conclusion that prolonged summer inundations have to be avoided as much as possible.

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