Yoshio Hatada

A STOCHASTIC TYPHOON MODEL AND ITS APPLICATION TO THE ESTIMATION OF EXTREMES OF STORM SURGE AND WAVE HEIGHT

A study of alternatives including a shoreline evolution numerical modelization has been carried out in order to both diagnose the erosion problem at the beaches located between Cambrils Harbour and Pixerota delta (Tarragona, Spain) and select nourishment alternatives.

A LONG TERM WAVE HINDCAST SYSTEM USING ECMWF WINDS

Detailed studies have been undertaken to assist in the design of major extensions to the port of Haifa. Both numerical and physical model studies were done to optimise the mooring conditions vis a vis the harbour approach and entrance layout. The adopted layout deviates from the normal straight approach to the harbour entrance. This layout, together with suitable aids to navigation, was found to be nautically acceptable, and generally better with regard to mooring conditions, on the basis of extensive nautical design studies.Hwa-Lian Harbour is located at the north-eastern coast of Taiwan, where is relatively exposed to the threat of typhoon waves from the Pacific Ocean. In the summer season, harbour resonance caused by typhoon waves which generated at the eastern ocean of the Philippine. In order to obtain a better understanding of the existing problem and find out a feasible solution to improve harbour instability. Typhoon waves measurement, wave characteristics analysis, down-time evaluation for harbour operation, hydraulic model tests are carried out in this program. Under the action of typhoon waves, the wave spectra show that inside the harbors short period energy component has been damped by breakwater, but the long period energy increased by resonance hundred times. The hydraulic model test can reproduce the prototype phenomena successfully. The result of model tests indicate that by constructing a jetty at the harbour entrance or building a short groin at the corner of terminal #25, the long period wave height amplification agitated by typhoon waves can be eliminated about 50%. The width of harbour basin 800m is about one half of wave length in the basin for period 140sec which occurs the maximum wave amplification.Two-stage methodology of shoreline prediction for long coastal segments is presented in the study. About 30-km stretch of seaward coast of the Hel Peninsula was selected for the analysis. In 1st stage the shoreline evolution was assessed ignoring local effects of man-made structures. Those calculations allowed the identification of potentially eroding spots and the explanation of causes of erosion. In 2nd stage a 2-km eroding sub-segment of the Peninsula in the vicinity of existing harbour was thoroughly examined including local man-induced effects. The computations properly reproduced the shoreline evolution along this sub-segment over a long period between 1934 and 1997.In connection with the dredging and reclamation works at the Oresund Link Project between Denmark and Sweden carried out by the Contractor, Oresund Marine Joint Venture (OMJV), an intensive spill monitoring campaign has been performed in order to fulfil the environmental requirements set by the Danish and Swedish Authorities. Spill in this context is defined as the overall amount of suspended sediment originating from dredging and reclamation activities leaving the working zone. The maximum spill limit is set to 5% of the dredged material, which has to be monitored, analysed and calculated within 25% accuracy. Velocity data are measured by means of a broad band ADCP and turbidity data by four OBS probes (output in FTU). The FTUs are converted into sediment content in mg/1 by water samples. The analyses carried out, results in high acceptance levels for the conversion to be implemented as a linear relation which can be forced through the origin. Furthermore analyses verifies that the applied setup with a 4-point turbidity profile is a reasonable approximation to the true turbidity profile. Finally the maximum turbidity is on average located at a distance 30-40% from the seabed.

A REGRESSION MODEL FOR ESTIMATING SEA STATE PERSISTENCE

A special reflecting wall 12 m long and 2.1 m high was built off the beach at Reggio Calabria, and 30 wave gauges were assembled before the wall and were connected to an electronic station on land. It was possible to observe the reflection of wind waves generated by a very stable wind over a fetch of 10 Km. The experiment aimed to verify the general closed solution for the wave group mechanics (Boccotti, 1988, 1989), for the special case of the wave reflection.Significant features on Wadden Sea wave climate are evaluated in respect of the state of the art. Main emphasis was laid on an analysis of the governing boundary conditions of local wave climate in island sheltered Wadden Sea areas with extensions being sufficient for local wind wave growth. Explanatory for significant wave heights a reliable parametrization of local wave climate has been evaluated by using generally available data of water level and wind measurements.

Estimating Wave Height Distributions in the Seto Inland Sea, Ise Bay and Tokyo Bay of Japan Generated by 3 Giant Typhoons in the Showa Era

Shallow water wave hindcastings are conducted in the Seto Inland Sea, Ise Bay and Tokyo Bay for each of the so-called 3 giant typhoons in the Showa Era (Muroto Typhoon in 1934, Makurazaki Typhoon in 1945 and Isewan Typhoon in 1959). The computations follow the spatial distribution of time-dependent wave height and maximum value. The sea wind distributions given as the driving forces are estimated using a method which transforms the land-based measurement wind data into the wind data at sea or coastal stations and applies a spatial interpolation technique to the data. The main conclusion is that any of the typhoons may have generated the largest wave height over the past 90 years in the sea area of the typhoon path.

Trend and Jump Analyses of Winds Speeds and Wave Heights Based on Their Long-Term Hindcasts in the Inner Sea Areas of Japan Using Measurement Data of Sea Level Pressure

Hourly wind distributions on 3 regional sea areas which include the Kanto Sea Area, Ise Bay and the Seto Inland Sea are estimated using the measurement data of sea level pressure around the areas over a 45-year period form 1961 to 2005, after which a 45-year wave hindcasting is conducted station by station. For monthly- and yearly-highest 1/3-averaged wind speeds and wave heights, hindcasts are in reasonable agreement with measurements. Trend and jump analyses for yearly-highest 1/3-averaged atmospheric pressures, wind speeds and wave heights yield the following results : 1) Pressure does not exhibit any trend or jump. 2) Both wind speed and wave height show a statistically significant increasing trend and positive jump putting a pivotal year at around 1986, and their intensities become weaker toward the western area.

A Long-Term Wave Hindcast System in Quasi-Closed Sea Areas

This paper presents a wave hindcast system for estimating climatic characteristics of waves over 23 years at an arbitrary point in a quasi-closed basin that is partly connected to an open ocean such as the Seto Inland Sea. A data set of hourly over-sea wind distribution is made using measured wind data acquired at many coastal and sea stations. A wave computation at each of the wave measurement stations is conducted using a backward ray tracing wave model on a grid with high spatial resolution. Comparison between calculated and measured wave data shows that the system yields a reasonable estimate of long-term wave characteristics and that the present system has a higher ability in a long-term wave estimation than previous systems.

INTERCOMPARISON OF EXTREME VALUE ANALYSES FOR CENSORED ANNUAL MAXIMUM SAMPLE

Accuracy of parameter estimation methods to be used in extreme value analyses for censored annual maximum samples is investigated using a Monte-Carlo simulation technique. The methods are maximum likelihood method (MLM), least square method (LSM) and partial probability weighted moment (PPWM) method, and probability distributions are Gumbel, shape parameter-fixed GEV and Weibull distributions. MLM yields more efficient estimates of quantiles than PPWM method and LSM even for censored samples. MLM-, LSM- and PPWM-based models are applied to extreme value analyses to several types of censored in-situ annual maximum samples. One finding is that inclusion of historical information in MLM- and PPWM-based models produces more efficient estimates of quantiles.

A System for Estimating Wave Climate and Wave Extremes Based on 20-Year Wave Hindcast and Its Verification at the Measurement Stations around Japanese Coasts

A long-term wave hindcast system which consists of the ECMWF wind data sets over a period of 20 years from 1979 to 1998 and a shallow water wave model based on backward ray tracing is applied to the estimation of year-long waves at each of almost all measurement stations deployed around the coasts of Japan. Comparison between 2-3 hourly measurement and hindcast is made for a time series of waves, wave climate parameters of each month or over the whole period, their climatic change and extreme wave height. One main finding is that the system is very useful not only for a proper evaluation of the wave climate and its interannual change but also for a first guess of the return wave height with confidence interval at any coastal location around Japan directly facing the open sea, particularly on the Japan Sea coasts. INTRODUCTION Proper and efficient estimation of long-term wave climate and wave extremes at any location in the coastal sea areas is an indispensable step for the analysis of the coastal process related to wave-induced sediment transport and the design of coastal defense facilities. Hatada et al. (2000) have established a long-term wave hindcast system for estimating wave climate over more than several years around the coasts of Japan, in which the analysis surface wind data sets provided by ECMWF (European Centre for Medium-range Weather Forecasts) are used. But a hindcast period of 8 to 13 years is too short to properly evaluate climatic change of wave conditions and wave extremes. Now the ECMWF analysis and reanalysis surface wind data sets over more than 20 years since 1979 have been released to the public domain. 1 Research Assistant, Department of Civil and Environmental Engineering, Faculty of Engineering, Ehime University, Bunkyocho 3, Matsuyama 790-8577, Ehime Prefecture, Japan, hatada@en2.ehimeu.ac.jp 2 Professor, Department of Civil and Environmental Engineering, Faculty of Engineering, Ehime University, Bunkyocho 3, Matsuyama 790-8577, Ehime Prefecture, Japan, myamag@en2.ehime-u.ac.jp

ESTIMATION OF TYPHOON-GENERATED MAXIMUM WAVE HEIGHT ALONG THE PACIFIC COAST OF JAPAN BASED ON WAVE HINDCASTING

A special reflecting wall 12 m long and 2.1 m high was built off the beach at Reggio Calabria, and 30 wave gauges were assembled before the wall and were connected to an electronic station on land. It was possible to observe the reflection of wind waves generated by a very stable wind over a fetch of 10 Km. The experiment aimed to verify the general closed solution for the wave group mechanics (Boccotti, 1988, 1989), for the special case of the wave reflection.Significant features on Wadden Sea wave climate are evaluated in respect of the state of the art. Main emphasis was laid on an analysis of the governing boundary conditions of local wave climate in island sheltered Wadden Sea areas with extensions being sufficient for local wind wave growth. Explanatory for significant wave heights a reliable parametrization of local wave climate has been evaluated by using generally available data of water level and wind measurements.

APPLICABILITY OF A NEW HYBRID PARAMETRIC WAVE PREDICTION MODEL

Tanah Lot Temple is situated in Tabanan Regency - Bali, on the coast of the Indonesian Ocean. Due to continuous wave attack, wind force, and weathering of the rock bank where the Temple stands, abrasion has occured which is more and more threatening the existence of the Temple. Considering that Tanah Lot Temple is a sacred place for the Hindu Balinese people and a place of high cultural value, and also an important tourism, steps to save the Temple are imperative. The Central as well as the Regional Authorities, and also the Bali nese community are very much interested in the effort to keep the Temple intact. Measures have been undertaken to protect both the seaside and land-side banks of the Temple rock bank. This paper only discusses counter measures of the sea —side bank of the Temple.