DOCSLIB.ORG

Coastal Processes 1

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Coastal Processes 1 The University of the West Indies Organization of American States PROFESSIONAL DEVELOPMENT PROGRAMME: COASTAL INFRASTRUCTURE DESIGN, CONSTRUCTION AND MAINTENANCE A COURSE IN COASTAL ZONE/ISLAND SYSTEMS MANAGEMENT CHAPTER 3 COASTAL PROCESSES 1 By PATRICK HOLMES, PhD Professor, Department of Civil and Environmental Engineering Imperial College, London Organized by Department of Civil Engineering, The University of the West Indies, in conjunction with Old Dominion University, Norfolk, VA, USA and Coastal Engineering Research Centre, US Army, Corps of Engineers, Vicksburg, MS , USA. Antigua, West Indies, June 18-22, 2001 THE PURPOSE OF COASTAL ENGINEERING RETURN ON CAPITAL INVESTMENT BENEFITS: Minimised Risk of Coastal Flooding - reduced costs and disruption to services in the future. Improved Environment, Preserve Beaches - visual, amenity, recreational…... COSTS: Construction costs & disruption during construction. Costs linked to avoidance of risks. (e.g., higher defences, higher costs, including visual/access impacts, but lower risks) ORIGINS OF COASTAL PROBLEMS 1. Define the Problem. • This needs to be based on sufficiently reliable INFORMATION and requires a DATA BASE. For example, is the beach eroding or is it just changing in shape seasonally and appears to have eroded after stormier conditions? Beaches change from “winter” to “summer” profiles quite regularly. • Many coastal problems result from incorrect previous engineering “solutions”. The sea is powerful and “cheap” solutions rarely work well. • If the supply of sand to a beach is cut off or reduced it will erode because beaches are always dynamic. It is a case of the balance between supply to versus loss from a given area. •A DATA BASE need not be extensive but in some cases information is essential and there is a COST involved. •A photographic record of a coastal area - photographs taken at the same locations at the same times of the year - is cheap and very helpful. More extensive data bases need surveys and other measurements, with increasing costs. STEPS TOWARDS A SOLUTION 2. A FEASIBILITY STUDY. • The size of the study is linked to the size of the problem. • Defines/sketches the options for a solution in sufficient detail to give an order of magnitude of the potential costs. • Indicates the availability of expertise and materials needed. • Provides a basis for discussion with and decisions of the client. MARINE “FORCES” TIDES: • Regular and predictable because they are generated by the attractions of the Moon and the Sun acting on the oceans. [High tide to Low tide ≈ Low tide to High tide, typically 6 hours and 26 minutes, but modified by the local land masses and coastal shape.] WAVES: • Generated by winds blowing over the ocean surface. Therefore they are not regular - they are RANDOM. This leads to the need to design for EXTREME EVENTS. STORM SURGES: • Increases in Mean Sea Level also generated by the wind, therefore also RANDOM. WATER LEVELS AND MOTIONS Mean Sea Level - Increasing due to Global Warming (+0.5m by 2050?) Tides - Moon and Sun, Regular and Predictable. “Spring Tides” “Neap Tides” - due to the changing influence of the moon and the sun every two weeks higher tides, Springs, and alternate two weeks lower tides, Neaps. HIGHEST ASTRONOMICAL TIDE MEAN SEA LEVEL LOWEST ASTRONOMICAL TIDE HIGHEST ASTRONOMICAL TIDE H.A.T. • Easily found by examining one year’s predicted tidal heights for the site and selecting the highest predicted level. This will be accurate to within a few millimeters. • It may be necessary to measure tide levels at a site to relate them to predicted tidal levels and times at the nearest port for which predictions are available. • It would also be useful to note L.A.T. -Lowest Astronomical Tide - indicates the width of a beach at low tide etc. • Levels MUST be related to the land-based vertical datum use for the design. LAND-BASED FACTORS WHAT LAND-BASED FACTORS CONTROL THE DESIGN? COASTAL ACTIVITIES Agriculture Fisheries Forestry Commerce Transport Tourism Infrastructure Environment Special Sites Sand/coral Mining Waste-water Disposal Quantify Scale and Economic Importance WINDS AND WAVES WINDS - variable in speed and direction, seasonal. IMPORTANCE: Wind Loading. Wind-induced “SET-UP” of the sea surface. Wave Generation. EXTREMES - as design criteria “Return Period” - usually 50 years for design of coastal structures, the “50 year Return Period” WIND INDUCED STORM SURGE WIND SHEAR FORCE ON THE WATER SURFACE WATER SURFACE SLOPES UPWARDS IN RESPONSE “STORM SURGE” Set up is related to the SQUARE of the wind speed - more extreme winds create a much larger set up the FIFTY YEAR RETURN PERIOD. EXTREME EVENTS Similar Extrapolation for Extreme Winds. 100 Design Return Period 50 years. 10 50 year Design 1 Wave, H = 6.2m Return Period (Years) Period Return One year’s data 0 0 2.0 4.0 6.0 8.0 Wave Height (m) WAVES UNIFORM WAVES - SAME HEIGHT AND SAME LENGTH Speed (m/s) Height (m) Length (m) Sea Bed Wave Period = Time between successive waves (seconds) Typically a 10 second wave will travel at 15 m/s. in deep water. Its length in deep water will be 156m. WAVES RANDOM WAVES different heights and lengths. Average Wave Height; Significant Wave Height [HS] (m) etc….. Highest Wave Height; (!) Zero Crossing Wave Period [TZ] (seconds) WAVES FOR DESIGN Record waves for Three hours and calculate Hs and Tz for each record Eight records per day, 2920 records per year. (with luck!) STATISTICAL analysis to predict EXTREME WAVE CONDITIONS. WAVE DIRECTION - a critical parameter for coastal engineering Can be measured but often has to be derived from wind data. MINIMUM OF ONE YEAR’S DATA REQUIRED [TAOS Wave Predictions for the Caribbean] WAVES IN SHALLOW WATER CHANGE: HEIGHT, DIRECTION AND (EVENTUALLY) BREAK SHOALING: BREAKING H1 H2 H2 > H1 REFRACTION: SPREADING FOCUSSING HH HB HH > HB SHORELINE WAVES : SURF ZONE AND BEACH BREAKING: WHEN THE WATER DEPTH EQUALS THE WAVE HEIGHT (APPROX.) Hb db ≈ Hb db SURF AND SWASH: MAXIMUM RUN-UP SURF ZONE - SWASH ZONE OVERTOPPING BROKEN WAVES FLOODING ! BACKWASH SEDIMENT TRANSPORT ON COASTS UNI-DIRECTIONAL FLOW: FLOW SUSPENDED LOAD BED LOAD WAVE-INDUCED TRANSPORT: q WAVES OFF qOUT SEDIMENT qIN qSHORE ALONGSHORE TRANSPORT ∆ q = qIN + qOUT + qSHORE + qOFF EFFECTS OF COASTAL STRUCTURES A POCKET BEACH: q = 0 q = 0 STABLE BEACH BARRIERS: (OFTEN MAN-MADE!) SUPPLY BLOCKED BY HARBOUR EROSION ACCRETION NET DIRECTION OF SEDIMENT MOTION BEACH CONTROL STRUCTURES GROYNES: BY-PASSING - BY DESIGN INCREASING COMPLEXITY - HIGHER EFFICIENCY ? DETACHED BREAKWATERS: TOMBOLA COAST PROTECTION - SEA WALLS, REVETMENTS WAVE REFLECTION OVERTOPPING REDUCED REFLECTION AND OVERTOPPING ENERGY ABSORBTION POTENTIAL EROSION STABLE FOUNDATIONS WAVE WALL - REDUCED STABLE CREST OVERTOPPING ROCK ARMOUR SLOPE FILTER LAYER TOE STABLILITY TOE STABILITY ARMOUR: NATURAL ROCK (BLENDS), MAN-MADE UNITS (ARTIFICIAL) BEACH NOURISHMENT VOLUME TO BE ADDED PER UNIT LENGTH OF BEACH Y x h = Ax2/3 NEW PROFILE h ORIGINAL PROFILE CONCEPT OF EQUILIBRIUM PROFILE FOR A GIVEN SAND DIAMETER 1. IF IMPORTED SAND DIAMETER = NATIVE SAND DIAMETER THE PROFILES WILL BE IDENTICAL. 2. IF IMPORTED SAND DIAMETER > NATIVE SAND DIAMETER THE NEW PROFILE WILL BE STEEPER, THE BEACH WILL BE MORE STABLE AND A LOWER VOLUME OF SAND WILL BE NEEDED. [NOTE: TOO STEEP - DANGEROUS FOR BATHING!] 3. COUPLE WITH MEASURES TO CONTROL SAND LOSS ALONGSHORE. BREAKWATERS BEACH, BERTH AND MOORING PROTECTION ARMOUR LAYER W OVERTOPPING UNDERLAYER W/2 TO W/20 FILTER LAYER CREST TOE STABILITY CORE PREVENT LOSS OF FINES FROM THE CORE COAST PROTECTION AS AN OPPORTUNITY 1. PRIMARY PURPOSE: PROTECT AGAINST OVERTOPPING/FLOODING 2. FACTORS: VISUAL INTRUSION ADDED AMENITY - SPORTS LEISURE/SOCIAL ENVIRONMENTAL IMPACT 3. MANAGEMENT: MONITOR 4. DESIGN FOR ENHANCEMENT: SEA LEVEL RISE HIGHER STORMS.
Load more

Recommended publications
  • Part II-1 Water Wave Mechanics
    Chapter 1 EM 1110-2-1100 WATER WAVE MECHANICS (Part II) 1 August 2008 (Change 2) Table of Contents Page II-1-1. Introduction ............................................................II-1-1 II-1-2. Regular Waves .........................................................II-1-3 a. Introduction ...........................................................II-1-3 b. Definition of wave parameters .............................................II-1-4 c. Linear wave theory ......................................................II-1-5 (1) Introduction .......................................................II-1-5 (2) Wave celerity, length, and period.......................................II-1-6 (3) The sinusoidal wave profile...........................................II-1-9 (4) Some useful functions ...............................................II-1-9 (5) Local fluid velocities and accelerations .................................II-1-12 (6) Water particle displacements .........................................II-1-13 (7) Subsurface pressure ................................................II-1-21 (8) Group velocity ....................................................II-1-22 (9) Wave energy and power.............................................II-1-26 (10)Summary of linear wave theory.......................................II-1-29 d. Nonlinear wave theories .................................................II-1-30 (1) Introduction ......................................................II-1-30 (2) Stokes finite-amplitude wave theory ...................................II-1-32
    [Show full text]
  • Waves and Weather
    Waves and Weather 1. Where do waves come from? 2. What storms produce good surfing waves? 3. Where do these storms frequently form? 4. Where are the good areas for receiving swells? Where do waves come from? ==> Wind! Any two fluids (with different density) moving at different speeds can produce waves. In our case, air is one fluid and the water is the other. • Start with perfectly glassy conditions (no waves) and no wind. • As wind starts, will first get very small capillary waves (ripples). • Once ripples form, now wind can push against the surface and waves can grow faster. Within Wave Source Region: - all wavelengths and heights mixed together - looks like washing machine ("Victory at Sea") But this is what we want our surfing waves to look like: How do we get from this To this ???? DISPERSION !! In deep water, wave speed (celerity) c= gT/2π Long period waves travel faster. Short period waves travel slower Waves begin to separate as they move away from generation area ===> This is Dispersion How Big Will the Waves Get? Height and Period of waves depends primarily on: - Wind speed - Duration (how long the wind blows over the waves) - Fetch (distance that wind blows over the waves) "SMB" Tables How Big Will the Waves Get? Assume Duration = 24 hours Fetch Length = 500 miles Significant Significant Wind Speed Wave Height Wave Period 10 mph 2 ft 3.5 sec 20 mph 6 ft 5.5 sec 30 mph 12 ft 7.5 sec 40 mph 19 ft 10.0 sec 50 mph 27 ft 11.5 sec 60 mph 35 ft 13.0 sec Wave height will decay as waves move away from source region!!! Map of Mean Wind
    [Show full text]
  • Marine Forecasting at TAFB Scott.Stripling@Noaa.Gov
    Marine Forecasting at TAFB Scott.Stripling@noaa.gov 1 Waves 101 Concepts and basic equations 2 Have an overall understanding of the wave forecasting challenge • Wave growth • Wave spectra • Swell propagation • Swell decay • Deep water waves • Shallow water waves 3 Wave Concepts • Waves form by the stress induced on the ocean surface by physical wind contact with water • Begin with capillary waves with gradual growth dependent on conditions • Wave decay process begins immediately as waves exit wind generation area…a.k.a. “fetch” area 4 5 Wave Growth There are three basic components to wave growth: • Wind speed • Fetch length • Duration Wave growth is limited by either fetch length or duration 6 Fully Developed Sea • When wave growth has reached a maximum height for a given wind speed, fetch and duration of wind. • A sea for which the input of energy to the waves from the local wind is in balance with the transfer of energy among the different wave components, and with the dissipation of energy by wave breaking - AMS. 7 Fetches 8 Dynamic Fetch 9 Wave Growth Nomogram 10 Calculate Wave H and T • What can we determine for wave characteristics from the following scenario? • 40 kt wind blows for 24 hours across a 150 nm fetch area? • Using the wave nomogram – start on left vertical axis at 40 kt • Move forward in time to the right until you reach either 24 hours or 150 nm of fetch • What is limiting factor? Fetch length or time? • Nomogram yields 18.7 ft @ 9.6 sec 11 Wave Growth Nomogram 12 Wave Dimensions • C=Wave Celerity • L=Wave Length •
    [Show full text]
  • Waves and Structures
    WAVES AND STRUCTURES By Dr M C Deo Professor of Civil Engineering Indian Institute of Technology Bombay Powai, Mumbai 400 076 Contact: mcdeo@civil.iitb.ac.in; (+91) 22 2572 2377 (Please refer as follows, if you use any part of this book: Deo M C (2013): Waves and Structures, http://www.civil.iitb.ac.in/~mcdeo/waves.html) (Suggestions to improve/modify contents are welcome) 1 Content Chapter 1: Introduction 4 Chapter 2: Wave Theories 18 Chapter 3: Random Waves 47 Chapter 4: Wave Propagation 80 Chapter 5: Numerical Modeling of Waves 110 Chapter 6: Design Water Depth 115 Chapter 7: Wave Forces on Shore-Based Structures 132 Chapter 8: Wave Force On Small Diameter Members 150 Chapter 9: Maximum Wave Force on the Entire Structure 173 Chapter 10: Wave Forces on Large Diameter Members 187 Chapter 11: Spectral and Statistical Analysis of Wave Forces 209 Chapter 12: Wave Run Up 221 Chapter 13: Pipeline Hydrodynamics 234 Chapter 14: Statics of Floating Bodies 241 Chapter 15: Vibrations 268 Chapter 16: Motions of Freely Floating Bodies 283 Chapter 17: Motion Response of Compliant Structures 315 2 Notations 338 References 342 3 CHAPTER 1 INTRODUCTION 1.1 Introduction The knowledge of magnitude and behavior of ocean waves at site is an essential prerequisite for almost all activities in the ocean including planning, design, construction and operation related to harbor, coastal and structures. The waves of major concern to a harbor engineer are generated by the action of wind. The wind creates a disturbance in the sea which is restored to its calm equilibrium position by the action of gravity and hence resulting waves are called wind generated gravity waves.
    [Show full text]
  • Detection and Characterization of Meteotsunamis in the Gulf of Genoa
    Journal of Marine Science and Engineering Article Detection and Characterization of Meteotsunamis in the Gulf of Genoa Paola Picco 1,*, Maria Elisabetta Schiano 2, Silvio Incardone 1, Luca Repetti 1, Maurizio Demarte 1, Sara Pensieri 2,* and Roberto Bozzano 2 1 Italian Hydrographic Service, passo dell’Osservatorio, 4, 16135 Genova, Italy 2 Institute for the study of the anthropic impacts and the sustainability of the marine environment, National Research Council of Italy, via De Marini 6, 16149 Genova, Italy * Correspondence: paola.picco@persociv.difesa.it (P.P.); sara.pensieri@cnr.it (S.P.) Received: 30 May 2019; Accepted: 10 August 2019; Published: 15 August 2019 Abstract: A long-term time series of high-frequency sampled sea-level data collected in the port of Genoa were analyzed to detect the occurrence of meteotsunami events and to characterize them. Time-frequency analysis showed well-developed energy peaks on a 26–30 minute band, which are an almost permanent feature in the analyzed signal. The amplitude of these waves is generally few centimeters but, in some cases, they can reach values comparable or even greater than the local tidal elevation. In the perspective of sea-level rise, their assessment can be relevant for sound coastal work planning and port management. Events having the highest energy were selected for detailed analysis and the main features were identified and characterized by means of wavelet transform. The most important one occurred on 14 October 2016, when the oscillations, generated by an abrupt jump in the atmospheric pressure, achieved a maximum wave height of 50 cm and lasted for about three hours.
    [Show full text]
  • Deep Ocean Wind Waves Ch
    Deep Ocean Wind Waves Ch. 1 Waves, Tides and Shallow-Water Processes: J. Wright, A. Colling, & D. Park: Butterworth-Heinemann, Oxford UK, 1999, 2nd Edition, 227 pp. AdOc 4060/5060 Spring 2013 Types of Waves Classifiers •Disturbing force •Restoring force •Type of wave •Wavelength •Period •Frequency Waves transmit energy, not mass, across ocean surfaces. Wave behavior depends on a wave’s size and water depth. Wind waves: energy is transferred from wind to water. Waves can change direction by refraction and diffraction, can interfere with one another, & reflect from solid objects. Orbital waves are a type of progressive wave: i.e. waves of moving energy traveling in one direction along a surface, where particles of water move in closed circles as the wave passes. Free waves move independently of the generating force: wind waves. In forced waves the disturbing force is applied continuously: tides Parts of an ocean wave •Crest •Trough •Wave height (H) •Wavelength (L) •Wave speed (c) •Still water level •Orbital motion •Frequency f = 1/T •Period T=L/c Water molecules in the crest of the wave •Depth of wave base = move in the same direction as the wave, ½L, from still water but molecules in the trough move in the •Wave steepness =H/L opposite direction. 1 • If wave steepness > /7, the wave breaks Group Velocity against Phase Velocity = Cg<<Cp Factors Affecting Wind Wave Development •Waves originate in a “sea”area •A fully developed sea is the maximum height of waves produced by conditions of wind speed, duration, and fetch •Swell are waves
    [Show full text]
  • Swell and Wave Forecasting
    Lecture 24 Part II Swell and Wave Forecasting 29 Swell and Wave Forecasting • Motivation • Terminology • Wave Formation • Wave Decay • Wave Refraction • Shoaling • Rouge Waves 30 Motivation • In Hawaii, surf is the number one weather-related killer. More lives are lost to surf-related accidents every year in Hawaii than another weather event. • Between 1993 to 1997, 238 ocean drownings occurred and 473 people were hospitalized for ocean-related spine injuries, with 77 directly caused by breaking waves. 31 Going for an Unintended Swim? Lulls: Between sets, lulls in the waves can draw inexperienced people to their deaths. 32 Motivation Surf is the number one weather-related killer in Hawaii. 33 Motivation - Marine Safety Surf's up! Heavy surf on the Columbia River bar tests a Coast Guard vessel approaching the mouth of the Columbia River. 34 Sharks Cove Oahu 35 Giant Waves Peggotty Beach, Massachusetts February 9, 1978 36 Categories of Waves at Sea Wave Type: Restoring Force: Capillary waves Surface Tension Wavelets Surface Tension & Gravity Chop Gravity Swell Gravity Tides Gravity and Earth’s rotation 37 Ocean Waves Terminology Wavelength - L - the horizontal distance from crest to crest. Wave height - the vertical distance from crest to trough. Wave period - the time between one crest and the next crest. Wave frequency - the number of crests passing by a certain point in a certain amount of time. Wave speed - the rate of movement of the wave form. C = L/T 38 Wave Spectra Wave spectra as a function of wave period 39 Open Ocean – Deep Water Waves • Orbits largest at sea sfc.
    [Show full text]
  • Meteotsunami Occurrence in the Gulf of Finland Over the Past Century Havu Pellikka1, Terhi K
    https://doi.org/10.5194/nhess-2020-3 Preprint. Discussion started: 8 January 2020 c Author(s) 2020. CC BY 4.0 License. Meteotsunami occurrence in the Gulf of Finland over the past century Havu Pellikka1, Terhi K. Laurila1, Hanna Boman1, Anu Karjalainen1, Jan-Victor Björkqvist1, and Kimmo K. Kahma1 1Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland Correspondence: Havu Pellikka (havu.pellikka@fmi.fi) Abstract. We analyse changes in meteotsunami occurrence over the past century (1922–2014) in the Gulf of Finland, Baltic Sea. A major challenge for studying these short-lived and local events is the limited temporal and spatial resolution of digital sea level and meteorological data. To overcome this challenge, we examine archived paper recordings from two tide gauges, Hanko for 1922–1989 and Hamina for 1928–1989, from the summer months of May–October. We visually inspect the recordings to 5 detect rapid sea level variations, which are then digitized and compared to air pressure observations from nearby stations. The data set is complemented with events detected from digital sea level data 1990–2014 by an automated algorithm. In total, we identify 121 potential meteotsunami events. Over 70 % of the events could be confirmed to have a small jump in air pressure occurring shortly before or simultaneously with the sea level oscillations. The occurrence of meteotsunamis is strongly connected with lightning over the region: the number of cloud-to-ground flashes over the Gulf of Finland were on 10 average over ten times higher during the days when a meteotsunami was recorded compared to days with no meteotsunamis in May–October.
    [Show full text]
  • Random Wave Analysis
    RANDOM WA VE ANALYSIS The goal of this handout is to consider statistical and probabilistic descriptions of random wave heights and periods. In design, random waves are often represented by a single characteristic wave height and wave period. Most often, the significant wave height is used to represent wave heights in a random sea. It is important to understand, however, that wave heights have some statistical variability about this representative value. Knowledge of the probability distribution of wave heights is therefore essential to fully describe the range of wave conditions expected, especially the extreme values that are most important for design. Short Term Statistics of Sea Waves: Short term statistics describe the probabilities of qccurrence of wave heights and periods that occur within one observation or measurement of ocean waves. Such an observation typically consists of a wave record over a short time period, ranging from a few minutes to perhaps 15 or 30 minutes. An example is shown below in Figure 1 for a 150 second wave record. @. ,; 3 <D@ Q) Q ® ®<V®®®@@@ (fJI@ .~ ; 2 "' "' ~" '- U)" 150 ~ -Il. Time.I (s) ;:::" -2 Figure 1. Example of short term wave record from a random sea (Goda, 2002) . ' Zero-Crossing Analysis The standard. method of determining the short-term statistics of a wave record is through the zero-crossing analysis. Either the so-called zero-upcrossing method or the zero­ downcrossing method may be used; the statistics should be the same for a sufficiently long record. Figure 1 shows the results from a zero-upcrossing analysis. In this case, the mean water level is first determined.
    [Show full text]
  • Chapter 42 Coupling Stokes and Cnoidal Wave Theories
    CHAPTER 42 COUPLING STOKES AND CNOIDAL WAVE THEORIES IN A NONLINEAR REFRACTION MODEL Thomas A. Hardy1, A.M. ASCE Nicholas C. Kraus2, M. ASCE ABSTRACT An efficient numerical model is presented for calculating the refraction and shoaling of finite-amplitude waves over an irregular sea bottom. The model uses third-order Stokes wave theory in relatively deep water and second-order cnoidal wave theory in relatively shallow water. It can also be run using combinations of lower-order wave theories, including a pure linear wave mode. The problem of the connection of Stokes and cnoidal theories is investigated, and it is found that the use of second-order rather than first-order cnoidal theory greatly reduces the connection discontinuity. Calculations are compared with physical model measurements of the height and direction of waves passing over an elliptical shoal. The finite-amplitude wave model gives better qualitative and quantitative agreement with the measurements than the linear model. INTRODUCTION Wave transformation models are commonly used in coastal engineering projects to provide nearshore wave height and direction. This information is needed at specified grid locations for input into nearshore circulation and shoreline change numerical models. Often, multiple simulations over a wide geographical area are required. Small-amplitude (linear) wave theory is the basis for almost all wave transformation models presently in engineering use. It is well known that finite-amplitude (nonlinear) wave theories predict greater shoaling and less refraction than does small-amplitude theory, and the nearshore wave properties predicted by nonlinear theories are expected to provide an improved description of real waves transforming in shallow water.
    [Show full text]
  • An 8-Yr Meteotsunami Climatology Across Northwest Europe: 2010–17
    APRIL 2021 W I L L I A M S E T A L . 1145 An 8-yr Meteotsunami Climatology across Northwest Europe: 2010–17 a b c a,c DAVID A. WILLIAMS, DAVID M. SCHULTZ, KEVIN J. HORSBURGH, AND CHRIS W. HUGHES a Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom b Department of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom c National Oceanography Centre, Liverpool, United Kingdom (Manuscript received 1 August 2020, in final form 29 November 2020) ABSTRACT: Meteotsunamis are shallow-water waves that, despite often being small (;0.3 m), can cause damage, in- 2 juries, and fatalities due to relatively strong currents (.1ms 1). Previous case studies, modeling, and localized climatol- ogies have indicated that dangerous meteotsunamis can occur across northwest Europe. Using 71 tide gauges across northwest Europe between 2010 and 2017, a regional climatology was made to understand the typical sizes, times, and atmospheric systems that generate meteotsunamis. A total of 349 meteotsunamis (54.0 meteotsunamis per year) were identified with 0.27–0.40-m median wave heights. The largest waves (;1 m high) were measured in France and the Republic of Ireland. Most meteotsunamis were identified in winter (43%–59%), and the fewest identified meteotsunamis occurred in either spring or summer (0%–15%). There was a weak diurnal signal, with most meteotsunami identifications between 1200 and 1859 UTC (30%) and the fewest between 0000 and 0659 UTC (23%). Radar-derived precipitation was used to identify and classify the morphologies of mesoscale precipitating weather systems occurring within 6 h of each meteotsunami.
    [Show full text]
  • Extreme Waves and Ship Design
    10th International Symposium on Practical Design of Ships and Other Floating Structures Houston, Texas, United States of America © 2007 American Bureau of Shipping Extreme Waves and Ship Design Craig B. Smith Dockside Consultants, Inc. Balboa, California, USA Abstract Introduction Recent research has demonstrated that extreme waves, Recent research by the European Community has waves with crest to trough heights of 20 to 30 meters, demonstrated that extreme waves—waves with crest to occur more frequently than previously thought. Also, trough heights of 20 to 30 meters—occur more over the past several decades, a surprising number of frequently than previously thought (MaxWave Project, large commercial vessels have been lost in incidents 2003). In addition, over the past several decades, a involving extreme waves. Many of the victims were surprising number of large commercial vessels have bulk carriers. Current design criteria generally consider been lost in incidents involving extreme waves. Many significant wave heights less than 11 meters (36 feet). of the victims were bulk carriers that broke up so Based on what is known today, this criterion is quickly that they sank before a distress message could inadequate and consideration should be given to be sent or the crew could be rescued. designing for significant wave heights of 20 meters (65 feet), meanwhile recognizing that waves 30 meters (98 There also have been a number of widely publicized feet) high are not out of the question. The dynamic force events where passenger liners encountered large waves of wave impacts should also be included in the (20 meters or higher) that caused damage, injured structural analysis of the vessel, hatch covers and other passengers and crew members, but did not lead to loss vulnerable areas (as opposed to relying on static or of the vessel.
    [Show full text]