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Coastal engineering

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Coastal engineering

  1. 1. P a g e | 350 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry COASTAL ENGINEERING UNIT – 1 1. Define coastal engineering. Coastal engineering is the study of the processes ongoing at the shoreline and construction within the coastal zone. The field involves aspects of near shore oceanography, marine geology, and civil engineering, often directed at combating erosion of coasts or providing navigational access. 2. Define coastal zone. Coastal zone is the interface where the land meets the ocean encompassing shore line environment as well as adjacent coastal waters. Its components can include river deltas, coastal planes, wet lands, beaches, reefs, mangrove forest, lagoons and other coastal features. The coastal zone is divided into four subzones. They are,  Coast  Shore  Shore face  Continental shelf 3. What is meant by coastal regulation zone? Under the Environment Protection Act, 1986 a notification was issued in February, 1991, for regulation of activities in the coastal area by the Ministry of Environment and Forests (MoEF). As per the notification, the coastal land up to 500m from the High Tide Line (HTL) and a stage of 100m
  2. 2. P a g e | 351 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry along banks of creeks, estuaries, backwater and rivers subject to tidal fluctuations, is called the Coastal Regulation Zone(CRZ). CRZ along the country has been placed in four categories. The above notification includes only the inter-tidal zone and land part of the coastal area and does not include the ocean part. The notification imposed restriction on the setting up and expansion of industries or processing plants etc. in the said CRZ. 4. Define coastal area. The coastal area is the land and sea areas bordering the shoreline. 5. Define setback area. A setback area is the strip of land along the coastal zone, where certain development activities are prohibited or significantly restricted. 6. How coastal regulation zone are classified? For regulation of developmental activities, the coastal stretches within 500m of HTL on the landward side are classified into four categories, viz.  Category I (CRZ-I)  Category II (CRZ - II)  Category III (CRZ-III)  Category IV (CRZ-IV) 7. List down the factors influencing coastal topography.  Population pressure  Wastewater disposal  Destruction of mangrooves  Increasing urbanization
  3. 3. P a g e | 352 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry  Solid waste disposal  Coastal constructions  Natural disasters 8. Write down the coastal types.  Cliff coast  Clayey bank coast  Intertidal / muddy coast  Sand dune coast  Sandy coast 9. Define waves. When wind blows over water it exerts a drag on water surface and water by virtue of its fluidity gets disturbed giving rise to waves. Such waves are referred as wind waves or storm waves. Waves are usually defined by their height, length and period. 10.Define tides. Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun, and the rotation of the Earth. 11.Define astronomical tide. The astronomical tide is generated by the rotation of the earth in combination with the varying gravitational impact on the water body of the sun, the moon and the planets. These phenomena cause predictable and regular oscillations in the water level, which is referred to as the tide. The
  4. 4. P a g e | 353 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry astronomical tide at a specific location can be predicted and is published in Tidal Tables. 12.Define tidal flat. Shallow and often muddy, the part of foreshore, which are covered and uncovered by the rise and fall of the tide. As a rule of thumb, a tidal flat normally develops when the relative tidal range RTR, defined as the ratio between the mean spring tidal range and the annual average HS, is higher than 15. 13.What is meant by high tide and low tide? At most places the tidal change occurs twice daily. The tide rises until it reaches a maximum height, called high tide or high water, and then falls to a minimum level called low tide or low water. 14.What are the types of tides?  Diurnal tide  Semi – diurnal tide  Mixed tide 15.Define diurnal tide. In the diurnal tide, only a single high and single low water occur each tidal day. Tides of the diurnal type occur along the northern shore of the Gulf of Mexico, in the Java Sea, the Gulf of Tonkin, and in a few other localities.
  5. 5. P a g e | 354 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 16.Define semi – diurnal tide. In the semidiurnal tide, there are two high and two low waters each tidal day, with relatively small differences in the respective highs and lows. Tides on the Atlantic coast of the United States are of the semidiurnal type. 17.Define mixed tide. In the mixed tide, the diurnal and semidiurnal oscillations are both important factors and the tide is characterized by a large inequality in the high water heights, low water heights, or in both. There are usually two high and two low waters each day, but occasionally the tide may become diurnal. Such tides are prevalent along the Pacific coast of the United States and in many other parts of the world. 18.Define gravity waves. As the wind speed increases, the next stage of waves are gravity waves, named for their restoring force, gravity as the wave height increases, it overcomes surface tension, and is instead dragged back down by gravity. 19.Define tidal waves. It is the combined effect of astronomical and meteorological surges - the popular expression for an unusually high and destructive water level along a shore. The expression of tidal wave also includes the influence of the associated waves. 20.Define progressive waves. If the whole profile moves in the forward direction the wave is a Progressive Wave.
  6. 6. P a g e | 355 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 21.Define sea water waves. If winds of local storm blow towards the shore, the generated waves will reach the beach in nearly the form in which they are generated. Under these conditions, the waves are steep; i.e. the wave length is 10 to 20 times the wave height. Such waves are called sea water waves. 22.What is meant by swell? If waves are generated by a distant storm, they may travel through hundreds or even thousands of miles of calm areas before reaching the shore. Under these conditions, waves decay – short, steep waves are eliminated, and only relatively long low waves reach the shore. Such waves have lengths from 30 to more than 500 times the wave height and are called swell. 23.How wind waves are generated? In fluid dynamics, wind waves, or wind-generated waves, are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They result from the wind blowing over an area of fluid surface. 24.Write the classification of waves. Based on repetition of wave form Regular, irregular Based on wave period Long period, short period Based on shape Sinusoidal, trochoidal, cnoidal, solitary, random, progressive, standing, oscillatory, translatory
  7. 7. P a g e | 356 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry Other types Capillary wave, ultra gravity wave, ordinary gravity wave, infra gravity wave, ordinary tide wave, trans - tidal wave 25.What are the types of wave theories?  Linear or Airy’s (or sinusoidal or small amplitude) wave theory  Non-linear (or finite amplitude) wave theory 26.Write the assumptions of wave theories.  The waves have regular profiles  The flow is two dimensional  The wave propagation is unidirectional  The fluid is ideal (i.e.) inviscid, incompressible and irrotational  The sea bed is impermeable and horizontal 27.State the assumptions to be made in linear wave theory.  Fluid is homogeneous and incompressible. Therefore the density is constant.  Surface tension can be neglected.  Pressure at free surface is uniform and constant.  The fluid is ideal.  The particular wave being considered does not interact with any other wave motion.  The bed is horizontal, fixed, impermeable boundary which implies that the vertical velocity at the bed is zero.  The wave amplitude is small and invariant in time and space.
  8. 8. P a g e | 357 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 28.What are the advantages of linear wave theory?  It is the simplest available theory to describe the water wave motion  Provides insight to all periodic wave behavior  Adequate for most of the practical problems  Reliable over a large sequent of the whole wave region 29.What are the disadvantages of linear wave theory?  This theory is unable to account for mass transport due to waves  This theory cannot provide the information correctly either in shallow water regime or in deep water regime for steeper waves, especially during wave breaking 30.What is meant by wave celerity? The speed at which a wave form propagates is termed as phase velocity or wave celerity, C. Since the distance travelled by a wave during one wave period is equal to one wave length. 𝐶 = 𝐿 𝑇 31.Define wave energy. The total energy, E of a wave system is the sum of its kinetic energy, Ek and potential energy, Ep. According to linear wave theory, the total wave energy in one wave length per unit crest width is given by, 𝐸 = 𝐸 𝑘 + 𝐸 𝑝 = 𝜌 𝑔 𝐻2 𝐿 8
  9. 9. P a g e | 358 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 32.What is meant by group velocity? The speed with which a group of waves or a wave train travels is generally not identical to the speed with which individual waves within the group travel. The group speed is called the group velocity, Cg. 33.Define wave amplitude. The maximum vertical displacement of the sea surface from still water level (half the wave height). 34.Define wave height, wave length, wave period. The vertical distance from the top of the crest to the bottom of the trough is called wave height. The horizontal distance between the successive crest is called wave length. The time between successive crest passing a given point is called wave period. 35.Define wave energy flux. Wave energy flux is the rate at which energy is transmitted in the direction of wave propagation across a vertical plane perpendicular to the direction of wave advance and extending down the entire depth. The average energy flux per unit crest width transmitted across a plane perpendicular to wave advance is given by, 𝑝̅ = 𝐸̅ 𝑛 𝐶 = 𝐸̅ 𝐶𝑔 Energy flux 𝑝̅ is called wave power.
  10. 10. P a g e | 359 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 36.What is high tide line? “The high tide line means the line on the land up to which the highest water line reaches during the spring tide". Here the word "highest water line reaches during the spring tide" refers to the mean high water spring (19 years average of spring water) that is the regular water level fluctuations caused by changes in relative position of the Sun, Moon and Earth. 37.What is spilling? The spilling type of breaking occurs in deep water or over gentle bed slope (m = 1: 50). This involves gradual release of energy and is characterized by appearance of foam on forward side of the crest. 38.What is surging? Surging takes place when the sea bed slope is steep with (m = 1: 10) or so. In this case the entire water gets piled up and the foam is seen on beach face. 39.Write the expressions for velocity potential function and stream function. VELOCITY POTENTIAL FUNCTION: 𝛷 ( 𝑥, 𝑦, 𝑧 ) = 𝑋 (𝑥) 𝑍 (𝑧) 𝑇 (𝑡) = 𝑔 𝐻 cosh( 𝑘 ( 𝑑 + 𝑧 )) 2 𝜔 cosh( 𝑘𝑑 ) sin( 𝑘𝑥 − 𝜔𝑡 ) STREAM FUNCTION: 𝜕𝜓 𝜕𝑥 = −𝑣
  11. 11. P a g e | 360 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 𝜕𝜓 𝜕𝑦 = 𝑢 40.What is meant by storm surges? Storms and hurricanes can produce large rises in water level near coasts, which are known as storm surges or wind set-up. In combination with springtide conditions the water level rise may reach a critical stage (flooding). 41.Write the expression for wave celerity in shallow and deep waters. 𝐶 𝑜 = 𝑔𝑇 2𝜋 𝐶𝑠 = √𝑔𝑑 Where, Co = wave celerity in deep water Cs = wave celerity in shallow water g = acceleration due to gravity T = wave period 42.Write down the dispersion relation or scattering formula. 𝜔2 = 𝑔 𝑘 tanh(𝑘𝑑) 43.Mention the expression for group velocity and energy flux. GROUP VELOCITY: 𝐶𝑔 𝑜 = 𝐶 𝑜 2 (For deep water) 𝐶𝑔 = 𝐶𝑠 = √𝑔𝑑 (For shallow water)
  12. 12. P a g e | 361 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry ENERGY FLUX (OR) WAVE POWER: 𝑃 = 𝑛 𝜌 𝑔 𝐻2 8 𝐿 𝑇 = 𝑛 𝐶 𝐸 = 𝐶𝑔 𝐸 44.What is meant by coastal hinterland? The land that extends landward of the coast and which is not influenced by coastal processes. 45.What is meant by coast? The strip of land that extends from the coastline inland to the first major change in the terrain features, which are not influenced by the coastal processes. The main types of coastal features are dunes, cliffs and low-lying areas, possibly protected by dikes or seawalls. 46.Define coast line. Technically the line that forms the boundary between the coast and shore,(i.e. the foot of the cliff or the foot of the dunes). In general the coast line that forms the boundary between the land and the water. 47.Define shore line. The shore line is the intersection between the mean high water line and the shore. The line delineating the shoreline on Nautical Charts (Sea Maps) approximates this Mean High Water Line. The shoreline is not easy to identify in the nature in contrast to the coastline, which is based on a clear morphological shift between the shore and the coast.
  13. 13. P a g e | 362 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 48.What is meant by beach or shore? The zone of unconsolidated material that extends from the mean low water line to the place where there is a marked change in material or physiographic form, or to the line of permanent vegetation (the effective limit of storm waves and storm surge), i.e. to the coastline. The beach or shore can be divided in the foreshore and the backshore. 49.Define backshore. The part of the beach is lying between the foreshore and coastline. The backshore is dry under normal conditions, is often characterized by berms and is without vegetation. The backshore is only exposed to waves under extreme events with high tide and storm surge. 50.Define foreshore. The foreshore, or swash zone, is the region of the profile that is alternately wet or dry as the waves rush up this steep portion of the profile. 51.Define beach berm. Beach berms are built naturally by waves to above the highest elevation reached by normal storm waves. When storm waves erode the berm and carry the sand offshore, the protective value of the berm is reduced and large waves can overtop the beach. The width of the berm at the time of the storm is, thus, an important factor in the amount of upland damage, a storm can inflict.
  14. 14. P a g e | 363 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 52.What do you understand by the term continental shelf? It is the shallow seafloor that borders most continents. The shelf floor extends from the toe of the shore face to the shelf break where the steeply inclined continental slope begins. UNIT – 2 1. Define waves of oscillation. Water particles move in near circular orbits which decrease in diameter with depth. 2. Define waves of translation. Water particles actually move forward. 3. What are wave forecasting and its methods? Forecasting of waves for operational or design purpose can be made by measuring and analyzing the actual wave data. But considering the difficulties and costs involved in gathering large scale wave data, many times, the readily available wind information is gathered and then converted into corresponding wave information. Though, this procedure is less accurate than the actual wave analysis. METHODS:  Simplified or parametric method  Sverdrup – Munk and Bretschneider (SMB)  Hasselmann method  Darbyshire and Draper technique
  15. 15. P a g e | 364 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry  Elaborate or numerical method 4. What is meant by wave hind casting? Wave hind casts refer to the predictions of wind waves on the water surface for a past event. Wave now casts and forecasts similarly refer to the predictions in real time and in the future, respectively. But the relations or models used for predictions for a past, present, or future event are the same. 5. What are the types of transportation occurs within the water?  Solution  Suspension  Saltation  Traction 6. Write short notes on beach profile changes. Beaches and dunes undergo a seasonal transformation from a “summer” beach to a "winter" beach. A summer beach has a wide, well- developed berm often with a vegetated dune where American beach grass grows seaward onto the berm. A winter beach is lower, may not have a berm, and often shows signs of loss of beach grass. 7. What are the factors controlling profile variations?  Variation in wave energy  Sediment variability  Nature of sediment transport process over the beach slope  Tidal variations  Wind variations
  16. 16. P a g e | 365 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 8. Draw a typical section of a coastal region. 9. Define the phenomena of wave transformation. When the waves approach the shoreline, they are affected by the seabed through processes such as refraction, shoaling, bottom friction and wave-breaking. However, wave-breaking also occurs in deep water when the waves are too steep. If the waves meet major structures or abrupt changes in the coastline, they will be transformed by diffraction. If waves meet a submerged reef or structure, they will overtop the reef. 10.What is meant by refraction of waves? When deep water wave crest line strikes the sea bed contours at some non – zero angle, it tends to change its direction and align its wave crest with the sea bed contours. This is called the wave refraction.
  17. 17. P a g e | 366 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 11.What is meant by reflection of waves? Wave reflection occurs when waves “bounce back” from an obstacle they encounter. Reflected waves can cause interference with oncoming waves, creating standing waves. 12.What is meant by diffraction of waves? Diffraction can be seen when there are sheltering structures such as breakwaters. Diffraction is the process by which the waves propagate into the lee zone behind the structures by energy transmittance laterally along the wave crests. 13.State the assumptions to be made in the development of diffraction theories.  Water is an ideal fluid (Inviscid and incompressible)  The small amplitude waves can be calculated by the linear wave theory  The flow is irrotational and follows a potential function, which satisfies the Laplace equation  The water depth shoreward of the breakwater is constant 14.What is meant by angle of incidence? The angle between the wave propagation direction and the normal to the coastline or the angle between the wave front and the coastline is called angle of incidence and it is denoted by the symbol α. The deep water angle of incidence is denoted by α0.
  18. 18. P a g e | 367 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 15.What is meant by deep water? For a water depth larger than half the wavelength( ℎ > 𝐿 2 ), the phase speed of the waves is hardly influenced by depth (this is the case for most wind waves on the sea and ocean surface). 16.What is meant by shallow water? For a water depth smaller than the wavelength divided by 20( ℎ > 𝐿 20 ), the phase speed of the waves is only dependent on water depth, and no longer a function of period or wavelength. 17.What is shoaling? As the wave moves from deep water towards the coast its height generally increases and its length reduces. This phenomenon is known as shoaling. 18.Define wave overtopping. Wave-overtopping takes place when waves meet a submerged reef or structure, but also when waves meet an emerged reef or structure lower than the approximate wave height. During over-topping, two processes important to the coastal processes take place: wave transmission and the passing of water over the structure. 19.Define white capping. White-capping or top-breaking is steepness-induced wave-breaking, which occurs in deeper water when the wave height becomes too large compared to the wavelength.
  19. 19. P a g e | 368 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 20.Write short notes on bottom friction. Bottom friction causes energy dissipation and thereby wave height reduction as the water depth becomes more and more shallow. Friction is of special importance over large areas with shallow water. 21.What is meant by tsunami? It also known as a seismic sea wave is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Tsunami waves do not resemble normal sea waves, because their wavelength is far longer. 22.How tsunami is formed? Tsunamis are waves created by ocean bottom earthquakes, submarine land – slides and volcanic explosions. These long period waves can travel across entire oceans at speeds exceeding 800 kmph causing extensive damage to coastal areas. 23.What is meant by sea level rise? The so-called greenhouse effect or global warming may cause a Sea Level Rise, which will have a great impact on the long-term coastal morphology. The possible and gradual Sea Level Rise will cause a general shoreline retreat and an increased flooding risk and has to be handled according to the local conditions. 24.What is Mean Sea Level (MSL)? The sea level halfway between the mean levels of high and low water.
  20. 20. P a g e | 369 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 25.What is Mean Tide Level? This is the average between mean low and mean high water, measured from datum. 26.Define still water level. The level that the sea-surface would assume in the absence of wind waves (not to be confused with mean sea level or mean tide level). 27.What is meant by stand? The period at high or low water during which there is no apparent change of level is called stand. 28.What is tidal range? The tidal range is the vertical difference between the high tide and the succeeding low tide. Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. The tidal range is not constant, but changes depending on where the sun and the moon are. UNIT – 3 1. Write short notes on wave forces on piles. Wave forces on vertical cylindrical structures, such as piles exerted by non – breaking waves can be divided into two components such as,  Force due to drag  Force due to inertia
  21. 21. P a g e | 370 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 2. What is meant by breaker zone? The breaker zone is the zone within which the waves approaching the coastline commence breaking. The breaker zone is part of the surf zone. However, the instantaneous width of the breaker zone varies with the instantaneous wave conditions. 3. Define near shore zone. The zone extending seaward from the low water line well beyond the breaker zone; it defines the area influenced by the near shore currents. The near shore zone extends somewhat further seawards than the littoral zone. 4. Define offshore zone. The offshore zone is not well defined. In relation to beach terminology, it is thus not clear if it starts from the littoral zone, from the breaking or from the near shore zone. In the present context, the offshore zone is defined as the zone off the near shore zone. 5. Define littoral zone. This zone extends seaward from the foreshore to some distance beyond the breaker zone. The littoral zone is the zone in which the littoral processes take place; these are mainly the long-shore transport, also referred to as the littoral drift, and the cross-shore transport. 6. Define surf zone. The surf zone is the region extending from the seaward boundary of wave breaking to the limit of wave uprush. Within the surf zone wave breaking is dominant hydrodynamic process.
  22. 22. P a g e | 371 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 7. Define non – breaking waves. When the depth of water against the structure is greater than about 1 1 2 times the maximum expected wave height, generally the non – breaking wave conditions occur. Forces due to non – breaking waves are essentially hydrostatic. ‘Sainflou Method’ may be used for the determination of pressure due to non – breaking waves. 8. Define breaking waves. In fluid dynamics, a breaking wave is a wave whose amplitude reaches a critical level at which some process can suddenly start to occur that causes large amounts of wave energy to be transformed into turbulent kinetic energy. There are four types of breaking waves. They are spilling, plunging, collapsing and surging. 9. Define broken waves. Locations of certain structures like protective structure will be such that waves will break before striking them. In such cases, no exact formulae have been developed so far to evaluate the forces due to broken waves, but only approximate methods based on certain simplifying assumptions are available. 10.What is breaking wave height? Wave height is limited by both depth and wavelength. For given water depth and wave period there is a maximum height limit above which
  23. 23. P a g e | 372 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry the wave becomes unstable and breaks. This upper limit of wave height is called breaking wave height. 11.Write the formula used to find the design breaker height. 𝐻 𝑏 = 𝑑 𝑠 𝛾 − 𝑚𝜏 𝑝 Where, 𝑑 𝑠 = 𝑑𝑒𝑝𝑡ℎ 𝑎𝑡 𝑠𝑡𝑟𝑢𝑐𝑡𝑢𝑟𝑒 𝑡𝑜𝑒 𝛾 = ℎ 𝑏 𝐻 𝑏 𝑚 = 𝑛𝑒𝑎𝑟 𝑠ℎ𝑜𝑟𝑒 𝑠𝑙𝑜𝑝𝑒 𝜏 𝑝 = 𝑑𝑖𝑚𝑒𝑛𝑠𝑖𝑜𝑛𝑙𝑒𝑠𝑠 𝑝𝑙𝑢𝑛𝑔𝑒 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 = 𝑏𝑟𝑒𝑎𝑘𝑒𝑟 𝑡𝑟𝑎𝑣𝑒𝑙 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 (𝑥 𝑝) 𝑏𝑟𝑒𝑎𝑘𝑒𝑟 ℎ𝑒𝑖𝑔ℎ𝑡 (𝐻 𝑏) 12.What is breakwater? Name its types. Breakwaters are one of the essential coastal structures and these are constructed to provide a calm basin for ships and to protect harbor facilities. Since sea waves have enormous power, the construction of structures to mitigate such power is not easily accomplished. Breakwaters are generally classified into three major categories according to the functional requirements. They are,  Mound breakwaters  Vertical breakwaters  Mixed or composite breakwaters 13.What are the points should be considered for the design of breakwater?  The required lifetime of the structure
  24. 24. P a g e | 373 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry  The return period of the design conditions  Allowable overtopping  Allowable wave disturbance behind a breakwater  Construction aspects (e.g. crest width and height) 14.What are the boundary conditions should be considered for the design of breakwater?  The design wave height and period  The design water level (high water and low water)  The bathymetry  The soil conditions  Seismic conditions 15.What are the functions of breakwater?  Protection against waves  Guiding of current  Protection against shoaling  Provision of a dock or quay 16.Define vertical breakwaters. Vertical breakwaters especially the single unit monolithic types are sometimes preferred to the rubble mound breakwaters mainly for reasons such as saving in material due to smaller body with and rapidity in construction. Obviously, the vertical structure is preferred in deep waters and when rock quarries are not located near the harbor site and transportation of large quantities of stones from distant quarries become expensive.
  25. 25. P a g e | 374 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 17.Define rubble mound breakwater. A rubble mound breakwater is composed of several layers of random shaped and randomly placed stones protected with a cover layer of selected armor units of either natural rock or specially shaped concrete units. The armor units in the cover layer may be placed at random or in an orderly manner to obtain good interlocking between the individual units. 18.Define composite breakwaters. This is a combination of a vertical monolithic breakwater founded on a rubble mound base. The advantage of a composite breakwater is the judicious and economical use of materials. It has the advantage of adopting itself to uneven bottom. The height of the monolith is reduced. The disadvantages are that the wave break on the structure and the impact forces are several fold larger than the forces exerted by standing waves. 19.What are the types of failures occurs on vertical walls?  Settling in quicksand when the breakwater is founded on fine sand  Horizontal sliding at the foundation level  Overturning 20.What are the types of vertical breakwater?  Small blocks  Large blocks  Monolithic caissons  Sloping faces  Hanstholm type of breakwater  Cellular sheet pile breakwater
  26. 26. P a g e | 375 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry  Vertical parallel sheet piles  Metal box caisson  Perforated breakwater 21.What are the types of rubble mound breakwater?  Berm breakwaters armored with natural rock  Conventional multi layer breakwater with armor over crest  Conventional multi layer breakwater with crown wall  Composite structure incorporating caisson with armor protection 22.How do you calculate the height of break water? 𝐻𝑓 = 𝑅 𝑐 + ℎ 𝑅 𝑐 = 1.2 𝐻𝑠 Where, 𝐻𝑓 = 𝑏𝑟𝑒𝑎𝑘𝑤𝑎𝑡𝑒𝑟 ℎ𝑒𝑖𝑔ℎ𝑡 (𝑚) 𝑅 𝑐 = 𝑓𝑟𝑒𝑒𝑏𝑜𝑎𝑟𝑑 (𝑚) ℎ = 𝑤𝑎𝑡𝑒𝑟 𝑑𝑒𝑝𝑡ℎ (𝑚) 𝐻𝑠 = 𝑑𝑒𝑠𝑖𝑔𝑛 𝑤𝑎𝑣𝑒 ℎ𝑒𝑖𝑔ℎ𝑡 (𝑚) 23.What are the forces acting on breakwaters?  Hydrostatic pressure  Buoyancy or uplift pressure  Non – breaking wave force on non – overtopping walls  Wave forces on overtopping vertical breakwaters  Impact pressure due to braking waves
  27. 27. P a g e | 376 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 24.What are the advantages of beach nourishment?  Widens the recreational beach  Structures behind beach are protected as long as the added sand remains 25.What are the disadvantages of beach nourishment?  Beach nourishment sand may erode, because of storms or lack of up- drift sand sources  Beach nourishment is expensive, and must be repeated periodically  The beach turns into a construction zone during nourishment  The process of nourishment may damage, destroy or otherwise hurt marine and beach life by burying it  The sand added to the beach is often different from the natural beach sand. It can be hard to find a perfect match 26.Define clapotis. When tidal wave is reflected back by solid wall of marine structure, the reflected water may fall on the incoming tidal wave; increasing height of water surface, which looks like a wall of water, such a wall of water is known as clapotis. 27.Write a note on spring tide. During full moon and new moon periods, we have high tides known as spring tide.  Sun and Moon on the same side (zero degree)  Sun and Moon at opposite sides
  28. 28. P a g e | 377 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 28.Write a note on neap tide. When the moon is in its quarter position, low tides occurs known as neap tide.  Sun and Moon at 90 degrees  Sun and Moon at 270 degrees 29.How is current created? Ocean currents can be generated by wind, density differences in water masses caused by temperature and salinity variations, gravity, and events such as earthquakes. Currents are cohesive streams of seawater that circulate through the ocean. 30.What are the types of current relevant to coastal engineers?  Ocean circulation  Tidal currents  Near shore currents  Long shore current  Rip current  On shore – off shore current 31.Define tidal current. The rise and fall of tide is accompanied by horizontal movement of the water is called tidal current. 32.Define non – tidal current. Non – tidal current includes all currents not due to the tidal movement. Non – tidal currents include the permanent currents in the
  29. 29. P a g e | 378 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry general circulatory system of the oceans as well as temporary currents arising from meteorological conditions. The current experienced at any time is usually a combination of tidal and non – tidal currents. 33.Define hydraulic current. A slight departure from the sine form is exhibited by the reversing current in a strait that connects two different tidal basins, such as the East River, New York. The tides at the two ends of a strait are seldom in phase or equal in range, and the current is called hydraulic current. 34.What is meant by slack water? In rivers or straits, or where the direction of flow is more or less restricted to certain channels, the tidal current is reversing; that is, it flows alternately in approximately opposite directions with an instant or short period of little or no current, called slack water. 35.Define near shore current. A system of currents that is caused by wave activity within and adjacent to the breaker zone. The current system includes the shoreward mass transport of water, long shore currents and seaward-moving rip currents. 36.Define the term long shore current and rip current. The long shore current is the dominating current in the near shore zone; it is running parallel to the shore. The long shore current is generated by the shore-parallel component of the stresses associated with the breaking process for obliquely incoming waves, the so called radiation stresses, and
  30. 30. P a g e | 379 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry by the surplus water which is carried across the breaker zone towards the coastline. An intermittent strong surface current flowing seaward from the shore is called rip current. UNIT – 4 1. What is known as lagoons? A lagoon is a shallow body of water separated from a larger body of water by barrier islands or reefs. Lagoons are commonly divided into coastal lagoons and atoll lagoons. They have also been identified as occurring on mixed-sand and gravel coastlines. There is an overlap between bodies of water classified as coastal lagoons and bodies of water classified as estuaries. 2. What is littoral drift? Littoral transport is the term used for the transport of non-cohesive sediments, i.e. mainly sand, along the foreshore and the shore face due to the action of the breaking waves and the long shore current. The littoral transport is also called the long shore transport or the littoral drift. 3. What is long shore drift? Long shore drift is a geographical process that consists of the transportation of sediments (clay, silt, sand and shingle) along a coast at an angle to the shoreline, which is dependent on prevailing wind direction, swash and backwash. This process occurs in the littoral zone, and in or close to the surf zone.
  31. 31. P a g e | 380 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 4. What is stokes drift? In reality, for finite values of the wave amplitude (height), the particle paths do not form closed orbits; rather, after the passage of each crest, particles are displaced slightly from their previous positions, a phenomenon known as Stokes drift. 5. Mention some of the environmental parameters.  Maximum tidal elevation  Wave characteristics  Storm surge  Long shore transport rate  Current  Soil characteristics of the backfill 6. What are the environmental parameters should be considered by coastal engineers?  Waves  Tides  Currents  Wind  Storm surge  Sediment transport 7. What is meant by fetch? The fetch, also called the fetch length, is the length of water over which a given wind has blown. Fetch is used in geography and meteorology and its effects are usually associated with sea state and when it reaches shore
  32. 32. P a g e | 381 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry it is the main factor that creates storm surge which leads to coastal erosion and flooding. 8. What is meant by scour? Rubble mounds may be subject to severe toe erosion by undermining and scour. Scour is a process of removal of materials on the sediment bed. 9. What is coastal erosion? Coastal erosion is the wearing a way of land and the removal of beach or dune sediments by wave action, tidal currents, wave currents, drainage or high winds. 10.List the natural causes of erosion.  Sea level rise  Protruding headlands, reefs or rocks in to the sea  Tidal entrances and river mouths causing interruption of free passage of sediments along the shore, natural protection of tidal entrances  Shoreline geometry causing rapid increase of drift quantity  Removal of beach material by wind drift  Removal of beach material by sudden outbursts of flood waters 11.List down the man induced causes of erosion.  Construction of dykes, dams and other coastal structures  Construction of breakwaters, groins, jetties, etc  Man-made entrances causing interruption of littoral drift. This includes construction of jetties
  33. 33. P a g e | 382 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry  Fills protruding in the ocean to an extent that they change local shoreline geometry radically  Removal of material from beaches for construction and other purposes  Digging or dredging of new inlets, channels and entrances offshore dumping of materials 12.What are the causes of coastal erosion in India?  Rise of sea level  Reduction of sediment supply to shore  Effect of severe cyclonic storms and tides  Natural and manmade littoral barriers  Change in near shore topography  Lack of coastal environmental data 13.What are the effects of coastal erosion?  Dislocation of coastal population and loss of life and property  Loss of beaches, accretion of beach, areas, dislocation of coastal transport system  Silting of ports, harbours and shipping channels  Stoppage of shore based fisheries  Loss of placer mining grounds  Scenic beauty affected, loss of agricultural land  Influx of saline water into coastal agricultural lands, causes erosion of beaches due to reduced supply of sediment
  34. 34. P a g e | 383 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 14.What are the remedial measures for coastal protection?  Construction of suitable structures to prevent wave energy from reaching the erodible shores or to trap and accumulate the littoral drift material on the beach  Artificial nourishment of the eroding beach to make up for the deficiency in sand supply. In some cases, a small structure such as a groyne may be required to reduce the rate of loss of material from the nourished beach 15.What are the long term and short term measures provided for the coastal zone management? SHORT TERM MEASURES:  Seawalls  Anti sea erosion bunds  Revetments  Groynes  Bulkheads LONG TERM MEASURES:  Offshore breakwaters  Beach nourishment by sand  Sand by passing  Vegetative plantation  Sand dunes
  35. 35. P a g e | 384 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 16.What is dredging? It is the process of removal of sediments and debris from the bottom of river bed, lake or sea for the purpose of deepening them. It is an important operation in navigation canals, harbors, dams etc. 17.Classify the dredging procedure.  Pre – treatment  Extraction  Disposal 18.What are the multiple uses of dredged material?  Construction purpose  Wetland creation  Sediment separation  Creation of harbors  Habitat restoration  Beach nourishment  Top soil creation 19.Mention some of the choice of dredging systems.  Nature of material to be dredged  Depth of dredging  Distance and height at which dredged material is to be deposited  Quantity of material to be dredged  The traffic conditions in area to be dredged  Weather conditions in area to be dredged  Availability of maintenance facilities
  36. 36. P a g e | 385 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry  Types of prime movers for dredgers  Kinds of fuel for prime movers 20.What are the types of dredgers?  Mechanical dredger  Hydraulic or suction dredger 21.Mention the types of mechanical dredgers.  Grab dredger  Dipper dredger  Rock breaker  Bucket dredger  Non – propelling type or stationary bucket dredger  Self propelling bucket dredger 22.Mention the types of hydraulic or suction dredger.  Stationary suction dredger  Cutter suction dredger  Suction dredger  Suction dredger with rotating bucket wheels  Hopper suction dredger  Trailing suction dredger 23.Define remote sensing. Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in
  37. 37. P a g e | 386 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry contrast to on site observation. Remote sensing is a sub-field of geography. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth (both on the surface, and in the atmosphere and oceans) by means of propagated signals (e.g. electromagnetic radiation). It may be split into active remote sensing (when a signal is first emitted from aircraft or satellites) or passive (e.g. sunlight) when information is merely recorded. 24.What are the advantages of remote sensing?  Observation of a large geographical area  Long-term and fast collection of data  Lower collecting costs  "Inaccessible" regions become accessible (e.g. Antarctica)  Object is not being destroyed 25.What are the disadvantages of remotes sensing?  Lower spatial resolution (depending on the type of sensor)  Need for the installation of complex systems (which have a long testing phase)  Captured data need to be calibrated via in-situ data  Noise caused by another source than the desired one  Atmospheric effects degrade the quality of the images and need to be corrected
  38. 38. P a g e | 387 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry UNIT – 5 1. Mention the methods of protection of shores.  Shore parallel structures  Seawall  Bulkhead  Revetment  Offshore breakwaters o Reef breakwater o Low created breakwaters o Submerged breakwaters  Shore perpendicular structures  Timber groynes  Concrete groynes  Stone groynes  Cellular groynes  High / low groynes  Beach nourishment 2. What is known as bulkhead? This is defined as a structure or a partition to retain or prevent sliding of the land. A secondary purpose is to protect the upland against damage from wave action. Bulkheads are next in size, their function along to retain the fill and are generally not exposed to severe wave action. Bulkheads appear in three forms. They are,  Concrete slab and king pile bulkhead  Steel sheet pile bulkhead
  39. 39. P a g e | 388 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry  Timber sheet pile bulkhead 3. What is meant by revetment? Revetment in general is a sloping face made up of a randomly placed stones, concrete, etc. built to protect an embankment, or shore structure against erosion by wave action or currents. They are the lightest because they are designed to protect the shorelines against erosion by currents or light wave action. Revetments are of two types. They are,  Concrete revetment  Rip – rap revetment 4. What is meant by sea walls? Seawall is defined as a structure separating land and water body, primarily designed to prevent erosion and other damage due to wave action. In general, seawalls are the most massive of the three types because they resist the full force of the waves. They are designed to face severe wave action and are provided with sheet pile cut off walls at the toe to prevent loss of foundation material by wave induced scour, leaching from wave overtopping water or storm drainage beneath the wall. Seawalls can be classified as,  Concrete curved face  Combination of a curve and steps  Step faced  Rubble mound
  40. 40. P a g e | 389 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 5. What is meant by offshore breakwater? Along certain coastal region, the shoreline is protected by a series of submerged or raised rubble mound structures positioned intermittently in the shallow waters. These breakwaters make the incoming waves to break before they reach the coastline and in the process the beaches are protected from the fury of the waves. These breakwaters are classified as,  Reef breakwater  Low created breakwater  Submerged breakwater 6. What are the materials to be used for building bulkheads and seawalls?  Concrete  Steel  Timber 7. What is Groynes? When the stretch of coast to be protected extends over a long distance, it would be advisable to install shore perpendicular structures for coastal protection. Usually finger like structures projecting into the sea for a short distances are constructed at a pre – determined spacing for the entire length of the coast to be protected. The finger like structures are known as groynes and a number of such groynes put together form a groyne field. DEMERITS:  Induces local scour at the toe of the structure  Causes erosion down drift; requires regular maintenance  Typically more than one structure is required
  41. 41. P a g e | 390 Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry 8. Mention the types of Groynes.  Timber groynes  Concrete groynes  Stone groynes  Cellular groynes  High / low groynes 9. Give a brief description about beach nourishment. Tidal inlets protected from waves by jetties face accretion along the up drift coast and erosion on the down drift coast. Under such circumstances the affected coast is nourished with sand from the up drift accretion zone. This process has been proven to be effective provided the process of by – passing the sediments is carried out without any interruption. The advantage of this system is that the beach maintains its natural beauty. 10.What are the applications of GIS? Current GIS applications in the coastal zone are diversified and case- based studies, mainly focusing on vector-based applications. These applications can be categorized as,  Coastal mapping  Environmental monitoring  Coastal process modeling  Navigation and port facilities management  Coastal environmental / hazard assessment  Coastal management / strategic planning  Coastal ecological modeling