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Coastal Midterm
| Term | Definition |
|---|---|
| Barrier: | shore parallel, subaerial and subaqueous accumulation of sediment formed by waves, tides and aeolian processes (any sandy shoreline, doesn’t need a dune) |
| Swash zone (aka foreshore): | the area of wave swash (uprush of water) and backwash (back rush of water). The area where the wave goes up and down the shore |
| Surf zone: | the zone landward of the breaking wave where there is the forward translation of water called wave bores |
| Breaker zone: | the zone of breaking waves. The line that starts the surf zone |
| Shoaling zone: | where the waves start to feel the seabed, slow down and increase in height prior to breaking |
| Foreshore: | the sloping portion of the beach between the limits of high tide and low tide swash. The area that is wet |
| Backshore: | region of a beach from the berm crest landward to a foredune ridge, vegetation line, seawall etc. The area that is not wet (dunes and vegetation) |
| Nearshore bar: | ridge of sand formed at the convergence of transport by waves and currents in the surf zone |
| Surf Similarity Parameter: | This is why beaches change!! Most important! Currents move the sand forward, backward, left or right. Waves and the crest move the sand up and down. Also because of Myles |
| Steady State Equilibrium: | a general average through numerous variations around the mean or base level |
| Anastomosing or Anabranch: | a river that drastically changes direction in a short period of time (a flood or storm) |
| Sediment Budget: | Quantification of excess (deposition) and defiancies (erosion) of sediment between source and sink: |
| Barrier Breaching: | when enough sand is pulled away and water leaks into a new area and begins to flood |
| Wave: | physical process whereby energy is transported through a medium without any significant transport of the material in that medium |
| Fetch: | the distance by which the wind blows |
| Capillary Waves (<1 s): | short period waves restored through surface tension. Very tiny waves, ripples |
| Infragravity waves (>20 s): | long period waves restored through gravity. When the wave slowly gets smaller and smaller then all of a sudden get bigger! |
| Groundswell: | produced by mid latitude depressions (lows) originating in the semi-permanent low-pressure systems |
| Wind swell: | results from strong regular winds with enough fetch and duration, but tend to be short-lived, messy and disorganized |
| Frontal winds: | winds associated with passage of warm air and cold fronts |
| Sea breeze: | winds associated with differential heating and cooling of land and water |
| Tropical storm swell: | large depressions that travel from east to west producing more east swells than west swells |
| Directional spreading: | loss of energy to sides |
| Dispersion: | waves of different length travel at different speeds |
| Friction: | energy of the largest waves dissipated through friction with bed |
| Viscous dissipation: | energy dissipated through viscosity |
| Wave interference: | constructive and destructive interference (wave groups) |
| Wave Set-Down: | A decrease in water level before waves break. |
| Wave Set-Up: | An increase in water level landward of wave breaking, affecting coastal structures. |
| Airy Wave (Linear Wave Theory): | Small departures from Still Water Level (SWL). |
| Stokes Wave (Nonlinear Theory): | Larger departures in crest height, but troughs remain relatively unchanged. |
| Effects on Water Mass: | Crest: Water mass increases. Trough: Water mass decreases. |
| Formation of Infragravity waves: | Groups of large waves lower the water level. Groups of small waves elevate the water level. This results in a long, superimposed wave that propagates toward shore. |
| Wave Period Influence: | Similar wave periods generate longer infragravity waves. |
| Wave Breakpoint: | Long waves do not break but are released at the breakpoint. |
| Leaky Wave: | Waves that escape from the nearshore zone. |
| Edge Wave: | Trapped waves that propagate alongshore. Rotate along the beach. Trapped waves are in phase- wave resonates |
| Forced Waves: | Waves trapped at the shoreline but dissipate due to turbulence. Trapped waves are out of phase- wave dissipates |
| Conditions for Trapping Waves: | Size! If its wavelength is bigger than the surf zone, the wave will leak out and become an edge wave (fast waves do not get caught!)If its wavelength is smaller than the surf zone, the wave will get trapped and become a forced wave |
| Stokes Wave: | Greater departure from still water level (SWL) as wave height grows. |
| Airy Wave: | Smallest deviations from SWL. |
| Wave Set-Down & Set-Up: | Water level decreases before breaking and increases near the shore. |
| Longshore Currents: | Caused by waves breaking at oblique angles; strongest at the breakpoint. |
| Cross-Shore Currents: | Depend on wave breaking and turbulence, with velocity influenced by horizontal mixing. |
| Undertow: | Offshore-directed flow near the seabed, balancing water transported landward by waves. |
| Bed Return Flow or Undertow: | offshore directed mean flow near the bed (at your toes) |
| Velocity of undertow: | The speed of the undertow. Ranges from 0.1 to 0.3 m/s, up to 0.66 m/s in extreme conditions. |
Created by:
Monkeyman07
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