The swash zone is located at the landward edge of the surf zone on the upper part of the beach profile that is subjected to inundation (Fig. 8.1 A). It is where incoming surf zone waves force oscillatory motion of the shoreline (land–sea boundary) at a variety of frequencies, typically greater than 0.003 Hz.
Full Answer
What is a swash zone and why is it important?
This is a challenge for coastal scientists, both in terms of measurement and modelling of the physical processes. For the purposes of this summary, the swash zone will be considered as the region of the beach face exposed to the atmosphere over wind, swell and infragravity wave durations, i.e., seconds to a few minutes.
What is the difference between the surf zone and the swash zone?
Other important distinctions are that friction becomes more important in controlling aspects of the shallow flow in the swash zone than in the surf zone, and that turbulence and sediment transport in the swash zone is generated locally in the swash zone and advected into the swash zone from the surf zone.
What is Swash in geography?
Swash, or forewash in geography, is a turbulent layer of water that washes up on the beach after an incoming wave has broken. The swash action can move beach materials up and down the beach, which results in the cross-shore sediment exchange.
What determines the characteristics of swash zone hydrodynamics?
The characteristics of the swash zone hydrodynamics and sediment transport are governed by the inner surf zone and the underlying beach, with feedback of course between the morphology and hydrodynamic processes. The beach slope is a controlling parameter .
Where is the swash zone?
The swash zone is located at the landward edge of the surf zone on the upper part of the beach profile that is subjected to inundation (Fig. 8.1A). It is where incoming surf zone waves force oscillatory motion of the shoreline (land–sea boundary) at a variety of frequencies, typically greater than 0.003 Hz.
What is swash zone in geography?
Definition of Swash zone: The zone where wave bores run up the beach. It extends from the limit of run-down to the limit of wave run-up.
What is swash in the ocean?
Swash is the name given to the waves that rush up the beach after a wave has broken. They are intriguing little waves that inhabit a world of their own. Most of the waves we see in the sea are known as 'waves of oscillation'. The water moves up and down in an orbital way, as energy moves from one place to another.
What is the swash of a wave?
Wave types When a wave breaks, water is washed up the beach. This is called the swash . Then the water runs back down the beach, which is called the backwash . With a constructive wave, the swash is stronger than the backwash. With a destructive wave, the backwash is stronger than the swash.
What is the swash zone quizlet?
The swash zone is the nearest off-shore zone to the beach. Longshore drift. What is the difference between Eustatic and Relative sea level? Eustatic refers to the global sea level; Relative refers to local sea level near land.
What is a groyne in beach terms?
A groyne is a shore protection structure built perpendicular to the shoreline of the coast (or river), over the beach and into the shoreface (the area between the nearshore region and the inner continental shelf), to reduce longshore drift and trap sediments.
Why is swash important?
The swash zone is important to the sediment budget of the nearshore because it is the region of shore- line erosion or accretion, and swash processes determine whether sediment is stored on the upper beach or is in- stead returned to the inner surf zone and potentially transported offshore.
What does a swash look like?
A swash is a typographical flourish, such as an exaggerated serif, terminal, tail, entry stroke, etc., on a glyph. The use of swash characters dates back to at least the 16th century, as they can be seen in Ludovico Vicentino degli Arrighi's La Operina, which is dated 1522.
What is it called when the waves go backwards?
Backwash waves are nothing but counter or reverse waves that move toward the ocean instead of traveling toward the coast. A backwash wave may be dangerous to beachgoers who are not comfortable in high surf or turbulent seas but are also a rare and unusual wave riding opportunity for surfers.
What is the swash direction determined by?
the prevailing windThe movement of water and sediment up a beach is known as the swash, and is the direction of swash is largely determined by the prevailing wind.
What is the top of a wave called?
the crestThe highest part of the wave is called the crest. The lowest part is called the trough. The wave height is the overall vertical change in height between the crest and the trough and distance between two successive crests (or troughs) is the length of the wave or wavelength.
What is backwash in surfing?
A short-lived counterdirectional wave or surge, usually produced as a dying line of whitewater rushes up a canted beach, turns, and flows back into the surf zone.
What is the swash zone?
The swash zone is alternately wet and dry. Infiltration (hydrology) (above the water table) and exfiltration (below the water table) take place between the swash flow and the beach groundwater table. Beachface, berm, beach step and beach cusps are the typical morphological features associated with swash motion.
Where does swash occur?
Greater swash generally occurs on flatter beaches. The swash motion plays the primary role in the formation of morphological features and their changes in the swash zone. The swash action also plays an important role as one of the instantaneous processes in wider coastal morphodynamics. Figure 1.
What is a berm in swash?
The berm is the relatively planar part of the swash zone where the accumulation of sediment occurs at the landward farthest of swash motion (Figure 2). The berm protects the backbeach and coastal dunes from waves but erosion can occur under high energy conditions such as storms. The berm is more easily defined on gravel beaches and there can be multiple berms at different elevations. On sandy beaches in contrast, the gradient of backbeach, berm and beachface can be similar. The height of the berm is governed by the maximum elevation of sediment transport during the uprush. The berm height can be predicted using the equation by Takeda and Sunamura (1982)
What are the phases of swash?
Swash consists of two phases: uprush (onshore flow) and backwash (offshore flow). Generally, uprush has higher velocity and shorter duration than backwash. Onshore velocities are at greatest at the start of the uprush and then decrease, whereas offshore velocities increase towards the end of the backwash.
How long does it take for a swash to move?
The time-scale of swash motion varies from seconds to minutes depending on the type of beach (see Figure 1 for beach types). Greater swash generally occurs on flatter beaches.
What is swashing in water?
Swash, or forewash in geography, is a turbulent layer of water that washes up on the beach after an incoming wave has broken. The swash action can move beach materials up and down the beach, which results in the cross-shore sediment exchange.
When is the beachface in equilibrium?
The beachface is in dynamic equilibrium with swash action when the amount of sediment transport by uprush and backwash are equal. If the beachface is flatter than the equilibrium gradient, more sediment is transported by the uprush to result in net onshore sediment transport.
Abstract
This chapter describes the morphological features and key processes related to the swash zone, situated at the landward edge of the inundated part of the beach system. It is where incoming surf zone waves force oscillatory motion of the shoreline at a variety of frequencies.
8.1. Introduction: definition of terms and chapter overview
The swash zone is located at the landward edge of the surf zone on the upper part of the beach profile that is subjected to inundation ( Fig. 8.1 A ). It is where incoming surf zone waves force oscillatory motion of the shoreline (land–sea boundary) at a variety of frequencies, typically greater than 0.003 Hz.
8.2. Swash zone morphology
The swash-dominated part of the beach profile is the beach face. Between the low tide water level and the back-beach, it takes on a variety of shapes ( Fig. 8.3 ). Accreted beach face profiles tend to be steep and convex on the upper beach, whereas eroded profiles tend to be gently sloped and concave.
8.3. Shoreline kinematics and swash zone morphodynamics
Research into the dynamics of shoreline motion and the swash flow interior was largely theoretical up until the 1970s ( Miche, 1944, Carrier and Greenspan, 1958; Shen and Meyer 1963; Freeman and LeMehaute, 1964, Meyer and Taylor, 1972 ). This reflected, at least partly, the significant challenges of using instruments in the shallow flows.
8.4. Fluid dynamics, sediment transport and the swash zone profile
Comprehensive reviews of swash zone processes are given by Elfrink and Baldock (2002), Butt and Russell (2000), Longo et al. (2002), Masselink and Puleo (2006), Brocchini and Baldock (2008), Briganti et al. (2016) and Chardón-Maldonado et al. (2016).
8.5. Swash as a component of coastal inundation
Coastal inundation can arise from swash processes (run-up and overtopping) or overwash from storm surge ( Donnelly et al., 2006) ( Chapter 22; Fig. 22.4 ).
8.6. Concluding remarks
The nature of swash zone morphology and sediments were well documented during the latter half of the last century. It was also well established during that period that there are differences in surf zone hydrodynamics between steep and low-gradient beaches which also extend into the swash zone.
About the author
Dale Beardsley is sales manager for Pressure Systems, Inc. Beardsley can be reached at 800.328.3665 or by e-mail at dale.beardsley@pressuresystems.com.
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Introduction
Characteristics of The Swash Zone
- The hydrodynamic processes in the swash zone are characterised by very different types of fluid flow compared to the open ocean and surf zone, as illustrated in figure 2, where the strongly orbital motion of waves is transformed into flow along the bed (velocity ), usually in thin shallow sheets (thickness ). In terms of fluid mechanics, the key difference is the occurrence of supercrit…
Wave Runup and Overtopping
- Wave runup is perhaps the most important aspect of swash zone flows. While the motion of the water volume as a whole may be considered as runup, conventionally wave runup refers to the landward limit of the swash motion on the beach face, usually defined vertically above the ocean level. The runup and rundown of the shoreline is referred to as the swash excursion or oscillatio…
Swash Zone Hydrodynamics
- Swash zone flows have several features that differ from those in the surf zone, but this is dependent on the dominant wave conditions in the inner surf zone as noted above. Many key characteristics again depend on the Iribarren number . For infragravity standing long waves, the variation in flow depth and flow velocity at a point is relatively symmetrical during uprush and ba…
Sediment Transport Mechanics
- Cross-shore sediment transport in the swash zone generally occurs as a combination of bed load under sheet flow conditions, with a flat bed, plus an additional component of suspended load, generated locally and advected into the swash zone by surf zone bores. For the bed load, the Meyer-Peter and Muller formulation, or derivatives, generally perform well with calibration, i.e. de…
Morphodynamics
- The evolution of the beach face in the swash zone is controlled by the sediment fluxes across the boundaries, both longshore and cross-shore. Thus, the morphology is influenced by the presence of dunes, cliffs and hard structures at the landward extent of the beach, by conditions in the inner surf one, notably bars, rip cells, beach steps, and by lateral boundaries such as groynes, breakwa…
Measurement Techniques
- Research on swash zone processes is both assisted and hindered by the nature of the swash. The beach face is generally accessible for deployment of instruments, particularly with the aid of large tides, it is close to the shore and associated infrastructure, and much wave energy has been dissipated in the surf zone. However, flows are very shallow and also intermittent, making meas…
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Overview
Swash, or forewash in geography, is a turbulent layer of water that washes up on the beach after an incoming wave has broken. The swash action can move beach materials up and down the beach, which results in the cross-shore sediment exchange. The time-scale of swash motion varies from seconds to minutes depending on the type of beach (see Figure 1 for beach types). Greater swash generally occurs on flatter beaches. The swash motion plays the primary role in the formation o…
Swash morphology
The swash zone is the upper part of the beach between backbeach and surf zone, where intense erosion occurs during storms (Figure 2). The swash zone is alternately wet and dry. Infiltration (hydrology) (above the water table) and exfiltration (below the water table) take place between the swash flow and the beach groundwater table. Beachface, berm, beach step and beach cusps are th…
Uprush and backwash
Swash consists of two phases: uprush (onshore flow) and backwash (offshore flow). Generally, uprush has higher velocity and shorter duration than backwash. Onshore velocities are at greatest at the start of the uprush and then decrease, whereas offshore velocities increase towards the end of the backwash. The direction of the uprush varies with the prevailing wind, whereas the backwash is always perpendicular to the coastline. This asymmetrical motion of swash can cause longshore …
Sediment transport
The cross-shore sediment exchange, between the subaerial and sub-aqueous zones of the beach, is primarily provided by the swash motion. The transport rates in the swash zone are much higher compared to the surf zone and suspended sediment concentrations can exceed 100 kg/m close to the bed. The onshore and offshore sediment transport by swash thus plays a significant role in accretion and erosion of the beach.
Management
The swash zone is highly dynamic, accessible and susceptible to human activities. This zone can be very close to developed properties. It is said that at least 100 million people on the globe live within one meter of mean sea level. Understanding the swash zone processes and wise management is vital for coastal communities which can be affected by coastal hazards, such as erosion and storm surge. It is important to note that the swash zone processes cannot be consi…
Research
It is said that conduct of morphology research and field measurements in the swash zone is challenging since it is a shallow and aerated environment with rapid and unsteady swash flows. Despite the accessibility to the swash zone and the capability to take measurements with high resolution compared to the other parts of the nearshore zone, irregularity of the data has been an impediment for analysis as well as critical comparisons between theory and observation. Variou…
See also
• Beach cusp
• Beach nourishment
• Coastal management
• Longshore drift
• Sea wall