an investigation into the morphology and sedimentology of dungeness gravel barrier
TRANSCRIPT
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An Investigation into the Morphology and Sedimentology of Dungeness
Gravel Barrier.
Tony Patrick Gregory
April 16, 2015
BSC Geography and Environmental Management
University of the West of England
Word count: 13,142
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Copyright statement
This study was completed as part of the (BSc) Geography and Environmental Management
degree at the University of the West of England. The work is my own. Where the work of
others is used or drawn on, it is attributed to the relevant source.
Name: Tony Patrick Gregory
Signed:
This dissertation is protected by copyright. Do not copy any part of it for any purpose other
than personal academic study without the written permission of the author.
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Abstract
There are ongoing debates of the relationship between beach slope and particle size upon
gravel beaches, and how this affects the ability of a beach to act as a coastal defence. Coastal
erosion and future sea level rise are an ever present threat to habitat, population and industry
in low lying coastal areas. Dungeness gravel barrier; a cuspate foreland, formed during the late
Pleistocene as a result of sea level rise, was chosen to be investigated. Justification of this area
is that the gravel barrier on this unusual shaped coastline, boasting an exposed beach and a
sheltered beach, collectively provide a coastal defence to the Romney Marsh. This area plays
host to important energy source in the form of the Nuclear power station, as well as being
home to wildlife biodiversity of national importance and high levels of tourism.
Throughout this report, factors influencing beach slope, particle size and sorting were
investigated for two transects; one on the south facing beach and the other on the east facing
beach. This was achieved by using existing techniques for collecting beach slope and particle
size data. The data was then analysed using relevant literature and compared to existing
academic models of sedimentology and morphology.
A relationship between the two variables was revealed; particle size influenced slope to a
certain degree, but the positioning of the coastline in relation to prevailing winds proved the
key factor for the sites sedimentology and morphology. The high wave associated energy
environment of the exposed beach created an erosive, shallower beach compared to the
sheltered accretive east beach. The academic models (Mclean & Kirk, 1969) were not able to
fully represent the study site due to lack of suitability and sophistication.
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Acknowledgements
I would like to thank Dr Chris Spencer for his support and guidance throughout the duration of
this project. Thank you also to my family and friends for their patience, help and support,
without which I would not have been able to complete this challenging project.
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Table of Contents
Introduction .......................................................................................................................... 1 1.
Site introduction: .......................................................................................................... 1 1.1
Context and reason behind study ................................................................................. 3 1.2
Aims and objectives ...................................................................................................... 5 1.3
Literature review .................................................................................................................. 7 2.
Introduction to coasts ................................................................................................... 7 2.1
Controls upon Gravel barriers ..................................................................................... 10 2.2
2.2.1 Waves .................................................................................................................. 10
2.2.2 Storm events ....................................................................................................... 15
2.2.3 Sediment supply .................................................................................................. 16
2.2.4 Sea level variation ............................................................................................... 17
Gravel barrier formation models ................................................................................ 18 2.3
Controls upon Dungeness gravel barrier .................................................................... 20 2.4
2.4.1 Waves and swash dynamics ................................................................................ 20
2.4.2 Storms ................................................................................................................. 22
2.4.3 Sediment supply .................................................................................................. 23
2.4.4 Sea level variation ............................................................................................... 24
Summary ..................................................................................................................... 26 2.5
Academic models ........................................................................................................ 26 2.6
Methodology ...................................................................................................................... 32 3.
Outline: ....................................................................................................................... 32 3.1
Locations for suitable data collection: ........................................................................ 33 3.2
Data collection: ........................................................................................................... 35 3.3
3.3.1 Beach morphology/slope: ................................................................................... 35
3.3.2 Particle size: ........................................................................................................ 36
Results ................................................................................................................................. 40 4.
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Beach profiles .............................................................................................................. 40 4.1
Particle size ................................................................................................................. 42 4.2
Overall distribution of particle size and sorting .......................................................... 46 4.3
Comparison with academic models ............................................................................ 48 4.4
Summary ..................................................................................................................... 50 4.5
Discussion ........................................................................................................................... 51 5.
Beach Profile slope variation ...................................................................................... 51 5.1
Particle size and sorting .............................................................................................. 55 5.2
Comparison to academic models ................................................................................ 58 5.3
Conclusion .......................................................................................................................... 60 6.
Summary ..................................................................................................................... 60 6.1
Limitations and improvements ................................................................................... 61 6.2
Appendices: ........................................................................................................................ 63 7.
Appendix 1 .................................................................................................................. 63 7.1
Appendix 2 .................................................................................................................. 65 7.2
References .......................................................................................................................... 67 8.
List of Figures
Figure 1.1: Study site location map: Google maps, Edina Digi map: Edited by Author ................ 2
Figure 1.2: Low lying land at risk of flooding. Plater (2009) ......................................................... 4
Figure 1.3: Areas under threat from the SLR, from Bugslife (2013) adapted by author .............. 5
Figure 1.4 Report structure, created by author (2015) ................................................................ 6
Figure 2.1: Beach profiles, Komar (1998, 46) in Haslett (2009) .................................................... 8
Figure 2.2: Seaward and landward beach face, Bluck (2011) ....................................................... 9
Figure 2.3: Wentworth scale of particle size, from Bird (2008), edited by author ....................... 9
Figure 2.4: Types of Wave refraction, Source: King (1980) ........................................................ 11
Figure 2.5: Landforms influencing swell modification, Source: Haslett (2009) ......................... 12
Figure 2.6: Longshore transport (a) and spit formation (b), Park (1997), found in Haslett (2000)
.................................................................................................................................................... 13
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Figure 2.7: Velocity thresholds for entrainment and deposition of particle size, Hjulstrom
(1935) in Summerfield (1991). .................................................................................................... 14
Figure 2.8: Summer and winter beach profile, Source: Bascom (1953) and Shepard (1950),
adapted by author. ..................................................................................................................... 16
Figure 2.9: Global SLR, source: BBC (2014) ................................................................................. 17
Figure 2.10: Morphological barrier formation, Cope (2004) ...................................................... 19
Figure 2.11: Sediment pathways leading to cuspate formation, source: May (2007) ................ 19
Figure 2.12: Formation of the bend, Source: Eddson et al (1998) .............................................. 21
Figure 2.13: areas of erosion and accretion at the study site, Source: (May 2007). .................. 22
Figure 2.14: Net Littoral drift, source: Nicholls (1991) ............................................................... 23
Figure 2.15: Sources of gravel, Pethick (1984) ............................................................................ 24
Figure 2.16: Holocene SLR, source: Waller (2010) ...................................................................... 25
Figure 2.17: Slope and particle size. Bascom 1954, in Pethick (1984) ........................................ 28
Figure 2.18: Particle zonation. Briggs (1977) .............................................................................. 29
Figure 2.19: Beach angle and particle size sorting. Mclean and Kirk (1969) from Pethick (1984)
.................................................................................................................................................... 30
Figure 2.20: Wave energy and slope angle. Komar (1976) in Pethick (1984) ............................. 31
Figure 3.1: Location of Transects at study site, from Buglife (2013), and taken by author........ 34
Figure 3.2: Slope measurement technique. CS.org.uk (2015) .................................................... 36
Figure 3.3: Udden and Wentworth, and Gradistat descriptive, Blott and Pye (2001) ................ 38
Figure 3.4: Gradistat Logarithmic, Folk and Ward (1957) Graphical measures, Blott and Pye
(2001) .......................................................................................................................................... 39
Figure 3.5: Example of Gradistat content output, Blott & Pye (2001) ........................................ 39
Figure 4.1: Beach Profile A, created by author ........................................................................... 40
Figure 4.2: Beach profile B, created by author ........................................................................... 41
Figure 4.3: Profile A: phi size histograms sample A-H, created by author ................................. 43
Figure 4.4: Profile B Particle size histograms samples A-F, created by author ........................... 44
Figure 4.5: Mean phi size for all sample sites, created by author .............................................. 46
Figure 4.6: Particle sorting for all sample sites, created by author ............................................ 47
Figure 4.7: Profile A comparison with Mclean and Kirk (1969) model, adapted by author ...... 49
Figure 4.8: Profile B comparison with Mclean and Kirk (1969) model, adapted by author ....... 49
Figure 5.1: Beach profile comparison, created by author (2015) ............................................... 52
Figure 5.2: Admiralty Chart, Beachy Head to Dungeness, ChartCo (2015) ................................. 52
Figure 5.3: Profile A and B comparison with the Mclean and Kirk (1969), created by author ... 59
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List of tables
Table 4.1: Summary of Calculated slope and sediment parameters, created by author ........... 45
Table 5.1: Particle size and sorting of transect A, created by author ......................................... 55
Table 5.2: Particle size and sorting of transect B, created by author ......................................... 57
Abbreviations
LSD: Longshore drift
SLR: Sea level rise
RSL: Relative sea level
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Introduction 1.
Site introduction: 1.1
The study site is located in the south east of England along the south and south-eastern
shores of Romney Marsh (Roberts, 2007), as demonstrated in figure 1.1. The Dungeness
foreland is located in the eastern part of the English Channel at the down-drift limit of a
sediment cell that extends from Selsey Bill to Dungeness (Nicholls, 1991). It consists of
over 500 gravel beaches which have accumulated since the mid- Holocene (Long, 1995).
The orientation of successive beach ridges indicates the initial growth of the foreland,
suggesting eastward progradation during the late Holocene with evidence of gravel from
the south west within the ridges caused by coastal erosion (Roberts, 2007). Boreholes
close to the Power station give substantial evidence for the broad sequence of coastal
emergence from shelf to shore face and the resultant creation of the current storm beach
gravel (Greensmith & Gutmanis, 1990). The initial formation occurred via a shingle bar
across Romney bay due to rising sea levels at the end of the Pleistocene between 3500-
6000 years bp (Maddrell & Osmond, in Telford, 2000). Estuarine deposits accumulated
landwards, which formed the marshes that remain in this location, whilst shingle
continued to accumulate on the seaward side forming the Dungeness seen today
(Greensmith & Gutmanis, 1990). The onset of estuarine deposits caused infilling of various
small ports in the area putting an end to the industry here (The Romney marsh, 2015).
From studies by Long and Innes, the initial barrier was comprised predominantly of gravel
and not sand (Long & Innes, 1993) which undermined the theory by Green (1968) and
Tooley (1988) that sand was found between gravel ridges and therefore post-dates gravel
deposition.
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Figure 1.1: Study site location map: Google maps, Edina Digi map: Edited by Author
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Context and reason behind study 1.2
There are ongoing debates as to the relationship between beach slope and particle size
found upon beaches (Mclean & Kirk, 1969; Bascom, 1951; Bauer et al, 2009) and currently
the mechanics of these coastal features remain relatively unknown (Dias et al, 2009). The
reason behind choosing the study site is that the beaches in this region are vital in the
protection of various important landforms and sites that have formed in this location due
to the presence of the gravel barrier. The marsh foreland itself is below sea level as
demonstrated by the white areas in figure 1.2. This raises the importance of the gravel
barrier as a flood defence for industry such as Lydd airport (CPRE, 2007), Dungeness
Nuclear power station and residential areas such as New Romney which has a population
of 7000 (The Romney Marsh, 2015). There are also a number of small caravan sites and
holiday parks which provide recreational and economic value to this coastal area.
Dungeness itself is an important ecological site with flora and fauna unique to the shingle
landscape with over 600 species of plant; designated a National Nature Reserve (NNR),
Special protection area (SPA), Special Area Of Conservation (SAC), and Site of Special
Scientific Interest (SSSI) as a result (Natural England, 2006; The Romney Marsh, 2015; Visit
Kent 2014). It is also home to an extensive range of unique migratory bird and insect
species as detailed by the RSPB (RSPB, 2015); examples of these areas are expressed in
figure 1.3. With sea level predicted to rise by up to 30 cm by 2100 (IPCC 2007; NSF, 2014)
the potential threat of breaching and overtopping to this low lying area is amplified.
This project looks to identify the formation of and reasons for the differences in the
unusual shaped barrier beach south and east of the foreland. The response of the gravel
barrier to external forces is analysed by Plater et al (2009); by identifying the significance
of sea level rise (SLR), coastal morphology, storm events, sediment supply and coastal
processes in the shaping of the Dungeness gravel barrier the current beach environment
becomes more understandable. As previously stated, the existence of the barrier is
paramount in terms of safeguarding the local habitat, wildlife, infrastructure and energy
source. Understanding the sedimentology and morphology of the barrier will identify if the
area is in need of human interference in order to assure the continued existence of this
coastal defence. Studies of gravel barriers lag behind that of sandy beaches (Buscombe &
Masselink, 2006) and so from this investigation there is scope for new insight into these
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high energy destructive coastal environments as well as gaining a better understanding of
the relationship between beach slope and particle size.
Figure 1.2: Low lying land at risk of flooding. Plater (2009)
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Figure 1.3: Areas under threat from the SLR, from Buglife (2013) adapted by author
Aims and objectives 1.3
The main aim of this project is: ‘to understand the geomorphology and sedimentology of the
Dungeness Gravel barrier’. To successfully answer this aim many factors will be considered and
data gathered from which a number of research objectives arise:
Objective (i): to identify appropriate sites either side of Dungeness spit, to test the validity of
academic models from beach slope and particle size literature.
Objective (ii): Characterise the morphology of the east facing and south facing beach.
Objective (iii): Characterise the sedimentology of the east facing and south facing beach
Objective (iv): Consider the above findings in relation to existing models of beach slope and
particle size literature.
Power station
Section of ecologically
important area
Populated areas
Gravel barrier
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To achieve the objectives above and ultimately answer the main aim, this report will be
structured as follows:
Figure 1.4 Report structure, created by author (2015)
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Literature review 2.
Introduction to coasts 2.1
A beach is an accumulation on the shore of loose, unconsolidated sediment, ranging in size
from very fine sand, up to pebbles and boulders (Bird, 2008). Gravel beaches have
characteristic size and shape sediment heterogeneity detailed by Zenkovich (1967) and Carter
(1988) and are spatially differentiated by these factors to a greater level than sand beaches
(Bluck, 1967). Physiographic context of gravel beach development is stated to be high
latitudinal through glacial and mountain weathering with long term sediment supply. These
wave dominated coastlines are found all around the world (Buscombe & Masselink, 2006); the
UK in particular is characterised by coarse- clastic barrier beaches composed of paraglacially
derived sediment inherited from previous glacial periods be it fluvio-glacial, marine-glacial or
periglacial conditions ( Carter, 1982; Orford & Carter, 1984).
A beach profile extends from the low water of spring tides to the upper limit of wave action
(King 1972). The landward limit of the beach is the high point reached by average storm waves,
and the seaward limit is the lowest tide level (USAID, 2001). Figure 2.1 shows a typical steep
profile (A) and flat (B) profile adapted from Komar (1998, 46); the beach profile is split into
three sections, the backshore, foreshore and nearshore; details of which are outlined by Jeong
et al (2011). They all consist of a series of ridges and troughs, the two extreme forms being
steep storm profiles and shallow swell profiles (Stripling et al, 2008). The furthest inland point
on storm beaches is known as the berm which marks the landward wave limit (Hugget, 2007).
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Figure 2.1: Beach profiles, Komar (1998, 46) in Haslett (2009)
Gravel barriers are elongated landforms situated along an inlet or bay, which enclose a lagoon
or swamp (Haslett, 2000). The Udden-Wentworth classification scheme for sediment (Udden,
1994; Wentworth, 1922) classifies gravel as sediment with a b-axis diameter of between 2-
60mm (Buscombe & Masselink, 2006), with further divisions expressed in figure 2.2.
Dungeness itself is a gravel barrier, exhibiting the correct sedimentology and morphology for
this landform; it is dominated by large material 2-2000 mm in diameter (Bird 2008), and two
beach faces, one landward and the other facing the coast (Orford et al, 2002; Goudie, 2004)
(figure 2.3). Necessary distinction between gravel and boulder beaches is also made by the
likes of Novak (1972) and Lorang (2002). Gravel dominated barriers tend to fall within the
reflective domain of morphological beach classifications by Short (1979) and Wright et al
(1979). These authors sufficiently outline the recognition criteria of reflective beaches, namely
steep beach face slope and a single swash berm (Short 1979; Wright et al, 1979). Powell (1986)
produced profile descriptors for shingle beaches through physical model studies schematised
by two hyperbolic curves (Powell, 1986), but fails to identify some key features over the crest
and so lacks accuracy.
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Figure 2.3: Wentworth scale of particle size, from Bird (2008), edited by author
Figure 2.2: Seaward and landward beach face, Bluck (2011)
Historically the insight into gravel beach dynamics has lagged behind the understanding of
littoral environments composed of finer sediments (Buscombe & Masselink, 2006), focusing
mainly on long-term evolution and distribution of larger clast sediment (Ivamy & Kench, 2006).
This is mainly due to logistical problems with laboratory and field experimentation (Buscombe
& Masselink, 2006) in what are quite often high energy destructive environments (Carter &
Orford, 1993).
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Controls upon Gravel barriers 2.2
Barrier coastlines to a large extent are determined by their substrate gradient, wave energy
versus tidal range, sediment supply versus space to accommodate, and the rate of sea level
change (Roy et al, 1994). Within these types of coastlines there is an array of environments in
which different drivers and processes are dominant and changing overtime, leading to barrier
evolution, migration or removal (Plater, 2009). The dynamics of drift aligned gravel barriers
such as Dungeness are controlled by a number of variables including the rate of SLR, sediment
supply, wave activity and storm intensity (Orford et al, 1991). These variables will be reviewed
on a general and site specific level throughout the following sections to identify how they
influence particle size and slope at the study site.
2.2.1 Waves
Wave action creates the dynamic nature of a beach, impacting any coastline in a number of
ways including the modification and distribution of sediment (Davies, 1985). Wave dimensions
are influenced by wind velocity (Banner & Song 2002), wave depth, strength, duration and
fetch (Bird, 2008). A thorough understanding of wave formation is essential in order to make
sense of the impacts upon a coastal zone. The influence of waves upon gravel beaches can be
subdivided; longshore drift, swash dynamics, wave refraction and storm events (Bird 2008,
Orford et al 2002, Pethick, 1984) are to be deliberated.
Waves are undulations on a water surface produced by wind action (Bird, 2008), where wind
exerts pressure upon the surface creating orbital movements of water (Garrison, 2007). The
incompletion of these movements signify the transfer of energy from the sea to the shoreline
(Bird, 1996; Hill, 2004). The height of waves, defined as distance between trough and crest
(Pethick, 1984) and the consistency of waves is dependent upon the conditions present. Under
normal conditions, characteristics of consistent swell are seen, but the stronger the wind, the
further distance travelled by a wave and the greater the depth of water (Holthuijsen, 2007) the
greater the wave power.
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Figure 2.4: Types of Wave refraction, Source: King (1980)
2.2.1.1 Wave refraction:
Wave refraction is of great relevance to nearshore currents, sediment transport and coastal
morphology (Masselink & Hughes, 2003). This process causes wave modification due to the sea
floor topography in shallow water creating frictional effects, which retard the advancing
waves, influencing the pattern of swell moving shoreward (Bird, 2008). The Wave velocity
decelerates as water depth decreases and so the wave front bends to become near parallel to
the bottom contours, although the adjustment is often incomplete (Hugget, 2007). The change
in velocity can be described in a similar way to that of bending light rays according to Snell’s
Law (Masselink & Hughes, 2003). King’s (1980) wave refraction diagram (figure 2.4) shows
zones of wave energy concentration and dissipation and how they impact a coastline.
2.2.1.2 Longshore drift
The sea floor, headlands, bays and submerged banks all influence modification of ocean swell
(figure 2.5); this modification directly affects sediment transport and erosion rates through a
process called longshore drift (LSD) (Davis & Fitzgerald, 2004; Bird 2008). This is the
predominant net movement of sediment parallel with the shoreline through longshore
currents (Summerfield, 1991) (figure 2.6).
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The likes of Davies (1985) state LSD to be a major contributor in the development and
distribution of sediment on gravel beaches, such as Dungeness, Chesil beach and Hawke Bay
Beach, New Zealand (Carr, 1969; Davies, 1985: Orford et al, 2002). It is therefore important to
understand how this process is shaping the study site. For coastal management purposes rates
of LSD are usually estimated using the CERC formula (Morfett et al, 1996; VanWellen et al,
2000). The contribution to the degree of LSD is directly affected by littoral drift within the
sediment cell and both influence slope and particle size upon a beach. Drift aligned barrier
beaches are inherently unstable due to their dependence on maintaining longshore sediment
input. It is noted by Carter et al (1987) that drift aligned barriers will remain as long as
sediment is delivered to the distal end by the transporting wave gradient (see section 2.4.1).
Figure 2.5: Landforms influencing swell modification, Source: Haslett (2009)
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Figure 2.6: Longshore transport (a) and spit formation (b), Park (1997), found in Haslett (2000)
2.2.1.3 Swash dynamics
Separation of comparative frictional and infiltration contributions to shear stress in sediment
transport will be more difficult for gravel beaches than sand beaches (Buscombe & Masselink,
2006). Waves propagate onto the dry beach in the form of swash; this motion consists of
deceleration flow velocities (uprush/ swash) occurring onshore and accelerating flow velocities
(backwash) occurring offshore (Masselink & Hughes, 2003). Swash processes interacting with
the groundwater table is widely acknowledged as key to controlling beach morphology (Mason
& Coates, 2001). The proclivity for gravel beaches to build steep beachface gradient and
prominent berms is attributed to onshore swash asymmetry that has arisen from infiltration
losses during uprush (Carter & Orford, 1993). The level of deposition is dependent on particle
size present and swash velocity as expressed in figure 2.7 (Hjulstrom, 1935). Larger particles
will be deposited first, as percolation weakens swash which create berm formations at the
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height of uprush, whilst smaller particles are suspended for longer and deposited further down
the beach.
Gravel beaches have high permeability’s and hydraulic conductivity (Horn et al, 2003) which
control the degree of infiltration occurring on a beach (Masselink & Li, 2001), giving rise to
their asymmetrical swash motion. Infiltration weakens backwash strength causing deposition
of sediment on the edge of the uprush (Orford et al, 2002; Hughes et al, 1997), and so swash
asymmetry increases sediment transport onshore creating a resultant steeper beach face
(Bagnold, 1940; Grant, 1948).The outcome is landward berm migration in the upper-swash and
these formations are important sources of sediment during storm events, when high levels of
erosion occur (Jamai, 2014; Baldock et al, 2005). On the opposite scale, if infiltration is reduced
due to a poor levels of sorting (Buscombe & Masselink, 2006), then backwash will remain
strong causing reduced accretion levels, forming a shallower beach face (Pethick, 1984).
Figure 2.7: Velocity thresholds for entrainment and deposition of particle size, Hjulstrom (1935)
in Summerfield (1991).
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2.2.2 Storm events
Unlike sandy beaches, there is a lack of measurement data collected under storm conditions
on gravel beaches and instead, process-based morphodynamic models from moderate wave
energy conditions have been devised. This has the potential for inaccuracy in representing
actual energetic storm events (McCall et al, 2010; Jamai et al, 2014; Pedrrozo-Acuna et al,
2006). Storms have a significant impact upon the sediment regime and profile of the coastline
due to higher wave energy and duration increasing the amount of erosion occurring (Komar,
1988). Winter months see a predominant rise in erosion with more fluctuations on the profile,
whilst accretion occurs in summer months when weather conditions are calmer usually
demonstrating a beach berm (Haslett, 2009). Figure 2.8 (Bascom, 1953) demonstrates the
differing summer and winter profile previously described (Komar, 1988). Barrier coasts in the
British Isles are rarely subjected to exceptional severity storms (Hurricanes); instead they are
affected by repeated lower magnitude storms from southwest to northeast cyclonic
depressions (Carter & Orford, 1984). Storm beaches can see stark contrast from day to day,
due to the high energy being applied to a beach causing removal and deposition of sediment in
large quantities. Deep water storm waves may be greater than 10 meters high and post storm
decay swell can reach 12-14s periods (Hogben & Lumb, 1967), drastically altering slope angles.
Storm surges produce catastrophic modification of the coast by raising the level at which large
associated storm waves attack; this is magnified in strong tidal environments when
accompanied with spring tides (Davies, 1972). This can lead to shoreward migration through
the rollover mechanism, where onshore sediment is thrown further shoreward forming a
coarse storm stranded lag (Carter & Orford, 1993). There is also the potential for breaching
and over topping of the gravel barrier itself as detailed by McCall et al (2010) leading to coastal
flooding in extreme cases (Bradbury & Powell, 1992; Pye, 2001).
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2.2.3 Sediment supply
The availability and quantity of sediment is paramount in influencing the shape of a gravel
barrier. Sediment is supplied from autochthonous and allocthonous sources; some gravel
beaches accumulate near the mouth of rivers (Damrat et al, 2013) due to the availability of
copious amounts of gravel clasts here. Many beaches have sourced sediment from local
erosional cliffs, transported from further down the coast by the aforementioned wave
processes, or from pre-existing glacial gravels (Bluck, 2011). Most present day gravel beaches
were created during the Devensian glacial period when large sediment was in abundance
(Buscombe & Masselink, 2006). The original rock source to a beach controls the clast shape
distribution, whether it is discoidal fragments or spherical grains which are abundant outcrops
composed of limestone, flint or quartzite (Carr, 1971). The nature of response of a barrier
beach to sea level rise (SLR) is moderated by the sediment budget, which gives rise to the
possibility of erosion and overstepping as detailed by Carter (1988), Orford & Carter (1995)
and Forbes et al (1991). This can lead to alongshore or shore-normal migration of barriers
depending on tide and wave imposed sediment influx.
Figure 2.8: Summer and winter beach profile, Source: Bascom (1953) and Shepard (1950), adapted by author.
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Figure 2.9: Global SLR, source: BBC (2014)
2.2.4 Sea level variation
Sea level is not consistent; it is always falling or rising either through eustasy which refers to
absolute changes in sea level, or isostasy which refers to the vertical movement of land mass
(Haslett, 2009; Masselink & Hughes, 2003). The process of sea level change is paramount in
creating and shaping the geomorphology of coastlines. The influence of historic sea level
change upon slope and particle size is evidenced by beach ridges, crests and core data,
particularly in the south east region (Warrick et al, 1993). Gravel Barriers such as Dungeness,
Chesil beach and others along the south coast of England, formed in the early to mid-Holocene
approximately 8000-5000 BP (Jennings et al, 1998; Long & Hughes, 1995) during periods of
fluctuating sea level.
Global SLR (Image 2.9) has continued to rise between 1.8+3mm/year over a 50 year period
(Church, 2010); the IPCC (2007) forecasts between 8- 29 centimetres in eustatic SLR by 2020,
not accounting for subsidence (Pethick, 1993). Further increase is expected by the year 2100
(NSF, 2014), which may impact upon the sediment regime and beach profiles of gravel
beaches.
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Gravel barrier formation models 2.3
The formation of gravel barriers remains a controversial topic; Zenkovich’s (1967) classification
of barrier coastlines suggests there are a number of discrete types of barriers divided into free
and fixed form categories. Summerfield (1991) indicates there are three possible formations
of gravel barriers like Dungeness and Chesil beach:
1. The formation of barrier islands or offshore bars due to near shore glacial sediment
accretion and a fall in the rate of relative SLR in the Holocene transgression.
2. Barrier islands initially developed above sea level on ridges and coastal dunes, and were
separated from the mainland by flooding or lagoons due to SLR during the early
Holocene.
3. Barrier growth, development during the past 4000 years in relative stable sea level
(Summerfield et al, 1991).
The most credible and relevant suggestion for Dungeness is suggestion 1; this formation allows
for an emergent substrate to create a bay barrier, and continued sediment supply from coastal
erosion up-drift results in cuspate foreland development.
Barriers may be subdivided into swash or drift aligned structures depending on their
orientation in relation to incident waves (Orford & Carter, 1991; Orford et al, 1995). There are
various papers (Carter & Orford, 1991; Forbes et al, 1995; King, 1972; and Swift, 1976)
suggesting the morphology of barrier beaches, which are aptly summarised by Copes (2004)
morphological model (figure 2.10).
Dungeness is a drift aligned cuspate foreland/ barrier (Holmes, 1944; Paskoff, 1985) (Figure
2.11); it originated as a spit which extended through eastwardly LSD into the path of storm
waves from the north, the narrow English Channel being crucial to this landforms construction
(Summerfield,1991, 2001). The newly formed marshland swamps or lagoons drained away
over time and infilled with sediment to transform from a cuspate barrier to foreland (Hugget,
2007). Foreland progradation was fed by Cannibalisation of the barrier complex, an
evolutionary sequence similar to Long & Innes (1995) three phase model of barrier initiation,
stability and breakdown. The barrier formed by an initial spit which curved round to meet the
land (looped spit) and on the sea ward side sediment build up continued to eventually form a
barrier beach (figure 2.11) (Hugget ,2007; Komar, 1967). This process resulted in the creation
of an exposed (south facing beach) and sheltered side (east facing beach).
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Figure 2.10: Morphological barrier formation, Cope (2004)
Figure 2.11: Sediment pathways leading to cuspate formation, source: May (2007)
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Controls upon Dungeness gravel barrier 2.4
2.4.1 Waves and swash dynamics
The effects of wave refraction and longshore drift (LSD) can be paramount in the formation
and alteration of slope and particle size of gravel barriers such as Dungeness and Chesil beach.
Work by Elliot (1847) Lewin (1862) and Drew (1864) recognised the formation of a natural
gravel barrier creating continuous gravel ridges, running from Fairlight to Hythe, with an
associated continuous foreshore for unrestricted drift of gravel (Lewin, 1862). This was driven
by coastal erosion that led to the formation of an offshore sub-tidal delta which gradually
developed into a bar through deposition of sediment transported by LSD, eventually extending
across the bay (Figure 2.12) (Gulliver, 1897). The formation of the ness/ bend and eventual
foreland development, was caused by associated wave processes creating a second breach in
the barrier near Fairlight in the roman era (figure 2.11), which reduced up drift supply causing
starvation (Lewis, 1932).
The south westerly prevailing winds result in a nearshore west to east LSD of gravel from
updrift sources (Green, 1968) at a rate of over 1770 tons of sediment per week (Williams et al,
2005). This frequent deposition during the swash phases, forms berms that are then reworked
by the longshore transport regime from the south facing beach towards the east facing beach.
This process drastically affects the sediment size and distribution, creating steeper or
shallower reflective profiles depending on the accretive or erosive nature of the coast. This
reflective topographic nature can engender sub-harmonic edge waves (Guza & Davis, 1974).
Long period swells increase the amplitude of waves resulting in swells that can frequently
exceed 10m in the North Atlantic (Hogben & Lumb, 1967), directly affecting the study site.
The longshore transport regime of sediment has been modified since the 1950s through a
replenishment program that returns shingle from the ness at the east point, to the western
end of the beach near Brommhill (Thorn, 1960). This scheme was introduced to protect the
power station located on the south east tip of the foreland (figure 2.13); an additional
30,000m of gravel (Summers, 1985) is added to the south eroding shore annually. This gravel is
sourced from the accreting east side of Dungeness and transported to the south side to build
the beach in front of the power station (Figure 2.13) (May, 2007) and so subsequently, human
influences are changing the slope and particle regimes at both beaches.
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Figure 2.12: Formation of the bend, Source: Eddson et al (1998)
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2.4.2 Storms
The East Sussex and Kent coastline located at the down end of the English Channel, experience
frequent storm events that originate in the North Atlantic (Lozano et al, 2004). Storms
potentially increase the rate of littoral drift, so therefore affect consolidation and breakdown
of gravel barriers, as well as initiating the creation of the landform (Waller, 2010). The
variation of magnitude and storm frequency influence sediment movement at this site (Figure
2.13). Historic records give valuable insight into past storm events that impacted the majority
of the south coast of England and the north sea low countries during the 13th century AD
(lamb, 1991; 1995). There is a strong link between storm events and increased accretion at the
study site; the coastal cell and sub-cell concept (figure 2.14) (Tanner, 1973; Swift, 1976;
Nicholls & Webber, 1987) demonstrates erosion of sediment west of Dungeness and
transported eastwards via littoral drift causing accretion to the east (Redman, 1852). Therefore
accretion occurs during storm periods at the study site and erosion during periods of calm as
sediment supply fails, directly affecting slope and particle size upon the south and east
beaches (figure 2.13).
Figure 2.13: areas of erosion and accretion at the study site, Source: (May 2007).
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2.4.3 Sediment supply
Eddison (1983) places the arrival of gravel at Dungeness around 5500 BP with a following
decline in supply due to the redistribution of inter glacial material causing a decrease in
availability (Bird, 2008). He argues also that longshore supply of gravel declined asymptotically
with a reduction in rate of SLR after 5500BP.
Nicholls (1991) suggested that under modern conditions the majority of sediment moves via
Easterly Littoral drift from Selsey Bill to the depocentre at Dungeness (figure 2.14); this process
has been dated no later than 3400 BP (Tooley & Switsur, 1988). Jennings and Smyth (1990)
identify two possible sources of gravel during the mid-Holocene; local cliff retreat/erosion, and
net onshore movement (Figure 2.15). Updrift sources include Pleistocene fluvial (River Rother)
(Long et al, 2004) where sediment was transported from Rivers to the English Channel sea
floor, during Pleistocene cold phases when RSL was low. Raised beach gravels and fine flints
eroded from the Sussex cliffs may also be contributors. Offshore gravel (Hamblin & Harrison,
1989) may also be a source of sediment for Dungeness gravel barrier (figure 2.15). After its
initial formation, onshore migration may have occurred in response to SLR by over-washing of
Figure 2.14: Net Littoral drift, source: Nicholls (1991)
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the barrier (Carter & Orford, 1984); the large quantities of gravel from the West Sussex coast
being a likely contributor (Crickmore et al, 1972). However the relative importance of offshore
gravel sources remains uncertain (Jennings & Smyth, 1990; Nicholls, 1991).
The dominant source of beach gravel of the study site is cherty sandstone, derived from upper
Greensand, fine-grained sandstones from the upper Greensand and various quartzites. The
gravel on the beach ridge crests are generally finer than that in the lows, with grain sizes
varying between c. 8mm and 150mm (Green, 1988), whilst Beach ridge amplitude also varies
between c. 0.5m and 2m (Plater & long, 1995).
2.4.4 Sea level variation
Relative SLR has generally risen during the Holocene (Waller et al, 2006; Long et al, 2006)
which is evident for the study site (figure 2.16). As mentioned earlier previously (2.2.4), long-
term sea level change is paramount to the geomorphology and sedimentology of a gravel
barrier like Dungeness. Accumulation of Holocene sediment more than 20m thick lies along
the Kent and east Sussex coast; RSL rise provided the height difference between sediment
surface and high tide required for barrier formation, with Crustal subsidence contributing an
Figure 2.15: Sources of gravel, Pethick (1984)
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estimated 0.9mm/yr-1 (Gehrels, 2010). Holocene RSL of the study area can be split into three
periods (Waller & Long, 2003): Rapid rise of 12mm/yr-1 between c. 9700- 7800 cal. yr BP
(Waller & Kirby, 2002), mid Holocene decline (c. 7800- 3700 cal. Yr BP) averaging >3mm yr-1,
and eventually slowing to <2mm yr-1 (Long et al, 2006a) (figure 2.16); this was due to a fall in
global melt water production. Sediment compaction has made interpreting data trends in the
late Holocene more difficult; Lewis and Balchin (1940) noted oscillations in sea level between
ca. 4000 and 3000 yrs BP evidenced by alternating gravel and marsh deposits at the site.
However altitude changes were too large to be product of sea level oscillations alone.
The present macrotidal environment (Plater et al, 2009) at Dungeness gives a tidal range of
6.7m, with a mean high water spring tide of 4.03m OD (Ordnance Datum) (Admiralty Tide
Tables, 1994). Increased water level exposes more of the beach profile to wave processes and
for longer periods which cause alterations to slope and particle size.
Figure 2.16: Holocene SLR, source: Waller (2010)
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Summary 2.5
The above processes have been evidenced to influence beach slope and particle size in certain
ways on gravel beaches like the study site. The two variables directly affect each other;
sediment size influences slope by altering percolation rates, and controls wave energy by
reducing or enhancing swash dynamics (Gama & Reis, 2010). The coarser the sediment, the
greater the infiltration rates (Blott & Pye, 2010), the less resistance to swash movement which
allows beach profile to build (Bagnold, 1940). The level of exposure determines slope and so
erosion results in shallow slope whereas accretion will create a steeper profile (Anfuso et al,
2008). Storms will increase erosive rates on more exposed beaches due to creating higher
wave energy which coupled with LSD will increase accretion down drift if sediment supply is
sufficient. SLR will expose higher areas of the beach to wave action for longer durations that
previously would remain unprocessed. Geology and wave energy control the particle size
distributed upon the beach (Curtiss et al, 2008); for Dungeness this is predominantly
composed of cherty sandstone (Green, 1968). In this study the variables slope and particle size
will be investigated by looking at the south facing (more exposed to prevailing winds) beach
and the sheltered east facing beach where wave energy is predicted to be significantly lower.
The results obtained are to be compared to relevant academic models identified below.
Academic models 2.6
The various controls and processes upon gravel barriers mentioned above and their impacts
upon beach sedimentology and morphology have been studied to create various academic
models. These physical or numerical based models allow for the prediction of beach response
to differing, variable conditions (Bird 2008). From this, gravel beaches can be characterised
and distinctions can be made about the coastline.
Historical data for beaches suggest a trend of increasing slope with grain size sorting and
decreasing slope with increasing wave energy (Wiegel, 1964). Bascom (1951) suggests that
steeper beach face slope will have larger particle size sedimentology than shallower slopes
(Figure 2.17). Mclean & Kirk (1969) also suggest a linear relationship between grain size sorting
and foreshore slope. Inman & Bagnold (1963) state that size of material through permeability
exerts primary control upon a foreshore slope but other factors can provide steeper or gentler
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slopes for any particle diameter, i.e. how exposed a beach is and whether erosion or accretion
is dominant (Mclean & Kirk, 1969). There are numerous graphical representations for the
relationship between slope and grain size for sand beaches (i.e. Bascom, 1951; Wiegel, 1964)
but no equivalent representations for gravel beaches, although some authors (King, 1959;
Guilcher, 1958; Zenkovich, 1967) have calculated individual slope values. The general
consensus among these authors is that gravel beaches are steeper than sand beaches.
Although Wiegels (1964) and Bascoms (1951) principles are based on sand dominant
coastlines, they may be applied to gravel beaches with a certain degree of accuracy (Shepard,
1963). It must be noted that all models differ slightly and these discrepancies can be put down
to scale effects that are inherent to model studies (Pethick, 1984).
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Figure 2.17: Slope and particle size. Bascom 1954, in Pethick (1984)
Bascom (1951), suggests another distribution trend between particle size and its distribution
upon a beach face; the concentration of larger particles are to be found in the more active
swash zone where the highest wave energy concentrates. This is because larger particles will
be deposited as the swash energy is reduced, but smaller particles will remain suspended in
the backwash and so deposited further down the beach (see section 2.2.1.3). Although
agreeing with Bascoms (1951) model, Briggs (1977) noted a temporal, progressive aspect to
larger particle size in the active swash zone; this emphasises that higher energy over a longer
time-frame is maintained in the upper swash zone compared to the middle and lower swash
zones. As shown in figure 2.18 (Briggs, 1977) this causes differing zones of particle size across
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the beach profile which may be the case for the study site. It must be stated that Briggs (1977)
study, like Bascoms was based on sand beaches and so factors such as Aeolian transportation
are present, which is not the case for the study site which creates scope for inaccuracy.
Figure 2.18: Particle zonation. Briggs (1977)
As well as sediment size distribution, it is important to discuss other variables that impact
slope, particle size and sorting. Mclean and kirk (1969) illustrate the interdependency of the
statement that there is a relationship between slope and particle size based on data from
beaches in New Zealand (figure 2.19). It shows that sorting and mean grain size is paramount
in determining the beach angle. Poorly sorted material in the centre of this graph represents
low beach angles due to a reduction in percolation rates. It is apparent that sorting improves
over a greater range of grain size which is reflected by the steepening of the slope curves
(Mclean & Kirk, 1969). A conceptual framework of beach studies by Krumbein (1963) is utilised
in a pilot study which identifies foreshore response as the ultimate element, the results of
which fit the trend described by Krumblein and Graybill (1965). Mclean & Kirks (1969) model
focuses on mixed sand-shingle beaches but the study site for this investigation is
predominantly gravel clasts. However it is sufficient for this model to be used on a
comparative basis with the study site in order to assess the sedimentology and morphology.
Wave energy has a vital role in changing the geomorphology of a beach (Pethick 1984). The
interrelationships between beach gradient, sediment size and wave energy are important for
gravel barriers as depicted by Komar’s (1976a) graph (figure 2.20) for slope and particle size at
Half-moon Bay, California; the higher the wave energy, the steeper the beach face slope and
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the larger the grain diameter. This model sums up an in-depth argument of wave theory that’s
documented by Pethick (1984) and provides a valuable base on which to compare the results
of Dungeness gravel barrier.
The models discussed above will be utilised as comparisons to the results obtained for the
study site in order to gain an understanding of the morphology and sedimentology of the
differing beach environments. It must be stated that beaches are often experiencing
contrasting processes and influences which ultimately will shape the slope and particle size
relationship.
Figure 2.19: Beach angle and particle size sorting. Mclean and Kirk (1969) from Pethick (1984)
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Figure 2.20: Wave energy and slope angle. Komar (1976) in Pethick (1984)
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Methodology 3.
In order to successfully carry out the ‘investigation into the sedimentology and geomorphology
of Dungeness Gravel barrier’, a comprehensive methodology was devised as an initial
structure, enabling thorough completion of the initial objectives set, which are restated below:
(i) To identify appropriate locations either side of Dungeness spit to test the validity of
academic models from beach slope and particle size literature.
(ii) Characterise the morphology of the east facing and south facing beach.
(iii) Characterise the sedimentology of the east facing and south facing beach
(iv) Consider the above findings in relation to existing models of beach slope and
particle size literature.
Outline: 3.1
The initial sites suitable for data collection were determined, one on the south beach and one
on the east beach of Dungeness. Identification of the appropriate locations enabled field work
to be completed during October 2014, aptly before the high-energy storm conditions of winter
had begun. Beach slope data was recorded using techniques devised by Bascom (1951);
samples would be collected and analysed using the Zingg’s (1935) field classification to
establish particle size data, to then be formulated in excel and then classified using the Udden
(1914)- Wentworth scale (1922). The information was then communicated in Gradistat (Blott &
Pye, 2001) to work out mean particle size and sorting. Data results were then analysed and
compared against the models of McLean and Kirk (1969), Komar (1976) and Briggs (1977) (see
section 2.6), to identify any correlation or stark variation for later discussion.
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Locations for suitable data collection: 3.2
To fulfil objective (i) a suitable study site for this investigation needed to allow for the
examination of beach particle size against beach slope in the coastal environment. The
locations identified in figure 3.1 represent one transect upon the south and east beach
respectively in central positions. The beaches were visually surveyed beforehand for so a good
representation of the entire south and east beaches sediment regime and slope values were
portrayed. Time constraints meant a preliminary study was not performed; however weather
conditions such as wind speed, direction and strength were acquired from the Met Office (Met
Office, 2014). These were noted along with sea conditions sourced from the Royal National
Lifeboat Institution (RNLI 2014) which helped with selecting the data collection site and with
the data collection process itself.
The data collection sites chosen were at an even distance from the Power Station to limit the
effect of any beach management strategies occurring directly in front of this industrial facility
(see section 2.4.1). These sites were also an even distance from the foreland point and
relatively easily accessible by way of roads. Selecting the site on personal perception is liable to
bias (Good & Hardin, 2003), but the above measures were taken to reduce this likelihood.
Weather conditions and other plausible factors that would influence the relationship between
slope and particle size were also recorded as stated above. The transects (figure 3.1) are
hypothesised to see contradictory conditions from one beach to another due to the
positioning and the controlling factors upon slope and particle size, as stated throughout the
literature review.
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F
Figure 3.1: Location of Transects at study site, from Buglife (2013), and taken by author.
Profile A
Profile B
South facing
beach
East facing
beach
Prevailing wind direction
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Data collection: 3.3
In order to characterise the sedimentology and morphology (objective (ii) and (iii)) of the
study sites an accurate strategy for recording slope and particle size data was necessary (King,
1972). Previous studies on gravel beaches by Caldwell (1985) used Blucks (1967) classification
scheme and identified that on higher-energy beaches, judgement of sediment sorting could be
made using particle size rather than shape. Other than the aforementioned authors, gravel
beach classifications have been developed with long term barrier evolution as a focal point
(Orford et al, 1996; Carter & Orford, 1988) much like the environment of the study site. Gravel
beach classification however has presented issues, established by Jennings and Schulmeister
(2002). The transects chosen spanned from the upper most wave limit (signs of sea weed) and
as far seaward at the lowest accessible tide. Data collection was undertaken at similar times of
day for comparable results and both sediment and slope sites correspond with each other so
that any relationship can be sufficiently assessed (Larson et al, 1997).
3.3.1 Beach morphology/slope:
To achieve objective (ii), the beach profile was measured using a technique similar to that
used by Bascoms (1951) and Mclean & Kirks (1969) study, comparable to that used by Emery
(1961). They dictate the use of an Abney level, ranging poles, and tape measure so as to
collect accurate representative data. Ranging poles were placed at the very top of the beach
profile, and another at every visible change in slope (figure 3.1); this seemed to occur in a
similar place to where berm formation of a typical beach profile is expected (see figure 2.1).
The Abney level was used to gauge the angle between the poles by lining up the markers on
the top of the poles and sighting these markers through the level (figure 3.2), simultaneously
adjusting the spirit bubble to the line of sight. The angle displayed on the graduated Arc (figure
3.2) element of the devise was noted down along with distance between each ranging pole in
order to construct an accurate cross sectional display of the beach profile using trigonometry.
Using the same sighting technique, the process was repeated at every change of slope down
both transects including inclines and declines which allowed the characterisation of slope at
Dungeness gravel barrier (objective (ii)). The recorded slope angles, beach height, and distance
between poles were then formulated in excel and so accurate cross-sectional graphs for both
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beaches were created for comparison purposes, whilst trigonometry (tan-1) was used to
double check the accuracy of the results.
The technique described is flawed due to the high probability of human error occurring
throughout, and so there are some alternatives to improve accuracy; an inclinometer/
clinometer (Zinn, 1969; Gougie, 1990) or a site surveyor with a rigid tripod stand are tried and
tested methods that could potentially reduce the effects of human error.
3.3.2 Particle size:
Grain size analysis provides clues to sediment provenance, transport history and depositional
conditions (Folk & Ward, 1957; Freidman, 1979). To achieve objective (iii), samples were
collected at each visible change in particle size; 8 samples at site A and 6 samples at site B. A
total of 100 clasts were taken from each sample site to give a large statistical range, with all
samples being taken from the top few centimetres of the beach in order to analyse the most
current beach conditions (Moss, 1962). The samples were bagged and taken away to be
Figure 3.2: Slope measurement technique. CS.org.uk (2015)
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measured using a method formulated by Zingg (1935); this involved direct measurement (Blott
& Pye, 2001) using electronic callipers to measure the ‘a’ (longest axis), ‘b’ (medium/width)
and ‘c’ (thickness/ smallest) axis (Blott & Pye, 2008). This technique was used throughout the
data collection process as it can be difficult to assimilate size data obtained using more than a
single method (Pye, 1994). Additionally by using the same person and electronic callipers, a
reduced degree of error resulted. The figures were then plotted in excel spreadsheets in order
to divide each clasts axis by 3 to find the mean diameter. The mean values were then
compared against the relevant models (Udden, 1914; Wentworth, 1922) (figure 3.4) and a tally
system was utilised to assign a Phi size for each sample to then convert into percentages when
inserting values into the Gradistat program.
To achieve objective (iii) the final stage was the use of Gradistat to create results for
comparison with academic models. Gradistat provides fast calculation of grain statistics; Folk
and Ward (1957) (Figure 3.4) and moments methods incorporate data into excel spreadsheets,
allowing for tabular and graphical output. Sample statistics are then calculated including mean,
mode, sorting, skewness and kurtosis (Blott & Pye, 2001). Whilst other methods are available
(e.g. Slatt & Press, 1976) they are sluggish and do not allow for modification for specific focus.
The mathematical method of ‘moments’ looks at a sample population in its entirety (Krumbein
& Pettijohn, 1938), which allows for accuracy but also can be greatly affected by outliers.
However the size of sediment at the study site is likely to be generally larger than what is
suitable for moments methods, and so the Folk and Ward (1957) graphical technique was
more suitable for this study (Blott & Pye, 2001).
The mean particle size and sorting for each sample site were extracted from Gradistat and
formulated into various line graphs using excel in order to provide a visual comparison
between transect A and B. This was done in conjunction with the previously completed beach
slope profile graphs to gauge where any trends or differences in particle size sorting were in
relation to slope. All the necessary numbers were organised into a table for cross-referencing
with the various graphical representations to aid and achieve the characterisation of
sedimentology of Dungeness gravel barrier (objective (iii)).
The graphs produced for particle size and beach slope were to then be compared to the
academic models of Mclean and Kirk (1969), and Komar (1976) in order to achieve objective
(iv). The results for the study site were plotted on the models so trends and differences could
be clearly identified and discussion points drawn from this. At this stage the differences
between the south and east beach in terms of slope and particle size were evident and so the
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reasons for this could be discussed. The various processes carried out in this methodology are
expressed in the following results section.
Figure 3.3: Udden and Wentworth, and Gradistat descriptive, Blott and Pye (2001)
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Figure 3.4: Gradistat Logarithmic, Folk and Ward (1957) Graphical measures, Blott and Pye (2001)
Figure 3.5: Example of Gradistat content output, Blott & Pye (2001)
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Results 4.
The following results section presents the primary data collected using the methods outlined
in the section 3. Results for beach slope and particle size at the south and east beaches of
Dungeness gravel barrier are to be analysed separately and then collectively to identify any
similarities and differences, and in doing so provide an answer to the objectives stated in
section 1 and 3. Weather conditions were similar for both days of data collection, with
average wind conditions for the time of year and light precipitation (Met office, 2014).
Beach profiles 4.1
Figure 4.1: Beach Profile A, created by author
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Cross sectional beach profiles were created using the data collected as outlined in section
3.4.1; figure 4.1 and 4.2 describe the morphology of transects on the south (Profile A) and east
(Profile B) beach at Dungeness with sediment sample points from top to bottom expressed by
the red dots.
Working from the landward extent, profile A begins with a flat area slightly slanting inland;
from this point the profile slopes seaward with a number of changes in slope angle and no
clear pattern emerging. Two berm formations displaying inclines are present, (figure 4.1) one
in the upper centre quartile of the profile and the other in the lower central zone. Transect A
depicts a shallower slope over a longer profile of 35 metres; height from the seaward extent to
the uppermost point demonstrates a 4.1metre increased elevation. In comparison, profile B
expresses a shorter profile of 30 metres with an increased elevation of 4.6metres from
seaward extent to the top of the beach, giving a steeper profile. This ties in with the prediction
stated in the literature review by Anfuso et al (2008) and Redman (1852), that the higher
energy south facing beach (A) is under erosion and therefore shallower than the accreting
lower energy east facing beach (B).
Figure 4.2: Beach profile B, created by author
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Transect B demonstrates a flat area at the top of the beach, sloping slightly inland; from this
point on it slopes down towards the sea at a more abrupt rate than profile A and with less
fluctuations in slope angle. There is only one berm present towards the centre of the profile
compared to two on profile A. While the profiles were different heights, lengths, gradients and
so on, there were some clear trends between them.
The first of these trends to be identified is both beaches evidence a flat/ landward sloping area
at the top of the profile (Figure 4.1 and 4.2) known as a storm/ swale berm. Both profiles have
a high tide berm central to the profile area around 20 metres from the seaward extent and
below the berm each transect has consistent slope down to the sea.
Particle size 4.2
Particle size and sorting was calculated using Gradistat and excel to formulate the data
collected into meaningful results for all sample points along both transects, as stated in section
3.4.2. These results are expressed in table 4.1 showing the mean Phi size, beach angle, Udden-
Wentworth size description, size in millimetres, and sorting descriptions. Phi size and sorting
histogram line graphs have been used to analyse each sample point as they are easy to
interpret, and then the transects were directly compared against each other later on.
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Observing the histogram line graphs for transect A (Figure 4.3) it is evident that the
predominant sediment clast size ranges between -3 and -5 Phi (ᵩ) for all eight sample sites with
little fluctuation or outliers. The grade of sediment was predominantly medium gravel as
expressed in table 4.1 with the exception of coarse sediment found at sample site A4 and A6.
The level of sorting ranges from well sorted to Very well sorted across profile A (table 4.1).
Figure 4.3: Profile A: phi size histograms sample A-H, created by author
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The Histograms line graphs for transect B, suggest the predominant sediment clast size ranges
between -3 and -5 ᵩ(Phi) for all size samples taken. The grade of sediment according to the
Wentworth description (table 4.1) sees an even mix of medium and coarse gravel across the
profile. However the level of sorting showed much more variation; it ranges between
moderately well sorted and very well sorted across the whole profile.
Figure 4.4: Profile B Particle size histograms samples A-F, created by author
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Transects: Sample Mean Grain size (Phi) Beach angle (º) Wentworth description Mean Grain size (mm) Sorting descriptor
Transect A:
(South facing beach)
A -3.7 4 Medium Gravel 13.7 Very Well sorted
B -4.0 9 Medium Gravel 16.2 Very Well Sorted
C -3.8 1 Medium Gravel 14.7 Well Sorted
D -4.3 3 Coarse Gravel 20.3 Well Sorted
E -3.7 10 Medium Gravel 13.7 Well Sorted
F -4.5 3 Coarse Gravel 22.7 Well sorted
G -3.9 8 Medium Gravel 14.9 Very Well Sorted
H -3.8 8 Medium Gravel 13.8 Well Sorted
Transect B:
(East facing beach)
A -4.2 3 Coarse Gravel 17.9 Moderately Well Sorted
B -3.3 12 Medium Gravel 9.8 Moderately Well Sorted
C -4.4 9 Coarse Gravel 21.3 Well Sorted
D -4.9 6 Coarse Gravel 30.6 Very Well Sorted
E -3.8 10 Medium Gravel 14.0 Very Well Sorted
F -3.6 10 Medium Gravel 12.1 Moderately Sorted
Table 4.1: Summary of Calculated slope and sediment parameters, created by author
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0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
A B C D E F G H
Ph
i siz
e
Sample sites
Mean Phi size Transect A
Transect B
Overall distribution of particle size and sorting 4.3
Dungeness gravel barrier is shown to be dominated by a mean grain size of -4.0 Phi with
fluctuations falling between outer bands of -3.0 and -5.0 ᵩ (figure 4.5), and so for both
transects the grade of gravel ranges between medium and coarse. Transect A (south facing
beach) demonstrates a much more consistent profile in terms of particle size as shown by the
blue line (figure 4.5) compared to the much more fluctuating red line ( east facing beach), and
expresses generally smaller particle size across the whole profile than that of Transect B.
There are little trends evident in terms of an increase or decrease in sediment size from top to
bottom due to regular fluctuations in Phi size; however some trends can be seen between the
two beaches. The most evident trend to appear is the relationship of the coarsest sediment
on both transects being located on the shallowest angles of slope. Referring to table 4.1 and
figures 4.1, 4.2, sample D on both transects and sample F on transect A are all located on berm
formations, demonstrating a small degree of slope that accommodate coarse gravel. Another
trend identified is the steeper slopes upon both transects i.e. samples B,E,G and H, (Transect
A) and B, E and F (Transect B) all demonstrate smaller phi size (medium gravel).
Figure 4.5: Mean phi size for all sample sites, created by author
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0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
A B C D E F G H
Sort
ing
Sample sites
Particle Sorting Transect A
Transect B
Figure 4.6: Particle sorting for all sample sites, created by author
Figure 4.6 shows the level of sorting of each sample point across both transects; transect A
demonstrated in blue has a very consistent level of sorting ranging between well and very well
sorted (0.5-0.3) with a mean sorting of 0.38. In comparison, transect B depicts a much more
inconsistent level of sorting ranging from moderately sorted to very well sorted (0.9-0.3). It is
clear that profile A demonstrates better sorting than profile B but there are some trends to be
drawn upon. The most noticeable trend is the furthest points seaward see a reduction in level
of sorting, with profile B expressing this to a larger extent than profile A but the trend remains.
Point F could be considered an outlier, but from viewing the sample in the field, it appeared
less well sorted and therefore is included in the study. Another trend is seen between the
central samples (C-E) of both transects, where sorting becomes much more comparable
between the profiles.
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Comparison with academic models 4.4
The initial idea was to compare the results against Mclean and Kirks (1969) and Komar’s (1976)
model; however on reviewing the results from the study site, they were too large to be applied
to Komar’s model. Therefore the model was discounted from the results process and in its
place more in-depth comparison to Briggs (1977) model (see section 2.6) took place. All
sample sites were plotted upon an adapted version of the Mclean and Kirk beach face slope
and particle size model (figure 4.7 and 4.8) to draw out any significant trends or variances
(page 48).
Figure 4.7 evidences transect A to have some relationship between beach slope and particle
size sorting; samples B, E, G and H (circled in orange) conform to the trend of the model, all
being located on the steeper gradients upon the profile. Samples A, C, D and F (circled in
green) do not show any correlation, as they were found on the shallower sloped areas within
the profile.
Figure 4.8 shows transect B to have a less clear relationship with the academic model; sample
points B, C, E and F (circled in orange) show a reasonably close correlation, all being located on
the steeper gradients of the profile, but sample points A and D (circled in green) do not
conform to the model.
Key trends identified between the two profiles are that all the outlier sample points expressing
little correlation to the model are located on the high tide berm features or low gradient
slopes. The sample points that agree with the model were located on consistent lengths of
high slope gradient.
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Figure 4.7: Profile A comparison with Mclean and Kirk (1969) model, adapted by author
Figure 4.8: Profile B comparison with Mclean and Kirk (1969) model, adapted by author
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Summary 4.5
From the results above, a number of points and trends have presented themselves that are in
need of discussion.
Beach profile ‘A’ is distinctly shallower than ‘B’ demonstrating a shorter height gain from
seaward to landward extent. They both demonstrate high tide berm formations and both
transects exhibit medium to coarse gravel across their profiles, with A being more consistent
with smaller mean phi size than profile B. Once compared to the McLean and Kirk (1969), the
trends between the profiles became clearer; samples upon steeper slope exhibited larger
sediment size and better sorting, whereas samples collected on shallower areas such as berms
did not correlate with the model. The following section titled discussion will look to clarify the
points raised in order to achieve the original objectives set (see section 1.3).
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Discussion 5.
Beach Profile slope variation 5.1
The morphology of Dungeness Gravel barrier beaches was characterised using techniques
mimicking that of Bascom (1951) and Mclean & Kirk (1969) as outlined in section 2.6. This
process allowed for the discovery of similarities and differences in the morphology between
the south facing beach (profile A) and the East facing beach (profile B). From the combined
beach profile graph (figure 5.1) it was evident that profile A has a shallower slope over a longer
expanse than profile B.
There are a number of potential reasons for the differentiation of slope; the first point of
discussion is the positioning of the beaches that each profile represents. Profile A is situated
on the south coast being exposed to the south-westerly prevailing winds, which dictate the
dimensions of wave creation as stated by Bird (2008) and Banner & Song (2002) (section 2.2.1).
The profile receives waves that have travelled a long distance from the North Atlantic,
enhanced by the strong prevailing winds, and from a greater water depth resulting in
increased wave power (Holthuijsen 2007). This is evidenced in figure 5.2 (admiralty chart); the
darker blue areas depict deep water on the south coast, and the green areas express the
shallower sand flat topography present in front of profile B on the eastward side. Profile B is
sheltered from the prevailing winds and associated waves due to being located round the spit
(see figure 3.1) which acts like a headland; therefore the erosional waves associated with this
process have far less of an impact here.
Wave refraction has been identified by the likes of Masselink & Hughes (2003) as a control
upon gravel barriers like Dungeness by influencing sediment transport and therefore beach
morphology. Referring to King’s (1980) wave refraction diagram (figure 2.4), profile A is
predicted to be affected by oblique wave refraction attacking the coastline from west to east.
This correlates with the direction of LSD, and areas of deep water (figure 5.2), so wave velocity
does not decelerate due to lack of frictional sea bed effects. In contrast, the shallower water
depth on the eastward side boasting extensive sand flats causes the already low energy waves
to be reduced in power as the frictional effect of the sea floor retards the advancing waves
(Bird, 2008), reducing their erosional impact on profile B.
As a result, profile A experiences high rates of erosion (see figure 2.12) (Green, 1968; Williams
et al, 2005) whilst high accretion rates at profile B are seen, creating a steeper beach profile
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Figure 5.2: Admiralty Chart, Beachy Head to Dungeness, ChartCo (2015)
here. The positioning of the beaches, associated wave refraction and LSD are therefore major
contributors in distributing sediment on gravel barriers as reviewed by Carr (1969) and Davies
(1985), causing the differentiation in slope at the study site.
Figure 5.1: Beach profile comparison, created by author (2015)
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The distinct shape of the foreland is of vital importance when discussing slope variation at the
study site as the vastly differing beach environment and processes to the south and to the east
are as a result of this shape. Figure 2.11 shows aerial views depicting the formation of the
cuspate foreland as outlined in section 2.3 and 2.4.1 (Lewin, 1862 & Gulliver, 1987). This
cuspate barrier formation ties in with the models by Summerfield (1991) and Cope (2004)
further emphasising the importance of LSD and associated coastal processes are having upon
this gravel barrier, creating the differing conditions on the south and east beach resulting in
slope differentiation.
Of the two extreme forms of profile stated by Stripling et al (2008), Profile A and B both fall
into the category of steep storm profile. Storms are a large contributor to the morphology of
these two sites, in particular the exposed profile on the south coast (Profile A). Frequent storm
events originating in the North Atlantic are linked strongly to the study site as stated in section
2.4.2 (Tanner, 1973 and Nicholls & Webber, 1987), which supply sediment sourced further
down the coast to the south beach (Profile A). This is shifted along by the processes previously
mentioned with littoral drift factored in, and deposited at the east beach (Profile B); in high
energy storm events the rate of erosion on transect A is drastically increased, and therefore
deposition increases round the ness/bend. The presence of storm berms at the top of both
profiles (figure 5.1) is evidence of storm waves causing deposition high up the profile where
over topping has occurred in spring/ neap tide conditions. This suggests that although Transect
B is sheltered in comparison to A, it is still influenced by storm events, hence the presence of a
storm berm.
Mean grain size (Phi) across profile A is generally smaller than B ( figure 4.5) and can be an
attributing factor to the shallower slope gradient as shown in figure 5.1, which agrees with
Bascoms (1951) model stating steeper profiles have characteristic larger particle size than
those with shallower slopes. The coarser sediment found on transect B creates greater
infiltration rates (see section 2.2.1.3) allowing water to percolate through into the water table,
reducing the power in the backwash. This causes less resistance to the swash movement upon
the east facing beach so sediment builds up creating a steeper profile. This agrees with Blott &
Pye (2010) and Carter & Orford (1993) (section 2.4.5) who states that swash processes are a
key controlling factor upon beach morphology (Mason & Coats, 2001). The east beach is less
processed by wave action which may be an influence in seeing this larger sediment size
present at transect B compared to the more processed smaller sediment at A; this agrees with
Briggs (1997) model which will be discussed later on. The relationship between particle size
and slope is therefore evident for the study site.
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The linear relationship between grain size sorting and foreshore slope must also be considered
for the study site. Wiegel (1964) identified the trend of increasing slope with grain size sorting
and decreasing slope with increasing wave energy. The results show that transect A is far
better sorted across the whole profile yet it demonstrates a shallower slope, and agrees more
with Komars (1976) model. There are possible reasons for the level of sorting not agreeing to
the trend suggested, and it must be considered that these models suit sand beaches rather
than gravel (Shepard, 1963). Swash processes often affect the whole of profile A from bottom
to top, constantly processing the beach sediment, resulting in a well sorted beach; this is
expressed by the consistent level of sorting (figure 4.6) which disagrees with the models by
Mclean and Kirk (1969) and Bascom (1951). The reduced wave power due to the sheltered
environment causes a less powerful wave processes and so sediment towards the top of the
profile remains unprocessed for long periods of time until infrequent large storm events occur.
This is evidenced in figure 4.5; the level of sorting is worse at the top of the profile, and
improves drastically in the swash zone area where the beach is being processed regularly. This
ties in with Bascoms (1951) model to a certain extent, but disagrees with their claim that less
wave energy should result in a shallower profile. This can be put down to the accreting nature
of this beach creating the steeper slope profile.
The slope of each profile does not differentiate as much as would have been expected before
undergoing this study, and one reason for this is the ongoing beach replenishment programme
(Thorn, 1960) (see section 2.4.1). Profile A was predicted to be a lot shallower than B, but the
accreted sediment from the east beach is regularly taken and deposited on the south coast to
protect the Nuclear Power Station. This management scheme is a necessity at the study site
because as suggested by Carter et al (1987), drift aligned barriers like Dungeness will remain as
long as sediment is delivered to the distil end, which the management process is catering for.
Sediment supply via littoral drift ( section 4.4.3) (Jennings & Smyth, 1990; Nicholls,1991) is not
efficient enough to replace the sediment being displaced from the south facing to east facing
beach by LSD. Therefore the management scheme is necessary so that the gravel barrier
remains a flood defence to the local area. This is one theory behind the surprisingly similar
morphology between the two profiles.
The above discussion of beach slope variation between the two beaches agrees with the
prediction in the literature review by Anfuso et al (2008) and Redman (1852) that erosive
beaches have a resultant shallower slope like transect A (south facing beach) compared to
steeper accreting beaches like transect B.
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Particle size and sorting 5.2
The sediment present upon Dungeness gravel barrier has variable grain size (table 5.1) that
complies with the particle size range that Green (1988) suggested form the gravel barrier
sedimentology here (see section 2.4.3). When analysing the particle size across both profiles
and displaying them against each other in the results section, no visible trends appeared and
instead, regular fluctuations were seen across the transects; however there are some clear
trends and differences to be discussed.
Sample Mean Grain size
(Phi)
Beach angle
(º)
Wentworth
description
Mean Grain size
(mm)
Sorting
descriptor
A -3.7 +4 Medium Gravel 13.7 Very Well
sorted
B -4.0 -9 Medium Gravel 16.2 Very Well
Sorted
C -3.8 +1 Medium Gravel 14.7 Well Sorted
D -4.3 3 Coarse Gravel 20.3 Well Sorted
E -3.7 -10 Medium Gravel 13.7 Well Sorted
F -4.5 +3 Coarse Gravel 22.7 Well sorted
G -3.9 -8 Medium Gravel 14.9 Very Well
Sorted
H -3.8 -8 Medium Gravel 13.8 Well Sorted
Table 5.1: Particle size and sorting of transect A, created by author
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Table 5.1 shows that the beach slightly fluctuates in particle size from shoreward (A) to
seaward extent (H) but remains relatively consistent with no real pattern. There are aspects of
the transect that agree with the models put forward by Bascom (1951) and Syvitski (1991) who
state larger particle size is found in the active swash zone of a beach. Sample D and F
demonstrate mean particle size of -4.3 and -4.5 respectively which is above the average trend
for this transect. These areas receive the highest wave energy over the lengthiest time
duration which has resulted in coarse gravel situated here, compared to medium gravel for the
rest of the transect. These flat berm formations are formed under the high energy storm swells
from the North Atlantic (Hogben & Lumb 1967), where the swash dynamics entrains smaller
particles in backwash carrying them further down the beach and leaving the larger particles on
the berms, suggesting Infiltration rates are low on this beach. Therefore the findings for
transect A show some correlation with the aforementioned models of Bascom (1951) and
syvitski (1991).
It is curious that sample E, located between the two coarse gravel sample sites demonstrates a
smaller particle size (-3.7). Similarly all the other samples on the profile demonstrate smaller
particle size than sample D and F, and are all located on gradients with the exception of sample
C. This tends to disagree with Bascoms (1951) and Mclean and Kirk (1969) models who state
particle size increases slope. Samples A, B and C are found on swale areas above the berm
which do not receive frequent swash dynamics with the exception of infrequent overtopping,
and so deposition occurs here aided by high infiltration rates. The other samples (G and H) are
in the lower swash zone which receives smaller particles that have been entrained in the
backwash and deposited in lower swash zone of the profile. This agrees with Bascom (1951)
and Briggs (1977) temporal model (figure 2.18).
Sorting across the whole transect shows very little variation with all samples being either well
or very well sorted. This can be put down to the conditions present on the south beach
impacting the particle size sorting, as stated by the Mclean and Kirk (1969) model. The whole
profile is being processed by continuous swash dynamics due to the exposed nature of the
beach to the strong west to east prevailing wind bringing long period swells mentioned above,
resulting in the well sorted profile.
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Table 5.2 and figure 5.4 demonstrate the mean grain size for transect B to be much more
inconsistent than transect A with larger particle size on steeper slopes which ties in with the
Mclean and Kirk model (1969). On initial examination the variations in results are very
consistent with Bascom (1951), and Syvitski’s (1991) models which predict to see increased
particle size at sample points C and D as these areas are in the active swash zone. The samples
have particle sizes of -4.4 and -4.9 respectively, way above average for the transect, which also
agrees with Briggs (1977) zonation model (figure 2.18) who predicts coarser sediment to be
found on these berm crest formations. Sample points B,E and F demonstrate medium gravel
and are located either on the swale area, above the berm and so unaffected by the swash, or
in the lower swash zone which again correlates well with the aforementioned models. Sample
point A however does not fit within the models as it demonstrates large particle size on the
inactive storm berm. This larger sediment was likely deposited in a high energy storm event,
hence the name of this part of the profile.
Sorting at transect B is much more varied than transect A which is in unity with the particle size
relationship. This is an important point as sorting is not an independent variable; instead it
works in combination with particle size to influence beach slope (figure 2.19) (Mclean & Kirk,
1969). As mentioned in section 5.1 this transect displays moderately well sorted areas in the
less processed parts of the beach which can be seen for sample point A and B. These are the
swale areas after the berm where swash action rarely reaches unless overtopping occurs. The
Sample Mean Grain
size (ᶲ)
Beach
angle (º)
Wentworth
description
Mean Grain
size (mm)
Sorting descriptor
A -4.2 +3 Coarse Gravel 17.9 Moderately Well Sorted
B -3.3 -12 Medium Gravel 9.8 Moderately Well Sorted
C -4.4 -9 Coarse Gravel 21.3 Well Sorted
D -4.9 +6 Coarse Gravel 30.6 Very Well Sorted
E -3.8 -10 Medium Gravel 14.0 Very Well Sorted
F -3.6 -10 Medium Gravel 12.1 Moderately Sorted
Table 5.2: Particle size and sorting of transect B, created by author
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areas in the active swash zone depict well or very well sorted sediment (table 5.2) accept point
F at the bottom of the transect. Possible reason for this is that the sample is located at the
bottom of a steep gradient (10 °), and so there is potential for larger particles to roll down the
profile and settle in this zone (Goudie 2004). The particle size results however do not agree
with this theory and so this could be treated as an error in the data collection process.
Comparison to academic models 5.3
When comparing the results of the study site against the Mclean and Kirk (1969) there is a
clear relationship shown by both transects once the model had been adapted slightly to suit
larger gravel beach values. As mentioned throughout the discussion, sample sites that were
collected from slopes on the profile correlated well with the trend line as shown in figure 5.5.
This suggests that the model works well for beaches with consistent slope profiles, although
not entirely for this study site. The shallower profile of transect A gave better sorting results
than the steeper slopes of transect B, which as stated before may be down to the varying
conditions present (Mclean and Kirk 1969).
Samples collected on the flat sections or berm features of both transects did not correlate
with the trend line. There are a few possible reasons for this, the initial being that differing
processes are occurring upon the berm areas than the slopes (See section 2.2.1.3, Briggs,
1977) which may not occur in the same way on sand beaches, of which the model was based
on. Another potential reason is that the model is not sophisticated enough to portray the
varying conditions occurring on the gravel barrier. This can be associated to the understanding
of gravel beach dynamics lagging behind that of littoral finer sediment environments as stated
by Buscombe & Masselink (2006), and so a more advanced model than the Mclean and Kirk
(1969) would be needed in order to represent the study site more effectively.
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Figure 5.3: Profile A and B comparison with the Mclean and Kirk (1969), created by author
Transect A samples
Transect B samples
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Conclusion 6.
Summary 6.1
To summarise the success of this project, analysis of how effective the various sections have
been at answering the initial objectives must be discussed.
Objective (i): to identify appropriate sites either side of Dungeness spit to test the validity of
academic models from beach slope and particle size literature.
The locations of both transects were chosen with the aim of limiting the effect of bias and to
achieve the highest accuracy possible. On completion of the results section it became apparent
that the sites chosen gave a representable set of data for both beaches from which trends and
discussion points were drawn upon throughout the project.
Objective (ii): Characterise the morphology of the east facing and south facing beach.
From using existing techniques in academic studies of beach slope and particle size, the
morphology of Dungeness gravel barrier revealed some key trends and differences. Transect A
demonstrated a longer and resultant shallower profile representing the south facing beach,
whilst transect B expressed a shorter and steeper profile for the east facing beach. From the
literature it was established that the positioning of the beaches created differing environments
and associated differing coastal processes; profile A is exposed to the prevailing wind which
brings wave associated processes i.e. refraction, littoral drift and LSD creating a shallower
erosive beach profile. Transect B is sheltered from these conditions as the spit acts like a
headland, and so an accretive steeper profile is present. This agreed with the theories of
Anfuso et al (2008) and Redman (1852). The difference in profiles was relatively minor which
has been attributed to the beach replenishment regime.
The profiles differ in terms of height, gradient and length but there were some trends evident;
both transects demonstrated storm/ swale berms at the top of the profile, indicative of the
high energy winter storms associated with this part of the English channel. The high tide
berms on each transect are located a similar distance up the profiles suggesting that at the
time of data collection tide levels were equal, characteristic of calmer autumn conditions.
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Objective (iii): Characterise the sedimentology of the east facing and south facing beach.
Using the existing academic techniques as a guide, the sedimentology of Dungeness gravel
barrier was achieved, revealing some trends between the study site and the models
themselves. Profile A and B exhibited many trends expected according to models by Bascom
(1951) and Syvitski (1991); larger sediment was found in the more active upper swash zones
where berms are located, and smaller sediment found on swale and lower swash zones. Profile
B exhibited larger sediment than profile A on a steeper profile which agrees with the Mclean
and Kirk (1969) model and demonstrated a stronger correlation than profile A. The level of
sorting was consistently better on profile A than B which correlates with the trend of particle
size and is caused by the more exposed active beach. This relates again to the coastal
processes that influence slope levels, manipulating particle size and sorting on the two
beaches.
Objective (iv): Consider the above findings in relation to existing models of beach slope and
particle size literature.
As mentioned above, the study site as a whole transmits relatively well to the models of slope
and particle size by Bascom (1951), Briggs (1977) and Syvitski (1991). This is also the case for
the Mclean and Kirk (1969) model to a certain degree; the samples obtained on consistent
slopes correlated well with the model (figure 5.5), but samples representative of flat berm
features showed no correlation. This can be put down to a lack of sophistication in the model,
not being able to cater for differing energies occurring on the beach. A more advanced model
based purely on gravel beaches is therefore needed in order to represent the study site.
Limitations and improvements 6.2
Throughout the project, some limitations of the methods used became apparent. The method
of measuring particle size using callipers has high scope for human error, mainly due to the
longevity of this task, although the use of electronic callipers helped reduce this likelihood. To
improve the accuracy perhaps measurement of clasts over a few days rather than in one sitting
may prove beneficial. The depth on the surface from which sediment was selected was
between 1- 5cm below the surface but no exact depth was measured so there is no guarantee
that the most recent beach conditions were sampled. The use of an abney level is liable to
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human error and so using alternative methods such as a site surveyor would reduce this
likelihood.
The models used in this study are limited in accuracy in relation to the study site because they
are based on finer sediment environments than that of Dungeness. This is limiting factor
throughout the entire study but the application of these models were deemed appropriate for
the objectives set. The Mclean and Kirk (1969) model lacked the sophistication to relate well
with the study site and so the identification of a more complex model is required in future,
along with more extensive academic reading.
The study was carried out in early autumn on one transect per beach and so only represents a
snapshot of the environment resulting in spatial and temporal issues. Further study of several
more transects across the beaches and samples collected at various times throughout the year
would give a greater insight into the sedimentology and geomorphology of Dungeness Gravel
barrier. Broadening the elements of the study for example, including variables such as particle
shape could be a way of further enhancing the accuracy and scope of this study in the future.
To conclude, this study has provided sufficient answers to the objectives set and in doing so,
providing a better understanding of the geomorphology and sedimentology of Dungeness
gravel barrier. Understanding of these high energy coastal environments has been improved,
and a better interpretation of slope and particle size relationship has been established. With
human management in place, the gravel barrier should remain as an important defence to the
local area from the threat of SLR.
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Appendices: 7.
Appendix 1 7.1
University of the West of England
Faculty of Environment and Technology Programme: BSC Geography and Environmental Management Student Name Tony Gregory
RISK ASSESSMENT FOR STUDENT ACTIVITIES (Project Work, Dissertation Research and Off-Campus Visits etc.)
As part of a programme of work, students are often asked to undertake activities which could, in certain circumstances, be risky if not carried out safely and with forethought. For example, project work may involve visiting areas away from the University and dissertations may involve the use of equipment or work in external environments such as coastal areas liable to flooding. The University needs to know that you have considered carefully the risks you may be running in undertaking these activities. Therefore, you are asked to answer the questions below seriously and thoroughly. The Faculty will not approve your undertaking these activities as part of University work unless you have completed the form, and it has been signed by the relevant module leader and, where necessary*, the Module Leader. Note: The activities covered by this Risk Assessment are quite separate from field trip and study visits organised by the Faculty.
You and your Visit:
Nature of activity proposed
Investigating sedimentology and morphology of Dungeness gravel beach
Description of tasks
Collect gravel for measurement of particle size. Collect slope angle data of the beaches.
Location(s) of activity
Dungeness, kent
Date/s of activity
18- 25th
October 2014
Reporting arrangements. Who knows what you are doing? Who has been informed where you will be working and when you will be expected back?
Dr Chris Spencer, Ella and Anthony Gregory
Who else will be present?
Sebastian Gregory (Brother)
How will you travel to the location?
Car
Lone work. What do you think are the potential risks?
Risk of drowning, or injury on hard stone surface
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Please give your mobile no. What other emergency communication arrangements have been made?
07703430493.
If relevant, where will you be staying overnight during the visit?
Description of the tasks you will be undertaking.
Collection of sediment particle size, and measurement of beach slope gradient.
Medical:
Availability of medical care and emergency services. If the visit is outside UK, what provisions have you made for health care?
N/A
Do you have any concern for the physical and mental well being of yourself or any other members of your group?
N/A
Have you made all reasonable provision to deal with any medical condition you have that may influence your ability to carry out the activity? If there are no medical issues, please indicate this and write N/A(Not applicable).
N/A
Physical:
Are there any potential hazards in the visit or the tasks you will be doing? If so what have you done to minimise these risks? Eg. I intend climbing ladders; I intend to enter the sea
Visited site at low tide.
Will you be exposing yourself to extreme climate condition? If so, what precautions are you taking? Eg. I intend camping on a beach
Will the nature of your task or location expose you to any potentially aggressive behaviour from others? eg. I will be asking questions of members of the public. If so what precautions have you taken? Eg. I will always be accompanied by ….; I will always have my mobile with me.
N/A
Comments by Dissertation Tutor: Signature and date:
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Appendix 2 7.2
ETHICAL REVIEW CHECKLIST FOR UNDERGRADUATE AND POSTGRADUATE MODULES Please provide project details and complete the checklist below.
Project Details:
Module name Final year project
Module code UBGMQD-30-3
Module leader Simon Arlidge
Project Supervisor Chris Spencer
Proposed project title To understand the geomorphology and sedimentology of Dungeness Gravel barrier.
Applicant Details:
Name of Student Tony Gregory
Student Number 11020965
Student’s email address [email protected]
CHECKLIST QUESTIONS Y/N Explanation
1. Does the proposed project involve human tissue, human participants, environmental damage, the NHS, or data gathered outside the UK?
N If the answer to this is ‘N’ then no further checks in the list need to be considered.
2. Will participants be clearly asked to give consent to take part in the research and informed about how data collected in the research will be used?
N
3. If they choose, can a participant withdraw at any time (prior to a point of “no return” in the use of their data)? Are they told this?
N
Faculty of Environment & Technology
Faculty Research Ethics Committee (FET FREC)
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CHECKLIST QUESTIONS Y/N Explanation
4. Are measures in place to provide confidentiality for participants and ensure secure management and disposal of data collected from them?
N
5. Does the study involve people who are particularly vulnerable or unable to give informed consent (eg, children or people with learning difficulties)?
N
6. Could your research cause stress, physical or psychological harm to anyone, or environmental damage?
N
7. Could any aspects of the research lead to unethical behaviour by participants or researchers (eg, invasion of privacy, deceit, coercion, fraud, abuse)?
N
8. Does the research involve the NHS or collection or storage of human tissue (includes anything containing human cells, such as saliva and urine)?
N
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References 8.
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