North East Isle of Wight

North East Isle of Wight (East Cowes to Culver Cliff)

The North-East Isle of Wight coast forms the southern margin of the East Solent and Spithead. It is widely recognised that this waterway occupies the axial line of an eastward trending Pleistocene drainage system (the Solent River) which was drowned during the Holocene (Flandrian) transgression (Dyer, 1975, 1980; Anon., 1997; Velegrakis, et al., 1999). Inundation was accompanied by erosion of previously extensive Pleistocene fluvial and niveo-fluvial gravel terraces leaving only small remnants, such as Sturbridge Shoal. It is likely that the sands and gravels were reworked and contributed significantly to: (i) palaeo-channel infilling (Lonsdale, 1970; Dyer, 1975; Tomalin, 1991; Long and Scaife, in press) (ii) the contemporary sediment transport pathways of the Solent eventually being delivered to major sinks such as Brambles Bank, Ryde Sand and the Portsmouth Harbour ebb tidal delta (Bray, Carter and Hooke, 1995). The pattern and diversity of offshore, nearshore and intertidal sediments of this coastline reflects in part this inheritance from the Pleistocene and Holocene evolution of the Solent, developed in more detail in the special Section covering the "Holocene Evolution of the Solent."

Tidal currents are less rapid in the East Solent (generally <1ms^-1) compared to the West Solent (>2ms^-1) so that only sediments up to the grade of medium sand are regularly mobile in these moderate depths (Dyer, 1980; Webber, 1980; Halcrow, 1996; HR Wallingford, 1992, 1993 1995, 1997). Gravels are only mobile within shallow waters especially close to the shoreline and over inshore banks. Net transport into Spithead and the East Solent is indicated by analysis of bedform asymmetry in Hayling Bay and in the vicinity of the Nab Tower (Lonsdale, 1969; Dyer, 1980). Mineralogical analysis of sediments suggests that material may be transported from the south and east Wight coast into the East Solent, whereupon a proportion is deposited on the north-east Wight coast, particularly at Ryde Sands (Lonsdale, 1969; Dyer, 1980, Ball, 1985; Algan et al., 1994). However, experimental and numerical modelling studies undertaken within the South Coast Seabed Mobility Study (HR Wallingford, 1992 and 1993) suggests that there is net transport of sand eastwards on the bed within Spithead and south eastwards in the vicinity of No Man’s Land Fort. Furthermore, eastwards transport is indicated strongly from Sandown Bay with a zone of deposition identified some 5-10km seaward of Culver cliff and Foreland. These studies are considered to be of medium to high reliability thus implying that any sediment supply to Ryde Sands from the SE is confined to the nearshore zone and is largely wave powered.

Irrespective of the net direction of long term transport further seaward, the large quantity of sediments that have accumulated at Ryde Sands exert a significant influence upon transport at the shoreline. The coast east of Nettlestone Point is open to waves generated in Hayling Bay and diffracted swell waves from the English Channel (Posford Duvivier, 1990b). Wave energy is therefore moderate and from a predominantly east or south-east direction. By contrast, Ryde Sands in combination with the presence of the Isle of Wight provides shelter against these waves for the foreshore to the west so that wave energy is significantly lower and locally generated wind waves from west or north west are significant. Analysis of wind speeds and fetch lengths indicates that a significant wave height of 1.2m is rarely exceeded on any part of the shore to the west of Ryde Sands (Hydraulics Research, 1988; HR Wallingford, 1995).

Offshore gradients are relatively gentle and the shoreline is not greatly affected by tidal currents except at the small inlets of Wootton Creek and Bembridge Harbour. Tidal flow through narrow entrances to these inlets generates rapid currents which interrupt littoral sediment transport causing local circulation effects and associated fluctuations in patterns of sedimentation at, and seaward of, harbour approaches (Posford Duvivier, 1991b; 1994a; 1999; 2000a). In common with the other tidal inlets of the Solent the hydraulic regimes are ebb-dominant. That is, the tide falls faster than it rises so that ebb currents are shorter in duration, but more rapid than their flood tide counterparts. It results in a tendency for net transport of bedload sediments (medium sands and gravels) out of inlets to become stored in ebb tidal deltas and net input of suspended sediments (fine sands, silt and clay) to infill estuaries and harbours. This process has not been understood directly from data studies of the IOW estuaries themselves, but is inferred based on detailed studies of the mainland harbours that have similar tidal regimes (see section on Chichester Harbour).

Coastal geology comprises a sequence of gently eastwards dipping interbedded Oligocene clays, silts and limestones of the Osborne Beds, Bembridge Limestone and Bembridge Marls units (Halcrow, 1996). Locally, these solid formations are capped by coarse clastic Pleistocene fluvial and marine deposits (White, 1921; Preece et al. 1990). The clays are soft and readily degraded; the limestones are more durable, but are permeable and act as minor groundwater reservoirs supplying water to the slopes at their coastal outcrop (White, 1921). Much of the coastal slope is therefore potentially unstable, especially during conditions of basal debris removal. Coastal topography is generally low and rises to a maximum of 30m, forming both active cliffs and relic partially stable degraded coastal slopes. The estuarine inlets of Bembridge Harbour and Wootton Creek are former tributaries to the Solent River which have been partially infilled by Holocene sediments. Documentary evidence covering most of the twentieth century suggests that Bembridge Harbour, at least, continues to trap sediment.

2 Sediment Inputs

2.1 Marine Inputs - F1 F2 F3 F4 References Map

Seabed sediment sampling studies within the eastern Solent have revealed a predominantly muddy sea bed between Old Castle Point and Ryde (Lonsdale, 1969; Dyer, 1972). On basis of correlations of sedimentological character, it is inferred that much of this mud has been transported into the Eastern Solent by tidal currents from sources in Bracklesham Bay and South and East Wight (Dyer, 1980; Algan et al., 1994). As evidence is not conclusive, transport pathways cannot be clearly indicated (HR Wallingford, 1993). A substantial proportion may have been derived from local erosion of clay cliffs and possibly the bed within the Solent as a whole (Posford Duvivier, 1999a & 1999b).

F1 Supply to Ryde Sands (see introduction to marine inputs)

Investigations of bedforms within the Eastern Solent and Spithead indicate predominantly westward transport of sand immediately seaward of the NE Wight Shore (Lonsdale, 1969; Dyer, 1972). This transport pathway probably supplies a proportion of its sediment to Ryde Sands (probably the coarser elements), whilst the remainder may continue further into the East Solent, possibly becoming deposited on Brambles Bank. Mineralogical analysis of sediments at Ryde Sands has revealed a high proportion of limonite, a mineral characteristic of sands derived from the Lower Greensand (Lonsdale, 1969; Dyer, 1972; 1980). Sandown Bay comprises the closest location of such materials and may thus be one of the source areas. The mechanisms of transport and the precise pathways are uncertain although bedload transport in the shallow nearshore waters driven by dominant south and south-east waves can be reasonably postulated on the basis of other established transport routes and hydraulic gradients. Reliability is considered to be medium for whilst the evidence itself is convincing, it conflicts partially with more recent numerical modelling studies as explained below. More recently, the South Coast Seabed Mobility Study (HR Wallingford, 1992 and 1993) has suggested that there is net transport of sand eastwards on the bed within Spithead and south eastwards in the vicinity of No Man’s Land Fort. Furthermore, eastwards transport is indicated strongly from Sandown Bay towards a zone of deposition identified some 5-10km seaward of Culver cliff and Foreland. These studies are considered to be of medium to high reliability thus implying that any sediment supply to Ryde Sands from the SE is confined to the nearshore zone and is largely wave powered.

F2 Supply to Hayling Bay (see introduction to marine inputs)

Divergence of the F1 sediment transport pathway is postulated at the Foreland with a proportion of material being transported northward into Hayling Bay (Dyer, 1972; 1980). This possibility is consistent with the mineralogical and sedimentological character of materials in Hayling Bay and with the dominant wave direction, but in the absence of further corroborative evidence reliability must be considered low.

F3 Suspended Sediment Input to Estuaries (see introduction to marine inputs)

Asymmetry of the tidal regime within the East Solent results in ebb flow of relatively shorter duration, but greater velocity than corresponding flood flow (Webber, 1980). This phenomenon favours input of suspended sediments into estuaries and has resulted in significant infilling of the Eastern Yar Estuary (and Bembridge Harbour) by fine sediments (Wallace, 1990; Posford Duvivier, 2000a). Similar tidal conditions operate at Wootton Creek but infilling is only partial.

F4 Bedload Input at Bembridge Harbour (see introduction to marine inputs)

Entry of coarse bedload sediments (medium sands to gravels) to inlets in the Solent is generally resisted by the ebb dominance of their tidal regimes. At Bembridge, the formerly extensive estuary of the Eastern Yar is now much reduced by successive stages of reclamation dating back to the seventeenth century (Howard, Moore and Dixon, 1988). The last major phase of reclamation was in 1874, with the construction of the railway embankment in 1879 limiting ingress of tidal waters. This has significantly diminished the tidal prism, reducing the flushing effect of ebb currents in the outer estuary and further seaward leaving the large ebb tidal delta as a relic feature. Wave action has therefore become relatively more dominant and has transported sands and gravels from the ebb tidal delta towards the shore and into Bembridge Harbour creating a sediment rich environment (Photo 1). Significant growth of Bembridge Point is attributable to this process in conjunction with littoral drift from Foreland. Accreting sand and gravel banks within the harbour provide further evidence of such input and a future requirement for dredging to maintain navigable channels (Howard, Moore and Dixon, 1988; Posford Duvivier, 2000a). These inputs are difficult to quantify, but fine and coarse sand and silts are strongly differentiated in the upper harbour with no apparent mixing (Posford Duvivier, 2000a). Sediments sampled from a grid of sampling sites revealed 50-80% medium sand and 15-20% gravel, the latter being restricted to lenses within the upper 1-1.5m (Posford Duvivier 2000a).

2.2 Fluvial Input - FL1 FL2 References Map

The streams draining catchments on this part of the Island are small and have very limited capacity to deliver sediments to the shore (Rendel Geotechnics, 1996).

FL1 The Eastern Yar (see introduction to fluvial inputs)

The eastern Yar flows into Bembridge Harbour and sandy sediments have been recognised at its point of entry (Howard, Moore and Dixon, 1988). These may indicate sediment input, although it can be argued that the agitation by river flow simply prevents sedimentation of finer marine sediments introduced by flood tidal currents. Any sediment input is likely to be extremely limited for river flow is low and subject to regulation (Howard, Dixon and Moore, 1989).

FL2 Wootton Creek (see introduction to fluvial inputs)

Fluvial transported sediment entering this inlet has been intercepted since circa 1830 by the dam at Wootton Bridge that impounds The Old Mill Pond. The latter continues to accumulate material that would otherwise provide a small input into estuary infilling.

2.3 Coastal Erosion - E1 E2 E3 E4 E5 E6 References Map

Most of this coastline is occupied by either active cliffs subject to basal marine erosion and mass movement processes or by a steep or moderately steep coastal slope currently removed from the influence of breaking waves. Both are developed in relatively unresistant sandstones, marls and clays which yield readily to both marine and sub-aerial geomorphological processes (White, 1921; Colenutt, 1891; 1893; 1938; Daley and Insole, 1984; Bird, 1997). Interbedded limestones outcrop at several localities, notably the Bembridge Limestone. This provides somewhat greater resistance and is responsible for the majority of headlands and offshore reef-like platforms. It breaks down into inter-joint blocks and creates a persistent local boulder apron that partly protects the upper foreshore and cliff toe by dissipating some incoming wave energy.

The rock outcrop pattern is determined by geological structure, in particular a series of shallow folds whose axes are roughly parallel with the north coast but are truncated by the approximately north to south alignment of the east coast (White, 1921; Bird, 1997). Stratal dips tend, overall, to be inland, thus contributing to slope stability. Nonetheless, there are several sites of present, or past, slope failure associated with critical pore water pressures in porous or permeable rocks, particularly where they are underlain by rocks which have less capacity for the storage of groundwater. Because the topography of the north-east Isle of Wight is less elevated than in any other part of the island, coastal cliffs and slopes are modest in height, nowhere exceeding 35m. This factor also helps to suppress the scale and frequency of slope failure and the dynamics of mass movement. The mature woodland cover of much of the north-facing coastal slope also contributes to stability.

The overall pattern, and localised rates, of coastal recession have been calculated from serial analysis of topographic maps from 1863 to 1975, with updating to 1995 from air photographs, where available (Halcrow, 1996; Posford Duvivier, forthcoming). Within the latter study there is also an evaluation of the likely patterns of future evolution and recession to 2050. These figures are expressed as mean values covering specific historical periods, and conceal fluctuations in time and space; they are selectively quoted in the following summaries for each of the units currently contributing sediment to littoral transport processes.

E1 Old Castle Point to Wootton Creek (see introduction to Coastal Erosion)

Much of this coastline is occupied by a steep, but relatively stable (in places graded) wooded coastal slope lacking active cliffing (Roberts.and Jewell, 2000; Hutchinson, 1965; Property Services Agency, 1985). Erosion has been most active at Woodside, where a slope failure plane has been intermittently triggered by loss of toe weight following marine erosion since at least the late nineteenth century (Harlow, 1980). Breaches of the now dilapidated defences at certain sites, e.g. Norris Castle, have recently reactivated old mudslides (Roberts and Jewell, 2000). Recession of MHWM averages between 0.15ma^-1 and 0.40ma^-1 (Posford Duvivier, 1994a), with evidence of some recent acceleration (e.g. some 18m of retreat at Woodside Point, 1975-1995). Posford Duvivier (1999a) calculate a cliff erosion yield of clay, silt and sand of 2,500m3a^-1 and shoreface erosion of between 2,600 and 7,800m3a^-1 for this unit. Where limestones are eroded, they tend to persist as large inter-joint blocks scattered on the foreshore and suffer loss from both solution and abrasion. Accelerating toe erosion together with future sea-level rise and climate change is likely to cause reactivation of landsliding on some of these slopes. It could result in rapid landward extension of the active backscar by up to 100m, together with major increases in sediment delivery to the shore (Posford Duvivier, forthcoming).

E2 Wootton Creek to Ryde (see introduction to Coastal Erosion)

Erosion is active between Fishbourne and Pelhamfield, but eastwards the coastal slope has either been incorporated into the built environment or fails to make any marked feature. Small-scale rotational sliding and cliff toppling is currently active at Fishbourne andin front of the Quarr Abbey estate (Photo 2). This has long been a locally active cliff line, as reported by Colenutt (1938) and deduced by archaeological excavation of the adjacent foreshore palaeolandscape (Tomalin, 1991; 1993; Long and Scaife, in press). The supposed impact of ferry movements in accelerating erosion (Robert West and Partners, 1990) remains an unresolved question (Photo 3). Toe erosion of the relic coastal slope and some reactivating slips are apparent eastwards to Binstead behind dilapidated defences (Photos 4 and 5). Indeed, landslip debris obscuring the cliffline at Ryde, exposed until about 1870, is described by Reid and Strahan (1889). A mean recession rate of 0.05ma^-1, 1909-1975 indicates low potential for supply to the shore, although there is evidence of an acceleration, to 0.71ma^-1, over the period 1975-1995 suggesting that this input should become more significant in the future. Posford Duvivier (1999a) have proposed a cliff erosion sediment yield of approximately 2,000m3a^-1 and a shoreface erosion of 9,750m3a^-1. Sediments released are fine sands, silts and clays and most are likely to be removed from the beach as suspended load by waves and currents.

E3 Nettlestone Point to Horestone Point (Seagrove Bay) (see introduction to Coastal Erosion)

Coastal slope instability has been reported from the southern part of Seagrove Bay (Hutchinson, 1965; Posford Duvivier, 1998), where a multiple rotational failure occurred in the mid-twentieth century. With the recent installation of new defences (completed in May 2000), this slope is, at least temporarily, stable. However, softening of the.Bembridge Marl (which accommodates the failure plane) in combination with elevated ground water levels could create reactivation. Foreshore steepening, and approximately 20m of retreat of MLWS since about 1910, indicates the probability of diminished sediment supply as a result of defence building. The progressive deterioration of the seawall between the early 1950s and late 1990s probably induced an increase in the supply of both limestone clasts and silt/silty sands; this, however, has now been excluded. There are no site-specific calculations for sediment yield in Posford Duvivier (1999a).

E4 Priory Bay to Nodes Point (see introduction to Coastal Erosion)

The partly unprotected cliffs and shore platform are subject to active erosion, but a significant source of loss of potential feed to the littoral drift pathways may result from on- to offshore transport of fines. Nodes Point is composed of limestone, which breaks down by solution as well as abrasion. An approximate, calculation of coastal recession of 0.3 to 0.5ma^-1 throughout most of the twentieth century would appear to relate to cliff top, rather than cliff toe retreat. The presence of privately-constructed defences dating back to the 1930s, although now largely ineffective, have in the past inhibited toe erosion and cliff sediment inputs to the shore. Major extension and intensification of the activity of these cliffs are anticipated due to sea-level rise and increased winter rainfall that is estimated for the future. Some sands and limestones would be yielded although the majority of supply will be clays. Interestingly the cliff landslides will at first accentuate the two headlands bounding Priory Bay as their toes extend seaward, but later will reduce their definition as debris is eroded and transported and the headlands are eroded back. There are no site-specific calculations for sediment yield for this sector, although Posford Duvivier (1999a) give a figure of between 13,000 and 38,000m3a^-1 of mostly fine grades for the shoreface erosion of the Pelhamfield to Bembridge frontage as a whole. A supply of coarse materials is available intermittently in the cliffs comprising a thickness of up to 5m of Pleistocene fluviatile gravels at the top of the succession (Samson 1976).

E5 Bembridge Point to Forelands Field (see introduction to Coastal Erosion)

Erosion of the low cliffs of this frontage provides an important source of beach shingle because the cliffs are capped by Pleistocene raised beach and fluvial deposits attaining maximum thickness of 10m and containing rounded flint pebbles (Posford Duvivier, 1990). Sands and clays are supplied from the matrix of the raised beach deposit which overlies the predominantly clay Bembridge Marls. Bembridge Limestone outcrops on the foreshore forming a series of ledges that provide protection to the cliffs against wave attack at low water (Photo 6). Erosion rates are generally between 0.30mpa and 0.75mpa and vary spatially depending on the presence of coast protection structures and shelter afforded by shore platforms (Posford Duvivier, 1983; 1989; 1993b; Halcrow, 1996). A rate of 0.3ma^-1 to 0.4mpa is reported for the Warners Holidays frontage and 0.5ma^-1 for the coast north of Foreland (Barrett, 1985). The 15m high cliffs between Bembridge Point and Tyne Hall exhibit relatively recent reactivations of a relic wooded cliffline. They evolve by a simple landsliding process in which failures of the backscar result in extension of debris accumulations across the upper beach. The extreme western part of the frontage at Bembridge Point is undergoing net accretion, but erosion at up to 0.15mpa is recorded for the coast eastwards to Tyne Hall (Posford Duvivier, 1983; 1985; 1990). A shoreface sediment yield of 12,500m3a^-1 for the sector between The Foreland and Ethel Point is proposed (Posford Duvivier, 1999a), but offshore loss of clay and fine sand and cliffs stabilised by coast protection probably significantly reduces the actual input to the beach. It has also been suggested that some 5.0mma^-1 depth of shoreface erosion is achieved along this coastline, some 2 or 3 times the rate experienced to the north. An estimate of cliff erosion yield of some 12,000 to 15,000m3a^-1 has been quoted (Posford Duvivier, 1989; 1990a; 1993b; 1995b; 1999a) although this could be an underestimate if calculations were to incorporate the release of materials from extensive cliff toe debris stores.

E6 Forelands Fields to Culver Cliff (see introduction to Coastal Erosion)

The cliffs, cut into the soft Eocene and Oligocene sands, clays and limestones, are unprotected along most of this frontage. They are subject to failure creating complex landslide morphologies of scarps and degradation terraces with major mudlsides developed in the Reading and London Clay strata in the extreme south of the bay (Photo 7). The small lengths of informal defences in Whitecliff Bay (Posford Duvivier, 1997) are of marginal significance in restraining sediment yield. They are unlikely to persist in view of the international geological conservation significance of this site. Much of the clay and silt sized sediment mobilised by periodic slope failures and other mass movement processes is probably transferred offshore in suspension. The sand fraction contributes to the exceptionally wide intertidal zone between Culver Cliff and Long Ledge. In the northern part of this unit, a set of curvilinear limestone ledges forms a nearshore-offshore reef, thus inhibiting erosion of the adjacent cliffs. The prominent, slightly oversteepened, chalk cliffs and fronting boulder-strewn platform form a distinctive, but slowly eroding, southern boundary.

Historical cliff top recession of some 0.3 to 0.5ma^-1 in Whitecliff Bay (1909-1975) contrasts with a rate of 0.10 to 0.15ma^-1 north of Black Rock. There are no reliable calculations for cliff foot retreat, though visual inspection proves this to be an active process. Recession is likely to accelerate in the estimated wetter winter conditions of the future that would promote landsliding. Major focal points are likely to be the Reading and London Clay mudslides in the south and around Bembridge School where the Bembridge Marls are susceptible to increased mudsliding and translational or rotational slides.

3 Littoral Transport - LT1 LT2 LT3 LT4 LT5 LT6 LT7 LT8 References Map

Two major drift pathways that converge upon Ryde Sands are identified. Transport is predominantly from west to east at low rates along the Eastern Solent shore powered by waves generated locally in the Solent by prevailing westerly winds. By contrast, the east coast is exposed to wind waves from the SE and diffracted waves from the south and south west that power a more significant net north or north-westward drift. These paths are interrupted to varying extents by several minor headlands and inlets. Some local drift reversals are identified at inlets resulting in zones of divergent transport that are potentially susceptible to beach erosion.

LT1 East Cowes to Old Castle Point (see introduction to Littoral Transport)

Marked accretion on the eastern side of Cowes breakwater since its construction in 1936/37 indicates a long-term trend for net westward littoral drift from Old Castle Point (Webber, 1981; Posford Duvivier, 1994b; Carter, 1996). Sand and shingle have accumulated on the upper foreshore, with mud on the lower, indicating that all grades of sediment are transported preferentially in the same direction.

LT2 Old Castle Point to Wootton Creek (see introduction to Littoral Transport)

Littoral drift is in a net eastward direction along this segment (Dyer, 1980; Harlow, 1980; Halcrow Maritime, 1996). Little data is available for this frontage and the transport pathway therefore is of low reliability. Twin spits composed of sand and gravel have developed at the entrance to King’s Quay and their orientation is indicative of transport both eastwards and westwards into the entrance (Photo 8). The eastern (westward trending) spit at King’s Quay therefore suggests a very local drift reversal, possibly associated with tidal current and wave interactions at the inlet, but no studies have examined this feature.

LT3 Wootton Creek to Ryde Pier (see introduction to Littoral Transport)

A general net eastward littoral drift is indicated along this unit by: (a) an eastward trending spit that has been pushed into the inlet to form Wootton Hard and (b) set-back of the east shore compared to the west at Wootton (Photo 9) and (c) widening of the foreshore towards Ryde in the presumed direction of drift (Harlow, 1980; Halcrow, 1996). Comparison with studies of adjacent beaches on the mainland indicate slow drift at less than 1,000m3pa (Harlow, 1980). Sediment transport is interrupted by Wootton Creek inlet where transport pathways have been identified on the basis of morphological evidence (Harlow, 1980; Robert West and partners, 1990).

(i) A small proportion of eastward moving sediment (especially gravels) is diverted into the inlet by littoral drift along the western shore, which supplies the shingle spit of Wootton Hard that has now migrated well into the inlet (Photo 9).
(ii) The majority of sediment is thought to be transported eastward from the western shore and crosses the tidal channel to be driven ashore 400m north of the Sealink terminal. At this point transport divides: some of this material is transported south further into the inlet and accumulates against the Sealink terminal (Hydraulics Research, 1988; Robert West and Partners, 1990). Some material would be deposited within navigable channels which are dredged periodically. The majority of material is thought to be transported eastward along the wide foreshore and a series of barrier-like banks on the lower foreshore towards Ryde Sand. A westward trending spit is discernible on eastern shore of Wootton Creek some 500m up the estuary (Photo 9). It would appear to have migrated into the estuary having been fed by a local westward-directed drift pathway from the western Quarr frontage into Wootton Creek. A transient drift divergence boundary may therefore once have operated on the Quarr frontage although recent erosion of this spit (Posford Duvivier, 1994) suggests that the pathway may no longer function as effectively as previously.

Some sediment crossing the inlet is intercepted by tidal currents, but these are insufficient for significant transport (Hydraulics Research, 1988) and it is hypothesised that most sediment entrained by currents is deposited in the channel a short distance seaward, whereupon it is liable to be driven onto the barrier banks to the east (Harlow, 1980). Wootton Creek therefore acts as a partial sediment sink, intercepting some of the eastward littoral drift, but allowing bypassing of the majority. Detailed studies of sediment transport have been undertaken within the inlet to determine the contribution of ferry generated wave and surge effects to coast erosion. A recent study involving on-site monitoring of wind waves and boat waves concluded that between 20% and 50% of sediment transport on the inlet shores could be attributed to boat waves with the remainder resulting from wind waves (Robert West and Partners, 1990). Both types of wave cause dominant sediment transport into the inlet so that increased storminess or increased ferry sailings are likely to increase sediment interception.

LT4 Ryde Pier to Nettlestone Point (see introduction to Littoral Transport)

Accretion on the eastern sides of groynes and outfalls at Spring Vale (Photo 10) indicate net westward drift (Posford Duvivier, 1990b; 2000b; 2000c). This transport pattern is attributed to dominant waves from the east and southeast and to diffracted southerly and south-westerly waves from the English Channel. Ryde is also exposed to such waves and beach accumulation occurs preferentially on the eastern side of Ryde Marina and other shore structures that intercept transport. This transport occurs in the opposite direction to that of LT3 so that drift therefore converges at Ryde and it is believed that the resultant predominantly sandy accumulation, Ryde Sands (Withers, 1979; Dyer, 1980; Gibson and Bone, 1987) represents a sediment sink (Harlow, 1980). Map comparisons undertaken for the design of Ryde Harbour in the early 1990s revealed relatively stable conditions with little net sediment transport (Gifford and Partners, 1990). Net transport may not be great, as no significant siltation of the dredged channel giving access to Ryde Harbour has been reported. As was observed by Gifford and Partners (1989, 1990) further research into sediment transport is required on Ryde Sands and should involve assessment of the contribution of diffracted waves from the English Channel.

LT5 Nettlestone Point to Priory Bay (see introduction to Littoral Transport)

Priory and Seagrove Bays have a similar orientation to the Bembridge coast to the south. The bays terminate at rock headlands so it is possible they function as isolated pocket beaches (Posford Duvivier, 1998). No specific information is available regarding drift on these beaches, but a north-westward trend is postulated by inference. It remains uncertain whether the two bays are linked and can supply sediment downdrift. The assumption is that the bays are partly closed systems for the gravels of the upper beach, but much less so for the sands of the extensive shallow nearshore and intertidal zones. Transport within these areas is probably effective in enabling supply of sands north westward around Nettlestone Point. Both have exhibited drawdown of their beach sediment stores in recent years (Posford Duvivier, 1998). Sediment transport in the nearshore zone, derived from assumed wave climate parameters may be in the order of 9,000m3a^-1 (Posford Duvivier, 2000a).

LT6 Priory Bay to St Helens Duver (see introduction to Littoral Transport)

Sediment accumulations against the northern sides of groynes on St Helens Duver indicate southward drift (Posford Duvivier, 1988, 1991, and 1996). The south trending alignment of the Duver, a sand dune covered spit, suggests that the feature developed during long-term north to south drift. A map dated 1791 showed the Duver spit in more or less its present position and indicates that north to south drift was dominant before this time (Shepard, 1970; Posford Duvivier, 1991, 1996). The present day spit is confined by a sea wall and its stored sediments are no longer available to nourish the foreshore. Beach sediments drift to the southern tip of the spit where they are intercepted by tidal currents within the Bembridge Harbour entrance and flushed offshore by dominant ebb currents (Photo 1). In the past, these sediments were possibly driven back onshore near St Helen’s Church, but dredging of Bembridge Harbour approaches (e.g. 200,000m3 in 1987 and 1989/90) may have interrupted this circulation (Posford Duvivier, 2000a). Beach levels have fallen significantly along the Duver and coast protection measures are aimed at reducing littoral drift so as to minimise further beach losses to the tidal channel. The Duver is particularly vulnerable because a very short drift pathway extending south from a littoral drift divide near Nodes Point supplies its sediments. Fresh sediment sources are therefore limited to local coastal erosion and onshore feed, although further research is required to evaluate the relative importance of each (Posford Duvivier, 2000a). The total longshore drift flux, passing from Bembridge Point across the harbour approaches towards Priory Bay, may be in the order of 80,000m3a^-1. If dredging records and hydrographic charts are acceptable approximations of the local sediment budget, up to 60,000m3a^-1 may be diverted into bank and channel storage (Posford Duvivier, 2000a).

LT7 Bembridge Point to Foreland (see introduction to Littoral Transport)

Dominant north-westwards littoral drift from Foreland to Bembridge Point is indicated by sediment accumulations on the east side of groynes and outfalls (Barrett, 1985; Posford Duvivier, 1989; 1990a; 1993a; 1993b). Sediment supplied by local coast erosion is transported along this pathway and deposited at Bembridge Point (Photo 1). Map comparisons covering the period 1862 to 1970 revealed seaward advance here of MHWM by up to 60m, despite periodic shingle removal under licence (Posford Duvivier, 1989; 1990a; 1995b).

Potential longshore drift driven by breaking waves has been calculated at 14,000m3a^-1 at Bembridge Point and 90,000m3a^-1 at Colonel’s Hard. Most of this would represent fine sands transported on the shoreface with only a proportion comprising beach drift (Posford Duvivier, 2000a).

A mean rate of coastal recession of between 0.25 and 0.33ma^-1 for the period 1866-1975 has been suggested (Posford Duvivier, 1983; 1989) for the frontage between Foreland Fields and the lifeboat station. Erosion releases coarse clastic material from the Ipswichian raised beach, thus providing a supply of shingle. Small quantities of shingle from occasional beach replenishments have also supplemented the supply since the 1970s. A littoral drift rate in excess of 20,000m3a^-1 may operate over limited periods of time (Posford Duvivier, 1989). Fine sand and silt is probably transported offshore and bypasses the Foreland. Small quantities of shingle from occasional beach replenishments serve to slightly exaggerate quantitative estimations of drift volumes.

LT8 Foreland to Culver Cliff (see introduction to Littoral Transport)

There are no reported measurements of the direction of the littoral drift pathway, but observation of the movement of sediment of known provenance suggests that it is north-eastwards. Cliff recession mostly yields sands and silts, with a potentially significant proportion moved offshore in suspension. The backshore coarse clastic sediment store was severely depleted by removal for aggregate in the early part of the twentieth century (Colenutt and Hooley, 1919), and may not have recovered subsequently, at least in southern and central Whitecliff Bay.

4. Sediment Outputs

4.1 Offshore Transport - O2 O5 References Map

Sediment transport within the channels of the Eastern Solent is complex being influenced primarily by the morphology of the main channels, the tidal flow patterns and the availability of seabed sediments. Although tidal currents determine the strength and direction of transport, wave action is nevertheless important in mobilising the sea-bed sediments. For this reason it might be expected that bed sediments should be increasingly mobile towards the mainland rather than close to the Isle of Wight shores which are comparatively more sheltered. The major study of sediment transport in this region is based on a detailed numerical modelling approach that includes the effects of waves and tidal currents and involved application of three alternative sediment transport equations for computations of potential transport rates (HR Wallingford, 1995). It did not however include assessments of the transport occurring around the Isle of Wight, but instead focused on the mainland coast and main channels. The main results were to identify a net long term eastward transport of sand and some gravel south eastwards out of the Eastern Solent towards the Nab Tower. An anticlockwise rotation of sand around the Brambles Bank was also identified. The implications of these findings for the NE Wight were not assessed. As these studies specifically focus on the mainland shores they shall be discussed further in those sections.

Some pathways operating parallel to the shore are identified from earlier studies of bedforms and bed sediments. Although their reliability might be considered uncertain in light of the results of the HR Wallingford (1995) studies, it should be remembered that the latter focused on the mainland and not on the NE Wight side of the main East Solent channels where there is a comparative information deficit. The following pathways are extracted from the section covering the mainland shores:

O2 Main Channel (see introduction for offshore transport)

Sediment transport in the main channel was determined from analysis of bedforms identified by a series of echo-sounding traverses across the East Solent (Lonsdale 1969). This information was coupled with details of sediment size, grading and sorting determined by a coordinated programme of sediment sampling involving 110 bottom samples taken using a Shipek grab (Lonsdale 1969). Sediment grading and to a lesser extent sorting were found to be strongly related to the direction and strength of tidal currents so that sediment transport paths followed the main tidal channels. The main channel in the East Solent is floored by silt and muds with increasing proportion of sand towards the margins where sandwaves were present. Asymmetry of these bedforms indicated east to west sediment transport with divergence of flow around the Ryde Middle Bank, a Tertiary remnant with relatively thick sediment cover (Lonsdale 1969). Sediments transported were assumed to be primarily muds and silts in the centre of the channel and sands on the margins. This direction partly conflicts with that established by HR Wallingford (1995), although it may suggest that there might be a net transport divergence in the East Solent at Ryde Middle Bank. Sediments east of the bank would tend to move south eastwards and those west of the bank would move north eastwards away from this feature. Survey by Lonsdale (1969) terminated east of Brambles Bank, a major sand accumulation and possible sediment sink for the main channel transport pathway. Studies by Dyer (1980) indicated anticlockwise sediment circulation on this bank, a finding that was confirmed by HR Wallingford (1995) numerical modelling studies. Sands in the eastern part of the transport pathway around Sturbridge Shoal were particularly rich in limonite, a mineral that becomes much less frequent in sediments further west at Ryde Middle Bank (Lonsdale 1969), but is abundant in Sandown Bay (off the south-east Isle of Wight coast) where similar medium sized, well sorted, limonite-rich sands are derived from erosion of Lower Greensand cliffs. Further sea-floor survey and bedform analyses are required to confirm this area as a major sediment source for the East Solent.

O5 Osborne Bay ( see introduction for offshore transport)

Studies based on bedform and sediment analysis indicated a transport divide offshore from Osborne Bay (Dyer 1980). The dominant rates of transport and grades of material were not described and this feature has not been identified by any subsequent work so that reliability is low.

4.2 Estuarine Outputs - EO1 References Map

Throughout the Eastern Solent the ebb tidal flow is of shorter duration than the corresponding flood flow (Webber 1980; HR Wallingford, 1995). As a result, ebb currents are of greater velocity than the flood causing net offshore transport of coarse bedload sediments at the mouths of estuaries and inlets.

Examination of the literature has failed to reveal any indication of significant offshore sediment loss either at the foreshore or from inlets. At Wootton Creek, dominant ebb tidal currents approaching 1.0ms^-1 were measured in the main tidal channel and distal ends of spits (0.8ms^-1) adjoining the channel (Hydraulics Research, 1980; 1988). These currents are sufficient to entrain sand and fine gravel, but offshore transport is limited because currents diminish rapidly seaward of the creek entrance (Hydraulics Research, 1980; 1988). Sediments are believed to be deposited within the channel whereupon they are driven onshore by wave action or possibly removed by dredging. Entry of ferries into the creek causes a notable surge effect comprising an elevation and subsequent lowering of water levels by up to 0.30m during low tides (Harlow, 1980; Robert West and Partners, 1990). Field investigations revealed that the down slope velocities produced by these surges are sufficient for erosion of both the soft and consolidated muds sampled in the field. Similar tests were conducted to evaluate the erosive power of wind waves and tidal currents but it was concluded that during low tide only ferry surges could generate sufficient shear stress to cause erosion of intertidal mudbanks. Lowering of mudbanks is well documented within the creek and has apparently occurred since 1938 (Hydraulics Research, 1988). With the introduction of larger ferries in 1982 (Photo 3), cross sections of the channel have been measured at frequent intervals and reveal marked increase of mudbank erosion, a change directly attributable to ferry surge erosion (Robert West and Partners, 1990). The fate of sediments released by this effect is uncertain because siltation has not increased in the main channel (Hydraulics Research, 1988) and offshore output is unlikely due to the hydraulic regime which favours suspended sediment input.

At Bembridge Harbour, offshore surveys involving boreholes and sediment sampling have revealed a substantial accumulation of at least 1.5 million m3 of sand and gravel lying off the entrance (Grontmij, 1972; Posford Duvivier, 2000a). It can be hypothesised that the accumulation is the relic ebb tidal delta comprising material flushed offshore by dominant ebb tidal flow prior to reclamation when the harbour had a larger tidal prism. Since reclamation, this process has ceased and the harbour approach channel has consistently silted up and requires semi-continuous maintenance dredging (Posford Duvivier, 2000a). It can be concluded that ebb currents are now reduced in velocity and transport sediment a shorter distance offshore, where it may be intercepted by dredging or driven back onshore by wave action. Net offshore loss is therefore unlikely.

EO1 Medina Estuary (see introduction for estuarine outputs)

There is some evidence of net offshore transport at this location. This is discussed further in the section covering NW Wight.

4.3 Dredging - References Map

Dredging comprises the major known sediment output from the north-east Wight coast and is practised for navigational purposes at Wootton Creek and Bembridge Harbour. The approach and entrance channel in Wootton Creek was widened and deepened in 1982 for the introduction of new ferries, and further widening and deepening was undertaken in 1989 and 1993. Maintenance dredging is not required as tidal flow, coupled with regular ferry passage, effectively prevents siltation (Robert West and Partners, 1990). Volumetric information on material extracted is not available but the dredging may have several effects:

(i) Widening and deepening of the channel may prevent sediment bypassing the inlet, so the eastern estuary margin and the Quarr Abbey frontage could become depleted (Harlow, 1980). Increasing erosion has been reported in these areas over the past 20 years (Harlow, 1980; Robert West and Partners, 1990).
(ii) Slumping or sliding of sediment into the dredged channel is possible, causing lowering of the intertidal zone. This lowering process was also evident in the 1980s (Robert West and Partners, 1990).
(iii) Removal of sediments by dredging may lead to sediment starvation and reduction of potential for rebuilding mudbanks eroded by the ferry surge phenomenon (Robert West and Partners, 1990).
(iv) Dredging results in increased water depths in the channel approaches, which may increase wave penetration and thus transport more sediment further into the inlet (Robert West and Partners, 1990). Increased wave energy at the shoreline could also cause increased erosion (Harlow, 1980) east and west of the inlet.

Dredging at Bembridge has been necessary to maintain a navigable approach channel subsequent to the major reclamation of the harbour completed in 1874. It seems probable that the subsequent change from a straight to a sinuous channel, and the pattern of siltation results from reduction of the effectiveness of the flushing effect of dominant ebb currents due to diminution of the tidal prism (Grontmij, 1972; Posford Duvivier, 2000a).

Comparison of charts for 1945 and 1967 revealed accretion of up to 1.2m in the approaches to the harbour, 2.5m offshore Priory Bay and up to 2m in Bembridge Harbour (Grontmij, 1972, Alluvial Mining Co. Ltd, 1981). Since 1967, dredging has periodically removed sediment from the harbour approaches, the navigable approach channel at the harbour mouth, a channel within the harbour and a basin at St Helens. Dredged totals are uncertain, but at least 8,000m3 of mud was dredged from the St Helens Basin (Grontmij, 1972) and 200,000m3 sand and gravel was extracted from the approaches in both 1987 and 1989/90. Between 1990 and 2000 an estimated 130,000m3 of sand and gravel has accumulated in this same area (Posford Duvivier, 2000a). Harbour hydrodynamics are likely to be quite stable due to limited tidal flow and negligible wave fetch. Outside the harbour sediments are more mobile (Grontmij, 1972; Posford Duvivier, 2000a) with evidence from hydrographic charts of a tendency for the harbour approach channel to rotate in a north-westwards direction, away from the entrance. Drying banks have also shifted progressively northwestwards and westwards since at least the 1890s, whilst the significant amount of accretion on the eastern side of the main approach channel is consistent with the by-passing littoral drift pathway. Dredging may have several potential effects:

(i) Drawdown of sediments from the beach fronting the Duver.
(ii) Interception of sediment which could potentially supply beaches on the Duver.
(iii) Increased water depths could allow larger waves to reach the shore, thereby causing increased nearshore erosion.
(iv) Alterations to bathymetry could cause variations in wave refraction leading to changes of sediment transport.
(v) Widening of the navigation channel may reduce tidal stream velocities.

These possible effects require further research so as to determine the potential contribution of dredging to shoreline changes, particularly in view of current proposals to realign the main channel and transfer excess sediment to the north-westwards moving littoral drift pathway.

5.0 Summary of Sediment Pathways and Budget - References Map

5.1 A major but as yet unquantified sediment feed to Ryde Sands from the south east, possibly originating from sources in Sandown Bay has been recognised. The exact pathway is uncertain, but it would appear to be an approximately shore-parallel bedload transport process operating in the shallow nearshore waters. Minor marine derived suspended sediment inputs to inlets are also characteristic.

5.2 Coast erosion is the only other significant sediment input as fluvial inputs are extremely small. Compared to the north-west and south Wight coasts, coast erosion is a relatively less active process due to geological and hydraulic factors. It should also be recognised that erosion rates have not been monitored systematically, so the importance of this process as a sediment supply is difficult to quantify precisely. Yield figures (Posford Duvivier, 1999b) remain estimates based on a range of assumptions. With the exception of raised beach deposits at Bembridge, the local geological types of the cliffs yield mostly fine sediments as they erode and tend to contribute to the suspended sediment load of the Solent waters rather than to local beaches. Excluding Ryde Sand, much of the coast has few other sources of supply and it is possible that local coast erosion is nonetheless the most significant sediment input.

5.3 Two major littoral drift pathways are identified, namely a predominantly eastward drift from Old Castle Point to Ryde and a net north-westward drift from the Foreland to Ryde. These result from variations in wave exposure and shelter from diffracted south-east and south-west waves approaching from the English Channel. At the mouths of each of the main inlets littoral drift is generally in opposite directions converging upon the entrances. Local drift reversals have therefore developed at East Cowes, King’s Quay and the Duver, St Helens, and a small scale, but complex partial sediment bypassing and circulation system operates at Wootton Creek.

5.4 Ryde Sands has developed at the convergence of these sediment transport pathways and can be regarded as a sediment sink. Significant convergence of drift also occurs at Bembridge Harbour and a major sediment accumulation close offshore suggests that this may also be a sediment sink. Accumulations of this type should not be regarded as immobile relics for they may display significant short term mobility and may be involved in sediment exchange with nearby beaches. The volumes of material stored within these features has yet to be quantified with any precision and is not monitored, excepting the intertidal portions which are covered by the EA Regional Beach Monitoring Aerial Photography.

5.5 Littoral drift divergences are recognised in the vicinity of Old Castle Point, Nodes Point and on the Fishborne shore of Wootton Creek entrance. These locations are susceptible to sediment starvation and are particularly sensitive to variations in sediment supply.

5.6 Offshore sediment transfers have not been quantified, although it is probable that significant quantities of sediment were flushed offshore and stored within an enlarged ebb tidal delta at Bembridge Harbour prior to reclamation of the Yar estuary. The extent to which this material has been returned to the shore by wave action following reclamation is uncertain.

5.7Major sediment output is effected by dredging the navigation and approach channels at Wootton Creek and Bembridge Harbour. This practice not only constitutes permanent sediment loss, but may also intercept transport pathways resulting in downdrift erosion. Drawdown of beach materials may also occur into depressions close inshore, and increased depths produced by dredging may increase wave exposure at the shore. Although these factors are relevant to operations at Wootton Creek and Bembridge no conclusive research has been achieved to assess the effects of dredging on sediment circulation and beach erosion and local sediment budgets.

5.8 The contribution of waves and surges produced by ferries to foreshore and mudbank erosion at Wootton Creek was clearly established by a series of studies culminating in a programme of detailed field measurements. Between 20% and 50% of upper foreshore erosion was attributed to ferry waves and virtually all mudbank erosion was considered to be the cause of ferry generated surges.

5.9 There is insufficient quantitative data on sediment inputs, storage and output to calculate formal sediment budgets for either the north-or east-facing sectors of this coastline. Data on sediment yields from cliff erosion (Posford Duvivier, 1999a; 1999b) is possibly the most definitive element, but even that is based on significant generalisations and assumptions such that its results are insufficiently site-specific. The few available calculations of rates and volumes of littoral drift are largely unchecked and uncalibrated due to lack of beach monitoring data. In general terms, the budget is negative (net loss) on most frontages excepting the inlets, Ryde Sand, Bembridge Point and possibly the Bembridge ebb tidal delta where net accretion may be dominant.

6.0 Key Coastal Defence and Habitats Issues - References Map

Opportunities for the enhancement and/or expansion of a variety of habitats within the inter-tidal backshore and adjacent terrestrial zones are identified broadly in the Isle of Wight SMP (Halcrow, 1996) and a more detailed consideration is undertaken in the North-East Isle of Wight Coastal Strategy Study (Posford Duvivier, forthcoming). Policies adopted will be a function of the strategic defence options selected for the Management Strategy Units in which each is accommodated. These, in turn, will be informed by evaluations of the island and Solent-wide significance of each habitat relative to their existing local, regional, national and international conservation status. Much key data relevant to this latter activity in currently undergoing consolidation within the in-progress (2000-2002) Solent Coastal Habitat Management Plan (CHaMP).

The possibilities for forms of managed retreat or realignment at Seaview Duver (Posford Duvivier, 1996; 2000b; 2000c and forthcoming) have benefitted from detailed assessment of the ecological characteristics of the wetland habitat currently confined by a seawall urgently requiring replacement. Within Bembridge Harbour there are additional opportunities for the re-establishment of saltmarsh and mudflat habitats through modification of existing marginal defences, possibly involving deliberate breaching or set back. St Helens Duver, a small area of virtually moribund sand dunes (Posford Duvivier, 1988; 1991a) overlying the southwards projecting spit has suffered erosional loss and possible ecological impoverishment resulting from the decoupling of dune: beach sediment exchange due to the insertion of protection structures (Posford Duvivier, 2000b). However, the sediment budget at this location is also affected by periodic dredging of the approach channel to Bembridge Harbour; the precise impact of this is not currently fully understood (Posford Duvivier, 2000d).

The coastal slopes between Old Castle Point and Ryde, and between Priory Bay and Culver Cliff are discontinuously occupied by mature or semi-mature woodland cover (Roberts and Jewell, 2000). It is of varying ecological importance but includes some areas of regional and national significance (Roberts and Jewell, 2000; Posford Duvivier, forthcoming). Locally, it probably provides some enhancement of slope stability and is everywhere a valuable landscape element. It is anticipated that a non-interventionist strategic defence policy will apply to much of this type of frontage.

Dredging of the approach and berthing channels to Bembridge Harbour and Wootton Creek is likely to have some impact on intertidal communities; the latter has been given a preliminary assessment (Posford Environment, forthcoming) in advance of any future proposals to increase the dimensions of the navigation channel. The internationally significant littoral and elittoral (nearshore) habitats of the Bembridge Ledges (Collins and Mallinson, 1988; 1989; Collins, Herbert and Mallinson, 1989) are located offshore of a coastline where a "do nothing" strategy will be adopted.

King’s Quay is a near pristine, small-scale example of a topographically controlled inlet regulated at its entrance by two convergent sand and gravel spits. It contains a sequence of mudflat, saltmarsh and reed bed habitats. Its natural form and unmanaged condition is extremely rare on the south coast of England. The spits that protect its entrance are vulnerable to overwashing, recession and potentially to breaching as sea-level rises (Photos 11 and 12). The eastern spit has retreated by 30-50m into the estuary since 1972. Both spits are vital to the estuary salt marshes as they provide protection from direct wave action from the East Solent. Spit maintenance depends upon continued sand and gravel supply by local cliff erosion, and could be threatened by cliff stabilisation schemes (though none are currently proposed) or attempts to control beach sediments. Furthermore, future sea-level rise is also likely to cause "topographic squeeze" of saltmarsh habitats against the steep valley sides.

7.0 Research and Monitoring Requirements - References Map

7.1 Ryde Sands, Bembridge Harbour (and ebb tidal delta) and Wootton Creek are significant sediment sinks in the context of both the local, and Solent-wide, sediment budgets. Whilst some quantitative data on rates of accumulation of sediment in outer Bembridge Harbour is available, there is little reliable information on their dynamics and stability. The provenance of sediments that constitute each of these sinks is uncertain, and it is possible that a proportion of retained sediment is mobilised under extreme hydrodynamic conditions. In that sense Bembridge ebb tidal delta and Wootton Creek, in particular, may function as stores rather than sinks, or traps. Long distance supply pathways originating in Sandown and Hayling Bays remain conjectural.

7.2 The efficacy of tidal currents acting in combination with shoaling or breaking waves in the entrainment, mobilisation and transport of sediment of varying size-ranges is poorly understood, particularly at the entrances of both the larger estuaries and smaller tidal inlets. It is very probable that nearshore tidally-induced transport has been underestimated; indeed, little is known about sedimentary structures and nearshore morphology in this environment. This may prove critical to resolution of the inferred process of sediment bypassing of both headlands and inlets.

7.3 Littoral drift pathways for several locations have not been experimentally proven, and currently rely on long term observations of sediment accumulations against various artificial and natural barriers. With a few exceptions, there is no reliable and representative data on the rates and volumes of littoral transport. Available figures are based on approximate calculations that use short-term data and assumptions on the width of the active intertidal "envelope"; the continuous availability of transportable sediment and historical trends of coastline change.

7.4 Available data on sediment yield from cliff erosion contains some inconsistencies currently contradictory, and ideally requires more controlled, site-specific analyses and breakdowns of distinct frontages. This deficiency partly reflects the lack of research into, and monitoring of, processes of cliff degradation along most parts of this frontage. The evidence of significant recent acceleration of coastline recession at a number of locations should be a focus of research into its causes and of the fate of sediment thus released. It is especially significant as it may be an early indication of the types of response that could become more widespread with future climate change.

7.5 Beach depletion and drawdown has been reported from several locations, notably those which appear to be semi-confined or otherwise isolated from littoral feed, eg Priory, Seagrove and Whitecliff Bays. Research into both local and general causes, carried out in the context of a wider, quantified analysis of sub-cell budgets, would be highly beneficial to informed strategic beach management. The possibility that some elements of contemporary beaches are relict, whilst others reflect the impacts of both formal and informal defences during much of the twentieth century, should be a stimulus to further research.

7.6 Despite several studies in the 1980s and 1990s, there remains considerable scope to evaluate the effects of navigation channel dredging at Wootton Creek, Ryde Harbour and Bembridge Harbour. Analysis of existing bathymetric data obtained from hydrographic charts should be combined with the archive topographic profiles obtained from post-dredging surveys. Whilst a general appreciation of basic patterns and trends of sedimentation is available, little is known of the impacts of dredging on wave refraction, sediment mobilisation in relation to adjacent beaches and nearshore banks, bars and shoals. More sediment analysis using shallow borehole samples would be of considerable value.

7.7 Virtually none of the beaches of the north-east Isle of Wight have benefitted from regular monitoring of levels or analyses of their sediments. Systematic spatial and temporal sampling, coordinated with routine beach profiling, would provide independent evidence of beach stability and offer valuable supporting information for beach management programmes. An example of the problem of lack of monitoring is provided at Ryde where much of the esplanade is built forward onto the beach and Ryde Sands so that historical map comparisons cannot reveal meaningful trends in MHW position. Contemporary behaviour of the important amenity beach therefore cannot be ascertained as there has not been any recent monitoring of beach levels, excepting the Environment Agency Annual Beach Monitoring Survey. Whilst the latter comprises a valuable archive of quality aerial photographs, the profiles measured from them are of uncertain reliability – being rather problematic in parts of Hampshire, but more reliable in West Susse. No independent validation of the NE Wight analyses are known to have been completed such that their reliability remains uncertain. Such a validation is recommended most strongly as it could open up a valuable, but under used resource in an area where there are no alternative data at present.

8.0 Opportunities for Calculation and Testing of Littoral Drift Volumes - References Map

The variation over short distances in coastal orientation and wave exposure together with the uncertain role of tidal currents in the transport process makes much of the Solent a difficult coast for the calculation and testing of littoral drift volumes (Bray et al., 2000). This situation is complicated further by the prevalence of headlands and pocket beaches that such beach drift systems are characterised by intermittent or periodic bypassing of headlands, possibly by occurrence of drift in the shallow nearshore waters. The lack of monitoring data (beach profiles, sediments, waves, and tidal currents) is a further constraint and means that drift formulations would be dependent on synthetic or inferred input data and results could not easily be calibrated or validated.

It is recommended therefore that efforts initially be devoted towards improving the availability of monitoring data, especially beach profile measurements. As a time series of profiles is collected, then it should be possible in the future to quantify the changes in terms of beach volume and thus derive estimates for the minimum net drift. Accumulations against major cross-shore structures having a high trapping efficiency offer the best opportunities to refine estimates by reducing the uncertainties associated with sediment throughput. Unfortunately, few such structures are available limiting options to a study of beach drift interception by major groynes eg at Ryde or Bembridge, or headland boundaries such as Horstone Point. The volumetric requirements for dredging of the Bembridge Harbour approach channel give some insights to rates of infilling by drift, allowing estimation of the minimum likely drift.

9.0 References - Map

Algan, O., Clayton, T., Tranter, M. and Collins, M.B. (1994) Estuarine Mixing of Clay Minerals in the Solent Region, Southern England, Sedimentary Geology, 92, 241–255.

Alluvial Mining Company Ltd (1981) Hydrographic and Sampling Survey of the Approach Channels to Bembridge Harbour, Report to Land Reclamation and Development Ltd, Haslemere, 11p.

Anon (1997) Time and Tide: An Archaeological Survey of the Wootton–Quarr coast, Internal report, Archaeological Unit, Isle of Wight Council.

Ball, N. (1985) Environmental Report, No 20/85: The Solent Estuarine System: Geomorphological Aspects of the Coastline (UETA/2), Department of Geography, University of Aberdeen, Report to Shell Exploration Co Ltd.

Barrett, M.G. (1985) Isle of Wight - Shoreline Erosion and Protection, in Proc of Conference on Problems Associated with the Coastline, Isle of Wight County Council, (unpaginated).

Bird, E. (1997) The Shaping of the Isle of Wight, Ex Libris Press, Bradford on Avon, 176p.

Bray, M.J., Carter, D.J. and Hooke, J.M. (1995) Littoral cell definition and budgets for central southern England. Journal of Coastal Research, 11, (2), 381–400.

Bray, M.J., Carter, D.J., Hooke, J.M and Clifton, J. (2001) Littoral sediment transport pathways, cells and budgets within the Solent. In: Collins, M.B. and Ansell, K. (ed.) 2000. Solent Science – A Review. Proceedings in Marine Science 1. Elsevier,

Carter, D.J. (1996) Physical Processes Topic Report, Medina Estuary Management Plan, Unpublished report to Cowes Harbour Commissioners and Isle of Wight Council, Coastal Zone Management Centre, University of Portsmouth, 31p.

Colenutt, G.W. (1891) Notes on the Geology of the North–East Coast of the Isle of Wight, Papers and Proceedings of the Hampshire Field Club, 2(1), 20–32.

Colenutt, G.W. (1893) The Bembridge Limestone ("Binstead Stone") of the Isle of Wight, Papers and Proceedings of the Hampshire Field Club, 2(2), 167–180.

Colenutt, G.W. (1938) Fifty Years of Island Coast Erosion, Proc Isle of Wight Natural History and Archaeological Society, 3(1), 50–57.

Colenutt, G.W. and Hooley, F. (1919) Report of Field Meeting to the Isle of Wight, Proc Geologists’ Association, 30, 133–138.

Collins, K.J. and Mallinson, J.J. (1988), Marine Flora and Fauna off Bembridge, Isle of Wight, Part I: Sublittoral Survey and Review of Existing Knowledge, Report CSD No 830, Nature Conservancy Council, 42p.

Collins, K.J. and Mallinson, J.J. (1989) Marine Flora and Fauna off Bembridge, Isle of Wight. Part II: Offshore Sublittoral Survey, Report CSD No 900, Nature Conservancy Council, 38p.

Collins, K.J., Herbert, R.J.H. and Mallinson, J.J. (1989) The Marine Flora and Fauna of Bembridge and St Helens, Isle of Wight, Proc Isle of Wight Natural History and Archaeological Study, 9, 41–85.

Daley, B. and Insole, A. (1984) The Isle of Wight: Geologists’ Association Guides, No 25 (Second Edition), Geologists’ Association, 36p.

Dyer, K.R. (1972) Recent Sedimentation in the Solent Area, in: Colloque sur La Géologie de la Manche, BRGM, Memoire, 79, 271–280.

Dyer, K.R. (1975) The Buried Channels of the "Solent River", Southern England, Proc Geologists’ Association, 86, 239–245.

Dyer, K.R. (1980) Sedimentation and Sediment Transport, in: The Solent Estuarine System: An Assessment of Present Knowledge, NERC (Swindon) Publication Series C, 22, 20–24.

Gibson, M.G. and Bone, D.K. (1987) The Ryde/Seaview marine treatment scheme: design and construction of the Ryde long sea outfall, Public Health Engineer, 14(5), 31–36.

Gifford and Partners (1989) Ryde Catamaran Harbour Feasibility Study, Report to Medina Borough Council.

Gifford and Partners (1990) Ryde Leisure Harbour Feasibility Study: Floating Harbour Study, Report No 45151.01, to Medina Borough Council, 44p.

Grontmij, N.V. (1972) Initial Sedimentological Survey of Bembridge Outer Harbour, Report to Bembridge Harbour Improvement Company Ltd, 11p.

HR Wallingford Ltd (1992a) Selsey Bill, Hayling Island and the Isle of Wight: Effects of Dredging on Nearshore Wave Conditions, Report EX2696, 13p.

HR Wallingford Ltd (1992b) South Coast Mobility Study: Sediment Sampling, Laboratory Analysis and Derivation of Hydrodynamic Conditions, Report EX 2597.

HR Wallingford Ltd (1993) South Coast Seabed Mobility Study. Summary Report, Report Ex 2795, 24p.

HR Wallingford Ltd (1995) Pagham to Portsmouth Harbour Strategy Study, Report EX 3121, Report to East Solent Study Group (Lead Authority: Chichester District Council).

HR Wallingford Ltd (1997) Eastern Solent Shoreline Management Plan. Report to Havant Borough Council and Environment Agency. 4 Volumes. Harlow, D.A. (1980) Sediment Movements in Wootton Creek, and the Likely Effect of the Proposed Dredging, Report to Fishbourne and Wootton Creek Protection Association, 26p.

Halcrow (1996) Isle of Wight Shoreline Management Plan, Report to Isle of Wight Council and Environment Agency, 2 volumes.

Howard, S., Moore, J.I. and Dixon, I.S. (1988) Survey of Harbours, Rias and Estuaries in Southern Britain: Newtown and Bembridge Harbours, Isle of Wight, Field Studies Council (Oil Pollution Research Unit), Report No CSD 852, Nature Conservancy Council.

Hutchinson, J.N. (1965) A Reconnaissance of Coastal Landslides in the Isle of Wight, Building Research Station, Note EN 11/65, 44p.

Hydraulics Research (1980) Wootton Creek, Isle of Wight: Effects of Sealink Operations, Report EX 932, 4p.

Hydraulics Research (1983) Bembridge Harbour: Effects of Proposed Dredging, Report No EX 1169, to Crown Estate Commissioners.

Hydraulics Research (1988) Wootton Hard, Fishbourne, Isle of Wight: Factors Causing Erosion of a Shingle Bank, Report EX1723, to Medina Borough Council, 25p.

Insole, A. and Daley, B. (1985) A Revision of the Lithostratigraphical Nomenclature of the Late Eocene and early Oligocene strata of the Hampshire Basin, Southern England, Tertiary Research, 7(3), 67–100.

Johnston, C.M. (1989) Surveys of Harbours, Rias and Estuaries in Southern Britain: minor south coast inlets, CSD Report No 978, Nature Conservancy Council.

Lewis and Duvivier (1979) Bembridge to Foreland: Preliminary Report, report to South Wight Borough Council, 17p.

Lewis and Duvivier (1982) Bembridge to Foreland, Second Report, report to South Wight Borough Council, 6p.

Long, A.J. and Scaife, R.G. (in press) Sea–level changes and coastal evolution at Wootton/Quarr, Isle of Wight, in Tomalin D. J, Scaife R G and Loader R (ed.) The Wootton–Quarr Survey, Isle of Wight Council.

Lonsdale, B.J. (1969) A Sedimentary Study of the Eastern Solent, Unpublished MSc Dissertation, Department of Oceanography, University of Southampton, 36p.

McInnes, R.G. (1994) A Management Strategy for the Coastal Zone, South Wight Borough Council, 43–61.

Posford Duvivier (1983) Bembridge to Foreland Coast Protection, Stage 1, Report to South Wight Borough Council.

Posford Duvivier (1985) Bembridge to Foreland Coast Protection, Stage 2, Report to South Wight Borough Council.

Posford Duvivier (1988) Report on Proposed Groynes, The Duver, St Helens, Report to Medina Borough Council, 3p.

Posford Duvivier (1989) Coastline Review, Report to South Wight Borough Council, 38p.

Posford Duvivier (1990a) Coast Protection at Bembridge, Report to South Wight Borough Council, 4p.

Posford Duvivier (1990b) Report on Sea Wall at Springvale, Report to Medina Borough Council, 5p.

Posford Duvivier (1991a) Report on Coastal Protection: The Duver, St Helens, Report to Medina Borough Council, 4p.

Posford Duvivier (1991b) Effects on the Coastline of Proposed Dredging near St Helen’s Fort, Bembridge, Isle of Wight, Report to Northwood (Fareham) Ltd, 14p.

Posford Duvivier (1993a) Coast Protection – Bembridge Frontage, Report to South Wight Borough Council, 12p.

Posford Duvivier (1993b) Coast Protection at Bembridge, Report to South Wight Borough Council, 9p.

Posford Duvivier (1994a) Wootton Creek, Fishbourne (Isle of Wight):Coastal Study, Report to Medina Borough Council, 42p.

Posford Duvivier (1994b) East Cowes Esplanade: Report on Seaweed, Report to Medina Borough Council, 37p.

Posford Duvivier (1995a) Coast Protection at Seagrove Bay: Preliminary Report, Report to Isle of Wight Council, 4p.

Posford Duvivier (1995b) Coastal Protection at Bembridge, Report to Isle of Wight Council, 30p.

Posford Duvivier (1996) Coast Protection at the Duver, Seaview: Preliminary Report, Report to Isle of Wight Council.

Posford Duvivier (1997) Report on Coast Protection in Whitecliff Bay, Isle of Wight, Report to Isle of Wight Council, 6p.

Posford Duvivier (1998a) Coast Protection at Seagrove Bay. Engineer’s Report, Report to Isle of Wight Council, 35 pp. and 7 Appendices.

Posford Duvivier Environment (1998b) Seaview (The Duver), Isle of Wight. Coastal Defence Works. Ecological Assessment, Report to Isle of Wight Council, 23pp and Appendices.

Posford Duvivier (1999a) SCOPAC Research Project. Sediment Inputs to the Coastal System. Summary Document, Report to SCOPAC, 20–26.

Posford Duvivier (1999b) SCOPAC Research Project. Sediment Inputs to the Coastal System. Phase 3: Inputs from the Erosion of Coastal Platforms and Long Term Sedimentary Deposits, Report to SCOPAC, 26–31.

Posford Duvivier (2000a) Coast Protection at Gurnard. Preliminary Report. Appendix F.1: Review of Proposed Navigational Dredging at Bembridge, Report to Isle of Wight Council, 14p.

Posford Duvivier (2000b) Coastal Defence and Habitat Creation: The Duver, Seaview, Report to Isle of Wight Council.

Posford Duvivier (2000c) Coastal Protection: The Duver, Seaview. Environmental Scoping Report, Report to Isle of Wight Council.

Posford Duvivier (2000d) Environmental Scoping Report. Coast Protection, The Duver, Seaview, Report to Isle of Wight Council, 57p.

Posford Duvivier, (forthcoming 2001) North East Isle of Wight Coastal Defence Strategy Plan. Report to Isle of Wight Council.

Preece, R.C., Scource, J.D., Hougton, S.D., Knusden, K.L. and Penney, D.N. (1990) The Pleistocene sea–level and neotectonic history of the eastern Solent, southern England, Phil. Trans. Royal Society of London, B, 328, 425–477.

Property Services Agency (1985) Shoreline Survey of Osborne House Property, Building Management Division, 48p.

Reid, C. and Strahan, A. (1889) Geological Memoir: Isle of Wight, HMSO.

Rendel Geotechnics (1996) SCOPAC Research Project. Sediment Inputs to the Coastal System. Phase 3: Inputs from Fluvial Sources. Report to SCOPAC.

Robert West and Partners (1989) Wootton Creek, Isle of Wight: Preliminary Re–Appraisal of Erosion Problems, Report to Medina Borough Council, 18p.

Robert West and Partners (1990) Wootton Creek, Fishbourne, Isle of Wight: Evaluation of Ferry–Induced Erosion, Report to Medina Borough Council, 39p.

Roberts, H. and Jewell, S. (2000) Soft Cliff Biodiversity Along the South Coast of England, Isle of Wight Centre for the Coastal Environment, 29–31.

Samson, F.R. (1976) Priory Bay: a study of an unstratified Palaeolithic site in the Isle of Wight, unpub BA Dissertation, Department of Archaeology, University of Southampton.

Shepard, W. (1970) St Helens Duver, Proc Isle of Wight Natural History and Archaeological Society, 6(5), 320–328 [published in 1971].

Tomalin, D.J. (1991) Wootton Haven: An Assessment of a multi–period Inter–tidal site, with an appraisal of select archaeological features on the Solent sea bed, Internal report, Isle of Wight Archaeological Unit, Isle of Wight County Council.

Tomalin, D. (1993) Maritime Archaeology as a Coastal Management Issue: A Solent Case Study from the SCOPAC coast, in The Regional Coastal Groups After the House of Commons (1992) Report: Proceedings of Seminar, Standing Conference on Problems Associated with the Coastline (Newport, Isle of Wight), 93–112.

Velegrakis, A.F. (1999) Late Quaternary Evolution of the upper reaches of the Solent River, Southern England, based upon marine geophysical evidence, Journal of the Geological Society, 156, 73–87.

Wallace, H. (1990) Sea-Level and Shoreline Between Portsmouth and Pagham for the past 2,500 years. Privately published by the author, 61p.

Webber, N.B. (1980) Hydrology and Water Circulation in the Solent, in The Solent Estuarine System: An Assessment of Present Knowledge, Publication Series C, No. 22, Natural Environment Research Council, 25–35.

Webber, N.B. (1981) A Preliminary Investigation into the Feasibility of a New Breakwater in Cowes Harbour, Report to Cowes Harbour Commissioners, 46p.

West, I.M. (1980) Geology of the Solent Estuarine System in The Solent Estuarine System: An Assessment of Present Knowledge, Publication Series C, No 22, Natural Environment Research Council, 6–18.

White, H.J.O. (1921, Reprinted 1968) A Short Account of the Geology of the Isle of Wight, Memoir of the British Geological Survey, HMSO, London, 201p.

Withers, R.G. (1977) Observations on the Macrofauna of the intertidal sands at Ryde and Bembridge, Isle of Wight, Proc Isle of Wight Natural History and Archaeological Society, 7(2), 81–89 [published in 1979].

TOP