3.3 Estuary Policy Areas Environment, Biodiversity and Geodiversity

Geodiversity

3.3.00 The estuaries were formed when 3.3.03 The Government is committed to ensuring sea levels rose and the North Sea basin that nature conservation, landscapes and subsided at the end of the last Ice Age. The enjoyment of the natural environment is geology is dominated by sedimentary rock promoted and enhanced, through the formations, mainly chalks, which create the work of Natural (NE), its statutory gently rolling landscape characteristic of adviser on such matters. The Environment the area. In the Deben valley river erosion Agency (EA), Suffolk County Council (SCC) of the Clay has exposed marine and District Council (SCDC) deposits of Coralline and Red Crag. The also have statutory responsibilities and oldest of these rocks, Coralline Crag, is duties to safeguard and protect aspects of found nowhere else in Britain and is rich in the environment. As a part of the AONB marine fossils. Sites such as Rockhall Wood the estuary is a category 4 protected area Pit at Sutton, Cliff and Ferry Cliff as recognised by the International Union for opposite Woodbridge are designated the Conservation of Nature (IUCN). It is of geological SSSIs and considered to be international importance for the breeding, important sites historically. Ferry Cliff wintering or the migration of rare and is noted for providing evidence of early vulnerable species of birds found within hoofed animals, our ancestral horses. European Union countries and is part of the Natura 2000 network. 3.3.01 The surface geology of the Deben Estuary is characterised by river terrace deposits 3.3.04 The Deben Estuary is designated as: of sands and flint rich gravels overlaid by floodplain deposits from rivers and glacial •• Special Protection Area (SPA) melt waters. The sediments give rise to for wintering Avocets and Dark-bellied Brent free draining acidic soils, assessed as lower Geese. grade agricultural land, which often requires irrigation if the land is to be productive. •• Ramsar site for regularly supporting internationally important numbers of wintering birds. Designations protecting the estuary environment •• Site of Special Scientific Interest (SSSI) for populations of overwintering waders and wildfowl and also for the extensive and 3.3.02 The importance of the natural environment diverse saltmarsh communities, estuarine and the biodiversity of the Deben Estuary plants and invertebrates. is widely recognised. The Estuary is small compared with many others but 3.3.05 The estuary is also notable for the nationally it holds significant numbers of birds of important numbers of migratory waterfowl : international and national importance, as Shelduck, Avocet, Grey Plover, Black-tailed well as other species in notable numbers. Godwit, and Redshank. As a consequence the conservation and (see Andrew Excell and Kieran O’Mahony - The River enrichment of this environment is of great Deben Estuary Ornithological Importance and Status for importance not only for the County of Waterbirds - The Deben Estuary and its Hinterland.2013) Suffolk but at a national and international level.

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Map of estuary environmental designations

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Andrew Excell

3.3.06 SSSIs are notified because of specific Cetti’s Warbler, Kingfisher, Meadow Pipit, biological or geological features and are Ring Plover, Sedge Warbler, Nightingale and measured by Conservation Objectives Oystercatcher. which define the desired state for each site in terms of the features for which it has 3.3.09 Some birds are listed as Suffolk Priority been designated. When these features are Species (previously known as BAP species) being managed in a way which maintains these include Barn Owl, Reed Bunting and their nature conservation value the site is Bittern. Others are also classed as Species said to be in ‘favourable condition’. The of Conservation Concern Conservation Objectives and definitions (ref. British Trust for Ornithology (BTO) Report of favourable condition for features on the : Birds of Conservation Concern ) SSSI will inform the scope and nature of any and these include Corn Bunting, Yellow ‘appropriate assessment’ under the Habitats Wagtail, Lapwing, Linnet, Grey Partridge, Regulations. Yellowhammer, Skylark, Starling and Grasshopper Warbler. Wildlife 3.3.10 In winter the floodplains regularly attract large numbers of waders and wildfowl for 3.3.07 There are extensive records of species and both roosting and foraging. These include numbers of birds in the estuary. Starting in Widgeon, Teal, Brent Goose, Golden Plover the 1960s as The Birds of Estuaries Enquiry, and Curlew (a Suffolk Priority Species). The Wetland Bird Survey (WeBS) has Several of these species are also dependent been carried out every year with only one on the arable land behind the estuary walls exception. The principal aims of WeBS is to for all or part of their life cycle. identify population sizes, determine trends in numbers and distribution and to identify 3.3.11 As well as birds and small mammals important sites for waterbirds. In addition the estuary also supports nationally bird counts are conducted in each month and internationally important flora and from September through to April. All the fauna, which includes a range of swamp counts are completed around high tide, on communities that fringe the estuary, the same day, when waders and wildfowl and occasionally form larger stands. In are on roosts. general, these are dominated by Common Reed, Eelgrass, Marsh mallow and Tufted 3.3.08 The different habitats across the estuary Saltmarsh grass. Endangered molluscs, and its hinterland support many bird including the Narrow-Mouthed Whorl Snail species including Water Rail, Snipe, Short and the Desmoulin’s Whorl snail, are also Eared Owl, Reed Warbler, Bearded Tit, found in the Deben Estuary.

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Wildlife habitats within the estuary 3.3.14 Fen and reedbeds support a diversity of plant and animal communities. An area of 3.3.12 The Deben Estuary includes extensive fen lies within Springs SSSI and stretches of saltmarsh and intertidal reedbeds are found at Kings Fleet, west of mudflats, which are delineated by estuary Kirton Creek, Creek and in the walls. The saltmarsh and intertidal habitats upper reaches of the estuary in are vulnerable to changes caused by Creek and above Wilford Bridge. This occasional storms, sea level rise, coastal habitat supports distinctive breeding birds squeeze and wash from some boats. which include Grasshopper Warbler, Cetti’s Warbler, Reed Bunting and Little Grebes Beyond the estuary walls lie a network of and is also important for wintering birds freshwater borrow dykes, reed beds, ponds coming in from elsewhere in the UK. and scrapes, flood-plain grasslands, arable fields with narrow field margins, scattered 3.3.15 Grazing marsh, found on the Deben at scrub, hedges and woodland. Shottisham, Ramsholt, Kirton, Newbourne and Martlesham Creek, is predominately 3.3.13 Borrow dykes are important for the freshwater pasture drained by ditches conservation of wetland species. Wider which are especially rich in plants and borrow dykes and the remnants of creeks, invertebrates. This habitat is particularly such as King’s Fleet, with open water, important for numbers of breeding waders fringing vegetation and thick stands and internationally important populations of of reeds will support quite large bird wintering wildfowl. At high tide Pintail can populations; the presence of scrub along be found on grazing marshes in the upper the margins increases the diversity of the stretches of the estuary. Teal feed mostly bird community. Water Rail, notoriously on grazing marshes inland of the seawall difficult to monitor as they are mainly as do Black-tailed Godwits and Redshank, nocturnal, have been heard ‘squealing’ on especially when the estuarine mud is Shottisham Creek and, together with water covered at high tide. voles, are likely to breed in the dykes. Management of the dykes and ditches will 3.3.16 River wall grassland Although walls are include a cycle of dredging and clearing, managed and cut the grass tussocks are a essential for effective land drainage. habitat for bank voles, field voles, shrews, as However to retain their value for wildlife, well as grass snakes, slow worms and lizards. ditches need appropriate management Meadow Pipits nest in the thick grass of the and good quality water. This involves seawalls. The small mammal populations two processes: removing sediment and are exploited by birds of prey such as Barn vegetation cutting, which starts a new Owls, Short Eared Owls and Marsh Harrier. cycle of plant growth. If large sections are completely cleared in one go, re- 3.3.17 Arable land Arable agriculture offers colonisation will be slow and will result in feeding and nesting opportunities to several drainage channels of low wildlife value. species - Dark -Bellied Brent Geese feed It is therefore important for the natural on the arable fields inland of the seawall environment to leave some areas uncleared between and Ferry, and take a ‘little and often’ approach to Lapwing breed along the length of the river cleaning slow-flowing lowland channels. mainly on the arable fields and there are Yellow Wagtail and brown hares.

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Suffolk Coast & Heaths AONB

County Wildlife Sites •• Melton Picnic Site; a wet meadow located next to the picnic site.

3.3.18 The Deben Estuary and its hinterland •• Kyson Meadows; cattle grazed unimproved includes many County Wildlife Sites (CWS). pasture bordering the Deben Estuary. Designation as a County Wildlife Site is non-statutory but recognises the high •• Sluice Wood; woodland adjoining value of varied habitats for wildlife. Such Martlesham Creek . sites are often designated because they support characteristic or threatened species •• Martlesham Creek Reedbed; freshwater or habitats included in Local or National reedbed adjoining the Creek. Biodiversity Action Plans. They play a key role in the conservation of Suffolk’s •• Brightwell Grazing Meadows; wet biodiversity and must be considered by the species-rich grassland. Local Planning Authority when determining applications that may impact on them. •• Newbourne Springs Meadows; wooded valley with marsh, fen and heathland. 3.3.19 A number of County Wildlife Sites are in or adjacent to the area covered by the Plan. •• The Mill River; flowing from Newbourne Those which include habitats influenced by Springs Meadows to the . the Estuary are : •• Falkenham Corporation Marshes; •• Green. freshwater reedbed and scrub drained by a dyke that flows into Falkenham Creek. •• Cliff Farm Meadows and Nettle Hill Wood. •• King’s Fleet; freshwater open water with a reed fringe. •• Shottisham Creek; small tributary flowing through arable fields and grazing marshes •• Felixstowe Ferry Golf Course; dykes, before joining the River Deben. reedbed, rough grassland, gorse and the Tomlin Wal. •• Ramsholt Marshes and Lodge Plantation; Agriculturally improved grazing marshes Consideration can be given to creating drained by a network of dykes. This further sites if the required criteria are met designation includes a woodland. and the sites pass the designation process.

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Map of County Wildlife Sites

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Haidee Stephens

Floodplain and intertidal habitats In sheltered areas, mudflats usually grade into saltmarsh. This is a dynamic habitat and its continued presence depends on 3.3.20 Many of the species which make the flood maintaining the balance between the rate plain habitats notable will not tolerate saline of deposition of sediments from the water conditions. Loss of grazing marsh and field column and the erosion of sediment by tidal margins as a result of flooding would affect and wave action. Mudflats are important the diversity of vegetation. If the vegetation in helping to dissipate wave energy and so changes because of increased salinity, the reduce the risk of eroding saltmarsh. This availability of naturally ocurring seeds may helps to prevent stress on coastal defences be affected and many birds, reliant on and protect low-lying land from flooding. seed resources over winter, could suffer. If permanent grassland were to be lost the 3.3.22 The Intertidal mudflats and sandflats which small mammal population would decrease, occupy the majority of the Deben SPA are which in turn would have an adverse effect an Annex 1 habitat under the EU Habitats on Barn Owls. Directive due to their European importance. They provide an important nursery and 3.3.21 Mudflats, deposits of mud, silt and clay feeding ground for many fish species such found in sheltered intertidal areas, are found as plaice and dab. They are feeding areas throughout the estuary. Ranging from soft for sole, gobies, sea bass and flounder muds in the most sheltered inner areas which feed on the worms, bivalve young and of harbours and estuaries to firm sands in crustaceans. They also provide a valuable areas exposed to waves and currents, the food source for internationally important habitat represents a transition from sub- populations of over-wintering waders and tidal sediment areas that are continually wildfowl such as Brent Goose, Redshank, covered by the sea to areas submerged Bar-tailed Godwit, Curlew, Oystercatcher, and exposed approximately twice daily. Turnstone and Dunlin.

51 Deben Estuary Partnership - April 2015 Environment, Biodiversity and Geodiversity Saltmarsh

Haidee Stephens

Saltmarsh wall. Saltmarsh in front of seawalls will continue to be under stress from increased inundation due to storms, wash from some 3.3.23 Saltmarsh and mudflats are important watercraft and sea level rise. This in effect for many reasons and, in many cases, ‘drowns’ the saltmarsh, which leads to its are protected under European and UK ongoing deterioration and fragmentation legislation. Where they are being lost or as well as greater tidal pressure and damaged the UK Government has a duty to subsequent damage to flood defence walls. restore or recreate them elsewhere. Monitoring saltmarsh within the 3.3.24 Statistically the River Deben has approximately 40% of Suffolk’s saltmarsh Estuary and contains the most complete range of vegetation types. This is largely due to the 3.3.27 Using mapping data derived from aerial loss of previously reclaimed land increasing photography from three different time the amount of intertidal space where periods it has been shown that, between saltmarsh could become established. 2000 and 2011, there was change to the extent of saltmarsh on the Deben Estuary. 3.3.25 The health of the saltmarsh is important for This change has been in the form of the health of the estuary as the marshes both erosion and accretion of saltmarsh. and mudflats filter pollutants, lock up toxins Throughout the estuary, erosion and and improve water quality as well as acting accretion have been occurring along the as valuable carbon sinks, taking carbon out leading (seaward) edge of the marsh and, of the atmosphere. Saltmarsh provides a while erosion in one area is largely balanced vital nursery and feeding ground for juvenile by accretion in another, fragmentation and fish, such as sea bass, which come into the sinking of saltmarsh is seen as a potential creeks with the tide to feed away from the precursor to future erosion and loss. ( see high flows in the main river channels. Fragmentation Index, National Vegetation Classification Studies, 2013) As such Natural 3.3.26 In the Deben Estuary most saltmarsh is England has classified SSSI saltmarsh areas in backed by sea walls and so it acts as a the Deben estuary as being in ‘unfavourable natural flood defence, breaking wave action, condition’ and, as a consequence, there is absorbing tidal currents within the network a need to restore, enhance and potentially of saltmarsh creeks and thus lessening tidal recreate marsh. pressure on the base of the flood defence (See map of saltmarsh fragmentation – erosion and accretion.)

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Map showing saltmarsh fragmentation – erosion and accretion

The Environment Agency can create and fund new intertidal areas through its Regional Habitat Creation Programme (RHCP). In the longer term, if saltmarsh continues to be lost it may be necessary to consider ‘recreating’ this habitat, which could be done by removing sections of estuary defence and allowing the low-lying land behind a wall to go back to being intertidal. This process of ‘managed realignment’ may have other benefits, such as absorbing flood water during storm events, but would require the full cooperation of the landowners concerned.

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Reasons for the changing condition flood through the site, washing out the of saltmarsh newly established saltmarsh and leaving an expanse of mudflat.

3.3.28 Sea level rise and isostatic change: 3.3.31 Sources of sediment likely As a consequence of global sea-level rise to replenish saltmarsh: and the post-glacial sinking of land of the The supply of sediment to the Deben South East Coast, sea levels are increasing estuary from offshore is greater than that by between 1.5 - 2mm per year. This results supplied via freshwater sources within the in the low water mark moving landward but river catchment. The amount of sediment being contained by the estuary defence coming from the north-south coastal walls, which in turn means that intertidal processes has reduced. The distribution of habitats are being “squeezed” between the sediments within the estuary is governed rising sea levels and artificial defence works. by the tidal dynamic - whether the ebb Under these conditions a stable accreting tide is more powerful than the flood tide saltmarsh develops a cliff-like front edge at any specific point in the system. A flood susceptible to wave attack, erosion and dominant tide transports sediments up river collapse. The saltmarsh vegetation starts and deposits them as the tide slackens, to be drowned out; the profile of the marsh whereas an ebb dominant current in the slumps, eventually reverting to pioneer middle and lower reaches of the river vegetation, such as cord grass, and then an can re-suspend sediment and cause it to uneven mudscape. be transported out to sea. The supply of sediment is a critical factor in replenishing 3.3.29 Wind, tide and wave action: saltmarsh threatened by sea level rise; any Although not common, strong north loss of sediment from the estuary threatens easterly winds can quite quickly alter the the sustainability of saltmarsh. configuration of the shingle Knolls, which normally protect the mouth of the river. 3.3.32 Previous excavation of saltmarsh: Erosion can occur in the lower reaches of the The historic excavation of mud to create estuary when there is increased wave action. winter lay-up berths or to provide material Storm surges will also cause damage to the for the cement industry and construction shore and saltmarsh. Similarly, wash from of estuary walls has not only damaged from boats generating a high energy wake, saltmarsh vegetation but also increased whatever their speed, will cause damage, the vulnerability of the marsh, by allowing especially to saltmarsh in the narrow, upper the tide to flow through the network of dug reaches of the estuary. channels. Rather than refilling with sediment these holes and channels allow sediment 3.3.30 Unforeseen breaching to be washed out by the tide on a daily of flood defences: basis, contributing to the proliferating creek The accidental failure of river defences will pattern and the incremental fragmentation allow flooding of the land behind and, if of the marsh itself. left to establish its own morphology, may develop healthy saltmarsh. However, over 3.3.33 Crustaceans: time a breach in a wall can only become There is an ongoing debate over whether wider and the channel that feeds through burrowing shore crabs and ragworms are it deeper. On a daily basis, as the channel having a negative effect on the stability of systems become established within the saltmarsh. Crabs burrowing into the mud new marsh, more water flows in and out. ‘cliffs’ created by fragmenting saltmarsh may There is a likelihood that further sections be making the saltmarsh more vulnerable to of the defence, attacked by the tide from collapse but further research and evidence the inside, will fail, allowing the tide to is required to substantiate this view.

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Saltmarsh management barrier to protect fringing saltmarsh below Sutton Hoo, the Deben Estuary Partnership has undertaken further 3.3.34 It is important to be aware of the high projects, on an experimental basis, to trial ecological value that saltmarsh has and a range of solutions designed specifically the important place that it holds within the to accommodate the characteristics and mosaic of habitats in the estuary. It acts as demands of particular sites. The emphasis a first line of defence in the overall flood has to be on fostering an enhanced defence system, without which the flood awareness of estuarine systems and a walls of a predominantly rural estuary could heightened sense of community ownership become economically unviable. of the estuary and its management. The work is being used as a basis for further 3.3.35 The process of drawing together a Plan research into the drivers for saltmarsh loss. for the Deben Estuary has included consideration of the viability of present 3.3.37 The main objective of the work is to use estuary walls and the value of the land that ways of impeding or mitigating the tidal flow they protect. It is recognised that, at some through eroding or fragmenting sections of point in the future, sea level rise and the saltmarsh, and to encourage the deposition imperative to maintain the high ecological of sediment. value of the estuary may demand the creation of new saltmarsh through managed 3.3.38 Various methods and materials can be used realignment. Evidence of saltmarsh loss to balance possible erosion: must provide a legal driver for this and, significantly, any scheme would require •• Use of small structures such as fencing, the agreement of landowners. Managed faggots or straw bales to help trap sediments, realignment to create new intertidal habitat build up the level of the saltmarsh and create has been put forward as a potential course the right conditions for new plants to grow. of action but this led to a counter-proposal from the community to explore the potential •• Use of the mud and sediments, dredged for for the existing saltmarsh to be stabilised, navigation purposes from within the estuary, managed and enhanced. to build up badly eroded areas and, in some cases, to raise the level of whole marshes, 3.3.36 Following the initiative of the River Deben encouraging new vegetation at the right Association in 2009 to introduce a tidal tidal level.

Sutton before Sutton after

Suffolk Coast & Heaths AONB Suffolk Coast & Heaths AONB

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Objectives interests of wildlife or set aside as wildlife reserves. 3.3.39 Conserve the landscape, natural environment, and heritage in •• Safeguard and sustain the long term the Deben Estuary, and take future of designated sites, improving opportunities to enhance them. sites which are in unfavourable condition, maintaining all sites and the relevant hinterland in favourable Outcome: To facilitate and support condition. the sustained conservation and enhancement of the natural and historic •• Safeguard all freshwater wetland landscape together with the distinctive areas from pollution, disturbance or and valued environment important deterioration in designated sites. for both wildlife and the well-being of residents and visitors. To safeguard •• Where sites are outside the SSSI the estuary landscape from the visual designation support appropriate intrusion of modern development. management through agri-environment grants or other mechanisms.

3.3.40 Ensure compliance with the •• Seek environmental gain when work requirements of environmental is undertaken on flood defences or legislation, including the Habitats development is planned in close and Wild Bird Directives and proximity to the estuary. Water Framework Directive. Saltmarsh

Outcome: To recognise, strengthen and •• Recognise Saltmarsh as a significant enhance the habitats and biodiversity environmental asset, juvenile fish of the estuary and its hinterland. To habitat, important element of flood maintain designated International, defence and a contributor to carbon European and national environmental sequestration. sites in good condition and ensure that any adverse impact on the adjacent •• Encourage and deliver projects to hinterland is answered by appropriate restore and regenerate intertidal compensation and mitigation measures. saltmarsh.

•• Advocate where practicable, the beneficial re-use of dredged silt as recharge for saltmarsh areas. Policy •• Monitor habitats and species within the 3.3.41 estuary, taking note of climate change •• Promote the good management and and coastal squeeze. enhancement of features which provide wildlife habitats and refuge. in accordance with legislation: Conservation of Habitats and •• Safeguard sites of geological, ecological Species Regulations (2010) and environmental importance and EU habitats and Birds Directive/Natura 2000 support other areas managed in the Wildlife and Countryside Act (1981)

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