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Lower Witham River Corridor Habitat Plan Draft Version II (17/01/2014) for External Consultation Consultation Deadline 02/07/14 1. Introduction 1.1. The lower river Witham catchment area For the purpose of this plan the lower river Witham is defined as starting at Stamp End Lock in Lincoln and finishing at Grand Sluice in Boston which is the extent of the Witham before it becomes tidal. The lower Witham catchment has seven separate sub catchments, two of which are below the tidal limit. For the basis of this plan we are focusing on the main river Witham and up to the first structure on each of the sub catchments that join above Grand Sluice. The remaining sub-catchments will be addressed separately. The landscape of the lower Witham catchment is predominantly agricultural with agricultural use on the land accounting for 88% of land use. Historically the lower Witham would have been a large fen fed by the upper Witham and various limestone springs flowing off the surrounding higher escarpments. During the roman occupation the first channel was dug to drain this fenland and aid navigation. Medieval records state that the Witham had tortuous meanders as it flowed towards Boston and over the last couple of centuries the more meandering river channel has been straightened, deepened, widened, impounded, embanked and strengthened using stone on the toe of the bank as part of fluvial engineering schemes designed to reduce flood risk, improve land drainage and to aid navigation. These modifications, together with catchment land management practices, have contributed to a decline in overall river corridor habitat quality in the catchment. The lower Witham historically was one of the renowned match fishing venues in the 1970’s and commercially very important with anglers travelling from all over the country to fish it throughout the week bringing in angling related revenues to the area. Many local clubs sprang up to capitalise on this with angling clubs formed in Boston and Lincoln. Since water quality improvements have led to the cleaning up of our river systems, the match fishing catches have declined which has led to a general loss of local clubs as memberships levels drop leading to leases on the river being relinquished. This decline has come about due to improvements in water clarity leaving the fish increasingly vulnerable to predation. This then leads to fish congregating around structures like bridges, mooring and areas of bank margins and under trees. This leads to the majority of the channel being underexploited by fish as it provides poor fish habitat and as a consequence doesn’t meets its expected fish density due to its open cover free aspect. Recent fish surveys on the lower River Witham have highlighted how poor the available fish habitat is and there is a real risk of a decline in WFD status for fish. The only real areas of fish habitat on the lower Witham correspond with areas of trees and good marginal vegetation. The lack of available habitat and cover becomes a bottleneck for fish populations reducing survival of different year classes of coarse fish and is the limiting factor to fish density. Whilst water quality improvements in clarity has had negative effects for fish populations due to an increase in predation pressure, the improvements to water quality will have had positive benefits for invertebrates, macrophytes and for recreational users. 1.2. The Water Framework Directive The EU Water Framework Directive (WFD) provides an approach to investigate, plan and deliver a better water environment, based on biological, chemical and physical assessment indicators. The Environment Agency (EA) has assessed the ecological status (or health) of all water bodies in England and Wales based on fish, macrophytes (plants), diatoms (algae), invertebrates (insects), on chemical factors such as phosphate and dissolved oxygen levels, and on stream flow and channel morphology. The WFD assessments have been used to assign every river water body to one of five ecological status classes: high, good, moderate, poor, or bad. A river in its pristine, or undisturbed, natural condition would be classified as being High Ecological Status. The various elements of the WFD classification procedure are shown in Figure 1.2, and a failure in any one of these elements results in the failure of a water body to achieve the target classification of Good Ecological Status or Potential (GES or GEP). Importantly, the WFD requires that all water bodies achieve GES/GEP by 2015: where this is not possible, a programme of mitigation measures must be identified and implemented to ensure that GES or GEP can be achieved in the longer-term. Figure 1.1: The Lower River Witham catchment The Lower Witham is designated as an artificial water body under WFD. This is due to the use of the watercourse for navigation, flood protection and land drainage purposes. Its status is currently moderate and the target is to achieve good ecological potential. It’s currently failing for high levels of phosphates, low levels of dissolved oxygen, poor invertebrate, macrophyte and phytobenthos diversity, mitigation measures, and the heavily modified flow and morphological condition of river channels. (Figure 1.3). As part of the process of deciding if good ecological potential is being achieved a number of criteria must be considered for the lower Witham, e.g. preserve and where possible enhance ecological value of marginal aquatic habitat, banks and riparian zone, and managing structures to enable fish passage. Unless these measures are deemed to be economically or technically infeasible they will be expected to be in place. A number of mitigation measures that are designed to restore the physical habitat component of the Lower Witham have been identified and include: Removal of obsolete structures. Removal of hard bank reinforcement / revetment, or replacement with soft engineering solution. Preserve and where possible restore aquatic habitat. Increase in-channel morphological diversity. Re-opening existing culverts and alteration of channel beds within culvert. Flood bunds (earth banks) in place of floodwalls. Set back embankments to increase flood storage. Improve flood plain connectivity. Structures or other mechanisms in place and managed to enable fish to access waters upstream and downstream of the impounding works; Manage the risks of fish entrainment in intakes for hydropower turbines or water resource purposes (or pumping stations) where there is downstream migration. Preserve and where possible enhance ecological value of marginal aquatic habitat, bank and riparian zones. Operational and structural changes to locks, sluices, weirs, beach control etc. Selective vegetation control regime, and appropriate vegetation control technique and timings. Overall Status / Potential Chemical Status / Ecological Status / Potential Potential Substances which Physico-chemical Biological elements Specific pollutants Hydromorphology present a significant (e.g nutrients, pH, (e.g. phytoplankton, (e.g. metals and their (e.g. depth, width, risk to the water dissolved oxygen). fish, invertebrates). compounds). flow, structure). environment. Figure 1.2: Components of the WFD assessment Figure 1.3: Map of WFD ecological status/potential 1.3. The Purpose of this Plan As this is a heavily managed watercourse for flood conveyance and navigation the aims for this plan are to protect and enhance existing habitat whilst scoping opportunities for further works to the river corridor. While the focus of attention is on habitat improvement for the benefit of riverine wildlife, the plan is also intended as a basis for improving the river environment for the public (e.g. by improving fisheries, aesthetic quality and other amenity resources). Acoustic fish surveys on the lower Witham have highlighted the lack of available habitat present. Where good levels of fish are recorded these correlate to structures such as bridge structures which provide overhead and structural cover, trees that provide shade, root structure and occasionally limbs that touch the water and marginal vegetation which has been allowed to develop. Part of this survey was linked in with acoustic bat surveying which provided evidence of a variety of bat species using the river corridor in particular where trees and margins were. A critical part of this report is to highlight these areas of good habitat and protect them from removal to retain a baseline habitat reservoir to build on improving wildlife populations from. As part of this plan a tree management strategy will be developed which will highlight the most important areas to preserve, maintain and plant. The preservation through appropriate management will ensure that the WFD current status does not deteriorate. APEM walkover surveys were carried out last year to identify key terrestrial areas to protect and enhance biodiversity on sections of the lower Witham. These habitat retention and improvement works identified in the plan are essential in order to achieve the objectives of the WFD, by implementing mitigation measures such as those listed previously in Section 1.2. Some of the typical approaches to river corridor habitat improvement outlined in this document include: Retaining marginal trees that provide shade and cover in different flows Introducing woody material; Retaining marginal vegetation and encouraging diversity when managing weed cutting to create bays and scallops within the channel providing different flow patterns. Creating refuge habitat; Reconnecting rivers and floodplains; Improving channel bed and bank vegetation; Reducing localised erosion and sedimentation; and Removing/altering impoundments to improve fish passage, flow continuity and sediment transfer. The second main objective is to engage local partners to coordinate, agree, design and deliver river corridor habitat schemes throughout the catchment. There is a wide range of stakeholders and potential partnership organisations in the lower Witham catchment, including the EA, local authorities, IDB, charities, interest groups and landowners. During 2014, all of these stakeholders will be identified and consulted for their views on how this action plan can be extended, improved and delivered. Together, our broad vision for the future is that the lower Witham will: Be cleaner and healthier; Support more fish, birds and other wildlife; Meet the needs of business; Provide a more attractive place for people to enjoy through a variety of uses including angling and navigation. Continue to provide drainage and manage flood risk; Be sensitively managed by everyone whose activities affect it. 1.4. The Wider Context The habitat improvement schemes outlined in this plan form one element of a wider spectrum of activity and projects that are being delivered across the lower Witham catchment. Adopting a catchment-wide approach is necessary because schemes that focus solely on the river corridor cannot remedy all of the WFD failures. Table 1.1 provides a list of recent, current and future projects/activities that are highly relevant to this river habitat action plan. Table 1.1: Other relevant projects/activities in the lower Witham catchment Activity Location Organisation Flood risk Opportunities Study Across the catchment Environment Agency, IDB Lincoln Urban Plan Lincoln Witham Partnership Witham Opportunities Scheme Across the catchment Fen creation Witham Peatlands Lincolnshire Wildlife Trust; Environment Agency, IDB Fens for the Future Navigational improvements Various Canal and Rivers Trust Black Sluice Catchment Works Study Black Sluice Wildlife Surveys Across the catchment Environment Agency, Canal and Rivers Trust, IDB Lincolnshire Wildlife Trust Project Delivery Across the catchment Eel Regulations compliance Across the catchment Lincolnshire Rivers Trust, Environment Agency, Canal and Rivers Trust, IDB Environment Agency, IDB, Canal and Rivers Trust, Land owners Water Abstraction Across the catchment Environment Agency, Anglian Water 2. Present-day habitats 2.1. River character The lower River Witham runs through a predominantly agricultural catchment area, with several large urban areas including Lincoln and Boston as well as scattered small towns and villages. The gradient is flat with the river dropping onto clay bedrock and into a heavily modified trapezoidal channel, flanked by embankments that protect arable land and properties from flooding and a series of sluices for navigation and flood alleviation. As the gradient flattens out the river geomorphology changes and the sediment balance shifts from one of erosion and deposition to a sediment depositional balance. The sediment that has been transported down the river from various sources including natural geomorphological processes and from catchment farming practices would naturally settle out in flood conditions when the water level overtops the banks into the flood plain. The way the river is managed and controlled throughout the year prevents connectivity with the flood plain and controlling water levels in summer leads to sediment deposition on the river bed and around flow control structures like sluices. The extra nutrients in the sediment combined with holding levels through water control structures leads to the river acting as a still water. This can promote excess blooms of algae and macrophytes creating the potential for the channel to choke up. Management and maintenance like weed cutting and de-silting is then needed to control this to aid flood management and navigation. Downstream changes in river management represent both opportunities and constraints for river corridor habitat improvement projects. Therefore, for the purposes of this action plan, the river has been categorised into three zone reaches of the catchment (see below and Figure 2.1). These zones include up to the first structures on waterbodies that join the main Witham and that provide habitat and refuge areas for riverine wildlife on the Witham. Zone 1: From Stamp End lock to Bardney lock. The water level on the main Witham is held at the same retained level all year. Zone 2: This section starts downstream of Bardney Lock following the main Witham to the downstream confluence of the River Bain. Along the main Witham are various interconnecting drains and watercourses which are also included in this zone. For the purpose of this report we are including them as available Witham habitat up to the first structure. This includes a very short section of the North Delph up to a pump station at the bottom of the system which joins the old Witham below Fiskerton sluice. Joining the old Witham the Barlings Eau comes in behind Branston Island and Snakeholme Drain meets the old Witham before it joins the main Witham below Bardney Lock. The South Delph meets here and extends into Lincoln. For the basis of this report the upper limit of the South Delph has been classified as level with Stamp End above which will be covered in a potential Witham urban plan. The South Delph is joined by Branston Delph. The main Witham flows south where it’s then joined by the Nocton Delph, the entrance to the Metheringham Delph, Timberland Delph, and Billinghay Skirth. The water level for zone 2 is subject to winter and summer water level management. Zone 3: The lower reaches of the lower Witham flows south from the confluence of the River Bain to Grand Sluice at Boston. This includes up to the first structure on the Kyme Eau. The water level for zone 3 is subject to winter and summer water level management 2.2. Catchment-scale habitat issues The character of existing river corridor habitats in the lower Witham catchment is to a large extent the product of past and present uses of the channel network and the surrounding landscape which it drains. Many of these uses create pressures which serve to hinder the natural processes and functions of the river system. Table 2.2 outlines the key pressures and associated negative impacts on the lower Witham river corridor, along with information about how habitat works can help to mitigate these impacts. Table 2.2: Key pressures, impacts and mitigation measures in the lower Witham catchment. Pressure Cause Impacts Water Level management Varying water levels set at summer and winter levels to aid navigation in summer and drainage in winter. Impoundments Weirs, sluices, and other obstructions have been placed in the river to control river levels for flood defence protecting against tidal surges, allowing monitoring of flood levels, aid navigation, ensuring sufficient water for irrigation and public water supply. Different water level heights ensure that marginal vegetation cannot establish reducing cover for fish and invertebrates in both summer and winter flows. Reduction in levels increases water speed reducing juvenile fish survival and increasing washing out of fish and invertebrates to the sea. Reduction in cover increases predation pressure. Increased risk of low flows with associated impacts on water quality (eg, low dissolved oxygen) and ecology. Un-natural flow and sediment regimes which can alter existing habitats. Prevention or hindrance to fish migration and ecological continuity. Routine maintenance regimes Routine maintenance of the bank side, marginal and in-channel vegetation (largely carried out for navigation Removal of marginal and in-channel vegetation reduces valuable food supply as well as cover and refuge for fish, invertebrates and riverine mammals. It also removes spawning media for certain fish species. Mitigation Holding retained levels year round would allow marginal vegetation to establish and provide cover. Fish passage can be improved through removal/lowering of an obstruction or creation of a fish pass. Removal or lowering of impounding structures will also allow a more natural flow and sediment regime but it is accepted that removal is not possible where the structures have an essential function. More sensitive and sustainable management regimes can be developed by working closely with the respective channel Pressure Cause purposes). Altered channel morphology Diffuse and point source pollution Invasive Impacts Removal of bank-side trees and scrub reduces cover and food supply for fish and other fauna, such as bats. A lack of trees has been linked to elevated water temperatures and reduced dissolved oxygen levels which can lead to death of fish and their eggs. Dredging to remove silt can reduce bed diversity and over deepen channel. Many species of freshwater mussels use the marginal areas for their lifecycles and can be removed by dredging. Nutrient-rich dredged material (silt and vegetation) is often left on the banks leading to a monoculture of nutrient-loving species (e.g. nettles and thistles which have poor ecological value). Mitigation managers using the suite of environmental options available Habitat enhancement works can be undertaken as part of these sensitive management regimes. Any works that involve dredging should try to concentrate in centre of channel where mussels are unlikely to be found, any works to margins should have a banksman to return mussels etc back to the river. Numerous enhancement options are available to create the desired channel morphology, from backwater refuge creation, bank lowering and river floodplain reconnection. Where high velocities and undesirable erosion occur, measures to protect banks and provide fish/wildlife refuge can be implemented. Historic alterations to the channel for industry and water conveyance including creation of mill streams, straightening, widening, deepening and construction of flood defences (e.g. walls and embankments). Removal and/or loss of natural features such as meander bends, low level sediment berms, leading to reduced diversity of substrate, flow and depth. This reduces habitat value for flora and fauna. Over-deepening and flood embankment disconnects the river from its surrounding floodplain, leading to high flow velocities during flood flows, with associated channel erosion and sedimentation. Over-widening and over-deepening reduces channel flow velocities often leading to a shallower river with high sedimentation rates and often excessive growth of inchannel vegetation. Inputs of sediment, nutrients and pesticides from fields, roads, industry and urban areas. Sources are throughout upper and lower Witham catchment and from fenland area drains and pump stations. Non-native flora and fauna, such as Himalayan balsam, Fine-grained sedimentation upon river gravels reduces habitat quality for fish, plants and invertebrates and provides a pathway and sink for adsorbed nutrients and pesticides. Excessive phosphate is a key issue in the river catchment that can lead to excessive plant growth which in turn can restrict flows, deplete oxygen and adversely affect fish, plants and invertebrates. In-channel works can also be undertaken to reduce excessive erosion and improve flows, thus minimising sediment inputs. Sediment sinks / silt traps can also be created to encourage deposition in selected areas (e.g. marginal berms). Although invasive species control is typically tackled on a Non-native flora can spread rapidly and out-compete the native vegetation. Their root systems can Pressure Cause Impacts species Japanese knotweed, Azolla, Pennywort, Mink, Signal crayfish, Chinese mitten crabs, and DH shrimp have been introduced from overseas and are difficult to control effectively. cause significant damage to structures and their rapid growth can choke rivers and leave the river banks devoid of vegetation in the winter (the latter increases the risk of bank erosion and potential flooding). Non-native fauna in the Lower Witham system have potential for ecological damage. The signal crayfish, currently present on the River Bain, out-competes our native white clawed crayfish (populations remain on the Upper Witham around Grantham) as well as carrying a fungal disease which kills the native species. They also cause damage to riverbanks by deep burrowing and can reduce fish stocks by eating large amounts of fish eggs. The mink provides a threat to fish stocks where populations are already suffering from other pressures and may also be a contributing factor to the decline of water voles in the catchment. Chinese mitten crabs have been found at Short ferry and are likely to be found throughout the lower Witham catchment. They burrow into banks causing sedimentation and can reduce fish stock through predation. DH shrimps have been found in several spots along the lower Witham and are thought to have been transferred through the Trent Witham Ancholme water transfer system. They out compete native invertebrate species. Trent, Witham, Ancholme water transfer for farmland irrigation, industrial use and public water supply. Risk of spreading invasive species within these catchments, entrainment of fish and invertebrates and water quality of receiving water. DH shrimp spread through water transfer scheme, potential for other invasive species transference. Potential for further transference if the Fens waterway link goes ahead linking the south forty foot to the River Glen. Mitigation catchment scale and may form a major project in itself, management of invasive species should be considered as part of any habitat enhancement works to avoid spread of the species. Azolla beetles have been trialled in the past. Bio-security measures should be undertaken when carrying out any works in-stream to ensure accidental spread is limited. Pressure Cause Impacts Mitigation Figure 2.1: Map of action plan zones 15 Figure 2.2: River engineering modifications showing obstructions and flood embankments 16 2.3. Reach-Specific Habitat Issues Zone 1 (upper reach) Over-deepened and embanked river channel disconnecting sediment transport within its natural floodplain River Witham below Stamp end Limited marginal habitat which is heavily managed for flood defence and navigation. Limited shading from bank side trees which are heavily managed for flood defence and navigation which can encourage excessive algal and macrophyte growth. Zone 2 (middle reach) River Witham below Fiskerton Stone toe and subject to winter and summer water level management. This extreme range in water heights prevents marginal vegetation establishing which limits cover for fish populations reducing survival rates for juveniles and adults. Over-deepened and embanked river channel disconnecting sediment transport within its natural floodplain Lack of channel bank tree/scrub vegetation 17 Zone 3 (lower reach) Barrier to fish movement; flow and sediment discontinuity Stone toe and subject to winter and summer water level management upstream restricting marginal vegetation, limiting cover for fish populations reducing survival rates. Over-deepened and embanked river channel upstream of Grand Sluice disconnecting sediment transport within its natural floodplain Lower River Witham at Grand Sluice 3. Dealing with Habitat Issues As stated earlier in the report the aim of this plan is to preserve the existing small patches of habitat which are essential to maintain fish population and provide diverse habitat for a variety of wildlife species whilst identifying opportunities for potential habitat improvements. In simple terms the river is lacking in a diversity of habitats and flow types with a resulting lower level of fish populations and other riverine wildlife supported. The aim is to reverse this trend and create a wider variety of river habitats which can then support healthier populations of flora and fauna. The key aspects that need to be considered when trying to deal with habitat issues are detailed below however full details of the systematic process undertaken in the planning and implementation of river corridor habitat works is provided in Appendix A. 18 3.1. Idealised river habitats A typical example of good river habitat comprises some of the following physical features: A natural functioning channel with connection to the floodplain, natural sediment transport regime, and good diversity in flow, substrate and depth; A sinuous profile with physical features such as low level sediment berms, backwaters, and eroded banks; A diverse mix of in channel, marginal and bank-side vegetation providing food, cover and shelter for fish, invertebrates and mammals; and Clean bed substrate and/or channel weed to provide spawning media for fish and also habitat for aquatic invertebrates. Barlings Eau:- Example of idealised river habitat for fish in a lowland section of embanked river- note the two stage channel with sediment berms supporting healthy marginal vegetation cover and tree cover touching and hanging over the water providing shade and habitat. To ensure retention of good habitat like the overhanging trees that are present, regular sensitive management like coppicing or pollarding on a rotation would ensure that there is always habitat available rather than reactive management when trees are deemed to be an issue to conveyance and are heavily managed. 3.2. Setting Realistic Targets It is not necessarily feasible or desirable to restore the river to a past condition when there was little modification or pressure on the watercourse. Where pressures remain present on the river a more realistic and sustainable target would be to replicate a section of river where present-day habitats are considered to be in good condition. These sections of relatively good habitat, where more natural processes have both developed and sustained the key attributes of a healthy river corridor (e.g. backwaters, low level sediment berms, woody material, retained water levels encouraging good marginal vegetation cover) can be used to inform improvement schemes on other sections of the river. 19 The data sheets provided below illustrate the nature of relatively good existing river corridor habitat within zones 1, 2, and 3 (see Section 2.1 and Figure 2.2) of the Lower Witham catchment. The sheets demonstrate the key physical features and processes that provide habitat to support and sustain healthy populations of fish, flora and invertebrates as well as the added benefits of an actively functioning river (e.g. improved recreational value). The data sheets also list some typical target species that provide key indications of a healthy river corridor. These sheets can be used as a guideline when conducting improvement works in the different zones of the river catchment. Lower Witham Zone 1 Retained levels: Target Habitats and Species Data Sheet Habitats Marginal and in-channel vegetation cover Lower Witham below Stamp End which is allowed to encroach into the river. Sustainable weed cutting using environmental options to create sinuous marginal bays providing a mosaic of habitats. Bank-side and in-channel large woody material; Riparian tree and shrub cover particularly where branches hang into the water providing refuge for fish in different flows and from predators. The tree cover provides cover and feeding stations for bats Downstream fish passage through Stamp End lock into lower Witham in summer when navigation in operation. Open access for fish into Zone 2 & 3 through a Larinier and eel pass on Fiskerton sluice. Online flow refuge provided by entrance to Branston Delph. There is potential to open up access into Branston Delph which is currently sealed where there is good upstream habitat. This would involve anti seepage works or a change in land use around the Delph. Mown grass banks maintained by EA Operations staff increases mosaic of habitats available encouraging variety of species of small mammals and owls. Unconnected wetland habitats increase diversity for mammals and birds at sites like Fiskerton Fen. Moorings, boats and bridges provide structural cover for fish. Species Grebes, Kingfisher: an indicator of healthy fish stocks and good physical habitat quality); Coarse fish (e.g. Common Bream, Silver Bream, Roach, Carp, Perch, Pike, Spined loach*). Migratory fish, eel and lamprey. Otter*, Bats (e.g. Daubenton’s, Noctule, Common and Soprano pipistrelle. ) Invertebrates (e.g. Dragonflies, Caddis, Compressed River Mussel*, Swollen River Mussel, Pea Mussels, Orb Mussels, including the Witham Orb Mussel** and the False Orb Mussel**) Plants, including Common Reed, Reed Sweet Grass and Fringed water lilies provide cover for invertebrates, wildfowl and fish. (* Biodiversity 2020 designated species)(**Red data species) 20 Lower Witham Zone 2 Target Habitats and Species Data Sheet Habitats Marginal and in-channel vegetation cover on main river in particular in areas behind where stone toe has been eroded and marginal vegetation has been able to colonise as not subject to variation in water levels. Backwaters/bays for still-water habitat and open access high-flow refuge available on the Nocton Delph. Riparian tree and shrub cover Lower Witham around particularly where branches hang Billinghay into the water providing refuge for fish in different flows and from predators. The tree cover provides cover and feeding stations for bats. Wetland wildfowl refuge provided at Branston Island and adjacent to Short Ferry pump station. Moorings, boats and bridges provide structural cover for fish Mown grass banks maintained by EA Operations staff increases mosaic of habitats available encouraging variety of species of small mammals and owls. Species Grebes, Kingfisher: an indicator of healthy fish stocks and good physical habitat quality; Coarse fish e.g.( Common Bream, Silver Bream, Roach, Carp, Perch, Pike, Spined loach*) Migratory fish e.g. fish, eel and lamprey; Water vole*, otter**, Bats (e.g. Daubenton’s, Noctule, Common and Soprano pipistrelle.) Invertebrates (e.g. Dragonflies, Caddis, Compressed River Mussel*, Swollen River Mussel, Pea Mussels, Orb Mussels, including the Witham Orb Mussel** and the False Orb Mussel**) Plants, including Common reed, Reed sweet grass and Fringed water lilies provide cover for invertebrates, wildfowl and fish. (* Biodiversity 2020 designated species) )(**Red data species) 21 Lower Witham Zone 3 Target Habitats and Species Data Sheet Habitats Marginal and in-channel vegetation cover on main river, in particular in areas behind where stone toe has been eroded and marginal vegetation has been able to colonise as not subject to variation in water levels. Backwaters/bays for still-water habitat and high-flow refuge available on Kyme Eau entrance. Riparian tree and shrub cover particularly where branches hang into the water providing refuge for fish in different flows and from predators. The tree cover provides cover and feeding stations for bats. Moorings, boats and bridges provide structural cover for fish Mown grass banks maintained by EA Lower Operations staff increases mosaic of Witham below habitats available encouraging variety of Kyme Eau species of small mammals and owls. Species Kingfisher: an indicator of healthy fish stocks and good physical habitat quality; Coarse fish (e.g. Common Bream, Silver Bream, Roach, Carp, Perch, Pike, Spined loach*) Migratory fish e.g. fish including smelt, eel and lamprey; Water vole*, otter*, Bats (e.g. Daubenton’s, Noctule, Common and Soprano pipistrelle) Invertebrates (e.g. Dragonflies, Caddis, Compressed River Mussel*, Swollen River Mussel, Pea Mussels, Orb Mussels, including the Witham Orb Mussel** and the False Orb Mussel**) Plants, including Common reed, Reed Sweet Grass and Fringed water lilies. (* Biodiversity 2020 designated species) )(**Red data species) 3.3. Choosing Appropriate Techniques Due to the intensive need for management that this system requires there are limited options for improvements. These options are limited by a need to provide flood defence, navigation and abstraction and selection may also boil down to other logistical factors such as local availability of materials or landowner preferences. However as the habitat is currently so poor any minor changes have the potential for large biodiversity impacts. The techniques that are potentially most suitable for habitat improvement works in the lower Witham catchment are listed in Table 3.1. It is important to note that often a combination of techniques will be required to provide a successful and sustainable solution. For example, opening up the delphs may require the use of a deflector upstream of the entrance to the delph to slow river flow providing slack water to allow easy access for fry to reach the refuge in high flows. It may also require significant engineering works or a change in land use as embankments on delphs are set lower than the Witham. 22 Table 3.1: Habitat improvement techniques Technique Purpose/Impacts Retain single water level all year round. Allow colonisation of marginal vegetation by retaining single water level all year round. This could provide soft bank protection as opposed to stone hard bank protection. Enables fish to access valuable spawning areas of marginal vegetation. Creation of a two stage channel Reduce need for maintenance by creating a low flow and higher flow channel increasing water retention within the channel and reducing sediment deposition in channel. This would improve biodiversity and aesthetics whilst reducing maintenance and allowing navigation. Flow deflectors Provide shelter around the entrance to the delphs allowing fish to access refuge in high flows. Provide food, cover, refuge and shade for fish, invertebrates, birds and other mammals. Create shade to reduce excessive in-channel weed growth and a stable environment in terms of temperature and oxygen levels. Use species of trees like Hawthorns and Blackthorn which are slow growing, needing minimal maintenance and having smaller root balls so less impact on embanked flood defences. Creation of a tree management strategy to highlight areas of good habitat and ensure appropriate traditional maintenance to preserve the longevity of the trees e.g. coppicing, pollarding, crown lifting etc dependent on species. Tree/shrub planting and maintenance Woody material introduction Remove/alter impoundments Reconnect rivers and floodplains including backwaters and washlands Create physical habitat for many species of plants, invertebrates and fish (e.g. refuge for fish.) Improve fish passage and ecological connectivity. Provide refuge and migration pathways for aquatic fauna during high flow events, currently South Delph acts as a refuge for fish in higher flows on the River Witham and potential for opening further delph access. Reconnect to floodplain habitats such as delphs. Creation of wetland habitat in washlands. Create backwater online fish refuges. 23 4 Action Plan Table 4.1 presents the ongoing and potential planned actions within the lower River Witham catchment that are aimed at improving the river corridor habitats and meeting WFD targets. The proposed action plans are specifically broken down for the three river zones, in addition to those that are relevant across the whole catchment area. Location Table 4.1: River corridor habitat action plan Driver Action Lead Type Catchment-wide Catchment Partnership working Catchment Operational management Operational management Operational management Operational management Knowledge acquisition Catchment Catchment Catchment Catchment Catchment Operational management Catchment Awareness raising Catchment Operational management Catchment Operational management Engage with the other relevant initiatives/projects as listed in Table 1.1 Review current river management plans and requirements. Develop Tree Management Strategy Develop single water level plan to encourage marginal vegetation. Develop and deliver Witham eel and fish pass plan. Establish woody material demonstration/monitoring sites. Install spawning media under all CRT moorings. All Partners Short Term Action All Partners Publish habitat improvement case studies and promote value of works when carried out. Creation of a two stage channel to improve habitat whilst reducing maintenance and dredging. Creation of wetlands and fens. Develop and encourage sustainable farming in upper and lower reaches of catchment with catchment sensitive farming. EA Short Term Action Short Term Action Long Term Plan Short Term Action Short Term Action Medium Term action Medium Term Action Long Term Plan All Partners All Partners All Partners All Partners CRT / EA EA EA Long Term Plan EA Short Term Plan Zone 1 (Upper reach) In terms of three zones this has the best current habitat. Stamp End to Bardney Lack of suitable in-stream, riparian vegetation and cover for fish life cycle Maintain existing tree cover and riparian vegetation providing a variety of terrestrial and aquatic habitat. Areas where in-stream aquatic vegetation present should be retained as it provides valuable invertebrate and fish cover and a medium for fish spawning. APEM report on Lower Witham highlights these areas for protection. 24 Stamp End to Bardney Lack of suitable instream, riparian vegetation and cover for fish life cycle Stamp End to Bardney Lack of suitable instream, riparian vegetation and cover for fish life cycle Stamp End Lock Barrier to fish and eel movement. Straightened channel, limited off line refuge for fry in higher water levels. Cherry Willingham Fen creation Washingborough Fens creation Straightened channel, limited off line refuge for fry in higher water levels. Fiskerton eel and fish pass Current fish and eel passage through Larinier and bristle boards. Hinge bankside trees and secure in margins to create overhead cover and provide spawning media. Use of mesh cages filled with brushwood and barley straw to provide overhead cover and spawning media. Install fish and eel pass solution. EA / CRT Short term started 1/2/16 EA Short term started 2015 EA Creation of online refuge, setting flood banks back, provides a online fish refuge and increases habitat diversity. Creation of wash lands, setting flood banks back, provides a online fish refuge and increases habitat diversity. Maintain fish passage on structure. EA Witham Opportunities Mapping Long Term Plan Long Term Plan EA Witham Opportunities Mapping Long Term Plan EA Short Term Plan Zone 2 (Middle reach) This zone has slightly less current habitat but a large scope for improvements. River Witham d/s Bardney Lack of suitable riparian vegetation and cover for fish life cycle, invertebrates and mammals. Maintain existing tree cover and riparian vegetation. Amount of habitat impacts on fish / ecology populations further downstream in zone 3 EA Short Term Plan Washlands Providing good wetland habitat for bird, plant and fish populations. Scope for further improvement works / scrapes and land management and for use as a template. Long Term Plan Billinghay Skirth, Snakeholme drain, River Bain, North, South, Branston, Nocton and Timberland Delphs Lack of suitable riparian vegetation and cover for fish life cycle, invertebrates and mammals. Maintain existing tree cover and riparian vegetation. Protect / enhance through widening entrance to create online refuge to Delphs, Skirth and drain as cover from high flows in Witham. EA / Landowner, Witham Opportunities Mapping EA LRT, EA, Landowners Short Term, works started 2013 Fish and eel passage Short Term Plan Open access through control structures where possible to allow access to spawning and juvenile coarse fish habitat in a range of flows. Deepen with selective dredging at bottom of delphs to increase fish habitat and access to spawning habitat upstream. Branston, Washingborough, Nocton, Dunston, Metheringham Sedimentation and providing good wetland habitat for bird, plant and fish populations. Develop community limestone becks projects to slow the flow into Delphs reducing sedimentation and improving fish populations 25 Tattershall Bridge Barlings Eau Langworth, Barlings Hall, and Lower Barlings Eau and Short Ferry Flood storage Branston island wash lands outfall All of Zone 2 Lack of suitable riparian vegetation and cover for fish life cycle, invertebrates and mammals Straightened, over-widened impounded channel. Wide low level grass berm providing some habitat. Barriers to fish and eel movement. Potential for fish refuge EA / CRT Short Term Plan Create wash land with flood banks set back. Retain bank side trees and marginal habitat cover. Provide fish passage either by removing barrier or installing fish / eel pass. Scope to add an online fish refuge by digging out an area to provide cover from winter flows. Maintain fish passage through control structures where available and improve passage beyond barriers. EA Witham Opportunities Mapping Long Term Plan EA Short Term Plan All Partners Short Term Plan Maintain existing tree cover and riparian vegetation. EA Short Term Plan Lowering the stone toe in selected places and excavation back into earth where appropriate to create online refuge for fish and invertebrates in high and low flows. Woody material to be added behind to protect banks and provide refuge. Remove barrier or install fish/eel passes. EA Short Term Plan EA Long Term Plan Zone 3 (Lower reach) This is the zone with the most limited habitat so critical to retain what habitat is present, and closer to the tidal influence. Lower Witham Lower Witham where appropriate trial at Kyme Eau Straightened, overwidened, embanked channel. Lack of suitable riparian vegetation and cover for fish life cycle. Limited marginal and online fish refuge in variety of flows for fish and invertebrates. Kyme Eau Barrier to fish movement. Chapel Hill Limited marginal and online fish refuge in variety of flows for fish and invertebrates. Create online flow fish refuge by excavating flood bank. EA Delivered Antons Gowt Straightened, overwidened, embanked channel. Barrier to salmonid, eels, and smelt migration. Barriers to fish and eel movement. Provide refuge behind moorings and jetties. EA Long Term Plan Ensure fish migration by installation of fish pass. Maintain fish passage through control structures where available and improve passage beyond barriers. EA Medium Term Plan Short Term Plan Grand Sluice All of Zone 3 All Partners APPENDIX A: Approach to river corridor habitat works 26 A systematic approach is required for river enhancement works from project inception through to delivery and monitoring. This ensures that not only is the work targeted to where it is most needed but also allows us to monitor its effectiveness and learn lessons for future works. The typical approach taken is illustrated in Figure A1 and each stage is described in more detail below. Desk study and site walk-over: Undertake an initial desk study and site walk-over to understand site specific and wider catchment considerations. Data reviewed typically includes the following: Existing data that has informed the WFD classification; and Long profile survey data of the river to characterise channel bed gradients, illustrate existing impoundments and assess their upstream ponding effects. During this early stage one would also consult with landowners and other relevant stakeholders to gauge their requirements and ideas. Desk Study and Site Walkover Identify Limiting Factors Identify Locations for Enhancement Consider Appropriate Techniques Prepare Strategy for Pre/Post Monitoring and Management Monitor and Review Figure A1: The 6 key steps involved in the approach to river habitat enhancement works Identify limiting factors: It is important to identify the limiting elements of the river reach and the wider river system, whether this be a lack of water for local landowner needs or a missing stage in the life cycle of a target species (e.g. lack of deep water for adult fish, lack 27 of aquatic vegetation for fish spawning, lack of refuge for fish/other aquatic fauna in times of high flow. Identify locations for enhancement: By identifying the limiting factors along both individual reaches and the longer river section, it is then possible to target suitable locations for enhancement works. For example, if aquatic vegetation is not provided on a short reach but are known to be present in a connected upstream reach, the requirements of the particular species (in this case fish) for spawning medium is still likely to be met. By contrast, if lack of refuge for juvenile fish in high flow periods were lacking throughout the system then it would be more beneficial to put time and resources into sustainable creation of this habitat for the benefit of the short and connected reaches. All elements can be tackled but realistically works should be targeted to where most gain under the WFD and other targets can be achieved within a given budget. Other factors influencing locations may include ease of site access and land ownership. Much of the recent habitat work has been targeted on sections of the lower River Witham which are currently classified under the WFD as being in moderate to poor ecological status. Choose appropriate techniques: Depending on the situation, there are numerous techniques that can be employed. Best practice guidance should be followed in terms of selection and siting of measures so that the solution is effective in the short and long-term. Selection may also come down to other considerations such as availability of local materials or landowner preferences. The main techniques that were considered appropriate for habitat improvement works on the lower Witham are outlined in Table 3.1. It is important to note that often a combination of techniques will be required to ensure sustainable habitat improvement (e.g. creation of online fish refuges may involve siting a flow deflector above to aid fry to take refuge in higher flows). Prepare strategy for pre/post monitoring and management: Successful restoration schemes include a sound programme of monitoring and management. As each river reacts differently to the outlined techniques, only monitoring will allow us to fully assess which techniques and methods are being successful, or otherwise. Low energy, low gradient rivers such as the lower Witham will also take time to respond and recover (typically 5 years or more dependent on the flow and sediment regime experienced during the years following the works). Although the aim is to create largely self-sustaining habitats, an element of management will also be needed. Monitoring: Typical approaches to pre/post monitoring include: Fixed point photography: a simple and effective means of recording physical changes/impacts; Biological surveys: fish, invertebrate and sediment surveys can be employed to quantify biological impacts; Water level recording: important to assess the impact of structural (e.g. hatch) removal or redesign, or to assist in the design of a fish pass; 28 Cross-sectional surveys and flow measurements: may be cost and resource prohibitive on smaller scale schemes but can inform selection and design of techniques as well as providing an evidence base for the results of the works; Expert advice and audit processes: external bodies such as the River Restoration Centre, Wild Trout Trust and Rivers Trust can be contacted to assist in the design, delivery and monitoring of habitat schemes. Given the dynamic nature of rivers, sharing of best practice and lessons learnt is the best way to improve and adapt techniques. Management: Ideally, channel works are designed to not only be easily adaptable but also the habitats created should be self-sustaining in order that management and maintenance requirements are minimal. An element of management is, however, vital to the long-term success of schemes and a commitment to this is needed. Management of the works may be undertaken by external organisations but the involvement of landowners and other interested parties, such as fishing clubs, is often the best arrangement. Management regimes and responsibilities need to be agreed at an early stage of the project. Scheme design and implementation: scheme design needs to be based on a sound understanding of the system and the needs of its users. Other requirements during the design and implementation stage are legal obligations, such as planning permissions, flood risk assessments, consents and licensing (e.g. impoundment licenses, flood defence consents, waste licenses or protected areas/species licensing) and health and safety requirements under the Construction (Design and Management) Regulations, 2007 (CDM). It is also important to use local materials where possible to reduce scheme and environmental costs. 29