Habitat Management Plan, Gloucester AC Upleadon July 2014
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Background The River Leadon The River Leadon rises in Herefordshire north of Evesbatch and merges with the River Severn in Gloucester. At over 45km in length the Leadon drains a predominantly rural catchment and the conurbations of Ledbury, Dymock and the west of Gloucester. Major issues within the catchment include; silt inputs from unsuitable land management, historic channel realignment for land drainage purposes, loss of floodplain connectivity through artificial flood embankments and periodic pollution events. The European Water Framework Directive (WFD) requires all European water bodies to reach good ecological status by 2027. Under the WFD classification system the River Leadon is currently classified as being in moderate condition. Elements contributing to this unfavourable status include invertebrates, macrophytes and phosphates. Fish populations within the River Leadon are currently classified as high.
Fig 1. Summary of how water bodies are classified under the Water Framework Directive. Ecological status is determined by biological, chemical and physical parameters. Fish constitute one part of the biological parameters. Other biological parameters include invertebrates, macrophytes and phytobenthos. Classification of a waterbody goes by the lowest scoring element, for the Leadon these are invertebrates and macrophytes
Upleadon Fishery Gloucester Angling Club (GAC) currently leases three stretches on the River Leadon for both coarse and game fishing pursuits. Upleadon is the middle stretch and is regularly fished for the main target species of brown trout (Salmo trutta) and chub (Squalius cephalus). Generally, habitat diversity and complexity increases in an upstream direction. At the downstream limit of the fishery, towards the old mill building, the River Leadon is relatively uniform in character with a trapezoidal cross section, steep banks and a straightened channel. This is likely to be a result of historical channel realignment to facilitate land drainage. At this location the channel is approximately 4 metres wide at low water, and has a relatively uniform depth with occasional scour pools caused by the addition of large woody debris. Riparian tree cover is sporadic, with dense patches of willow (Salix sp) and hawthorn (Crataegus sp) interrupted by long sections devoid of any trees. The substrate is dominated by fine sediment, with occasional gravel deposits suffering from compaction and high sediment loadings. In channel macrophytes are sparse throughout with occasional stands of water crowfoot (Ranunculus sp) and some areas dominated by filamentous algae an indicator for nutrient enrichment.
Fig 2. Lower section of river showing steep banks, trapezoidal channel and uniform width throughout
Upstream, past the second field boundary, habitat diversity increases with a variable channel depth and width and several meanders creating a sinuous river channel. However, the river banks remain steep and channel incised, resulting in a loss of floodplain connectivity and limiting gravel retention. Furthermore, a distinct riffle-pool sequence synonymous with a salmonid watercourse is lacking throughout the river, and is likely to be a legacy of previous land drainage activities. Dense riparian tree cover provides dappled shading along a good proportion of the river; species include willow (Salix sp), alder (Alnus sp), hawthorn (Crataegus sp), blackthorn (Prunus sp) and field maple (Acer sp). Macrophytes include water crowfoot (Ranunculus sp) and water cabbage (Nuphar sp).
Fig 3. Further upstream more diverse conditions are apparent with variable flows, riparian tree cover and good bank side habitat.
Adjacent land use is exclusively agricultural and predominately pastoral. In some sections the steep banks prevent livestock from accessing the watercourse, where bank profiles are of a shallower gradient livestock have unfettered access to the watercourse. This will certainly be contributing the high sediment loadings in the Leadon. There is evidence of previous attempts to restrict livestock access with both livestock drinking bays and fencing being apparent. However, this is now in a redundant state and in need of extensive repairs or replacement to bring back into operation.
Habitat enhancement techniques Background A diverse habitat is required to ensure that any resident fish population is sustainable. Different habitats are required for each stage of a species life cycle. If any one of these habitats is lacking or of a sub-optimal quality then there will be a negative effect on recruitment and a decline in species abundance.
Fig 4. Diagram showing how habitat availability can effect recruitment within a fish population. If the habitat for any life stage is lacking this will ultimately result is less adult fish within the population, these are called bottlenecks to recruitment.
Brown trout have three distinct habitats requirements to ensure a population is selfsustaining: 1. Trout lay eggs on gravel substrates in nests known as redds and therefore 2. Once the fry have – coarse gravels, not too fast water, plenty of habitat complexity due to being territorial 3. Adult trout, deeper pools for resting, undercut banks tree roots some deeper water with flow
Techniques 1. Flow deflectors Flow deflectors use the natural flow of the river to create pools and riffles. They work by raising the water level upstream of them thus providing slightly deeper water and encouraging siltation. Below the deflector water depth is reduced and water speed increases, this helps to expel any silt in the gravels present and can create a localised scour hole.
Fig 5. Diagram showing how appropriately positioned flow deflectors can create diverse flow conditions
Flow deflectors are generally made of hardwood logs which can be pinned in place using sweet chestnut, rebar and/or wire. One novel technique for securing in deflectors is the platypus anchor. These wire anchors can be driven into the bank and provide a secure point of attachment for log deflectors.
Fig 6. Diagram showing how to install a platypus anchor into the river bank
Once a deflector is suitably secured they will remain in situ for many years and will not exacerbate flooding. NB. Flow deflectors must be put in appropriately positioned or they will have no benefit to the ecology of a watercourse and may increase bank erosion. 2. Faggot bundles Brash wood faggot bundles are inexpensive and easy to make when clearing fishing pegs at the start of the fishing season. They provide excellent habitat for juvenile fish and numerous invertebrate prey species and can also be used to protect eroding banks. Brash wood faggots can be comprised of any small diameter twig (10-50mm) with alder (Alnus sp) being the favoured species as it does not readily decompose in water. Willow (Salix sp) is the ideal species for bank stabilisation as it will root and consolidate over time.
Fig 7. Series of brash wood faggots pinned into the edge of the channel to provide juvenile fish habitat and bank protection
3. Gravel introduction Gravel riffles are an important habitat feature for all gravel spawning (rheophilic) fish species. On natural lowland rivers they should generally occur about every seven widths of the channel usually on straight sections and at the entrance and exits of bends. However in many rivers, including the River Leadon, these habitat features have been lost through channel realignment with the aim to increase the capacity to convey floodwater. On the Leadon it is unlikely that riffle pool features will return naturally due to the underlying geology, and therefore the artificial introduction of gravel is a viable option. The length of each gravel riffle should be a minimum of two times the channel width, and a length of 15-20m is not uncommon when the opportunity to create a series of ideally spaced riffles is not an option. For trout, a gravel size of 7.5-75mm diameter is ideal as spawning substrate. The cost of gravel can range from ÂŁ15 - ÂŁ30 per tonne depending on the source location, and installation costs are highly dependent on site access. Further guidance on the installation of gravel riffles and possible funding sources are available from the Environment Agency.
Fig 8. Some examples of suitable riffle placements
NB. The installation of gravel riffles are subject to Flood Defence Consent. Any plans to install gravel riffles must be agreed with the Environment Agency 4. Tree hinging Tree hinging is an inexpensive and effective way of increasing channel cover and provides a good refuge from aerial predation, in addition to increasing light penetration. In channel woody debris can also create varying flow conditions and helps to vary bed profiles.
Fig 9. Tree hinging in practise, provides a good refuge from predation and diversifies flows.
Hinging involves partly cutting a riparian tree so that it is felled into the watercourse but remains attached to the stump. To ensure the tree is fixed in place, the stump can be drilled and a wire passed between the stump and the trunk, this will prevent mobilisation during flood conditions. Most tree species can be hinged into the watercourse although be aware that willow will continue to grow and may eventually choke the entire channel. 5. Willow spiling Willow spiling is used as an environmentally friendly method of erosion protection, and provides good marginal habitat once established. It involves weaving willow withies (thin willow branches) between fresh winter-cut willow stakes to form a fence-like structure. This method has the advantage that over time the willow roots and sprouts, providing living protection and additional stability. Care must be taken to use fresh-cut willow as dead willow will not sprout. In addition excessive shading from overhanging vegetation may affect the ability of the willow to establish. This method is suitable for the protection of steep or vertical banks. In some cases, a biodegradable geotextile (see below) may be needed behind the willow initially in order to prevent the loss of fine soil while the spiling establishes itself.
Fig 10. Schematic diagram of a bank protected by willow spiling
Willow spiling is an inexpensive method for providing erosion protection while retaining riparian and marginal habitat. It can also be used as a cost effective and sympathetic way of formalising coarse fishing pegs.
6. Tree planting Riparian trees are a very important part of the river ecosystem. The provide a source for in channel woody debris, a food source for many invertebrate prey species, refuge from aerial predation and keep rivers cool by providing dappled shading. On a trout river the ideal ratio of shading is approximately 70% shaded to 30% exposed.
Table 1. Summary of the benefits of riparian tree cover
Tree planting is relatively inexpensive and grants are available from various sources to increase riparian tree cover and thus resilience to climate change. 7. Livestock drinking bays and fencing Where livestock have unfettered access to the watercourse sediments loading can increase considerably. This can result in reduced water quality, reduced light penetration for in channel macrophytes and the degradation of suitable spawning gravels. The best solution is to restrict livestock access by fencing off the water course and installing hard standing drinking bays. Other techniques can involve complete isolation from the watercourse and the provision of pump operated drinking bays. The cost of fencing can vary considerably and is dependent on the specification required for the livestock present. There are occasionally grants available for fencing works if the landowner is amenable. Environment Agency guidelines stipulate that fencing should be set
back from bank top by at least 8 metres to provide an adequate buffer strip to intercept field run off. a)
b)
c)
d)
Fig 11. Examples of a) live stock fencing, b) a hard standing drinking bay, c) animal operated pasture pump, d) water gate to prevent unfettered access
8. Backwater fish refuges Backwater fish refuges are pools which are connected to the watercourse which provide an important foraging habitat for juvenile fish and also a refuge during periods of high flow. Backwaters are particularly important in watercourses which have been straightened for land drainage purposes, as there are very few places to seek refuge from the high flows that are synonymous with a straight river channel.
Fig 12. Example of a backwater connected to a watercourse which provides a refuge during high flows
Habitat management plan
Funding opportunities Small scale habitat works can be achieved by organised work parties while carrying out bank side maintenance. Tree hinging, brash faggots and flow deflectors can all be installed at limited or no cost. Live stock management, tree planting, fish refuges and gravel introduction are more costly and may require help from external funding streams. Woodland trust grants The Woodland trust regularly offers funding for tree planting schemes. There is currently funding available for farm owners, which offers free farm assessments, planting schemes and tree supply. See website for details – https://www.woodlandtrust.org.uk/plant-trees/on-farms Sport England Sport England is funded by the National Lottery and awards funding to improve or maintain a host of sports facilities. There are currently three possible funding streams: Small grant, Inspired facilities, Flood relief funds. These funding streams would be suitable to fund the creation of coarse fishing pegs. Facilities are more likely to receive funding if they are available to the public and therefore day ticket stretches would be necessary. Environment Agency Fisheries staff would be happy to help work up a bid if necessary. See website for details - https://www.sportengland.org/funding/ Environment Agency Environmental Improvement Grant The Environment Agency regularly have funding available to undertake environmental improvements in the local area, this can include livestock and riparian management as well as in channel habitat works. To apply for funding please contact Environment Agency Fisheries Staff. Catchment Sensitive Farming advisories A joint project between the Environment Agency and Natural England aims to deliver practical solutions and targeted support to enable farmers and land managers to take voluntary action to reduce diffuse pollution from agriculture. While this fishery does not fall within the priority area of the Leadon farm advisories may still be provided. For more information please visit the Natural England website – http://www.naturalengland.org.uk/ourwork/farming/csf/ Wild Trout Trust Habitat days The Environment Agency fund the Wild Trout Trust to host free practical habitat demonstration days for angling clubs across the country. These days are awarded on a first come first serve basis. To apply for the next round of free habitat demonstration days please contact Environment Agency Fisheries staff.