Download Lower Witham River Corridor Habitat Plan

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:
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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:
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Retaining marginal trees that provide shade and cover in different flows
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Introducing woody material;
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Retaining marginal vegetation and encouraging diversity when managing weed
cutting to create bays and scallops within the channel providing different flow patterns.
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Creating refuge habitat;
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Reconnecting rivers and floodplains;
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Improving channel bed and bank vegetation;
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Reducing localised erosion and sedimentation; and
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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:
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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.
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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.
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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.
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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.
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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.
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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
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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
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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.
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3.1. Idealised river habitats
A typical example of good river habitat comprises some of the following physical features:
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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.
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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