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Final Report

May 2013

Prepared by: Angela Bartlett Reedbed Survey Dates: 3rd to 7thand 28th August 2012; 30th November 2012. Cover Photograph: K Maddams 2012 Foreward Photograph: Julia Briscoe 2012 Site Photographs: A Bartlett 2012

Published by: Thames21 Registered Charity 1103997 Walbrook Wharf, 78-83 Upper Thames Street, London EC4R 3TD www.thames21.org.uk Email: [email protected] Theo Thomas Senior Programmes Manager Thames21 Email:[email protected] Tel: 0207 0936395 Mobile: 07968 012828 © Thames21 All rights reserved May 2013


Foreword Theo Thomas, Thames21

Cody Dock Reedbed, 2011

When we first visited the Cody Dock Reedbed, close to the mouth of the River Lea, in late 2010, it was instantly clear what a wonderful place it was and how damaged it had become. In amongst the reeds it was beautiful and peaceful, but we stood calf-deep in rubbish and Japanese Knotweed had grown across the reedbed, eating out its heart.

It became a Thames21 priority to save Newham’s largest reed bed, and two years later we had - in great part because of the tenacity of so many volunteers. Special thanks go to Aimee Felus and Simon Reddecliffe at Thames21.

While we were happy to have preserved a reedbed that cleans the sick River Lea and offers a home to wildlife, we knew that many others would be at risk. That’s why we commissioned this report.

Some new reedbeds have been created in recent years, and what the report clearly shows is that there is great potential for many more to flourish along the Lea, cleansing the water, providing sanctuary to wildlife and vital oxygen to breathe life back into this great river.

Theo Thomas.

Thames21 April 2013


Executive Summary

The River Lee has undergone historic modifications and continues to be

modified primarily for navigation routes to be developed. As a result, much of

the natural banks and associated vegetation have been removed or inhibited. In

recent years, the increased incidence and awareness of environmental issues

has led governments and communities to consider river management with such

issues in mind. Consequently, there is an increasing need and desire for natural

processes or ‘ecosystem services’, to be restored, enhanced or created to

provide cost-effective benefits for people and the wider environment. Reedbeds

have been shown to provide a cost effective and productive method for

providing numerous environmental benefits, including: water quality

improvements; enhanced aesthetics; and biodiversity. In addition, reedbeds can

be utilised to help meet the objectives and targets of significant legislative

drivers such as the Water Framework Directive (WFD) and UK Biodiversity

Action Plan (BAP).

The survey which was conducted on the Lower Lee (Lea) Navigation for this

report identified over 60 potential reedbed sites (some with multiple sites within

them). Approximately 8% of the surveyed area had existing reedbeds,

comprising 48 individual sites. Construction, enhancement and protection of

reedbeds along the Lee Navigation could provide multiple and far-reaching

benefits for a relatively small financial cost. The benefits of reedbeds, potential

reedbed sites and reedbed construction are discussed within this report.


Note on Spelling: The Lea Navigation and Lee Navigation are both widely used and refer to the same waterway. This report uses the spelling Lee. Abbreviations

EA - Environment Agency

GEP - Good Ecological Potential

GES - Good Ecological Status

GIS - Geographic Information System

GPS - Global Positioning System

HMWB - Heavily Modified Water Body

JNCC - Joint Nature Conservation Committee

OS - Ordnance Survey

RBMP - River Basin Management Plan

Spp. - Species (plural)

STW - Sewage Treatment Works

UK BAP - United Kingdom Biodiversity Action Plan

WFD - Water Framework Directive


Glossary

Channelisation - manmade alterations to river channels, e.g. hard engineered

channel banks and channel straightening.

Diffuse source pollution - pollution that enters water from a wide area, generally

associated with agricultural pollution.

Ecosystem services –benefits people derive from nature

Eutrophication - excessive algal growth that results from excess nutrients in

water. A reduction in dissolved oxygen and light levels in the water result from

excessive algal growth.

Faecal coliforms - bacteria that originate from faecal matter.

Hydrogeomorphology - spatial and temporal interaction of both hydrological

processes and river channel and landscape geomorphology (shape and form),

e.g. bank erosion due to water movement through a channel.

Macroinvertebrates - an invertebrate that is large enough to be seen without the

use of a microscope.

Macrophyte - an aquatic plant that grows in or near to water and is either:

emergent, submerged, or floating.

Parameter - one of a set of measurable factors, such as temperature and

pressure, which define a system and determine its characteristics and are

varied in an experiment.

Point Source Pollution - Pollution that enters water from a specific point, e.g.

sewage treatment works.


Reedbed - natural habitats that are dominated by reed vegetation. Reedbeds

are found in floodplains, waterlogged depressions and estuaries.

Remediate - a cleaning or correcting process, e.g. bacterially mediated removal

of pollutants from a polluted water body.

Resuspension - a renewed suspension of insoluble particles in the water

column.

Sequester - storage or segregation, e.g. trees can store or sequester carbon.

Suspended solids - insoluble particles that are buoyant. Suspended solids can

move freely within the water column.

Turbidity - the cloudiness of a fluid caused by individual particles, such as

suspended sediment solids.


Contents

Title Page .......................................................................................................... 1 Final Report ...................................................................................................... 2 Foreword ........................................................................................................... 3 Executive Summary ......................................................................................... 4 Abbreviations ................................................................................................... 5 Glossary ............................................................................................................ 6 Contents ............................................................................................................ 8 List of Figures and Tables ............................................................................. 10 Introduction and brief history of the Lee Navigation .................................. 12 Objectives of the Reedbed Survey and Report ............................................ 15 Background Information for Key Legislative Drivers .................................. 16

Water Framework Directive (WFD) ............................................................... 16

UK Biodiversity Action Plan (UK BAP) .......................................................... 17

1. Literature Review on Benefits of Reedbeds ......................................... 18 1.1 Reedbed definition .............................................................................. 18

1.2 Water Quality ...................................................................................... 19

1.3 Sediment and Flow Dynamics ............................................................. 23

1.4 Biodiversity .......................................................................................... 24

1.5 Aesthetic and Social Benefits .............................................................. 25

1.6 Meeting Water Framework Directive and UK Biodiversity Action Plan 26

Objectives and Targets ................................................................................. 26

2. Case studies ............................................................................................ 27 2.1 Habitat Creation in the Grand Union Canal for Biodiversity ................. 27

2.2 The use of Reedbed Construction and Restoration to Meet WFD ...... 29

Targets and Objectives ................................................................................. 29

2.3 Constructed Reedbeds for Wastewater Treatment ............................. 31

3. Reedbed Survey Methodology ............................................................... 32 3.1 Criteria for Identifying and Classifying Existing Reedbeds .................. 32

3.2 Criteria and Specification for Identifying Potential Reedbed Sites ....... 32

4. Reedbed Survey Results ......................................................................... 34 4.1 Existing Reedbeds Map ......................................................................... 34


4.2 Potential Reedbed Sites Map ................................................................ 35

4.3 Individual maps and descriptions of potential site types ......................... 36

5. Reedbed Management ............................................................................ 49 6. Reedbed Construction ............................................................................ 50 7. Conclusions ............................................................................................. 53

7.1 Existing Reedbeds .............................................................................. 53

7.2 Potential Benefits of Reedbed Enhancement and Creation ................ 53

7.3 Further Research and Considerations ................................................. 54

References ...................................................................................................... 56 Brooks, A. 1988. Channelized rivers: perspectives for environmental management. John Wiley and Sons, Inc., USA. ........................................... 56 Appendix I: Potential Reedbed Sites ............................................................ 59 Appendix II: Existing Reedbed Site Survey Data ......................................... 81 82


List of Figures and Tables

Figure 1 A conceptual model explaining why the structural complexity provided by macrophytes increases the diversity of other aquatic assemblages. Source: Tomaz and Cunha, 2010. .................................................................... 25 Figure 2 Created marginal reed habitats on the banks of the Grand Union Canal. Established Coir Rolls with native wetland plants. Source: Salix website, 2013. ................................................................................................................ 28 Figure 3 Photos showing before and after restoration, habitat improvements and biodiversity improvements. Source: Naturstyrelsen website 2010. ............ 30 Figure 4 Map showing locations and numbers of existing reedbeds along the Lee Navigation. ................................................................................................ 34 Figure 5 Map showing locations and numbers of potential reedbed sites along the Lee Navigation. .......................................................................................... 35 Figure 6 Location and photo of Navigation Inn (Ponders End) potential reedbed site ...................................................................................................... 38 Figure 7 Location and photo of Lock Keepers Cottages (Tottenham Hale) potential reedbed site ....................................................................................... 40 Figure 8 Location and photo of Reedham Close (Tottenham Hale) potential reedbed site ...................................................................................................... 41 Figure 9 Location and photo of Mabley Green (Hackney) potential reedbed site ......................................................................................................................... 42 Figure 10 Location and photo of Eastway (Hackney) potential reedbed site .. 43 Figure 11 Location and photo of Armadale Close (Tottenham Hale) potential reedbed site ...................................................................................................... 44 Figure 12 Location and photo of Olympic Park Area (Pudding Mill Lane) potential reedbed site ....................................................................................... 46 Figure 13 Location and photo of Towpath Road (Upper Edmonton) potential reedbed site ...................................................................................................... 47 Figure 14 Location and photo of Lock Keepers Cottage (Pickets Lock) potential reedbed site ...................................................................................................... 48 Figure 15 Floating supports for establishing weed reedbeds (Coops and Geest, 2007). .................................................................................................... 52


Table 1 Examples of significant point and diffuse sources of nutrients (N and P) for urban environments (Adapted from Foundation for Water Research website, 2010). ................................................................................................. 20 Table 2 Categories associated sites and totals for each potential reedbed site. ......................................................................................................................... 37


Introduction and brief history of the Lee Navigation

The Lee (or Lea) Catchment spans from Bedfordshire to North East London,

and drains a catchment area of 1420km2. The River Lee has a length of 85.2

km, from its source in Bedfordshire to its confluence with the River Thames at

Bow Creek in East London (Flynn et al., 2002). The Lower part of the catchment

focused on in this report extends through Greater London (Environment Agency

Publication, 2010).

The River Lee would have once been a natural meandering lowland river

system with marginal reedbeds and channel vegetation. However, historic and

current uses of the Lee as a major navigation route have resulted in numerous

hard-engineered modifications, of which the Lee Navigation is a significant

example. Unlike traditional purpose built canals, the Lee Navigation is a

canalised or straightened section of the River Lee (Snook and Whitehead,

2004).

Construction of the Lee Navigation commenced following the 1767 River Lee

Act, which authorised the construction of straightening cuts, towpaths, locks and

Limehouse Basin for navigation purposes (Skempton, 1981). While

channelisation of the Lee is beneficial from a navigational and economical

perspective, the negative environmental impacts of channel straightening have

been well-documented within the last few decades (Brooks, 1988).

Channelisation along the River Lee has contributed to dramatic changes to the

physical and chemical functions of the River. There is a large body of recent

research that has demonstrated linkages between physical and chemical river

modifications and a rivers ecological or biological structure and function. While

there are many types of flora and fauna that have been found to be impacted by

river modifications, impacts on reedbeds are described for the purposes of this

report. For instance, the replacement of soft edges with vertical concrete banks

requires removal of large areas of marginal and channel vegetation, including

reedbeds. In addition, hard engineered river banks and channel deepening


inhibit natural re-colonisation by plants such as reeds, due to the removal of

substrates for the reeds to grow upon. In addition, there is less opportunity for

reedbeds to grow on adjacent floodplains because they are disconnected from

the channel due to channelisation (Brooks, 1988).

In addition to the aforementioned impacts, physical, chemical and ecological

characteristics of the Lee Navigation have been altered as a result of flood

management practices and water abstraction for drinking water supply

(Environment Agency, 2005). However, the impacts and management of

pollution in the Lee Navigation is the major focus in this report, as reedbeds

have special functions that can enable them to remove and store significant

quantities of aquatic pollutants (Mitsch and Gosselink, 2007).

A recent report on the water quality of the Lower Lee Catchment found that the

River Lee and the majority of the six tributaries that were studied had ‘severe

problems with water quality’. The types and levels of pollutants noted, such as

low dissolved oxygen and excessive faecal coliforms pose potential risks to

both ecological and human health (Davies, 2011). Furthermore, potentially

damaging levels of a wide range of pollutants have been recorded in the Lower

Lee Catchment and specifically the Lee navigation through Environment

Agency (EA) water quality monitoring and past scientific research papers (e.g.

Williams et al., 2003; Snook and Whitehead, 2004; Environment Agency

Publication, 2010). While there are a large number of possible point and diffuse

sources of pollution to the Lower Lee Catchment, including: Sewage Treatment

Works (STW), urban diffuse pollution, and historic and current agricultural,

commercial and industrial practices (Swords and Strange, 2006), further

investigations need to be carried out to confirm the sources of some pollutants

(Davies, 2011). As well as the need for further investigation, there is an

apparent urgent need for development of pollution management strategies for

the Lower Lee Catchment.


The preservation of existing reedbeds and introduction of new reedbeds within

the Lower Lee Catchment could provide a cost-effective and balanced method

for improving key water quality parameters within the catchment, while taking

into account the navigational and economic requirements of the Lee Navigation.

Reedbeds can also provide benefits for biodiversity by providing habitats, and

for public well-being by improve the aesthetic qualities of water environments

for people. Furthermore, reedbeds can help the UK to meet Water Framework

Directive (WFD) objectives by improving the ecological status of the Catchment.

In addition, reedbeds are currently classified as a UK Biodiversity Action Plan

(BAP) habitat, meaning that they must be preserved and promoted where

possible to help us to meet biodiversity objectives. The multiple benefits of

reedbeds are discussed further in the literature review section of this report.

In addition to the proposals made in this report for the Lee Navigation, many

other developments are being made in areas in the Lee Catchment. Including

but not limited to, the on-going development of the Queen Elizabeth Olympic

Park and Lee Valley Park; the Upper Lee Valley Landscape Strategy and the

Walthamstow Wetlands project. While these opportunities are not outlined in

this report, all development adjacent to the watercourse should look to enhance

existing habitats and develop reedbeds where possible. The proposals for

reedbed enhancements and creation in this report aim to complement and add

to existing plans for habitat creation and green landscaping in the Limehouse

Cut and Olympic Park reaches of the Lee Navigation.


Objectives of the Reedbed Survey and Report

The objectives of the reedbed survey were to: (1) identify and record the

location and specific details, such as area and species, for existing reedbeds

along the Lee Navigation, within the M25; (2) to identify potential reedbed sites

along the Lee Navigation within the M25, and to take specific notes about the

potential sites, including location and area; and (3) to create GIS maps showing

both existing reedbed site details and locations, and potential reedbed site

details and locations.

The main objective is for the data collected from the survey to be used to

preserve, enhance and create reedbeds along the surveyed reach of the Lee

Navigation. For example, knowledge of reedbed locations and health could

better enable groups of volunteers to preserve reedbeds by collecting litter from

sites that have been flagged as having a litter problem.

Data collected for potential reedbed sites will hopefully lead to the creation and/

or expansion of reedbeds in parts of the channel that are not used for

navigation, and could support reedbeds. Expansion or creation of new reedbeds

will contribute to EA River Basin Management Plans (RBMPs), WFD and UK

BAP objectives.

The aims of this report are to: (1) inform the reader about the specific functions

and benefits of reedbeds; (2) illustrate the results of the reedbed survey using

GIS mapping; and (3) to propose potential sites for reedbed construction.


Background Information for Key Legislative Drivers

Water Framework Directive (WFD)

The principle objective of the WFD is to achieve ‘good ecological status’ (GES)

in all European Union (EU) Member State water bodies by 2015. However, if a

water body is classified as a ‘Heavily Modified Water Body’ (HMWB), then the

objective is to reach ‘good ecological potential’ (GEP) by 2015 (WFD;

2000/60/EC).A HMWB is a water body that: ‘has significant physical alterations

leading to changes in hydrogeomorphology, as a result of human activity’ (Borja

et al., 2007); and where achieving GES would have significant impacts on

factors such as flood risk management.

Ecological status refers to the quality of; biological (e.g. macrophytes and fish)

and hydromorphological (i.e. the hydrological (flow etc.)) characteristics of rivers

together with the physical structure that they create (e.g. meanders); and

physico-chemical (e.g. temperature and nutrient level) elements. An example of

the impact of alterations to the hydromorphological elements and the

subsequent impact on biological elements could be: straightening a channel

(changing morphology) leading to increased flow velocities (changing

hydrology), which could impact macrophyte vegetation if, for example, young

macrophytes were less able to take root in faster flow velocities.

The difference between GES and GEP is that the former requires the physical,

chemical and biological status of the river to be at or close to reference

conditions (i.e. the conditions that would exist if the water body was pristine),

while GEP requires that mitigation measures are in place to ensure that a river/

water-body achieves the best biological status that it can, given its status as a

HMWB. In addition, nutrient concentrations should not exceed levels that would

negate functioning of the ecosystem and biological quality; and pollutants must

not be in excess of European Commission (EC) or EA standards (Borja and

Elliott, 2007).


The Lee Navigation is a HMWB because the alteration that would be necessary

to achieve GES would have significant adverse impacts on navigation, flood

management and water resource supply for consumption. Consequently, in

order to meet WFD objectives GEP must be achieved for the Lee Navigation.

UK Biodiversity Action Plan (UK BAP)

UK BAP1 is formed of a list of species and habitats that have ecological

significance and are threatened by human activities. All UK BAP species and

habitats have specific targets that aim for them to be conserved and promoted.

Reedbeds are classified as a UK BAP priority habitat because they provide

important habitats for wildlife and promote natural biodiversity. In the UK,

reedbeds are important habitats for native mammal species, including: harvest

mice; water shrews; otters; and water voles, which are now the most

endangered mammal in the UK as a result of habitat loss and American mink

predation (Water for Wildlife UK, undated). In addition, reedbeds support a

number of rare or endangered (Red Data Book) bird and invertebrate species

such as the Bittern and Leopard moth (Worcestershire Biodiversity Partnership,

2008). Reedbeds also support native amphibians and fish, including European

eels which have suffered a significant decline in recent decades (Starkie, 2003).

UK BAP targets for reedbed habitats are as follows (from Defra, 2006):

1. Maintain the extent of the existing resource of reedbed habitat by active management and with no net loss.

2. Maintain the condition of wet reedbed habitat where already favourable and establish management to secure favourable condition for all areas of targeted reedbed currently judged as unfavourable. The target condition for all such areas should be ‘favourable’ or ‘unfavourable recovering’ by 2020.

1In 2012, UK BAP was succeeded by the UK Post-2010 Biodiversity Framework. However, the priority species and habitats agreed under UK BAP remain the same (JNCC and Defra, 2012).


3. Continue creating reedbed from land of low nature conservation interest with the objective of expanding reedbed habitats by 3,000 hectares across the UK by 2020.

4. Establish eight new landscape scale wetland complexes by 2020, at least one in each county in which reedbeds are a major component along with other wetland types.

1. Literature Review on Benefits of Reedbeds

1.1 Reedbed definition

Reedbeds are a type of vegetated habitat that falls within the wider category of

wetlands (i.e. an area of land where water is the dominant factor for determining

soil and vegetation species cover). Wetlands are amongst one of the most

important ecosystems on earth, both for their positive influence on biodiversity,

and their ability to sequester and transform a number of important chemicals.

As such, wetlands are sometimes described as “the kidney of the landscape”

because they can remove pollutants from aquatic environments (Mitsch and

Gosselink, 2007).

Reedbeds are usually dominated by stands of common reed (Phragmites

australis). They are found in areas where the water table is at or above ground

level for most of the year, such as open water and ditches, and small areas of

wet grassland. Reedbeds that are dominated by common reed can support a

range of other plants that are adapted to wet conditions, for example, reed-

mace (Typha latifolia), reed sweet-grass (Glyceria maxima), and Canary reed-

grass (Phalaris arundinacea). Species such as reed-mace and reed sweet-

grass have a greater tolerance of drier conditions, compared with common

reed, meaning that they may be dominant in shallower areas (Brig, 2008).

In the UK in 2008, Phragmites australis dominated reedbeds cover about fifty

square kilometres (Brig, 2008).


1.2 Water Quality

The abilities of reedbeds and wetlands in general to store and transform

pollutants are well-documented. For the purpose of this paper, I will focus on

some key pollutants and water quality parameters that are known to be

problematic for the Lower Lee Catchment. However, it should be noted that

reedbeds may also be able to sequester and remediate other pollutants such as

radiation and pesticides.

There are two main pathways through which reedbeds are able to sequester

and/ or transform pollutants: (1) within the reed structure, once water has been

taken up through the roots; and (2) via bacterially mediated transformations that

occur within the sediments that form the substrate of the reedbed (Brix, 1997).

Nutrients: high levels of nutrients, i.e. nitrogen and phosphorous, have been

recorded in the Lower Lee Catchment (Environment Agency Publication, 2010;

Davies, 2011). Nutrient pollution in aquatic systems can originate from both

diffuse and point sources. Diffuse pollution usually originating from agricultural

practices tends to be a more important source of nutrient pollution in rural

settings, whereas in urban areas, nutrient pollution usually originates from point

sources. An important factor for defining whether pollution originates from a

diffuse or point source is that diffuse sources can be difficult to manage due to

their spatial and temporal heterogeneity; in contrast, point sources can be

identified and managed with relative ease. Typical significant point and diffuse

nutrient pollution sources for environments such as the Lower Lee are

summarised in Table 1.


Table 1 Examples of significant point and diffuse sources of nutrients (N and P) for urban environments (Adapted from Foundation for Water Research website, 2010).

*N: Nitrogen; P: Phosphorus

Excessive nutrients in aquatic systems have been linked with a range of

negative environmental impacts, in particular: (1) eutrophication, which

depletes oxygen and light availability as a result of excessive algal growth.

Eutrophication can seriously damage biological communities, such as fish,

which can die as a result of oxygen depletion within the water column

(European Commission Publication, 2010). (2) Excess nitrate (a form of

Pollution source example

Point source or diffuse

Associated nutrient(s)*

Effluent discharges from sewage treatment works

Point source N and P

Industrial effluent discharges treatment Point source

N

Domestic plumbing misconnections

Point source - connection of domestic appliances and toilets to rainwater drains

N and P (e.g. P from dishwasher tablets)

Urban stormwater discharges

Point source -arising from storm water runoff (from paved areas and roofs in towns and cities) entering the sewer network

N and P

Landfill sites Point source N

Fish farming Point source

N and P

Organic waste recycling to land

Point source N and P

Allotments (fertiliser applications)

Diffuse - could be point source if originating from a small area)

N and P

Soil cultivation Diffuse - could be point source if originating from a small area)

N and P

Power generation facilities

Diffuse

N


nitrogen) poses a significant long-term threat to safe drinking water supply, as it

is linked to degraded water aesthetics, and negative human health conditions

(Addiscott et al., 1991; Burt et al., 1993).

Reedbeds can provide a mitigation option for nutrient pollution because they

can store, transform and remove nutrients from water columns and sediments

via a number of pathways. For instance, an important process known as

denitrification is optimised within reedbeds. Excessive levels of nitrates in

aquatic systems pose a significant management issue for the UK. While

technological methods can be used to remove excess nitrates from drinking

water, this process is very expensive and energy intensive. Denitrification is a

natural ‘ecosystem service’ that leads to removal of nitrate from the water, as it

is converted to a gas. Most of the gas is completely harmless within the

atmosphere (i.e. di-nitrogen gas N2), although small variable quantities of

nitrous oxide, which is a greenhouse gas is sometimes released (Burt et al.,

1993). Reeds can also uptake nutrients directly from the water to be used for

growth and reproduction. In addition, reedbeds can be utilised to mitigate

phosphorus pollution. Phosphorous can be found both in the water column and

sediments, sediments are often a long term supply of historic nutrient pollution.

When sediments are deposited around reedbed roots, phosphorous and other

sediment associated pollutants can be stored within the reedbed substrate

rather than being transported downstream (Hyatt & Naiman, 2011).

The potential for reedbeds to remove phosphorus pollution is of particular

significance because phosphorous pollution has recently been cited as a

significant cause for UK water-bodies failing to meet WFD objectives (UK

Technical Advisory Group for WFD publication, 2012). The use of reedbeds for

mitigating phosphorus pollution is important because even if point sources such

as sewage treatment works and pipe mis-connections are managed, significant

amounts of historic phosphorus can be re-released from sediments. Re-release

of phosphorus from sediments can negate results from direct management

efforts. However, if the reeds are not harvested or consumed by fauna that die


elsewhere, the nutrients can be returned to the water and substrate once the

reed dies. In addition, as dead vegetation and sediments build up, reedbeds

can dry and become terrestrial habitats, negating positive water quality effects

(Withers and Jarvie, 2008). Therefore, management of reedbeds is an important

consideration which is expanded on in section 7.5.

Dissolved Oxygen: significantly low levels of dissolved oxygen have been

identified within the Lower Lee Catchment (Environment Agency Publication,

2010; Davies, 2011). Low dissolved oxygen levels are likely to have resulted

from: eutrophication caused by excess nutrients; and/ or excessive sediment

within the channel that has large amounts of organic matter, which can lead to a

depletion of dissolved oxygen levels as it is decomposed (Environment Agency

Publication, 2010). Many macrophyte species are known to exude oxygen from

their roots, creating aerobic (oxygenated) zones within the sediment and water

column. For example, two common reed species Phragmites and Typha, that

were identified at most existing reedbed sites along the Lee Navigation take

oxygen from the air and release it through their roots as dissolved oxygen

(Gries et al., 1990; Sasikalaet al., 2009). Eutrophication resulting from excess

nutrients and decomposition of excess organic matter can create extreme low

oxygen zones which can lead to fish kills. However, the ability for reeds to

introduce oxygen to the sediments and water column can create oxygenated

refuges for fish and invertebrates when oxygen levels are low (ECON

Ecological Consultancy Limited publication, 2010).

Organic Matter: excessive quantities of organic matter which include bacterial

pollutants such as faecal coliforms have been identified within the Lower Lee

Catchment (Davies, 2011). The dissolved oxygen supply from reedbed roots

allows for aerobic degradation of organic matter and remediation of

contaminated organic matter, such as faecal coliforms (Brix, 1997).

Particulate Heavy Metals: heavy metal pollution results primarily from roads

(car exhausts) and commercial and industrial sites. Metals then enter aquatic


systems in particulate form via rainfall run-off. High concentrations of certain

metals, such as aluminium, have been found to be detrimental to both

environmental and human health. Numerous studies have found that reedbeds

are able to significantly reduce metal concentrations in polluted waters. A

contributing factor for particulate heavy metal removal from waters is the

increased quantities of clay and organic matter in reedbeds. Both clay and

organic matter provide sites for potentially toxic heavy metals to attach to for

further remediation (Wenzel et al., 1992; Begg et al., 1991).

1.3 Sediment and Flow Dynamics

A major impact of channelisation includes alterations to the natural flow regime

and sediment budget within a channelised river system. Alterations to the river’s

flow regime and sediment budget result from a number of factors, including:

meander bend removal, which creates more homogeneous and generally faster

flows through the river system; construction of barriers such as locks, which

lead to interruptions to flow and sediment transport; and removal of marginal

and channel vegetation, which would have trapped sediment and created

heterogeneous flow structures by slowing flow around submerged roots and

stems.

In lotic systems, reed root structures can stabilise sediments, thus decreasing

potential for resuspension and erosion (Brix, 1997; Madsen et al., 2001).

Deposition of fine sediments within reedbeds would be particularly beneficial

within the Lee Navigation, because excess sediments and turbidity are

documented pollution problems within the Lee (Environment Agency, 2012).

Trapping of sediments in reedbeds can increase the contact time between

pollutants, microbes and macrophyte roots, thus enhancing potential pollution

removal (Brix, 1997).


1.4 Biodiversity

The decline in reedbed habitats as a result of human practices such as

drainage for agriculture and river straightening, has contributed to reductions in

the biodiversity of flora and fauna that are associated with them. Preservation of

existing reedbeds and creation of new reedbeds can help to promote rare and

endangered species that use reedbeds as a habitat. For example, reedbeds are

amongst the most important habitats for birds in the UK. They support a

distinctive breeding bird assemblage including six nationally rare ‘red list’ birds;

the bittern Botaurus stellaris, marsh harrier Circus aeruginosus, crane

Grusgrus, Cetti’s warbler Cettia cetti, Savi’s warbler Locustella luscinioides and

bearded tit Panurus biarmicu. Reedbeds also provide roosting and feeding sites

for many bird migratory species. In addition, five Great Britain Red Data Book

invertebrates are also closely associated with reedbeds including red leopard

moth and a rove beetle (Brig, 2008). Furthermore, submerged root and stem

structures in reedbeds provide nursery sites for juvenile fish. Reedbed

substrates also provide habitats for a wide variety of macroinvertebrates that

are a food source for fish and birds. Below is a conceptual model explaining

why the structural complexity provided by macrophytes such as reeds increases

the diversity of other aquatic assemblages.


Figure 1 A conceptual model explaining why the structural complexity provided by macrophytes increases the diversity of other aquatic assemblages. Source: Tomaz and Cunha, 2010.

1.5 Aesthetic and Social Benefits

Members of the public are increasingly interested in the health and biodiversity

of their local rivers. For example, organisations such as Thames21 and the

Wandle Trust who work with members of the public who would like to protect

and enhance their local rivers. Such organisations rely heavily on volunteers to

carry out frequent long term tasks such as river clean-ups and biodiversity

monitoring. In addition, the constant supply of keen and often long-term

volunteers whose hard work to improve their rivers, is testament to the general

public’s interest in local river environments. Existing and newly created

reedbeds can provide many beneficial services to members of the public. For

example, they could be used as bird watching sites, or educational tools to

educate children who live in urban areas about natural environments that they


don’t often get a chance to see. If reedbeds are well managed, they can

dramatically improve the visual aesthetics of the environment, particularly in

industrial and urban areas.

Numerous studies have shown that creating, enhancing and restoring ‘green

spaces’ in urban areas is likely to have contributed to reduced incidences of

crime and increased psychological well-being in surrounding neighbourhoods

(Pataki et al., 2011). For example, a recent UK study found that green spaces

are important for developing social ties in urban communities. Developments

which benefit social community structures are increasingly important in urban

areas, due to increased mobility, changing communications and alienation

(Kaymierczak, 2013). Cattell et al. 2007, carried out a similar study in East

London, they also found that green spaces could strengthen a positive sense of

community in residents. In addition, they found that access to public green

spaces contributed to a sense of wellbeing amongst local residents, and that

they can be enjoyed by people from diverse age groups and socio-economic

backgrounds, an important benefit for diverse East London communities.

1.6 Meeting Water Framework Directive and UK Biodiversity Action Plan

Objectives and Targets

The use of reedbeds as a mitigation measure against necessary

hydrogeomorphic alterations can be a low cost and effective measure for

meeting WFD objectives. While there are no studies known to the author which

quantify the economic benefits of reedbeds, studies have reported that the

water quality benefits that reedbeds supply can greatly outweigh costs of

improving water by other non-natural means (Ibiam and Igewnyi, 2012). In

addition, studies have found that the multiple social benefits of public green

spaces can help reduce the cost of local health services and crime (e.g. Comb

Valley Countryside Park publication, 2012). Reedbed expansion and creation

projects can positively impact on key water quality elements of the WFD. For

instance, reedbeds directly promote biological quality because they are


macrophytes, and the existence of non-invasive macrophytes is a measure for

good ecological status. Reedbeds further promote biological quality because

they provide habitats and nursery sites for fish and macroinvertebrates. In

addition, reedbeds can help remove pollutants such as excess nutrients.

As a priority UK BAP habitat, existing reedbeds within the Lee Navigation must

be protected (see target 1.). The map of existing reedbed locations and areas

within this report can be used to ensure that existing sites are correctly

managed and enhanced (see target 2.). Enhancements, extensions and

creation of new reedbeds will help the UK to meet objectives in target 3, by

creating reedbeds in areas of low conservation interest.

2. Case studies

The following case studies use examples from both wetlands in general and

reedbeds, to give an idea of the scope of projects and benefits which can be

achieved.

2.1 Habitat Creation in the Grand Union Canal for Biodiversity

This project consisted of marginal reedbed and island habitat creation on the

banks of the Grand Union Canal with the aim of benefiting local wildlife and

fisheries. A particular aim of the project was to create habitat for water voles.

The project was carried out by Salix, a company which works to enhance

wetland habitats, and was completed in 2011. A post construction ecological

survey concluded that the site had experienced an increase local in aquatic

invertebrates such as damselflies and dragonflies. In addition, the survey

showed that the general area had a greater biomass and diversity of

invertebrates after completion of the works. In addition, the newly created

islands vertically cut banks contained holes that could be used by kingfishers for

nesting. Kingfisher passes were observed over the backwater and islands


during the survey, for more information see: http://salixrw.com/project/grand-

union-canal-habitat-creation.

Figure 2 Above: Created marginal reed habitats on the banks of the Grand Union Canal. Below: Established Coir Rolls with native wetland plants. Source: Salix website, 2013.


2.2 The use of Reedbed Construction and Restoration to Meet WFD

Targets and Objectives

Numerous wetland restoration and construction projects have been carried out

across Europe, particularly in Germany, the United Kingdom and France, which

aim to help Member States meet Water Framework Directive objectives. The

restoration project used as an example here is the Skjern Aa restoration project

in Denmark. The project involves the restoration of the lower reaches of a

lowland river system that was heavily impacted by hydrological regulation,

channelisation and eutrophication.

The project objectives were: (1) to restore the nutrient retention capacity of the

river and river valley (2) to restore internationally important habitats for wetland

birds (3) to improve fisheries in the downstream estuary (including the

conservation of the trout and salmon populations) (4) to increase recreational

value of the area’ (Coops and Geest, 2007). A key requirement of the project

was that there would be no decrease in the flood protection standard. This was

a large-scale project involving restoration of meandering channels along

specific sections of the river, wetland restoration and removal of some barriers

to flow and fish migration. In a Danish study, the estimated removal of nitrate

pollution in restored wetlands met nutrient reduction objectives. In this study,

nitrate and phosphate levels entering receiving water bodies were

approximately ten percent lower after the restoration had taken place. Surveys

made after project completion also found beneficial effects on biological

diversity, including the establishment of vegetation cover and recovery of

macroinvertebrate communities.

The main conclusions of the project were that: (1) river restoration of the Skjern

River provided benefits for society through improved water quality and quantity,

better fisheries, recreation and flood risk reduction; (2) floodplain wetland

restoration has clear benefits in Water Framework Directive, in terms of water

quality improvement and enhancement of ecological quality elements (e.g. fish);

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While the aforementioned case study is on a much larger scale to the proposed

improvements for the Lee Navigation, it highlights the multiple benefits that can

be achieved through wetland restoration and creation.

2.3 Constructed Reedbeds for Wastewater Treatment

Many studies have demonstrated the effectiveness of reedbeds for improving

multiple water quality parameters. However, the types of pollutants that are

removed and the efficiency of removal or storage in reedbeds depend on

numerous complex factors. Here, two examples of constructed wastewater

reedbeds and their performances are detailed, both studies were conducted in

the Czech Republic, on horizontal flow reedbeds, where water can flow around

the plant stems. The first reedbed had an area of 18 m2 and consisted of similar

reed species to those that were surveyed along the Lee Navigation for this

report (i.e.: common reed (Phragmites australis); reed mace (Typha latifolia);

and yellow flag (Iris pseudacorus). Water quality testing results found that there

had been a very high removal of suspended solids, such as organic matter, with

an efficiency of over 90%. These results were found to be typical of the

performance that would be expected for similar sites. The second reedbed site

had a bed area of 2500m2 and was dominated by common reed (Phragmites

australis) and reed canary grass (Phalaris arundinacea), both of which were

found along the Lee Navigation. Water quality testing results found that again

there had been a very high removal of suspended solids, such as organic

matter, and 40 percent efficiency for nitrate removal (Vymazal, 2005). Other

studies have found that wetlands were capable of removing over 90% of nitrate

from surface water (Ying-Feng et al., 2002).


3. Reedbed Survey Methodology

The reedbed survey was conducted in August 2012. The survey was carried out

along the Lee Navigation between Limehouse Basin (OS Grid Reference: TQ

36372 80895) and the M25 boundary near Rammey Marsh (OS Grid

Reference: TQ 37542 9975). GPS locations for the GIS map were calculated

with a GARMIN etrex 10 handheld device.

3.1 Criteria for Identifying and Classifying Existing Reedbeds

Existing reedbeds were identified as: marginal or in-channel areas with greater

than 0.5m2 reed species cover. Areas with less than 0.5m2 reed species cover

that had potential for expansion were recorded as potential reedbed sites. Reed

species were identified using: Haslam et al., 1982 - Field Studies Centre -

British Water Plants. Relative species abundance within reedbeds was recorded

in accordance with the JNCC classification system for assessing vegetation

communities of British rivers (Holmes et al., 2009). Where: 1 = Rare; 2 =

Occasional or Frequent; and 3 = Abundant or Dominant. Photographs, area

measurements, locations and notes, such as health and management needs,

were taken at each site.

3.2 Criteria and Specification for Identifying Potential Reedbed Sites

Potential reedbed sites were identified as sites without reedbeds, but where

reedbeds could potentially be created or expanded. Sites where reedbeds could

be expanded had less than 0.5m2 reed species cover, or intermittent reeds

covering a long (more than 30m) reach, where existing reeds could be

expanded to cover gaps where there were no reeds. All areas without reedbeds

were considered within the survey site. The general criteria for potential sites

were as follows:


Potential benefits of having a reedbed in that location. For example, reedbed creation would be particularly beneficial for waste water treatment near potential sources of pollution, e.g. a sewage treatment works (STW).

What is the approximate slope angle and material of the bank and/ or substrate which the reedbed would be connected to? Soft edges such as gently sloping soil banks would better suit reedbed creation. However, reedbeds can be constructed along hard man-made banks if a supportive substrate were created.

Are reedbeds likely to impact upon navigation in a particular location? Sites with obvious moorings and very narrow channels were not considered as potential sites. The maximum extent into the channel of proposed sites will depend on the navigation width requirements in the particular stretch of channel.

Light availability - reedbeds need significant levels of sunlight throughout the day, so sites under bridges or that are likely to be shaded for more than 40% of the day were not considered as potential sites.

Are there any other species, particularly UK BAP species such as Water Voles, which would benefit from reedbed construction in the area?

Photographs, area measurements, locations and notes, such as other types of

vegetation present, were taken at each site.


Figure 4 Map showing locations and numbers of existing reedbeds along the Lee Navigation. The reedbed markers are not to scale, reedbed dimensions are detailed in the appendix. Each reedbed or stretches of reedbeds marked in this map are on one side of the channel, channel side can be found in the appendix. Most tributaries of the Lee are not shown in this map; the Ching and Small Lee are shown for illustrative purposes.

4. Reedbed Survey Results

4.1 Existing Reedbeds Map


4.2 Potential Reedbed Sites Map

Figure 5 Map showing locations and numbers of potential reedbed sites along the Lee Navigation. The site markers are not to scale; site dimensions are detailed in the appendix. Each site, or stretch of sites marked in this map are on one side of the channel, channel side can be found in the appendix. Most tributaries of the Lee are not shown in this map; the Ching and Small Lee are shown for illustrative purposes.


A total of 44 existing reedbed sites and 53 potential reedbed sites were

identified along the Lee Navigation. Some of the potential sites include both

sides of the channel. The total approximate length and area for existing

reedbeds along the Lee Navigation from Limehouse Basin to the M25 is 1.5km

and 2.5km2 respectively. The total approximate length and area for potential

reedbed sites along the Lee Navigation is 5.5 km and 7.1 km2 respectively. For

potential reedbed sites, the maximum potential area has been given. However,

in some instances the site area may need to be reduced in final construction

plans to cater for restrictions such as navigation.

4.3 Individual maps and descriptions of potential site types

Potential reedbed sites were split into categories depending on their

characteristics e.g. long stretches with hard engineered banks. The category

descriptions and associated sites are summarised in the table below. In the

following section an example from each category is shown.


Table 2 Categories associated sites and totals for each potential reedbed site.

*P: Potential site; Last number starts Bromley By Bow (1) to M25 (53).

Category Reference Code* Total

Extension of an existing reedbed.

PA

4

Small site (<30 m2) in ‘unused’ channel section. Hard engineered bank.

PB

10

Small site (<30 m2) with hard engineered bank.

PC

5

Small site (<30 m2) in areas where the channel expands. Hard engineered bank.

PD

5

Small site (<30 m2) in areas with existing non-reed vegetation which could be replaced with reeds. Hard engineered bank.

PE

4

Small site (<30 m2) in areas with existing non-reed vegetation which could be replaced with reeds. Sloped bank.

PF

6

Long stretch. Hard engineered bank.

PG

11

Long stretch, existing non-reed vegetation. Sloped soil bank.

PH

6

Long stretch, existing non-reed vegetation. Hard engineered bank.

PI

4

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provide habitats for water voles, which were once strong in numbers here but

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straightforward. One consideration is that the Lee Cut enters the Lee here,

supplying water from the Flood Relief Channel system. The Lee Cut is an

important refuge and spawning area for fish and invertebrates etc. Therefore, it

is important that we maintain the connection between the two by not completely

vegetating the mouth.

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5. Reedbed Management

To achieve their full potential in terms of environmental, conservational,

economic and social benefits, urban reedbeds need to be managed.

Management can be carried out by volunteers, to conserve and enhance

reedbeds in the long-term, and provide additional social opportunities, such as

‘green gyms’ and education.

Litter management: Litter should be removed before reedbed creation or

enhancement to help new reeds establish (Water for Wildlife UK publication,

undated). Reedbeds have a tendency to trap litter, however, if regular

maintenance is applied, the net impact of reedbeds trapping litter could be

positive, because less rubbish would sink or be transported downstream, where

it could continue to cause aesthetic, ecological and management issues. Litter

management can be carried from the towpath using litter pickers, or if the reeds

can only be accessed by water, canoes can be used to enable litter removal.

Both of these methods are already used to manage litter in existing reedbeds

on Thames21 events.

Non reed vegetation management: When reed plants are young, controlling

competing vegetation helps reeds establish. Vegetation should be ideally be

removed before new reeds are established (Water for Wildlife UK publication,

undated). Volunteers could provide some management of vegetation, but

clearing and removal of larger vegetation would need to be carried out by a

contractor.

Reed management: Rotational harvest of reeds is required to prevent the

build-up of dead material and drying out of the habitat. Reed management can

also encourage diversity and reduce encroachment by non-reed vegetation.

Reed harvesting can also lead to the removal of excess nutrients from the

environment, so they will not be returned to the water once the reed dies. Reed

should be harvested in November to March, and dead reed can be removed

with relative ease during the winter when they die back. Summer reed cutting


can be carried out to enhance diversity by providing resource opportunity for

younger reeds. Traditionally reedbeds were managed sustainably by reed

cutters who used the reeds for thatching material. The demand for good quality

thatching reed currently outstrips supply and much of the UK’s thatching reed is

currently imported from abroad. It may be worth exploring the possibility of

using harvested reeds commercially. Otherwise reeds should be suitably

disposed of because they could cause nutrient enrichment if they are left near

the site.

All forms of reed management would need to be designed and planned for

specifically different sites and corresponding long-term management plans

would need to be put in place.

6. Reedbed Construction

This section gives a brief overview of some of the methods that could be used

to construct the types of reedbeds that have been proposed for the Lower Lee

Catchment. However other methods could be explored, and all methods would

need to be amended to the bespoke aspect and details of the site.

Constructed reedbeds along the Lee Navigation would usually be placed along

the channel edge to allow space for navigation. As much of the channel has

hard engineered banks, a substrate (where not present), would need to be

provided to support reedbeds. In addition, reeds would need sufficient light

throughout the day, generally more than 5 hours sunlight. Growth of common

reed species such as Phragmites australis are inhibited by immersion in water

and excessive sediment build up around their roots. Thus, temporal changes in

the depth of water and susceptibility of the site to sediment build up would also

need to be assessed. In areas where the water level maybe too high to support

a semi-submerged reedbed, the bed can be raised so that the reeds will not be

immersed by water. Around 40% of the potential sites that have been identified


in this report already have some sediment build up, which could provide the

initial foundation for a raised reedbed.

When designing the size and shape of the reedbed, long term management

implications and physical restrictions would need to be considered. For

example, changes in local soils and slopes may restrict the area where reed will

grow and survive. While any reedbed size will provide conservation and

aesthetic benefits, larger reedbeds are more suitable for bitterns and marsh

harriers. However, small reedbed are particularly valuable for encouraging fish,

invertebrates and rare mammal species such as water voles. Reeds should be

planted as soon as possible after the last frost to reduce competition from other

plants.

Reedbed expansion: A number of the proposed sites already have some

reeds growing, but expansion would be beneficial. In these sites, non-reed

vegetation that has encroached on to the potential site could be cleared back to

encourage reed growth. In some instances proper management may lead to

natural reed colonisation. However, planting reed seedlings would ensure faster

development and possibly reduce management of other vegetation, because

the reeds can establish faster. Planting reeds generally has a 90% success

rate, but care should be taken to use reeds which grow in similar environmental

conditions to the site. Great care should be taken to ensure that invasive

species are not introduced to the site with new plants.

Reedbed construction: Raised reedbeds can be constructed against river

walls using natural materials such as coir rolls, and bundles of willow faggots.

Stakes, soil filled hessian sacks and optional gabions can be used to support

the constructed raised reedbed. However, reedbeds created along the Lee

Navigation will generally be wet. For wet reedbed construction, a substrate can

be created and floating supports can be used to establish the reedbed, see

figure 15. Reed turf, reed plugs, actively growing rhizomes or soil containing

rhizomes can be used to establish vegetation in new reed sites or for the

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2007).


7. Conclusions

7.1 Existing Reedbeds

The overall cover of existing reedbeds along the Lee Navigation within the M25

was very small, less than 8%. The existing reedbeds that were identified and

recorded were generally in good health, thus indicating that new or expanded

reedbeds could be supported within the existing environment. A number of the

existing reedbeds that were identified would benefit from management in order

to preserve them. The main forms of management required includes: weed-

cutting; litter removal; and invasive species management.

7.2 Potential Benefits of Reedbed Enhancement and Creation

There is a great potential for reedbed creation and expansion along the Lee

Navigation within the M25. Up to 60% of the survey sites have been identified

as a potential site for reedbed creation and/or expansion. While further

consideration may identify some proposed sites that may not be suitable for

reedbed expansion or creation, most of the proposed sites would be able to

support reedbeds while not interfering with navigation. While navigational

activities are supported in the EA’s RBMP for the Lower Lee Catchment,

mitigation measures must be put in place for ‘good ecological potential’ to be

achieved for the Lower Lee Catchment. Reedbed creation and expansion along

the Lee Navigation within the M25 would provide a low cost enhancement which

helps to meet mitigation measures and WFD objectives. Furthermore, creation

and expansion of reedbeds would contribute towards national UK BAP targets

for reedbed habitats and possibly other UK BAP species such as water voles

etc.

Creation and expansion of reedbeds will likely lead to improvement of multiple

water quality parameters, as a result of the special functions that reedbeds

possess for filtering and cleaning water. In addition, it is likely that biodiversity in

the survey site would increase if reedbed area is increased, as a result of

greater habitat availability.


Another major benefit of reedbed conservation, enhancement and expansion,

are the positive influences that reedbeds can have on local communities. The

Lee Navigation flows through a number of deprived urban areas; Tower

Hamlets, Hackney, Haringey, Waltham Forest and Newham which all suffer

from a deficiency of green space. Natural spaces such as reedbeds have been

found to; improve physical and mental well-being, provide recreational spaces,

reduce crime rates, and enhance social cohesion. Additionally reedbeds can be

used as an educational tool, informing residents about the environment. These

benefits would be welcomed in urban areas such as the Lower Lee catchment,

where positive societal impacts are needed, and would be extremely far

reaching (Cattell et al., 2007).

7.3 Further Research and Considerations

The implementation of this report should be monitored from an ecological and

social aspect. It would be useful to monitor the impacts of any expanded or

constructed reedbeds, to quantify for example, improvements to biodiversity.

Some aspects of biodiversity, particularly damselflies, dragonflies and birds can

be monitored by members of the public who can add their findings to a publicly

available Google or GIS map. Other wildlife such as fish may be able to be

monitored through catch returns, while more detailed studies such as

Environment Agency fisheries surveys should also be considered.

There are some external factors that may threaten existing and constructed

reedbeds, which should be considered within management plans for reedbeds

within the survey site. The removal of pollution from reedbeds may be offset by

increased pollution concentration. For example, increased rainfall intensity

resulting from climate change could increase the amount of rainfall run-off and

associated pollutants being transported into the river. However, a significant

increase in current reedbed quantities along the channel margins could provide

full or partial mitigation. Long-term monitoring of benefits of constructed or

enhanced reedbeds would be required to appraise the project. Monitoring of


water quality benefits provided by reedbeds on the Lee Navigation would be

essential under WFD objectives. Biodiversity benefits could be carried out via

volunteer organisation and resident monitoring, for example, a publicly

accessible map could be used for recording ecological survey results and

observed wildlife. It may be possible to assess social benefits via statistical

studies and questionnaires.


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Documents

PROJE CT REE DBED - Thames21 · damaged it had become. In amongst the reeds it was beautiful and peaceful, but we stood calf-deep in rubbish and Japanese Knotweed had grown across