Utilising GIS technology, the Fish Migration Roadmap provides a method that focuses on a ‘whole system’, sea-to-source approach that, similarly to an underground or road network, looks at rivers as interconnected migratory routes. By considering rivers as 'Highways', 'A-roads' and 'B-roads', barrier locations and river network connectivity can be easily visualised on one or more rivers, or in entire river catchments. This can help reprioritise barriers and provide a blueprint for strategic steps that can help open up entire migratory routes.

1. Greater Thames Estuary Fish Migration RoadmapGreater Thames Estuary Fish Migration Roadmap
A short summaryA short summary
Wanda BodnarWanda Bodnar
Copyright © 2020 Thames Estuary PartnershipCopyright © 2020 Thames Estuary Partnership 1/141/14

2. © Johannes Plenio 2/14

3. Introduction
Rivers play an important role in our environment: regulating floods,
transporting sediments, and supporting biodiversity. Many of these services
performed by rivers are also linked to factors that indicate river health, such
as river flow and connectivity. River network connectivity influences species
migration, diversity, and habitat occupancy.
Rivers in the North Sea region are some of the most fragmented by human
development in the world. Artificial structures, like weirs, sluices and locks,
installed for water management purposes on rivers can be found at almost
every kilometre. These barriers can significantly delay and hinder the
movement of migratory fish species, subsequently reducing their diversity
and abundance.
Diadromous fish species such as the European eel (Anguilla anguilla), sea bass
(Dicentrarchus labrax), sea lamprey (Petromyzon marinus) and flounder
(Platichthys flesus) move large distances between marine and freshwater
environments and thus maintaining connectivity is important to sustain their
healthy and diverse population.
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4. Introduction
To address the issue of river fragmentation and fish passage, Thames Estuary
Partnership (TEP) and Nature at Work (NAW) launched the Greater Thames
Estuary Fish Migration Roadmap project in January 2018.
The project seeks to bring together all barrier, pass, priority, and habitat
location data in one place and develop a ‘whole system’, sea-to-source
approach that, similarly to the tube network, looks at rivers as interconnected
roads.
By considering and identifying rivers as 'Highways', 'A-roads' and 'B-roads',
barrier locations and river network connectivity can be easily visualised on
one or more rivers, or in entire catchments. This can help reprioritise barriers
and provide a blueprint for strategic steps that can help open up entire
migratory routes.
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5. 5/14

6. Methodology
The Fish Migration Roadmap project had three objectives:
To gather information on fish migratory barriers and river connectivity
within the Thames River Basin.
To develop an online, easy-to-access and easy-to-use GIS platform
visualising all relevant data.
To develop a replicable, strategic roadmap method which also includes
the Fish Migration Vision.
These objectives were executed via the following steps:
Data science
Designation of project area
Data collection
Data pre-processing and merging
Data analysis
Data visualisation
Stakeholder and community engagement
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7. Methodology
Data science
Designation of project area
The project area was defined within the Thames River Basin and two
adjacent catchments. The boundary on the migratory routes was drawn at
30km from the tidal limit.
Data collection
Data was collected from: AMBER, Catchment Based Approach,
Environment Agency, River Obs app, Zoological Society of London,
London Wildlife Trust, South East Rivers Trust and Canal and River Trust.
Data pre-processing and merging
The different datasets were merged together using a 100 metres buffer
zone to concentrate on those barriers that occurred on the migratory
routes only. (The sources of the datasets were kept in the finalised barrier
dataset.)
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8. Methodology
Data science
Data analysis
Calculation of the river connectivity index (RCI %)
Creation of connectivity maps
Introduction of 'Category' variable into the final barrier dataset
Integration of river habitat data into the final barrier dataset
Data visualisation
An online, easy-to-use platform was developed where barrier
locations and upstream river connectivity can be visualised.
The most important element of the interactive map is the filter
function which allows the barrier data to be filtered based on barrier
type, priority, pass type, river, category, and upstream river habitat.
Overlaying this on top the connectivity layers can help develop a
more targeted approach when it comes to improving river
connectivity and fish passage.
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9. Methodology
Stakeholder and community engagement
Stakeholder and communtiy engagement was carried out predominantly in
the Combined Essex Catchment.
Over a series of engagements the methodology could be developed and
refined.
In the meantime, an interactive Roadmap was developed specifically for this
catchment.
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10. The Roadmap Method
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11. The Roadmap Method
The most important steps of The Roadmap Method are:
Calculation of RCI and visualisation of river connectivity that can help
highlight the level of river fragmentation.
Stakeholder engagement that can help gather local knowledge and
understand local needs. This can subsequently lead to the development
the Fish Migration Vision.
The Fish Migration Vision is a shared, ambitious long-term goal that
envisions what a healthy river and connected river corridor could be
with collective action across sector initiatives e.g. catchment
management, flood asset management and land development.
The introduction of the ‘Category’ variable that can help the barrier
reprioritisation process.
Coupled with the stakeholder engagement, the barrier reprioritisation can
help pinpoint priority barrier locations, for example, closed river sections
with diverse habitat.
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12. Next steps
Further project plans include:
Inclusion of additional waterways as ‘C-roads’ and ‘D-roads'.
Collation and creation of Roadmap specific fish database for each river.
Further stakeholder engagment and linking into other local plans and
strategies.
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13. © Jack Perks 13/14

14. If you are interested in working together or would like to find out more aboutIf you are interested in working together or would like to find out more about
the project, please do get in touch.the project, please do get in touch.
Thames Estuary PartnershipThames Estuary Partnership
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Slides were prepared using R Studio's R MarkdownSlides were prepared using R Studio's R Markdown
Copyright © 2020 Thames Estuary PartnershipCopyright © 2020 Thames Estuary Partnership 14/1414/14