PIANC joint InCom/EnviCom WG 237
Sustainable Management of the Navigability of
Free Flow Rivers
Terms of Reference
(29 Nov. 2020)
1. Background
This WG concerns only free-flowing currents or rivers in their natural state, entirety or partially,
in which the flow is not constrained by any hydraulic infrastructure. We shall refer to these as
"natural rivers."
Most navigable natural rivers are “large rivers.” They are alluvial rivers, with hard points (rock
outcrops) in the low-flow and middle riverbed, with specific bottom morphologies. As
opposed to regulated rivers, the evolutions of morphological variables (bottom slope, width,
cross sections and plan view) of natural rivers makes it difficult to fix a navigation channel in a
permanent alignment.
Therefore, there needs to be a change in paradigm and methodologies for navigation in
natural rivers.
This WG is dedicated to the improvement of navigability natural rivers that are not intended
to be regulated. The goal is finding ways to guaranty/improve navigability without
conventional training structures, concrete, rock etc. inside the natural rivers.
More info about the motivations and background are given in the ANNEXE.
2. Objectives
The objectives are:
- to develop guidelines to improve and maintain the navigability in free-flowing
current rivers, and to design, build and operate training river works.
- to assess the sustainability of river training works designed to improve the navigability
and maintain an adequate navigation channel in large rivers subjected to
morphological changes.
- to assess the sustainability of dynamic river management (monitoring and shifting of
navigation aids to adapt the navigation channel to the river dynamics)
- to highlight the technical, operational, economic and environmental considerations
for navigation in free-flowing current rivers compared to that in regulated rivers and
canals.
- to improve the understanding of the physical processes of the flow in free-flowing
current rivers, developed with or without river training works. That also includes
understanding of the temporal and spatial morphological evolution of a fluvial
hydrosystem and its reactions to natural effects and anthropogenic actions.
River training works typically include the following hydraulic river works: sills, bottom weirs,
spur-dikes most of the time called groynes, longitudinal and transversal dikes, submerged
panels, bank protection, pilot channel, deepening and bend cut-off.
WG recommendations be useful in evaluating the effectiveness of any hydraulic structures or
river training works, and develop recommendations for a dynamic river considering:
PIANC InCom - EnviCom WG ToR Sustainable Management of Navigability of Free Flow Rivers
• Hydrofluvial system
• Natural or large rivers
• Morphological evolution
• Navigability requirements in free flow current
• River training works
• Morphological dredging
• River survey technologies and maintenance
The benefit of this WG is to propose a new integrated methodology for “dynamic river
management” and “working with nature” to analyze and improve the navigability in free
flow rivers, while maintaining natural flows and ecosystem functions.
3. Earlier Reports and documentations
• Existing PIANC WG reports from InCom and EnviCom
• Given the multidisciplinary nature of the areas addressed, it is recommended to
collect relevant information produced by several international associations such as:
- IAHR - International Association for Hydro-Environment Engineering and Research
- IAHS - International Association of Hydrological Sciences
- ASCE - American Society of Civil Engineers
- INBO - International Network of Basin Organization’s
- CEDA - Central Dredging Association
- SedNet – European Sediment Network
- USACE - U.S. Army Corps of Engineers
- Others as identified
• Relevant books and papers
4. SCOPE
4.1 Matters to be investigated
The scope of the investigation is to:
• Improve the understanding of the current and forecast temporal and spatial
morphological evolution of a river to support its sustainable management;
• Assess and formalize the technical, operational, socio-economic, and environmental
considerations for navigation in free-flowing current rivers and regulated rivers;
• Inventory and review current training river works including sills, bottom weirs, groynes,
dredging etc, as well as channel realignment. This shall include applicable codes and
standards;
• Inventory and review existing tools, methodologies, investigations, and other research
to assess morphological behavior of large rivers and to evaluate its dynamic response
under the impacts of both natural and human impacts and the impact on
navigation,
• Review and assess design tools including topo-bathymetry surveys, remote sensing
(GIS), hydrography, hydrometry, physical and numerical modelling, trends analysis,
marking, etc. to manage free-flowing current rivers, including morphological
dredging methodology (smart dredging) and associated innovations (such as
realignment of navigation channel).
In many countries, mostly outside EU, the navigability problems in (large) natural rivers
require:
- a continuous knowledge of the river’s situation,
- tools to evaluate trends in the evolution of river morphology,
- marking of the navigation channel,
- stabilization of the banks,
- dredging.
• Develop a better understanding of river morphology, which is a key element
influencing the ecological values of the rivers. Today, numerical modeling is the
preferred tool for studies but many users do not know enough about the limitations of
numerical modeling of morphological and ecological effects.
• Review and assess monitoring methodologies that allow for dynamic response of the
navigation channel
PIANC InCom - EnviCom WG ToR Sustainable Management of Navigability of Free Flow Rivers
• In the area around many rivers, societal aspects such as poverty, population
movement, economic situation, flood protection, and biodiversity have a major
influence in the choice of the river training works.
4.2 Proposed Methodology
• Establish a detailed work program, further detailing the scope, tasks and
responsibilities, approach, and deliverables
• Conduct desk research to collect, analyze, and consolidate the current available
information concerning river training works and maintenance in large rivers
• Due to the multidisciplinary nature of the WG, it would be advisable to create
privileged links with the IAHR and INBO communities, as well as other PIANC sister
associations. Certain InCom members, already members of these communities, could
act as liaison between these bodies and the WG. The WG can use IAHR
works/publications to summarize and provide guidelines (support) for the
understanding of non-highly specialized hydraulic engineers, as is the case of most of
IW managers.
• Evaluation of the monitoring, mitigation, modeling systems and approaches used for
operational engineering, financial and policy decision-making in actual free-flowing
current rivers. This will include listing of metrological technologies, methods of
equipment deployment and data analysis, methods of mitigation, desktop, physical
and numerical models as well as analytical models, which are used to address
navigability improvement (Dynamic river management)
• Development of a method of systematically mapping the hydromorphological
effects of all training river works. This could concern both local effects and cumulative
effects of the various measures that can move downstream and upstream
• Project reviews and cases studies to analyze the feasibility of existing practices and
the possible innovations
• Presentations and workshops to share knowledge and spread awareness. The results
of the WG may also be presented in various conferences.
The WG will avoid duplication of existing research performed by other scientific communities.
Existing scientific literature may only need to be “rephrased” to provide it in a manner useful
to IW managers and stakeholders.
5. Intended product
The intended product is a set of guidelines to improve navigability and develop navigation in
free-flowing current rivers. It will deliver an understanding of the specificities of navigation in
natural rivers.
The WG report will highlight the needs, requirements, and strategies to design a navigable
channel in free-flowing current rivers.
Practical insight will be provided through the use of case-studies.
An essential part of the report will be development of a guiding analytical framework to be
used as an outline for future management.
6. Recommended Members
The WG should ideally include managers of inland navigation systems in natural rivers, fluvial
hydraulics and morphological engineers, waterways designers/development; river training
works engineers, navigation and navigation aids experts, hydrographical experts, dredging
operators, researches, and national and international environmental offices/authorities.
Members should represent areas with large rivers, including North and South America, Asia
and South Asia, and Africa.
Support of international associations as ECLAC (South America) and the Mekong River
Commission would be helpful.
The membership should include a good balance of members representing all stakeholders
and from navigation companies, IW organizations, and members with an expertise in:
• navigation in free-flowing current rivers including hydrographic techniques and
marking,
• fluvial hydraulics, sediment transport and morphodynamics,
• physical and numerical modelling including navigation simulations,
• dredging,
• environmental impacts.
PIANC InCom - EnviCom WG ToR Sustainable Management of Navigability of Free Flow Rivers
This joint WG (INCOM and ENVICOM) will work in close collaboration in order to promote the
“Working with Nature” concept.
7. Relevance for Countries in Transition
This report is intended to support the growth of inland navigation with reduced investment in
river regulation and sustained protection of ecosystem functions of natural rivers.
The report will be of value in protecting the interests of developed countries and countries in
transition. The report will be of particularly use to decision makers in the assessment of
navigation improvement of free-flow rivers and also prepare technical terms of reference to
aid in development and presentation of a tender.
This report will enable these countries to quantify the support of Inland Waterway use in the
context of the development of their hydrofluvial systems.
8. Climate Change, Working with Nature, Sustainable Goal (SDG)
Climate change is increasingly leading to extreme conditions and may drastically affect
navigability of rivers with natural flow discharge, due to stronger dry seasons. It is expected
that an approach based on following the natural river dynamics will be more resilient than a
rigid regulation approach.
The objective is to develop guidelines to improve and maintain the navigability of free-
flowing current rivers and to design, build and operate navigation, in line with the "Working
with Nature" concept. This should be included in river management methodology to improve
navigation as measures to guarantee navigability in free-flow rivers
This WG is intended to support primarily the following “Sustainable Development Goals (UN’s
SDG)”:
- Goal 8 "Promote sustained, inclusive and sustainable economic growth, full and
productive employment and decent work for all”;
- Goal 9 “"Build resilient infrastructure, promote inclusive and sustainable industrialization,
and foster innovation".
PIANC InCom - EnviCom WG ToR Sustainable Management of Navigability of Free Flow Rivers
ANNEX: Additional details about the motivations and background of the proposal
Inland Waterway Transport (IWT) can be classified as utilizing three kinds of waterways: rivers,
lakes and canals. For rivers, there are two possible situations: natural rivers (or free-flowing
current) and rivers regulated by hydraulic infrastructure.
The scope of this WG concerns only free-flowing currents or rivers in their natural state,
entirety or partially, in which the flow is not constrained by any hydraulic infrastructure. We
shall refer to these as "natural rivers."
Natural rivers can naturally provide an adequate depth for navigation, especially in the
downstream reaches of these rivers.
Most navigable natural rivers are “large rivers.” 1 They are alluvial rivers, with hard points (rock
outcrops) in the low-flow and middle riverbed, with specific bottom morphologies such as
meandering, braided, multi-branched, anastomotic configurations. As opposed to regulated
rivers, the temporal and spatial evolutions of the morphological variables (bottom slope,
width, cross sections and plan view) makes it difficult to fix, in the long term, a navigation
channel.
The hydrofluvial system of a river relates to the territory used by the river, consisting of the
entire riverbed, its tributaries and wetlands forming an integrated part of its environment.
Rivers flow through two natural elements, water and sediment, coupled by temporal and
spatial physical and environmental relationships.
If a river is in a morphological equilibrium, any changes in one of the geometric variables
(width, depth, bottom slope, etc.) due to natural events (e.g. climate changes) or
anthropogenic actions (e.g. river training works) can result in more or less significant
evolutions in the short, medium, and long term.
Many rivers around the world provide striking examples of such adaptations generated by
both natural and human effects, for example, Congo and Kasai, Senegal, Niger (inner delta),
Mississippi, Ichilo--Mamore, Mekong (upper delta), Brahmaputra, and others.
The majority of European navigable rivers are pseudo-free-flowing rivers because river
training works have usually been established (Rhine, Danube, Volga, Meuse, etc.).
The river training works and maintenance usually consist of hydraulic structures and/or
dredging works. The goal of river training works is to provide a desired channel dimension
and alignment.
However, in many river configurations, it is not technically possible nor environmentally
desirable to improve river training works. The only solution is to “help” the river maintain a
navigable channel through specific actions such as morphological dredging.
Recurring problems of navigability are typically solved by maintenance dredging. The need
for dredging is due to the appearance of bed deformations, sills and shoals due to the
morphological configuration of the river. Dredging as a permanent measure is not
sustainable and must be replaced by morphological dredging or “smart dredging” taking
into account the evolutionary trends of the river. To achieve this, it is first necessary to
understand the physical functioning of the river and not to act against it, but with it.
In the past, these hydrofluvial responses were not always well understood.
A solid understanding of the actual and forecast temporal and spatial morphologic
evolutions are required to develop sustainable management of a river. Any project to
maintain river navigation must start with a fluvio-morphological diagnosis explaining why and
how geometrical variables have evolved in the past and will evolve in the future.
It is also necessary to differentiate the methodology to evaluate the impact of river training
works, either for a significant part of the river (global model) or for small part of the river (local
model). Physical models can only be made to local scale, primarily because of the expense
of these models. Numerical models are more appropriate for the study larger parts of a river.
In order to validate the results of modeling, the use of hybrid models by combining the two
types of modelling is preferred. Field studies are also necessary no matter what model or
combinations of models are used.
1 A “large river” is based on its basic characteristics, the most objective and quantitative criteria: length,
watershed area, median discharge (modulo), specific discharge and annual sediment load (UNESCO, IAHR).
PIANC InCom - EnviCom WG ToR Sustainable Management of Navigability of Free Flow Rivers
Therefore, there needs to be a change in paradigm and methodologies and development
of a set of methods (a "toolkit") such as physical and numerical modelling, field studies,
specific measurements, data collection and improved interpretation of these methods
based on experience.
Based on analysis of InCom WG reports it has been observed that no WG has investigated
specific navigability aspects of the hydrofluvial system of (large) free-flow rivers.
In order to conduct such investigation, it is recommended that a WG dedicated to the
improvement of navigability with river training works in free-flowing current rivers while
ensuring the stability of the navigation channel be established.
PIANC InCom - EnviCom WG ToR Sustainable Management of Navigability of Free Flow Rivers
PIANC
The World Association for
Brussels, 15 December 2020.
Waterborne Transport Infrastructure
To the First Delegates of the
Qualifying Members of PIANC
To the National Sections’
Secretaries of PIANC
To the Platinum Partners of PIANC
To the Sister Associations of PIANC
Subject: Setting up of a joint InCom/EnviCom PIANC Working Group 236 on “Sustainable Management
of the Navigability of Free Flow Rivers”.
Dear Madam,
Dear Sir,
The setting up of joint InCom/EnviCom PIANC Working Group 236 on “Sustainable Management of the
Navigability of Free Flow Rivers”, has duly been approved as well as its terms of reference, which are
herewith enclosed.
We kindly ask you to inform the secretariat of InCom by 28 February 2021 (copy to the General Secretariat –
[email protected]) about the name, qualification and (e-mail-) address of the expert, proposed
by your country/organisation. Please enclose a brief curriculum vitae of the proposed expert together with
some details about her/his professional experiences.
An additional expert per country/organisation, being a young professional, can participate in the Working
Group activities. Further I would like to remind you that Working Group Members should either be Individual
Member of PIANC, working for a Corporate Member or Platinum Partner, be an invited expert or a be a
member of a Sister Organisation.
We remind you that in accordance with PIANC rules, the costs incurred in taking part in Working Group
activities are borne by the member countries/organizations.
We thank you beforehand for your collaboration.
Yours sincerely,
Geert Van Cappellen,
Secretary-General.
Reply to:
Ms Jasna Muskatirovic – (
[email protected])