ISO/TR 9210:2017

Hydrometry - Measurement in meandering river and in streams with unstable boundaries

ISO/TR 9210:2017 provides guidelines for discharge measurements in meandering and braided rivers, and from bridges, following the provisions of ISO 748.

Hydrométrie — Mesurage en rivières à méandres et en cours d'eau à limites instables

General Information

• Status: Published
• Publication Date: 23-Nov-2017
• ICS: 17.120.20 - Flow in open channels
• Technical Committee: ISO/TC 113/SC 1 - Velocity area methods
• Drafting Committee: ISO/TC 113/SC 1 - Velocity area methods
• Current Stage: 6060 - International Standard published
• Start Date: 24-Nov-2017
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO/TR 19441:2018 - Petroleum products - Density versus temperature relationships of current fuels, biofuels and biofuel components
• Effective Date: 06-Jun-2022
• Revises: ISO/TR 9210:1992 - Measurement of liquid flow in open channels - Measurement in meandering rivers and in streams with unstable boundaries
• Effective Date: 10-Aug-2013

Overview

ISO/TR 9210:2017 provides practical guidance for hydrometry - specifically for discharge measurement in meandering rivers, braided rivers, and streams with unstable boundaries, and for measurements made from bridges. It supplements and elaborates the velocity-area method given in ISO 748, addressing site selection, measurement tactics and special problems that arise where channel geometry and bed stability vary in time and space.

Key topics

• Site selection for gauging stations in alluvial and meandering rivers:
  • Prefer transitions between bends when straight reaches are unavailable.
  • Consider seasonal changes in flow direction; adjust gauging section orientation if necessary (while following ISO 748 requirements).
• Stable vs. unstable meanders:
  • Use nodal points (natural or artificial constraints) as preferred stable locations on otherwise unstable meandering reaches.
  • Install two level gauges at consecutive nodal points where bed movement or gravel bars complicate stage measurement.
• Braided rivers and unstable beds:
  • Recognizes high bed mobility, multiple channels and variable roughness; recommends rapid measurements, simplified velocity methods (single- or two-point) and multiple level gauges to capture shifting rating curves.
  • Subtract reverse (negative) flows where local gyres occur to obtain net discharge.
• Measurements from bridges with piers:
  • Discusses upstream vs downstream measurement advantages, safety and debris considerations.
  • Recommends estimating discharge in pier-affected zones by using discharge intensity at adjacent verticals and multiplying by the affected width rather than direct risky measurements.
• Instrumentation and methods:
  • Emphasizes velocity-area method and use of direction‑measuring current meters for angle correction where transverse flows and secondary flows occur.
  • Notes application of non-contact acoustic/radar gauges deployed from bridges to measure surface level/velocity across wide, unstable sections.

Applications

Who uses ISO/TR 9210:2017 and why:

• Hydrologists and gauging station operators - for selecting sites and adapting measurement programs in meandering or braided reaches.
• Water resources and flood engineers - to design monitoring strategies and to interpret stage–discharge relationships where channels shift.
• Environmental agencies and researchers - to standardize discharge data collection in complex channels and improve data comparability.
• Bridge inspection and infrastructure teams - when using bridges as platforms for hydrometric measurements and estimating flows near piers.

Practical benefits include improved accuracy of discharge estimates in unstable channels, guidance for rating-curve development under variable bed conditions, and safer, more reliable bridge-based measurements.

Related standards

• ISO 748 - Hydrometry: measurement of liquid flow in open channels using current-meters or floats (normative reference for velocity-area methods).
• ISO 772 - Hydrometry vocabulary and symbols (terms and definitions used).

Standards Content (Sample)

TECHNICAL ISO/TR
REPORT 9210
Second edition
2017-11
Hydrometry — Measurement in
meandering river and in streams with
unstable boundaries
Hydrométrie — Mesurage en rivières à méandres et en cours d'eau à
limites instables
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
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Tel. [phone]
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www.iso.org
ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Site selection in rivers . 2
5 Site selection in rivers with relatively stable meanders . 2
6 Site selection in rivers with unstable meanders . 3
7 Discharge measurement in braided rivers . 3
8 Discharge measurement from a bridge with piers . 4
Bibliography . 7
Foreword
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URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 113, Hydrometry, Subcommittee SC 1,
Velocity area methods.
This second edition cancels and replaces the first edition (ISO/TR 9210:1992), which has been
technically revised.
iv © ISO 2017 – All rights reserved

Introduction
Various methods of measurements of discharge in open channels are available, of which the velocity-
area method is most extensively used. The principles of this method are published in ISO 748.
However, there are rivers and streams, in which there are no river sections with constant bed levels and
constant flow conditions. This document deals specifically with measurements of flow in meandering
and braided rivers, and elaborates some of the provisions in ISO 748.
TECHNICAL REPORT ISO/TR 9210:2017(E)
Hydrometry — Measurement in meandering river and in
streams with unstable boundaries
1 Scope
This document provides guidelines for discharge measurements in meandering and braided rivers, and
from bridges, following the provisions of ISO 748.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 772, Hydrometry — Vocabulary and symbols
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 772 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
alluvial river
river, which flows through alluvium, formed from its own deposits
Note 1 to entry: The sediment carried by an alluvial river, except for the wash load, is similar to that in the bed.
3.2
braided river
river characterized by a wide and shallow open channel, in which flow passes through a number of
small-interlaced channels separated by shoals
Note 1 to entry: Frequently, there is little or no erosion of the main banks of a braided river.
Note 2 to entry: Generally, there is little or no meandering of the main channel of a braided river, but meandering
in the minor channels is usual.
3.3
meandering river
channel following a sinuous path, characterized by curved flow leading to bank erosion alternating
with shoaling
3.4
transition
crossover
inflection reach between two meander loops in which the main flow crosses from one side of the
channel to the other
Note 1 to entry: The depth of flow in a transition is usually reduced from normal depth and is more uniform than
in the curved reach.
3.5
transverse flow
flow horizontally perpendicular to the main direction of flow parallel to the axis of the open channel(s)
Note 1 to entry: Transverse (lateral) flow is frequently associated with secondary flow.
Note 2 to entry: Transverse (lateral) flow in open channels with a curved plan form causes superelevation of the
water surface at the outside of the bend.
3.6
nodal point
node
inflection point
point in a transition at which the sinuous path crosses the mean axis of the meander system
Note 1 to entry: In a meandering stable channel, the nodal point migrates downstream with the meander loops.
Migration can be prevented by the creation of a natural or artificial obstruction in the channel.
3.7
gauge
device installed at a gauging station for measuring the level of the surface of the liquid relative to a datum
4 Site selection in rivers
However, when the flow directions during flood and low flow seasons are very different, it is
permissible to suitably adjust the orientation of gauging section during that season, taking into account
the requirements in ISO 748:2007, 5.1 a) and b).
ISO 748:2007, 5.1 b) further states that the accuracy of the determination of discharge is increased if
the flow directions for all points on any vertical are parallel to one another, and at right angles to the
measurement section.
ISO 748:2007, 5.1 c) recommends that the bed and the margins of the channels should be stable and
well-defined at all stages of flow in order to facilitate accurate measurement of the cross-section, and
...