ISO/TR 19234:2016

TECHNICAL ISO/TR
REPORT 19234
First edition
2016-12-15
Hydrometry — Low cost baffle
solution to aid fish passage at
triangular profile weirs that conform
to ISO 4360
Hydrométrie — Projet de chicane à faible coût pour faciliter le
passage des poissons au niveau des déversoirs à profil triangulaire
conformes à l’ISO 4360
Reference number
©
ISO 2016
© ISO 2016, 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
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved

Contents  Page
Foreword .iv
Introduction .v
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Symbols . 2
5  Principles . 3
6  Installation . 4
6.1 Site selection and application . 4
6.1.1 Restriction . 4
6.1.2 Background. 4
6.1.3 Preliminary survey . . . 4
6.1.4 Limitations . 6
6.2 General arrangement . 6
6.3 Suitability for fish species. 8
6.4 Location of the first baffle . 9
6.5 Baffle dimensions .10
6.6 Baffle material and construction .10
7  Maintenance considerations .11
Bibliography .13
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html
The committee responsible for this document is Technical Committee ISO/TC 113, Hydrometry,
Subcommittee SC 2, Flow measurement structures.
iv © ISO 2016 – All rights reserved

Introduction
Flow gauging structures are commonly used for the measurement of open channel flows. To operate
satisfactorily, these structures require a head difference to be generated between the upstream and
downstream water levels. At structures designed to operate in the modular flow range, an upstream
head measurement is used to interpret flow rates. At structures designed to operate in both the
modular and drowned flow ranges, the upstream head measurement is augmented by a second
measurement which senses tailwater conditions. The former type tends to require higher head losses
over the structure.
In recent years, greater emphasis has been placed on environmental issues, including the free migration
of fish in watercourses. It is acknowledged that flow measurement structures, with their requirement
for a head loss between upstream and downstream conditions, may inhibit the movement of fish. It has
become important, therefore, to consider ways of aiding fish migration without seriously affecting flow
measurement accuracy.
TECHNICAL REPORT ISO/TR 19234:2016(E)
Hydrometry — Low cost baffle solution to aid fish passage
at triangular profile weirs that conform to ISO 4360
1  Scope
This document specifies the requirements for the integration of baffles on the downstream face of
triangular profile flow measurement structures to aid the passage of fish.
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
diadromous fish
fish that migrate between fresh water and sea water to complete their life cycle
3.2
potamodromous fish
fish that migrate wholly within fresh water to complete their life cycle
3.3
baffle
wall or block attached to the downstream face of the structure to aid fish passage
3.4
aerobic swimming
sustainable swimming using red muscles, which incur no oxygen debt
3.5
anaerobic swimming
time limited swimming using white muscles, which incur oxygen debt
3.6
riverine species
fish species typically found in and adapted to a flowing water environment
3.7
structural head difference
SHD
difference in elevation between the crest of the triangular profile weir and the downstream water level
at a flow equivalent to Q exceedance
Note 1 to entry: Q is the flow that is exceeded for 95 % of the time.
Note 2 to entry: See Figure 2.
3.8
streaming flow
flow which occurs when H /H ≥ 0,60, where
2 1
H is the head on the downstream side of the baffle;
H is the head on the upstream side of the baffle
3.9
plunging flow
flow which occurs when H /H is less than 0,50, where
2 1
H is the head on the downstream side of the baffle;
H is the head on the upstream side of the baffle
Note 1 to entry: Values between 0,50 and 0,60 can be in hysteresis.
4  Symbols
Symbol Term Unit
b Breadth of the weir crest perpendicular to the flow direction m
h Gauged head relative to the crest (upstream head is inferred if no sub- m
script is used)
H Total head relative to the crest level m
H Head on the upstream side of the baffle m
H Head on the downstream side of the baffle m
L Distance from the crest to the front of the first baffle m
L Distance from the crest to the centre of the first baffle m
L ’Rounded up’ value of L m
2 1
L Maximum apron length m
a
3· −1
Q Flow that is exceeded for 95 % of the time m s
T Height of the first baffle m
Ts Height of subsequent baffles m
c Slot offset distance immediately downstream from the reflection m
d Distance between baffles, centre to centre m
p Height of the weir crest above the upstream bed level m
q Slot width m
a
A spreadsheet tool associated with this document is used to design the layout of the baffles in accordance with this
document. A link to the spreadsheet is given. http://standards.iso.org/iso/tr/19234
When opening the spreadsheet, be sure to click on the “Enable Macros “dialogue box.
2 © ISO 2016 – All rights reserved

Symbol Term Unit
f Offset distance between the position of slots in successive baffles m
SHD Crest level above Q downstream water level m
a
zL Intermediate variable used in the spreadsheet to determine local
coordinates (left hand side) for determining the slot location
a
zR Intermediate variable used in the spreadsheet to determine local coor-
dinates (right hand side) for determining the slot location
a
dL Intermediate variable used in the spreadsheet for calculating cutting
lengths for the baffles – left hand side baffle
a
dR Intermediate variable used in spreadsheet for calculating cutting
lengths for the baffles – right hand side baffle
a
A spreadsheet tool associated with this document is used to design the layout of the baffles in accordance with this
document. A link to the spreadsheet is given. http://standards.iso.org/iso/tr/19234
When opening the spreadsheet, be sure to click on the “Enable Macros “dialogue box.
5  Principles
Baffles are placed in parallel rows on the downstream sloping face of a triangular profile weir. There
is a slot in each row of baffles that runs at an angle progressively across and down the weir face. This
oblique channel can be reflected from side to side in narrower channels forming a V-shaped pattern
in plan view, see Figures 1 and 3. The baffles retard flow, maintain a consistent depth of water, and
prevent water velocities increasing down the weir. The oblique channel formed by the slots provides a
passage route with greater flow depth and lower velocities than over the baffles. The baffles also break
the often significant hydraulic jump that typically occurs down the face of weir and moves it further up
the weir face where its intensity is greatly reduced.
The solution creates conditions that fish are able to exploit to find passage over a wide range of flows.
Fish may exploit the low velocity channel or, when flow tops the baffles, they may swim straight up the
slope, taking advantage of the retarded velocity flows created by the baffles.
The difference in elevation between the invert of the weir crest and the top of the first baffle downstream
is of critical importance. The dimensions and location should be determined in such a manner that it
does not affect the coefficient of discharge of the triangular profile weir by more than 1 %. The range
of level measurement of the gauge will determine the distance of the first baffle downstream from
the crest. However if the range is set too high, the first baffle will be set so far downstream that fish
w
...